Treating big people (adults) with COVID…

Cite this article as:
Vicki Currie. Treating big people (adults) with COVID…, Don't Forget the Bubbles, 2021. Available at:
https://doi.org/10.31440/DFTB.32313

Reflections from a Paediatric Registrar

‘I won’t touch the feet- I’ll do ANYTHING else’. Avoiding adult feet was one of the reasons I chose a career in paediatrics was one of my responses when I found out that the PICU I was working in was being converted to an adult COVID ITU. I chose paediatrics as a career for so many other reasons, but this was the first thing that popped into my head. 

The world has been turned upside down by this pesky virus.If one year ago you would have told me that I would be looking after adult ITU patients with this new disease I would have refused to believe it. For so many, working lives have changed, roles have been adapted or learnt at lightning speed and working outside your ‘comfort zone’ has become part of the ‘new normal’. 

After a few weeks of looking after adult COVID ITU patients on a PICU I have had some time to reflect on how different things have been. Some things will change my practice forever, some of the big differences in ways of working between those looking after big and littler people. As a general paediatrician doing a stint on PICU, intensive care was new but the steep learning curve after 6 years of looking after ‘littler people’ was even steeper. 

After working closely with adult ITU team members for the last few weeks, we have had a chance to see how each other works. It has proven an opportunity to learn form each other. There are a lot of similarities, and a few differences. There are also some things which both sides can hopefully take forward into our future practice. 

Handover

As paediatricians we LOVE a handover- in some places I have worked it can feel like handovers take over the entire day. One of the biggest differences is the way the adult team do handover.  It seems so much more business-like – especially at the end of a nightshift. There’s no messing around. Any issues? Who is stable or not\? Salient points only. The paediatrician’s in the room added their own twists ‘Had the family been updated? What had they eaten today? What did their poo look like? And how had they slept?’

After a few weeks a happy medium had been found. There was a nice balance achieved between getting the night team off on time, and reducing information that could be found out easily on the morning round whilst including some of the more holistic aspects of care.

Communication with relatives and patients

Those who look after children are used to having to flip between conversing with patient and family. This is a great advantage. We are constantly thinking about updating relatives and keeping family informed. Using FaceTime allowed us to communicate with relatives. They could see their loved ones when they could not be with them. 

The adult team, who have had much more practice with the difficult conversations, seemed to be so slick, having the same realistic and honest conversations. It was business-like and well-rehearsed. Delivering the information succinctly meant that time could be spent talking to more families. 

Patients told me that the way medical and nursing staff spoke with them was different when they made the move to the PICU. Many patients told me that they could tell we were used to dealing with children. The way we spoke was cheery, informal, and most importantly, personal.  I wonder if this was always what they wanted though, especially when delivering difficult news. With the help of the adult ITU team, a delicate balance was maintained. 

Attachment

The adults with COVID in the ITU seem to be long- stayers.Having the same set of patients for a few weeks is great in some ways; and hard in others. Often, with PICU patients, there can be prolonged stays but one of the things the adult team found hard was the attachment they formed to their patients  from seeing them shift after shift. Couple this with the need to look after so many patients on adult ITU , whilst rotating through different pods. On PICU it was one area with the same patients.

On the plus side, you knew the patients REALLY well. You understood things in detail things, like what ventilation strategies they responded to- or didn’t. You knew what previous infections they had been treated for and you knew what families had been told. The downside: you became more attached. It was harder, emotionally, when a patient you knew deteriorated or didn’t better. I wonder if we carry more of an emotional burden in paediatrics because of this. Any doctor will get emotionally attached to certain patients. But are we more likely to do so by seeing fewer patients but more often than our adult counterparts? 

Teamwork

Without question, the amazing paediatric ITU nurses stepped up to the challenge of looking after grown-ups. The incredible camaraderie, between nursing staff, paediatric doctors and the adult ITU team, proning the most unwell patient at 2 in the morning is something which should be bottled up and stored for reuse when this is all done. Truly working together to pull, not only the patients but also each other through the difficult shifts. 

The adult ITU team helped whenever they were needed. They supported us and also credited us paediatricians on many occasions for out strict attention to detail – with anything from charting blood results to charting fluid balances. 

This has been an eye-opening experience. It has been challenging, terrifying, devastating at times. It has also provided opportunities to work with amazing colleagues and witness teamwork between medical and nursing staff like never before. It has been a unique opportunity for adult and paediatric teams to work side by side and siphon bits of each other’s practices. 

As for the feet- it wasn’t as bad as I expected- but I drew the line at a request for a foot massage!

An excellent resource for those working on the front line who are struggling or just looking for that little bit of extra support…

https://www.rcpch.ac.uk/key-topics/your-wellbeing-during-covid-19-pandemic

PEM adventures chapter 3

Cite this article as:
Team PEM Adventures. PEM adventures chapter 3, Don't Forget the Bubbles, 2021. Available at:
https://doi.org/10.31440/DFTB.31888

It’s time for another PEM adventure. Join us on another journey (with an inbuilt time travel machine) in managing Francesca, a teen who dreams of being a pop star…

Meet Francesca, a 15 year old girl who dreams of being a pop star.  She is making ripples in the world of teen music videos and has a HUGE audition tomorrow for a music video. But for the last 24 hours she’s been feeling a little shaky and pretty nauseous. Putting it down to nerves, her mother (who is also her agent) continued packing for the big trip. But Francesca vomited, had two episodes of diarrhoea and then spiked a fever and her mother knew she needed to get her fixed. Fast.

It’s the middle of a run of the mill shift for you. You’ve just fished a bead from a child’s ear, reduced a decently angulated forearm fracture and admitted a child with a pyelonephritis. When you take a look at Francesca though you know she’s sick. She is agitated, clammy and flushed, and febrile at 39.3°C. She’s tachycardic at 130, with a bounding pulse, blood pressure of 128/74 and normal heart sounds. She tachypnoeic at 24, with sats of 98% in air and a clear chest. Her abdomen is tender in the epigastric region, with no guarding or rigidity. Her GCS is 15 with no focal neurology. Her triage weight is 44kg.

You grab the sepsis trolley. Cannula in you, send some bloods: FBC, coagulation, CRP renal and liver function and blood cultures. You run a venous gas and this is what you see…

That lactate is horrific. You hastily prescribe a 20ml/kg bolus of 0.9% saline and a broad-spectrum third-generation cephalosporin. But, what’s your next step?

You prescribe some paracetamol. Easy enough. And then you go back and think about what to do next.

Close the tab and have a think about some more choices or move on to the next section.

You give another 20ml/kg of 0.9% saline and reassess.

Her heart rate drops down a couple of beats per minute but it bounces up again. So you give more saline. But her heart rate goes up a bit higher. And higher again. She begins to hyperventilate. Heart sinking, you repeat her gas. Her pH has dropped, her lactate has climbed and her potassium looks horribly high. This was NOT supposed to happen. The saline has done exactly the opposite of what you’d like it to do… how could that be? 

You wish you could go back in time and make that choice again. Luckily for you, that’s exactly what the inbuilt time travel machine is for.

Close the tab and take another look at the choices. If there’s nothing else you’d like to do then move on to the next section.

You give another 20ml/kg, but this time, instead of reaching for the saline, you go for Plasmalyte (or Hartmann’s, if that’s your fluid of choice). You reassess. Her heart rate drops down a couple of beats per minute but it bounces up again. Her pulses remain bounding, BP holds and JVP isn’t raised with no rales in her chest so you give another bolus and reassess. Same thing happens: a miniscule response but nothing substantial. You don’t make things worse, but you can’t seem to make things better either. Why isn’t fluid bringing down Francesca’s heart rate?

Close the tab and take another look at the choices. If there’s nothing else you’d like to do then move on to the next section.

Her ECG shows a sinus tachycardia. She’s in sinus rhythm with a p wave before each QRS and a normal p wave axis; her QRS axis is normal and intervals are normal too. There are no voltage criteria for ventricular hypertrophy and you can’t spot any subtle ST changes or delta waves. You use a handy ECG proforma to double check, but apart from the tachycardia, it all looks fine. So you go back to Francesca and have a think about what to do next.

Close the tab and take another look at the choices. If there’s nothing else you’d like to do then move on to the next section.

You have recently been on a POCUS course so you want to try out your ultrasound skills. You ultrasound her abdomen. It looks normal. The eminent professor of ultrasonography wanders by. You ask him to double check your findings. He agrees, ultrasound is normal. 

Close the tab and take another look at the choices. If there’s nothing else you’d like to do then move on to the next section.

While you’re pondering what to do, you receive a phone call from your bank. It’s noisy in ED so you pop into the corridor. The bank tells you they’ve just realised they owe you a couple of hundred pounds (*replace pounds with Euros, Dollars, Australian Dollars or any other local currency). That’s great news! Smiling, you type out a quick text to your best friend. “Epic windfall. Celebrate later in China Town?” You can almost smell the chow mein. Your stomach rumbles. It’s definitely time for some lunch. You let Francesca’s nurse know you’re going for a break.

Just as you’re finishing your sandwich, Francesca’s nurse comes rushing to find you. What with the phone call, the texting and the lunchtime queue in the canteen, it’s been almost three quarters of an hour since you last reviewed Francesca. She is far more agitated. The monitor is alarming. Her temperature is now 40.2°C and she’s very sweaty. She looks a little blue. With a heart rate of 159, BP of 108/72, respiratory rate of 32 and O2 saturations of 93% in air, things are not looking good.

Her mother wails, “Will she be better for her audition?!”

You repeat her gas. It’s not good – her lactate’s now 9.3 and her pH is down to 7.03.

Her nurse hands you an ECG. Scanning it you spy peaked T waves, wide QRS complexes and a prolonged PR.

Hang on! What was the potassium on that gas?! You snatch up her gas – her potassium’s 7.2! How are you going to bring that potassium down? What will you prescribe first?

This is a great first choice. Calcium gluconate stabilises Francesca’s cardiac membrane, buying you some time. The gluconate’s in. But that potassium still needs to come down. How are you going to do that?

Close the tab and choose a second drug or drug combination to bring that potassium down. If you’ve already done that and you’re happy with your choice then move on to the next section.

Fabulous! Sodium bicarbonate is an ideal drug in a child or young person who has hyperkalaemia AND acidosis (but you might want to stabilise the cardiac membrane first, if you haven’t done this already). You prescribe a sodium bicarbonate bolus once Francesca’s had her calcium gluconate and ask your amazing resus nurse to start to prepare for an insulin and dextrose infusion.

Close the tab and move on in the story.

On goes the salbutamol nebuliser while the infusion is drawn up. Up goes the infusion. But then something terrible happens. Francesca’s heart rate climbs higher and higher. And then higher again. Her pulse is thready, she’s more diaphoretic. You didn’t think it was possible but she looks even worse. A repeat ECG confirms your worst fears: she’s in SVT. 

Let’s jump back in that time machine and try that vote again. Close the tab and have a look at your other options.

Insulin and dextrose sounds like a good choice. But do you want to give it as your first line agent to bring Francesca’s potassium down? Or after something else?

You get out your phone – there must be an app there somewhere that tells you how to prescribe insulin dextrose infusions for hyperkalaemia. After much tapping and scrolling you find what you’re looking for and write it up. Your amazing resus nurse starts making up the infusion. 13 minutes later it’s up and running. But it’s too late. Francesca’s potassium has continued to climb and she’s going into a VT arrest. No!

It’s time for the time machine. Close this tab and click on “after something else”

This sounds very sensible. After all, insulin-dextrose infusions can take ages to draw up and you need to give something that will work quickly to stabilise her myocardium as well as something that will help drive the potassium back into the cells.

Close the insulin and dextrose tab and choose two drugs: one to stabilise the myocardium and one to bring down the potassium. Hint: she’s acidotic.

Phew! Francesca’s ECG rhythm is improving. Crisis averted. Or is it?

By now Francesca is so agitated, it’s becoming impossible to keep her in bed. “I have to rule out an intracranial infection”, you think to yourself. She needs a CT.

Her nurse begs you to give her a sedative. This makes you a little anxious (pun totally intended). You know that sedation in a sick child can be lethal. So, how will you manage her agitation?

You don’t want to risk giving her a sedative. You’re quite fond of being a doctor and this is a high stakes situation – you don’t want to lose your medical licence if she arrests. Her nurse rolls his eyes – you’re not the one trying to hold her in bed. But as Francesca rips out her cannula and throws herself against the wall you come to the realisation that you are going to have to prescribe something.

Close this tab and go back to choose a sedative.

You like ketamine, you use it a lot and it’s got an excellent safety profile, right? You give Francesca 1mg/kg. She drifts off into a dissociative state. Unfortunately you weren’t as right as you thought. Because it inhibits reuptake of catecholamines it tends to push heart rates up. Francesca becomes extremely tachycardic. After 20 minutes she starts to develop emergence phenomena and becomes even more agitated. She arrests. But don’t worry, we’ve given you a time travel machine for this very reason.

Close the tab and go back to make a different choice.

Unfortunately haloperidol, like Olanzepine, lowers seizure thresholds. You remember this just as it’s infused. Francesca starts fitting. And to make matters worse, it has also prolonged Francesca’s QTc. Her cardiac rhythm becomes unstable and she arrests. Not what you intended. You hop in your time travel machine and go back to make that choice again.

Close the tab and go back to make a different choice.

Unfortunately Olanzepine, like Haloperidol, lowers seizure thresholds. You remember this just as it’s infused. Francesca starts fitting. And to make matters worse, it has also further prolonged Francesca’s QTc. Her cardiac rhythm becomes unstable and she arrests. Not what you intended. You hop in your time travel machine and go back to make that choice again.

Close the tab and go back to make a different choice.

You give Francesca a nice calming benzodiazepine. She settles, buying you some time.

Close the tab and read on to the next part of the story.

You want Francesca out of ED – this is too stressful! Thankfully PICU have a bed. You compassionately explain to Francesca’s mum that the PICU team will work very hard to treat Francesca but she’s very, very sick. Her mum starts crying, “She’s such a beautiful girl! She was going to be famous! She’s worked so hard to lose weight for her audition!”

Internal alarm bells start ringing. “Hang on! How has she lost weight?” Eyes wide, you ask her mother, “Has she been taking something?!?”

Just as you garble this, Francesca’s dad arrives. He’s found a bottle of pills in Francesca’s room. The label says DNP. They were next to her exercise bike.

You ask switchboard to put you through to the national toxicology advice line. The toxicologist who answers the phone tells you that DNP, short for dinitrophenol, is a diet pill that’s illegal in most countries but quite freely available over the internet. It’s called a fat burner because DNP short circuits mitochondrial ATP production by uncoupling oxidative phosphorylation. Because ATP can’t be produced, metabolic rate increases and energy is instead released as heat. People who take it literally burn fat. But even a single pill can lead to uncontrolled hyperpyrexia and its toxic effects are increased with exercise.

They tell you that Francesca’s bloods must be monitored closely; her liver function will deteriorate as her liver literally cooks from within; she will become hypoglycaemic as her glycogen stores are consumed; and she’ll become hyperkalaemic. Monitor her methaemoglobin and if it reaches 30% or if there are signs of tissue hypoxia, give methylene blue.

They give you a long list of treatments including…

Cold intravenous fluids…

…ice packs…

…gastric and bladder cold fluid lavage with peritoneal cooling if you can…

…and Dantrolene…

…and if that fails… then a cooling heat-exchange central line… or ECMO if you’re really stuck.

That temperature just has to come down.

You thank toxicology and replace the handset and think to yourself, “Now where will I find Dantrolene?”

But while you’re pondering this, things go from bad to worse. Francesca’s temperature continues to climb. She’s now 41°C. She’s boiling. Sweat drips onto the sheets. She starts to have a generalised tonic-clonic seizure. You give her a dose of IV. Lorazepam but she continues to seize.

What will you give next?

But a second benzo doesn’t do the trick. She continues to seize. What will you give next?

Close the tab and have another look at the options.

Phenytoin seems like a sensible idea. It’s the second line anticonvulsant in APLS after all. You prescribe 20mg/kg and the infusion’s set up. But it wasn’t a sensible idea. In fact, it was a terrible idea. The phenytoin has exacerbated sodium channel blockade, making her QRS becomes extremely wide. Despite your best efforts to manage her arrhythmia she arrests. It’s time for the time machine. Let’s go back in time to try that one again.

Close the tab and take another look at the options.

You decide to avoid phenytoin because in the context of a toxin you were worried it would prolong her QTc and make her arrest. And ECLIPSE and CONSEPT showed it’s non-inferior to phenytoin in the management of seizures. It’s a good choice.  Her seizure stops.  What a relief.

Close the tab and move on in the story.

You decide to avoid phenytoin because you were worried its sodium channel blocking properties will widening her QRS complexes and make her arrest. And you’ve heard phenobarbital remains the second line recommended treatment in seizures secondary to recreational drugs. It’s a good choice.  Her seizure stops.  What a relief.

Close the tab and move on in the story.

Things can’t get any worse, right? Wrong. She is making a funny snoring noise. You’re really worried about her airway. You fast bleep the anaesthetist. Finally something’s going right, he’s just walking past, and he’s in resus in less time than you can say “dinitrophenol.” He’s up to speed in no time, and definitely agrees she needs a tube. Your RSI cocktail of choice is ketamine (1-2mg/kg), fentanyl (1mcg/kg) and rocuronium (1-2mg/kg). It’s the least cardio-unstable combination of drugs and you definitely don’t want to make things worse. (Take a look at ‘The curious incident of the wheeze in the night time’ for more on this.) But, luckily for you, the  anaesthetist is a clever guy and says, “Let’s avoid fentanyl since she’s hyperpyrexic as fentanyl’s serotonergic – we don’t want to raise her body temperature any higher than it is already.”

The resus nurse mishears his instruction and almost makes a fatal mistake. Spying a syringe labelled suxamethonium, the anaesthetist (who you decide is your new best friend) calmly says, “No suxamethonium. Her potassium is high. She’ll arrest with sux.”

He intubates successfully using midazolam, propofol and rocuronium.  She’s easy to ventilate.

Finally Francesca’s ready for PICU. With cold fluids, ice packs and Dantrolene her temperature comes down to 37.9 °C. You hand her over with clear instructions to avoid…

…serotonergic drugs (put away that fentanyl)

… or drugs that prolong QRS (don’t even think about phenytoin if she fits again)

…and to set up ECMO if her temperature climbs again.

18 months later you watch Francesca perform live in Eurovision. She receives “Douze points!” from every country, setting the record for the highest ever Eurovision score. She campaigns for better awareness of body image in girls and is vocal about the dangers of diet pills.

But let’s hop back in that time travel machine one last time and see what your learning was from her case…

You find this review article about DNP.

Grundlingh J, Dargan PI, El-Zanfaly M, Wood DM. 2,4-dinitrophenol (DNP): a weight loss agent with significant acute toxicity and risk of death. J Med Toxicol. 2011;7(3):205-212

Fascinatingly, as well as all the clinical management advice you received from your friendly toxicologist, it also tells you a bit about the history of DNP. You’re intrigued to read that the first death from DNP was over 100 years ago in 1918 secondary to occupational exposure of DNP powder.  It was used in France for the manufacture of munitions during the First World War.  In 1933 it was discovered that human consumption led to significant weight loss. It became very popular as a weight-loss drug but within 5 years it was recognised as being extremely dangerous and was labelled as “not for human consumption” by the FDA in 1938.  Anecdotally, it was prescribed to Russian soldiers during World War II to keep them warm.

It all went wrong in the 80s (didn’t it all?).  An American doctor prescribed DNP tablets to thousands of patients through his private weight loss clinic.  In 1986 he was convicted for drug law violations, fined and prohibited from dispensing DNP to patients.  But this didn’t stop him.  He was eventually jailed for fraud in 2008. But DNP is still out there and sadly widely available on the internet…

So, what has Francesca’s case taught us (aside from reminding us how very cool the Eurovision Song Contest is)?

1. Infection isn’t the only cause of fever

Keep your differentials open. You only need to Google ‘differentials fever + tachycardia’ and the first thing that pops up is a 2013 article titled, ‘Intoxications Associated With Agitation, Tachycardia, Hypertension, and Fever: Differential Diagnosis, Evaluation, and Management.’ (True as of 1st November 2020). Toxicological agents include drugs that cause:

  • Serotonin Syndrome: some antidepressants including SSRIs, SNRIs and lithium, anticonvulsants such as valproate, analgesics such as fentanyl, antiemetics such as ondansetron and street drugs such as cocaine, ecstasy, methamphetamine and LSD.
  • Neuroleptic Malignant Syndrome: ‘typical’ antipsychotics such as haloperidol, newer ‘atypicals’ such as risperidone and olanzepine, antiemetics such as metoclopramide and promethazine.
  • Malignant Hyperthermia: an inherited skeletal muscle disorder triggered by inhaled anaesthetics, succinylcholine, heat or exercise.
  • Sympathomimetics: cocaine, ketamine, ecstasy, amphetamines, synthetic cannabinoids.

Toxicology isn’t where it ends though. In our COVID world we’ll be used to including inflammatory syndromes like PIMS-TS to our list of differentials, but don’t forget other inflammatory syndromes including inflammatory bowel disease and rheumatological; oncological presentations; intracranial causes (bleed, tumour, basically anything that damages the hypothalamus can dysregulate temperature control); endocrine causes like thyroid storm, adrenal crisis… and the list goes on.

2. Engage your toxicology colleagues early

Even if you don’t think the primary cause is toxicological, as soon as it could be then pick up the phone to your regional / national toxicological service. Sedatives, anticonvulsants, anaesthetic induction cocktails… there are many ways things can go wrong. Ask a friend for advice before prescribing drugs in a potentially unstable situation.

3. Familiarise yourself with the management of acute behavioural disturbance

Acute behavioural disturbance can be a very challenging situation to manage. RCEM, the Royal College of Emergency Medicine in the UK, has a short guideline explaining the pros and cons of the different drugs of chemical restraint. Although not specifically tailored to paediatric presentations, the explanation of the drug side effects is a useful guide to frame your management. From a paediatric perspective, NICE (The National Institute of Health and Care Excellence, UK) have a pathway specific for children. If behavioural techniques don’t work and you need to move onto a pharmacological approach, NICE only advocates the use of IM lorazepam. The Royal Children’s Hospital in Melbourne’s ‘Acute Behavioural Disturbance: Acute Management’ CPG has an escalation ladder from behavioural management, to oral, then IM / IV medications, clearly stating antipsychotics should only be given to children who have previously taken antipsychotics or who have a normal ECG. Read it in conjunction with the RCEM guideline to understand the risks of each drug.

4. Think about the approaches to managing fever

We love a bit of paracetamol or ibuprofen to bring down a fever. But do you know how they work? Although paracetamol’s been used for over 100 years, we’re still not entirely sure how it works. Its antipyretic actions are thought to be due to inhibition of prostaglandin synthesis, resulting in a reset of the temperature centre in the hypothalamus. Nonsteroidals, such as ibuprofen, also inhibit prostaglandin production, although via a different cyclooxygenase (COX) pathway (all sounding vaguely familiar?).

However, fever caused by toxins is not caused by prostaglandin or COX inhibition and needs a different approach to resolve.

Start with non-pharmacological measures. Fans, ice packs in the groins and axillae, ice baths and internal techniques such as gastric and bladder cold fluid lavage, or, more invasively, Intravascular Heat Exchange Catheters (the ICY Catheter). The ICY catheter is placed in the inferior vena cava via the femoral vein, acting as an extracorporeal cooling device. Cold saline circulates through the catheter, which is closed so does not infuse saline into the bloodstream, instead returning the now-warmed saline back out of the body. The patient’s core temperature is measured via a thermometer in the bladder and an automated feedback loop between the thermometer and the ICY Catheter ensures the patient’s temperature is brought down to a target range, which can be adjusted by the treating clinician. Add benzodiazepines to prevent shivering and for sedation to help the child or young person tolerate these techniques.

There’s an extremely high mortality in severe hyperthermia – if these measures don’t work then RSI with muscle paralysis (but avoiding suxamethonium), with benzodiazepine infusions.

And reach for the antipyretic drugs. Dantrolene is frequently used in the management of anaesthetic-induced malignant hyperthermia and neuroleptic malignant syndrome. It works as a postsynaptic muscle relaxant, inhibiting calcium ion release and therefore decreasing the amount of excitation-contraction coupling from muscle cells. It’s usually found in theatre, to keep it ready to hand for the treatment of malignant hyperthermia. But, theatre is often far from the ED, and unless you know it’s there, it can take a while to hunt it down in the hospital – don’t let this delay you using it emergently in ED. Although the use of Dantrolene in DNP toxicity is currently under debate with only a few case reports citing its efficacy in DNP toxicity, its use is still recommended to bring down temperatures above 39-40 °C by Toxbase (the UK National Poisons Information Service) because of the high lethality of DNP.

Other options include Cyproheptadine, a first-generation antihistamine with additional anticholinergic properties and antagonist to serotonin, used in the treatment of serotonergic-driven hyperpyrexia (Serotonin Syndrome). To date, there are no case reports of cyproheptadine being used in DNP toxicity.

And don’t forget to monitor CK and renal function.

5. Consider your resuscitation fluid

You may have heard the phrase ‘(ab)normal saline’ before. Sure, one bolus with 0.9% saline is probably fine, but we should be reaching early for a balanced crystalloid like Hartmann’s or Plasmalyte, and probably from the outset.

Francesca has a pure metabolic acidosis and is trying to compensate by dropping her PaCO2. (Ab)normal saline is 0.9% NaCl – that’s one chloride ion for every sodium ion. Chloride binds with hydrogen to form HCl, hydrochloric acid. Giving Francesca more acid in the form of chloride will plunge her pH lower. This will cause her to hyperventilate to compensate further, which will tire her out faster.

And then Francesca becomes hyperkalaemic. Worsening Francesca’s acidosis by giving more saline will only serve to make the hyperkalaemia worse for a number of reasons, the simplest one being that acidosis drives intracellular potassium to the extracellular (intravascular) space. ‘Why is that?’ you might wonder. Remember, we use alkaline sodium bicarbonate to treat hyperkalaemia by driving potassium into the intracellular space. Giving acidic sodium chloride does the opposite: the hydrogen potassium pump exchanges extracellular hydrogen for intracellular potassium, pushing potassium out of the cell into the intravascular space. Giving acid, makes hyperkalaemia worse. Have a look at this Paediatric FOAM post, ‘Hartmanns in hyperkalaemia: Is that (O)K?’, for a more detailed account as to why we shouldn’t use saline in hyperkalaemic patients.

6. Have a strategy for your emergency treatment of hyperkalaemia

The treatment of life-threatening hyperkalaemia has three facets. All three are important but there is physiological and clinical  merit in doing these in order:

1) Membrane stabilisation

2) Shifting K+ into the cells

3) Reducing total body K+

The first two are the quick fix solutions for the ED. The last solution involves potassium diuresis and haemodialysis or haemofiltration and will traditionally be dealt with on the renal unit or PICU – we will expand on these in a separate blog.

IV Calcium Gluconate

Calcium is vital for stabilising the myocardium. Avoidance of a lethal arrhythmia is our primary concern in life threatening hyperkalemia and so giving calcium first is a priority.

Initial dose: Assuming we have peripheral access the dose is 0.1-0.3 ml/kg IV calcium gluconate 10%  over 10 minutes, diluted fivefold to 20mg/ml. Aim for an ionised calcium >1.15  and repeat if required, remembering that a one-off dose will usually last between 30 minutes to an hour. In the case of persistent arrhythmias or particularly resistant hypocalcaemic state further doses of calcium may be indicated or an infusion can be considered (0.2ml/kg/hr of calcium gluconate 10% diluted as above).

Bicarbonate

It is important to understand that bicarbonate will only work in hyperkalaemia if the patient is in an acidotic state. In this context not all bicarbonate solutions have been created equal.  8.4% bicarbonate is very hypertonic and a number of RCT’s suggest that, if given neat, it will not work in reducing serum potassium levels in hyperkalemic patients. This is thought to be due  to the phenomenon of solvent drag; the hypertonic fluid drags potassium ions to the extracellural compartment due to an osmotic shift. This essentially neutralises the effect a neutral or alkali pH has in the direction of movement of the K+ ions making the overall net shift minimal.

On the other hand, isotonic bicarbonate works in patients in an acidotic hyperkalemic state. Isotonic bicarbonate isn’t commercially available in most UK based hospitals but can be made by diluting each milliliter of 8.4% sodium bicarbonate with 4.6 ml of sterile water for injection or 5% dextrose.  A 1.5% solution of sodium bicarbonate is approximately isotonic. Isotonic bicarbonate can rapidly improve hyperkalemia if the patient is acidotic in three ways: a) by shifting potassium intro the intracellular compartment, b) by increasing potassium diuresis due to alkalosis and c) due to a dilutional effect.  1mmol/kg of isotonic bicarbonate can be given to alkalinise the pH and cause a K+ shift.

Insulin

Insulin shifts potassium into cells by stimulating the activity of the Na+– H+ channel on cell membranes. This in turn promotes the entry of sodium into cells, which leads to activation of the Na+– K+ ATPase, causing an influx of potassium. The decline in serum potassium levels by insulin is dose dependent. Due care must be taken to avoid hypoglycaemia, especially in infants and children with nephropathies.  The doses of IV insulin are as follows:

Neonates: 0.3 – 0.6 units/kg/hour

Children > 1 month: 0.05 – 0.2 units/kg/hour 

Run with glucose 0.5 – 1 g/kg/hour (5-10 ml/kg of glucose 10% via peripheral administration)

Salbutamol

Salbutamol causes a small shift of potassium into cells but a high dose is needed for an adequate effect, around 10-20mg on average. This equates to 4 to 8 back to back nebulised doses depending on the patient’s age. Salbutamol use comes with a caution however; it can both worsen a pre-existing acidosis by driving up lactate (essentially having a neutral effect  on potassium clearance) and will also cause a tachycardia, and in patients prone to arrhythmias, it can cause SVT’s or even VF. It should not be first line treatment, and certainly not before the membrane has been stabilised with calcium nor before the pH has been made less acidotic.

7. And DNP?

DNP toxicity is a well reported presentation to the ED, including a case report of a fatality in a teenage girl, using it as a weight-loss drug

Features usually occur within 4 hours, with agitation, flushing, hyperthermia and diaphoresis. As with Francesca, there may be abdominal pain, vomiting and diarrhoea. There may be yellow discolouration to the skin and urine, which can be confused with jaundice, and rash and desquamation can be a feature, (mis)leading you down the path of toxic shock. The deterioration can be very rapid with grossly elevated temperatures, heart rates and respiratory rates.

And the investigations? A metabolic acidosis secondary to raised lactate, methaemoglobinaemia, hyperkalaemia, hypocalcaemia and hyperglycaemia (at least until glycogen stores become depleted, when the blood sugar will drop).

Have a read of the letter to the editor in response to this case report, two case reports from the States, and a further report from London and decide for yourself whether you’ll be reaching for Dantrolene to treat DNP toxicity.

But, let’s finish on a cautionary tale. Dantrolene can be hepatotoxic so monitor liver function closely. This case report describes a child who developed hepatitis after dantrolene at a pretty low dose.

We would LOVE your feedback about these DFTB PEM adventures so if you can spare a minute, please complete our survey at www.tiny.cc/DFTBpemadventure or use your smartphone to let the QR code take you straight there. We timed ourselves completing it and it takes less than a minute. Thank you.

A HUGE thank you to Dr Laura Hunter, EM and Toxicology consultant at Guy’s and St Thomas’ NHS Foundation Trust in London, UK. As well as a wicked sense of humour, Laura has an encyclopedic knowledge of all things toxicological. Thank you Laura.

And we are absolutely delighted to announce that our friend, Costas Kanaris, has joined the PEM adventures team, bringing with him his wisdom of all things critical care and general brilliance.

References

Keary CJ, Nejad SH, Rasimas JJ, Stern TA. Intoxications associated with agitation, tachycardia, hypertension, and Fever: differential diagnosis, evaluation, and management. Prim Care Companion CNS Disord. 2013;15(3):PCC.12f01459. doi:10.4088/PCC.12f01459

Blumberg A, Weidmann P, Ferrari P. Effect of prolonged bicarbonate administration on plasma potassium in terminal renal failure. Kidney Int. 1992;41(2):369-374.

Kim H. Acute therapy for hyperkalemia with the combined regimen of bicarbonate and beta(2)-adrenergic agonist (salbutamol) in chronic renal failure patients. J Korean Med Sci. 1997;12(2):111-116.

Kim H. Combined effect of bicarbonate and insulin with glucose in acute therapy of hyperkalemia in end-stage renal disease patients. Nephron. 1996;72(3):476-482.

Conte G, Dal C, Imperatore P, et al. Acute increase in plasma osmolality as a cause of hyperkalemia in patients with renal failure. Kidney Int. 1990;38(2):301-307.]

Fraley D, Adler S. Correction of hyperkalemia by bicarbonate despite constant blood pH. Kidney Int. 1977;12(5):354-360.

end-stage renal disease. Miner Electrolyte Metab. 1991;17(5):297-302.

Gutierrez R, Schlessinger F, Oster J, Rietberg B, Perez G. Effect of hypertonic versus isotonic sodium bicarbonate on plasma potassium concentration in patients with

DeFronzo RA, Felig P, Ferrannini E, et al. Effect of graded doses of insulin on splanchnic and peripheral potassium metabolism in man. Am J Physiol. 1980;238(5):E421–E427

Grundlingh J, Dargan PI, El-Zanfaly M, Wood DM. 2,4-dinitrophenol (DNP): a weight loss agent with significant acute toxicity and risk of death. J Med Toxicol. 2011;7(3):205-212. doi:10.1007/s13181-011-0162-6

Allen L. Hsiao, Karen A. Santucci, Patricia Seo-Mayer, M. Rajan Mariappan, Michael E. Hodsdon, Kenneth J. Banasiak & Carl R. Baum (2005) Pediatric Fatality Following Ingestion of Dinitrophenol: Postmortem Identification of a “Dietary Supplement”, Clinical Toxicology, 43:4, 281-285, DOI: 10.1081/CLT-58946

Kim Barker, Donna Seger & Suparna Kumar (2006) Letter To The Editor: “Comment on “Pediatric Fatality Following Ingestion of Dinitrophenol: Postmortem Identification of a ‘Dietary Supplement’””, Clinical Toxicology, 44:3, 351, DOI: 10.1080/15563650600584709

Siegmueller C, Narasimhaiah R. Fatal 2,4-dinitrophenol poisoning… coming to a hospital near you. Emergency Medicine Journal 2010;27:639-640.

Kopec KT, Kim T, Mowry J, Aks S, Kao L. Role of dantrolene in dinitrophenol (DNP) overdose: A continuing question? Am J Emerg Med. 2019 Jun;37(6):1216.e1-1216.e2. doi: 10.1016/j.ajem.2019.03.035. Epub 2019 Mar 23. PMID: 30948257.

Divij Pasrija, Shilpi Gupta, Amanda Hassinger. Dantrolene-Induced Hepatitis: A Rare Culprit in the PICU. J Pediatr Intensive Care 2020. DOI: 10.1055/s-0040-1710496

Van Schoor J, Khanderia E, Thorniley A. Dantrolene is not the answer to 2,4-dinitrophenol poisoning: more heated debate. BMJ Case Rep. 2018 Dec 19;11(1):e225323. doi: 10.1136/bcr-2018-225323. PMID: 30573533; PMCID: PMC6303589.

PEM Adventures Chapter 2

Cite this article as:
Team PEM Adventures. PEM Adventures Chapter 2, Don't Forget the Bubbles, 2020. Available at:
https://doi.org/10.31440/DFTB.30926

Are you ready for another PEM adventure? This time the stakes are a little higher. Join us on another journey (with an inbuilt time travel machine) as we manage Grace…

Teenager holding mobile phone

Meet Grace. Grace is a 15-year-old vegetarian environmental activist. She’s thrilled because she’s recently hit a TikTok following of 10,000 – social media is SO the way to spread the word.

She spent yesterday at an illegal climate strike rally outside parliament. Buoyed up on the adrenaline of a thrilling protest, she and some buddies went back to her friend, Zak’s house where they celebrated in style with vodka pops. But this morning, horrified by the fact Grace was impossible to wake, Zak called the emergency services.

Meanwhile, you’ve just fished a pea out of a child’s ear when the red phone rings. Hearing the pre-alert, you mobilise the team and prep a bay in resus. Minutes later, Grace is wheeled in with Zak in tow and she’s transferred to a trolley.

Whiteboard containing vital signs

Your SHO, Lucy, does a primary survey:

  • A: Tolerating an oropharyngeal airway. No stridor or stertor.
  • B: Self-ventilating in 15L O2 via a non-rebreathe mask. Respiratory rate is a bit raised but her chest is clear and she doesn’t have any other signs of respiratory distress.
  • C: Warm and well perfused, heart rate 68 with normal heart sounds and normal pulse volume. Blood pressure is 115/70 and capillary refill time is less than 2 seconds.
  • D: GCS 7, made up of M4, V2, E1. Pupils are size 3 bilaterally and normally reactive to light. Tone is generally low but reflexes are normal and plantars are down going.
  • E: No rashes, no bruises and Grace is currently afebrile.

Lucy gets Grace’s mum’s number from Zak and phones her to get a bit more information. Grace is a healthy adolescent with no significant past medical history. She’s not on any medications, is not allergic to anything and is fully vaccinated. She’s been completely well with no fever, cough, coryza, or any other symptoms. She did have a cold sore a few months ago – could that be relevant?

Grace’s parents, who had gone away for the first time since covid-lockdown lifted, are running to the train station to make their way back home.

Back in resus, you put in a cannula, and send off some bloods: FBC, U&E, LFT, CRP, blood culture and an alcohol level.

Her venous gas shows a pH of 7.47, pCO2 of 2.7, bicarb 14, lactate of 2.7 and normal glucose.

Blood gases showing respiratory alkalosis

That’s odd, you think to yourself, a respiratory alkalosis with some metabolic compensation. You pause for a second and work through your list of possible causes.

  1. Could this be a central cause of hyperventilation? A bleed? A tumour? A meningoencephalitis? You put up a request for CT brain. 
  2. Could this be a respiratory cause? Asthma? Pneumonia? Pneumothorax? Better get a chest x-ray too.
  3. Could this be sepsis? You prescribe ceftriaxone and add acyclovir. There was that coldsore after all…
  4. Pregnancy?
  5. Endocrine or hypermetabolic cause? Maybe DKA? No… her blood sugar’s normal. Or thyrotoxicosis?
  6. Maybe it’s something toxicological? You remember, from your undergraduate days, learning that salicylates cause a respiratory alkalosis.

You add a salicylate level, and paracetamol for good measure, add thyroid function and ask for a catheter urine for beta HCG and a tox screen.  

But her catheter urine doesn’t give you any extra clues. Grace’s urine beta-HCG is negative, her tox screen is negative and her dip is negative.

The resus nurse gently touches your elbow and quietly says, “Do you want to call the anaesthetist?

Good question, you think to yourself. Her GCS is 7 and she’s tolerating the oropharyngeal airway, but she’s breathing well for herself at the moment. What do you want to do?

There are some compelling arguments not to intubate; Grace is maintaining her airway and she’s obtunded and may have seizures – if you give her a paralysing agent as part of her RSI you’ll never be able to tell. Sure, if you really want to monitor for seizure activity, AND you’re in a a tertiary centre with a PICU with capability of CFM or EEG monitoring, you could keep arguing you can monitor for seizure activity while she’s intubated and ventilated, but it takes a while to set up, and time is of the essence.

So you make the brave decision not to intubate. 

You later decide it was less brave and more foolhardy. While Grace is in CT she drops her GCS further and then has a respiratory arrest, which quickly deteriorates into cardiac arrest. The scanner is a terrible place for CPR. While you’re trying to run an arrest on a narrow CT bed you wish you could go back in time and make that choice again. Luckily for you, the inbuilt PEM adventures time travel machine can do just that. In you hop and whizz back to resus.

Close the toggle and this time click on the ‘intubate’ choice.

There are some compelling arguments not to intubate; Grace is maintaining her airway and she’s obtunded and may have seizures – if you give her a paralysing agent as part of her RSI you’ll never be able to tell if she’s seizing. 

But there’s something niggling you… Grace is heading for a CT scan and the LAST thing you need is for her to arrest in the scanner.

And yes, it’s true, there is a risk you could miss a seizure if she was paralysed, but you can give her a long-lasting anticonvulsant to prevent seizures. 

So… you decide to follow your gut and make the decision to intubate.

Thankfully the anaesthetist is nifty with a tube and she’s already drawn up the RSI drugs – fentanyl, ketamine and rocuronium in a 1:1:1 ratio (that’s fentanyl 1mcg/kg, ketamine 1mg/kg and rocuronium 1mg/kg). She’s intubated without difficulty. 

Grace has bilateral equal breath sounds and a mobile chest x-ray shows the tube to be in a good position, with clear lung fields and normal heart size. You mentally cross respiratory causes of an alkalosis off your list.

You’re doing great.

The anaesthetist asks you, “How should I ventilate Grace? Should I match her raised respiratory rate?

That’s a good question, you think to yourself. What should you do?

This is a very good question and you’re not sure you know the answer. Grace is hyperventilating for some reason, and maybe mimicking this is the right thing to do…

But, you’re worried about her ultra low pCO2. At 2.7 it’s likely to be causing cerebral vasoconstriction and hypoperfusion. It’s time to start some simple, proactive neuroprotective measures.

On reflection, you decide it would be better to slow Grace’s breathing so resolutely you turn back to the anaesthetist and ask him to SLOW Grace’s respiratory rate to keep her end tidal CO2 tightly between 4.5 and 5; you want to prevent secondary brain injury.

He nods his assent, while tilting the head of the bed up to 30 degrees.

But, remembering a great DFTB post by Costas Kanaris, you know you can do more than that to neuroprotect. As well as maintaining normocapnia and nursing her at 30 degrees head in line, Grace needs strict normothermia and hypoxia should be avoided at all costs. She needs vigilant glucose monitoring, tight circulatory monitoring and support and an anticonvulsant to prevent seizures. 

Close the toggle and move on to the next part of the story.

You think this through. The alkalotic pH doesn’t matter quite so much, what’s really troubling you is Grace’s pCO2. With a pCO2 of 2.7, there’ll be huge amount of cerebral vasoconstriction and hypoperfusion. It’s time to start some simple, proactive neuroprotective measures.

Resolutely you turn back to the anaesthetist and ask him slow Grace’s respiratory rate to keep her end tidal CO2 tightly between 4.5 and 5; you want to prevent secondary brain injury and so now’s the time to start some neuroprotection.

He nods his assent, while tilting the head of the bed up to 30 degrees.

But, remembering a great DFTB post by Costas Kanaris, you know you can do more than that to neuroprotect. As well as maintaining normocapnia and nursing her at 30 degrees head in line, Grace needs strict normothermia and hypoxia should be avoided at all costs. She needs vigilant glucose monitoring, tight circulatory monitoring and support and an anticonvulsant to prevent seizures. 

Great choice! Close the toggle and move on to the next part of the story.

With fortuitous timing, CT ring down to say they’re ready for Grace.

Satisfied that A, B and C are all stable, you turn to take the brake off the trolley when Lucy, your SHO, asks, “But do we only want a plain non-contrast CT?

That’s a good question, you think to yourself. Is that all I want? What neuroimaging will you choose?

“Yes”, you say to Lucy. “A non-con CT is quick and will show us most tumours and bleeds. She can have an MRI later to get a bit more detail.” 

But,” your SHO counters, “a non-con CT won’t always detect an ischaemic stroke. Perhaps we should ask for a CTA too?

You remember a case from a few weeks ago, a little boy called Tomas. You’d bookmarked the RCPCH Stroke in Childhood guideline on your phone. You quickly bring it up and Lucy’s right, the guideline says to consider stroke in children with focal neurology, speech disturbance, focal seizures, severe headache, cerebellar signs… and unexplained decreased conscious level.

Smiling gratefully at Lucy you pick up the phone and ask the radiologist if you can add a CTA. They say yes.

Minutes later, Grace has her CT with CTA… but it’s normal. No abscess… no tumour… no bleed… and no stroke.

Well that’s good news for Grace, you think to yourself, but it doesn’t give you any much-needed clues.

Great work. Close the toggle and move onto the next part of the story.

You know what”, you say to your SHO, “let’s ask for a contrast-enhanced CT. It’s still quick and will give us a little more detail than a non-con CT.

But,” she counters, “do you think we should be considering stroke in our differential? Perhaps we should ask for a CTA too?

You remember a case from a few weeks ago, a little boy called Tomas. You’d bookmarked the RCPCH Stroke in Childhood guideline on your phone. You quickly bring it up and Lucy’s right, the guideline says to consider stroke in children with focal neurology, speech disturbance, focal seizures, severe headache, cerebellar signs… and unexplained decreased conscious level.

Smiling gratefully at Lucy you pick up the phone and ask the radiologist if you can add a CTA. They say yes.

Minutes later, Grace has her CT with CTA… but it’s normal. No abscess… no tumour… no bleed… and no stroke.

Well that’s good news for Grace, you think to yourself, but it doesn’t give you any much-needed clues.

Great work. Close the toggle and move onto the next part of the story.

You know what”, you say to your SHO, “let’s ask for a CT plus CTA. The CT will show us most tumours and bleeds and she can have an MRI later for a bit more detail, but we should consider stroke in our differential, and to detect that we need to add angiography to our CT.

You think back to a case from a few weeks ago, a little boy called Tomas. You’d read the RCPCH Stroke in Childhood guideline and remember that it says to consider stroke in children with focal neurology, speech disturbance, focal seizures, severe headache, cerebellar signs… and unexplained decreased conscious level.

Smiling gratefully at Lucy you pick up the phone and ask the radiologist if you can add a CTA. They say yes.

Minutes later, Grace has her CT with CTA… but it’s normal. No abscess… no tumour… no bleed… and no stroke.

Well that’s good news for Grace, you think to yourself, but it doesn’t give you any much-needed clues.

Great work. Close the toggle and move onto the next part of the story.

You haven’t ruled out infection. So, when you’re back down in resus, you ask Lucy if she’d like to do the LP.

Really? Is that safe with her low GCS?” she questions. 

What do you think? Should you LP?

It’s fine,” you reply, “she doesn’t have physiological signs of raised ICP: she’s not bradycardic or hypertensive, she’s not posturing and she didn’t have focal neurology. Plus, her CT doesn’t look like there’s cerebral oedema.

Feeling reassured, Lucy picks up the spinal needle and performs an LP. 

But it’s not your finest decision. Grace cones and arrests. 

Luckily for you and Grace, there’s an inbuilt time travel function in your PEM adventure and you return back to resus just as your SHO asks if it’s safe to LP Grace.

You have a strange feeling of déjà vu, while a little voice tells you that although a normal CT is usually reliable for ruling out raised intracranial pressure, this isn’t failsafe and it might be safer to defer the LP for when she’s a little more stable. You’ve already started the ceftriaxone and acyclovir, so this time you decide that the LP can wait until she’s a bit more stable and can have an MRI first. 

Thank goodness for that time machine! Close this toggle and move onto the next part of the story.

Lucy’s right. Although a normal CT is usually reliable for ruling out raised ICP, this isn’t failsafe and there’s no rush to get CSF now. You’ve already started ceftriaxone and acyclovir anyway. And when she’s a bit more stable she can have an MRI to check the LP’s safe. The LP can wait for now.

Great teamwork! Close the toggle and continue the next part of the story.

You’re still not sure what’s causing Grace’s low GCS though. Maybe the bloods will help. So you log in to the computer to check Grace’s results.

Results showing a mild transaminitis

Huh, you think to yourself. Grace’s FBC and CRP are normal; it’s sounding less and less like infection.

Her urea is low and her liver enzymes are raised, with a slightly prolonged INR.

Her salicylate and alcohol levels are undetectable. This isn’t feeling so toxicological anymore.

You mull this over with Lucy. Maybe this is a viral picture. There was that cold sore…

Just then Maureen, the ED cleaner, pops her head into the office. “Might this be of any use?” she asks. She’s holding the RCPCH Decreased Conscious level guideline.

You quickly flick through. Bloods… imaging… you’ve done pretty much everything it suggests. But then you take a closer look at the list of bloods it suggests. And there, in black and white, it says ammonia.

Of course!” you say out loud. “That would explain the respiratory alkalosis!

You draw off an ammonia sample, get it on ice and ask Raymond, the dashing porter, to run it down to the lab. You give the lab a ring so they can get the machine primed.

While you’re waiting for the result to come back, Zak comes running over. He’s just been looking in Grace’s backpack for her mobile and found a high protein Diet book. Apparently she’s been trying to lose weight for TikTok. Could it be relevant?

The cogs begin to whir… Hang on a minute… A high protein diet in a vegetarian environmental activist?

The lab phones with Grace’s ammonia level.

It’s over 500! And normal is less than 40.

It all falls into place. Selective vegetarian… Recent protein load… Raised transaminases… High ammonia… This is all beginning to sound a bit metabolic.

But what should you do about that ammonia? As far as you can see, the DeCon guidance only tells you to take it, not what you do when it comes back at over 10 times the upper limit of normal.

Just a sec,” says Lucy scrolling through her mobile phone, “The British Inherited Metabolic Disease Group have got this covered. They’ve produced a whole range of easy access emergency guidelines, including this one, for the management of an undiagnosed hyperammonaemia.”

It says, turn off protein catabolism by giving a 10% dextrose bolus followed by a dextrose infusion to provide an alternative energy source. If her glucose climbs, add insulin but don’t reduce the dextrose – otherwise, she’ll just start breaking down more protein. And, finally, mop up that ammonia with scavengers like phenylbutyrate and sodium benzoate.

The words ‘ammonia scavengers’ remind you of another post you read on Don’t Forget The Bubbles, about the different types of metabolic conditions, how they present and the various treatment strategies. You make a mental note to read it again later to remind yourself of the differences between an amino acid and organic acid.

Meanwhile, you hastily prescribe…

  •       A 2ml/kg bolus of 10% dextrose
  •       a dextrose infusion
  •       And those ammonia scavengers, sodium benzoate and sodium phenylacetate

Grace is subsequently diagnosed as having a urea cycle disorder. You’re amazed to discover that although most diagnoses are made in neonates, diagnoses are sometimes made in adolescents and adults presenting encephalopathic after a big protein load or when catabolic, such as after trauma, childbirth, major surgery, major haemorrhage, critical illness, rapid weight loss or simply after switching to a high protein diet. This is particularly true for ornithine transcarbamylase (OTC) deficiency, which although is X-linked, can present in symptomatic female OTC carriers. Little diagnostic clues include autoselective vegetarianism (that protein makes them feel a bit ‘ugh’) and subtle or behavioural difficulties from chronic low-level hyperammonaemia.

You bookmark a fantastic review article to read later and flick back through your undergraduate biochemistry textbook to remind yourself about urea cycle defects… and hastily close it again when you remember how little you knew even then, at the prime of your undergrad years.

Wow, what a shift. You pack up your stethoscope and head home, reflecting on your day as you walk to the bus stop.

Grace has taught you the importance of…

Reaching for the RCPCH DeCon guideline when looking after a child with an unexplained low GCS.

Not ever forgetting to send an ammonia in an encephalopathic child, young person or even adult; these tricksy urea cycle disorders can present in adulthood. If the ammonia comes back high, BIMDG have a handy guideline telling you exactly what to do.

And, remembering that a normal CT does not ALWAYS rule out raised ICP. In a child with low GCS, put away that LP needle and neuroprotect instead.

But what happened to Grace? Let’s jump in the time travel machine and find out…

Your epic diagnosis of a late presenting metabolic disorder was the talk of the ED. The RCPCH DeCon poster was put up in the ED staff room and from that point onwards, everyone remembered to check an ammonia in a patient presenting with an unexplained low GCS. 

Lucy was nominated as employee of the month. This shift was a pivotal moment in her career as she decided PEM was her vocation.

The ammonia scavengers did the trick and Grace made a full recovery.

Grace focussed her efforts on reducing plastic waste in hospital and successfully petitioned for the introduction of plastic-free PPE, reducing plastic waste during the COVID-19 pandemic by an incredible 275%.

She hit 3 million TikTok followers (and you’re one of them).

This PEM adventure wouldn’t have been possible without some help from some amazing people. Thank you to Roshni Vara, Consultant in Paediatric Inherited Metabolic Disease at the Evelina London, Costas Kanaris, PICU and retrieval consultant at the Royal Manchester Children’s Hospital and Jon Lillie, PICU and retrieval consultant at the Evelina London Children’s Hospital.

Here are some of their wise words of advice…

As Costas says in The N of 1 matters, we’ve outlined our take on Grace’s case and how we’d manage her in our own resus bays. Medicine’s not always so clear cut and there are often different approaches to the same problem, but this is our consensus on minimising risk using, as Costas says, a rational, evidence-based and pharmacologically prudent approach (I love that phrase Costas!)

Should we intubate Grace?

Grace is self-ventilating but the fact that she is tolerating an oropharyngeal airway means some of her airway reflexes have gone. Scanning a child with a GCS of 8 or less, without securing the airway, puts them at risk. If they vomit, they aspirate. If they stop breathing and arrest in the scanner, the CT room is one of the least fun places to run an arrest, perhaps second only to an elevator. Are there any counter-arguments? Yes, and they’re soft.  One is “this patient is encephalopathic/obtunded and may have seizures; if the child starts fitting we won’t be able to tell as they’ll be paralysed”.  Costas says he usually stands his ground and says that if someone is worried about seizures then the child can be given a long-acting antiepileptic. Levetiracetam is his preference, although phenytoin would work just as well unless there’s suspicion of an overdose of an arrhythmogenic agent. The last thing you need is to tip this child into an arrhythmia.

When should a lumbar puncture be performed in a child with a decreased conscious level?

CT is a useful tool for ruling out raised intracranial pressure before proceeding to lumbar puncture. And we’d agree. But Grace has a low GCS and this changes the picture.

If we take a look at the full RCPCH DeCon guideline it dedicates a whole section to answering the question about LP in decreased conscious level. So, let’s start there.

The DeCon guideline advises a lumbar puncture if your differentials are viral encephalitis or tuberculous meningitis and advises that we consider lumbar puncture when our differentials are bacterial meningitis, sepsis, or the cause of the low GCS is not known. This is cloaked with the phrase “when no acute contraindications exist” and this is key. So what are those contraindications?

  • Signs of raised intracranial pressure: dilated pupil(s), abnormal pupil reaction to light, bradycardia, hypertension or abnormal breathing pattern.
  • A GCS equal to or less than 8, or a deteriorating GCS
  • Focal neurology
  • A seizure lasting more than 10 minutes with a GCS less than 13
  • Shock or clinical evidence of meningococcal disease
  • CT or MRI suggesting obstruction of the CSF pathways by blood, pus, tumour or coning.

What’s the evidence? Well, it’s mostly been derived by expert opinion, and there aren’t many people who’d dispute them.

But what about when you have a normal CT? The radiologists can look for midline shift and for signs of impending herniation by assessing the position of the cerebellar tonsils. So, surely that can rule out raised ICP, allowing an LP to be done?

The DeCon guideline quotes a study published in 2000 that showed that in 124 CT scans from 65 children with traumatic brain injury, CT had an excellent sensitivity of detecting raised ICP of 99.1%, with a specificity of 78.1%. But, a 2019 revision to the guideline says that no further evidence about the sensitivity or specificity of CT in detecting raised ICP in children has been found. None. Although the sensitivity in the one quoted study was very high, it was felt that one study, in children with traumatic brain injury, could not be extrapolated to all children with a decreased conscious level. And so the guideline states that a normal CT scan does not exclude raised ICP. If other contraindications are present, don’t use a normal CT to justify LP.

What does this mean in practice? Well, in a child with a GCS of 8 or less, like Grace, there’s no rush to do an LP. It’s unlikely to change your management acutely in the ED. Her infection can be treated empirically and once she’s more stable, and you have more information including, potentially, an MRI, she can then have an LP for PCR.

What neuroimaging should we do?

That’s a good question, answered beautifully by an article by Hayes et al, published in 2018. Although this article focuses on neuroimaging for headaches, it has a great section on when you might choose each type of scan.

We’d all agree that the ideal imaging to look for a brain tumour is an MRI. It gives excellent detail about the brain tissue as well as other intracranial soft tissues and the extra-axial CSF spaces.

But, if you want a quick answer, or your access to MR is difficult, a non-contrast CT can be performed easily from the ED. If there’s no possibility of a later MR, then contrast-enhanced CT might be better as it gives more detail, but it’s more radiation – this is one for discussion with the radiologist.

CT is very sensitive in detecting blood, and it can be done quickly, in an emergent setting from the ED. So, in children with thunderclap headache, when you want to exclude subarachnoid hemorrhage, a non-contrast CT will be your first choice scan. If blood is detected, then add in arterial imaging: CT or MR angiography (CTA or MRA). Contrast is injected and images taken in the arterial phase.

CTA or MRA are also useful in the investigation of suspected stroke. In practice, you need an answer fast, particularly if the child’s within the thrombolysis window and could be a candidate if there’s evidence of ischaemic stroke, so a CTA is a more practical scan. The CT component looks for blood or large areas of parenchymal infarct, while the angiography looks for filling defects in the arteries that could indicate a thrombus.

If you’re looking for intracranial extension of infection, such as from an orbital cellulitis, mastoiditis or a brain abscess, then a contrast-enhanced CT will highlight suppurative collections.

And if you suspect a venous sinus thrombosis, such as in children with coagulopathies, sickle cell disease, infective spread from meningitis / mastoiditis / sinusitis, or secondary to dehydration or renal failure? Then you need to look at the venous spaces. CT or MR venography (CTV or MRV), when contrast is injected and images obtained in the venous phase, will give you the answers you need.

And what ARE the causes of a respiratory alkalosis?

There are a few! Here are the main ones:

  • Central: brain tumours, meningoencephalitis; stroke
  • Respiratory: asthma, pneumonia, pneumothorax, PE
  • Sepsis
  • Pregnancy
  • Endocrine and hypermetabolic cause: DKA, thyrotoxicosis
  • Toxicology: salicylates 
  • Hyperammonemia: liver and metabolic disorders 
infographic of causes of respiratory alklosis

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Select references

The management of children and young people with an acute decrease in conscious level. A nationally developed evidence-based guideline for practitioners. RCPCH. 2015 update, with 2019 revisions. Management of children and young people with an acute decrease in conscious level – Clinical guideline | RCPCH

Undiagnosed Hyperammonaemia. Diagnosis and Immediate Management. British Inherited Metabolic Disease Group. Last reviewed 2017. The major causes are as follows (bimdg.org.uk)

Hirsch, W., Beck, R., Behrmann, C. et al. Reliability of cranial CT versus intracerebral pressure measurement for the evaluation of generalised cerebral oedema in children. Pediatric Radiology 30, 439–443 (2000). https://doi.org/10.1007/s002470000255

Expert Panel on Pediatric Imaging:, Hayes LL, Palasis S, Bartel TB, Booth TN, Iyer RS, Jones JY, Kadom N, Milla SS, Myseros JS, Pakalnis A, Partap S, Robertson RL, Ryan ME, Saigal G, Soares BP, Tekes A, Karmazyn BK. ACR Appropriateness Criteria® Headache-Child. J Am Coll Radiol. 2018 May;15(5S):S78-S90. doi: 10.1016/j.jacr.2018.03.017. PMID: 29724429.

Mitani H, Mochizuki T, Otani N, Tanaka H, Ishimatsu S. Ornithine transcarbamylase deficiency that developed at the age of 19 years with acute brain edema. Acute Med Surg. 2016;3(4):419-423. doi:10.1002/ams2.214

Summar ML, Barr F, Dawling S, Smith W, Lee B, Singh RH, Rhead WJ, Sniderman King L, Christman BW. Unmasked adult-onset urea cycle disorders in the critical care setting. Crit Care Clin. 2005 Oct;21(4 Suppl):S1-8. doi: 10.1016/j.ccc.2005.05.002. PMID: 16227111.

Kanaris C, Ghosh A, Partington CG389(P) A case for early ammonia testing in all encephalopathic patients: female patients with x-linked ornithine transcarbamylase deficiency. Archives of Disease in Childhood 2015;100:A158-A159. http://dx.doi.org/10.1136/archdischild-2015-308599.343

Summar, Marshall. (2005). Presentation and management of urea cycle disorders outside the newborn period. Critical Care Clinics. 21. IX-IX. 10.1016/j.jccc.2005.08.004.

Petechiae in Children – the PiC Study

Cite this article as:
Tessa Davis. Petechiae in Children – the PiC Study, Don't Forget the Bubbles, 2020. Available at:
https://doi.org/10.31440/DFTB.30782

Today the Lancet has published the long-awaited results of the Petechiae in Children (PiC) study. Team DFTB got our hands on a pre-publication copy to read, summarise, and analyse for you. So let’s get to it.

This PERUKI study by Waterfield et al. is a prospective, multicentre cohort study:

Waterfield T, Maney J-A, Fairley D, Lyttle MD, McKenna JP, Roland D, Corr M, McFetridge L, Mitchell H, Woolfall K, Lynn F, Patenall B, Shields MD, Validating clinical practice guidelines for the management of children with non-blanching rashes in the UK (PiC): a prospective, multicentre cohort study, The Lancet, 2020

Why is this study needed?

We are all somewhat terrified of children with fever and a non-blanching rash. We don’t want to miss meningococcal sepsis. Current guidelines are based on data from before the introduction of the Meningococcal B (2015) and C (1999) vaccines and consider a prevalence of 10-20% of meningococcal infection in children with fever and non-blanching rash.

Who were the patients?

The paper looked at children under 18 years old presenting to 37 Paediatric Emergency Departments in the UK over a 16 month period. Children were included if they had a fever (>38oC) and new onset of a non-blanching rash or features suggestive of meningococcal infection. Children were excluded if they had a pre-existing haematological condition or if they already had a diagnosis of Henoch-Schonlein purpura.

1513 patients were screened. 179 were excluded due to not meeting the criteria, not consenting, or a language barrier. Five that were enrolled had incomplete data leaving 1329 children were enrolled and included – the median age was 24 months, and 59% were male. Most children were vaccinated with 73% having had at least one dose of the Meningococcal B vaccine, and 77% having had at least one dose of the Meningococcal C vaccine.

What was the intervention?

There was no intervention here. Included patients were recruited at the point of meeting the criteria, using ‘recruitment prior to consent‘ and then consent was obtained soon after (usually within 24 hours). Data were collected contemporaneously: patient symptoms, blood test results, and treatment. A positive case was identified by being positive on PCR, or with a positive growth from another body sample (e.g. blood culture, or CSF). Patients were also checked for re-attendance to the hospital within 7 days. Results were also confirmed with the Public Health Agency – as meningococcal disease is a notifiable condition, this was a good method of picking up any missed cases.

What were the outcomes measured?

The primary outcome was assessing the performance of eight clinical guidelines on identifying children with invasive meningococcal disease (NICE meningitis (CG102); NICE sepsis (NG51); London; Chester; Bristol; Nottingham; Newcastle-Birmingham-Liverpool; and Glasgow).

The secondary outcomes were: performance of the eight guidelines in identifying children with other bacterial infections; and also looking at a cost comparison of each of the eight guidelines.

What were the results?

Of all 1334 children, 86% had a blood test and 45% had antibiotics. For patients admitted to hospital, the median length of stay was one night. 11 patients were admitted to PICU (2%) and two patients died (<1%).

Eight of these 11 PICU patients had N. meningitidis as did both of the patients who died. Seven patients had invasive bacterial infection (five with pneumococcal infection, one with E. Coli, and one with Group A Strep).

19 (1%) of patients in the cohort had meningococcal disease. 17 of these had N. meningitidis B, one had N. meningitidis C, and one had N. meningitidis W. Overall there were 26 patients (2%) with invasive bacterial infection (19 with meningococcal disease and 7 with an invasive bacterial infection).

346 patients (26%) did not have standard testing, and of these 19 patients (5%) had one unplanned re-attendance within seven days. However, none of these required readmission, antibiotics, or bacterial infection.

And how did the guidelines do?

All eight guidelines identified all of the 19 cases of meningococcal disease and all 26 cases of invasive bacterial infection (so the sensitivity of all of them is 100%). Specificity varied though. The NICE sepsis guideline stratified every patient as having a bacterial infection and therefore had a specificity of zero, making it the lowest specificity out of all the guidelines (closely followed by NICE meningitis guidelines with a specificity of 1%). This strategy clearly has cost implications too which is why the two NICE guidelines were also the most expensive per patient (£660.41 for the NICE sepsis guidelines).

Coming out top of the guideline ranking was the Barts Health NHS Trust guideline with a sensitivity of 100%, a specificity of 36%, and a cost of £490.29. This makes it the most accurate and also the cheapest.

Here’s the Barts Health NHS Trust guideline:

What about when we don’t follow the guidelines?

In practice, the guidelines were adhered to in 46% of the patients in the cohort. Deviation from guidelines resulted in fewer antibiotics being given. However, it also resulted in two patients being discharged with early meningococcal disease (they were subsequently treated and did not need PICU admission). Clinician decision-making increased the specificity (i.e. clinicians treated fewer people with antibiotics who didn’t have an invasive bacterial infection), but unfortunately reduced the sensitivity to 89%. Clinician decision-making did have the lowest cost per patient.

You’ve heard the facts, but how good was the paper?

As Ken Milne says…let’s get nerdy (and consider the CASP checklist for cohort studies)

Yes.

Research without prior consent was used to avoid recruitment delaying any treatment plans. However consent was obtained as soon as possible after inclusion in the study (usually within 24 hours).

Yes. Objective measurements were used for a blood test and PCR results. Risk factors for meningococcal disease are subjective and were based on contemporaneous clinical assessment – but this is what we do in practice so is a good reflection.

Yes. Note, however, that two patients with meningococcal disease were not included – one was not enrolled and the other was deemed by local staff to be inappropriate for inclusion.

Yes.

Yes, and also results were also checked with the Public Health Agency which would have allowed pick up of any missed meningococcal positive results.

There is a 1% prevalence of meningococcal disease in a mainly immunised population of children with fever and a non-blanching rash. The Barts Health NHS Trust guideline was the most accurate out of all the guidelines and with the lowest cost per patient.

Yes.

Yes. However, they would not be transferrable to populations with lower rates of vaccine uptake or a higher disease prevalence. The data was not shared on whether those with meningococcal disease were unimmunised or not, and therefore it would be prudent to be more cautious if your patient is not vaccinated.

Previous data was from prior to the meningococcal vaccination so this is the first and largest study since then.

What did the authors conclude and what can we take away from this study?

Since the advent of a vaccination programme and increased vaccine uptake, the rates of meningococcal disease are lower. Although previous data suggested 10-20% of children with fever and a non-blanching rash had meningococcal disease, in fact this study shows that only 1% had meningococcal disease.

Using a cautious guideline like NICE results in a lower specificity and higher cost. Tailored guidelines can increase the specificity and reduce the cost per patient without compromising on 100% sensitivity. The Barts Health NHS Trust guideline was the top performing guideline.

And finally, a comment from the authors themselves:

From Tom Waterfield:

The Petechiae in Children study represents the best available evidence regarding the assessment and management of febrile children with non-blanching rashes in the UK and clearly demonstrates that a lighter touch, tailored approach, is favourable to a test/treat all approach as currently advised by NICE. Moving to a tailored approach will reduce the need for invasive procedures, improve antimicrobial stewardship and save money. 

In vaccinated populations where the prevalence of invasive meningococcal disease is low the presence of Petechiae alone should no longer be viewed as a red flag and should not be used to justify immediate treatment with broad spectrum antibiotics. The emphasis and teaching should shift away from worrying about all non-blanching rashes with greater emphasis on the importance of identifying purpuric rashes as they confer the greatest risk of invasive meningococcal disease. 

Finally the PiC study demonstrates the importance of well designed prospective research studies in identifying risk factors for sepsis. Traditional approaches utilising retrospective reporting of symptoms from convenience samples of children with sepsis results in an over estimation the risks. This in turn leads to the development of overly aggressive clinical practice guidelines that are poorly adhered to. 

Note from Tessa: I am an employee of Barts Health but was not involved in the PiC study or in writing the Barts Health NHS Trust guideline.

Post ROSC care

Cite this article as:
Costas Kanaris. Post ROSC care, Don't Forget the Bubbles, 2020. Available at:
https://doi.org/10.31440/DFTB.29109

Or some pointers on clinical management following the successful return of spontaneous circulation in children. 

It’s 5:40 am at Bubblesville ED. The red phone rings. The paramedic crew informs you that they are five minutes away with a 7 kg, 6-month-old, previously thriving, baby boy called Tarquin. He has had a witnessed out of hospital cardiac arrest at home and there was no prodromal illness according to the family. He choked during a breastfeed, turned blue, and stopped breathing. He had 5 minutes of CPR by the parents by the time the ambulance arrived and had ROSC by the paramedic team after a further 8 minutes. The rhythm strip was consistent with a PEA arrest. They are hand-ventilating him through an LMA.

This is his capillary gas on arrival in the ED
  1. What are your clinical priorities?
  2. What clinical problems do you anticipate in the immediate post-arrest phase?
  3. Who do you call for help?
  4. What do you do with the family whilst you’re managing the patient?
  5. What investigations do you need?

A systematic, collaborative, well-led approach to advanced paediatric life support can maximize the chances of the clinical team achieving a return of spontaneous circulation in a child that has arrested. We’ve seen the drill be before. We can go through our algorithms expertly and the 5-H’s and 5-T’s roll off the tongue, even under duress. The return of a pulse is heralded as the “hallelujah moment”, almost as if the patient is now healthy and safe and all we have to do is wait for the paediatric critical care retrieval team to arrive.

Whilst traditional APLS teachings are vital for the dissemination of knowledge and it’s application in everyday clinical life, their main focus is on the initial phase of achieving a pulse with very little attention placed on the all-important post-resuscitation phase.  This part of care is crucial, not only if we are to minimize secondary brain injury to the child but also to improve the chances of permanent returns of spontaneous circulation. Good short and long term outcomes rely heavily on how well we manage the post-resuscitation stage. 

There are four phases of cardiac arrest:-

Phase one: Prevention. This is the pre-arrest phase. Child safety and injury prevention strategies are in place to recognize deterioration. Adequate monitoring by using early warning systems and a pro-active approach to management is likely to contribute to avoiding an arrest.

Phase two: No flow arrest. This is a period of cardiac arrest prior to us commencing CPR. Our aim here is to minimize the time it takes to start life support. It is key that we involve the cardiac arrest team quickly, we start chest compressions early, and that we do not delay defibrillation if this is needed. 

Phase three: Low flow resuscitation. This phase describes when CPR is in progress. The aim is to achieve high-quality CPR in order to allow adequate coronary and cerebellar perfusion. Maintaining good ventilation and oxygenation whilst avoiding aggressive over-ventilation is paramount. It is during this phase that we systematically approach and threaten the reversible causes of cardiac arrest. 

Phase four: This is the post-resuscitation phase after ROSC has been achieved. Our aim here is to optimize coronary and cerebral perfusion. Neuroprotection and treatment of arrhythmias as well as treatment of post-cardiac arrest syndrome come under this phase. 

Adult v paediatric arrest: What’s the difference?

Out of hospital cardiac arrests in children >16 years of age are relatively rare – reported at 8-20/100000/ year. The incidence is only comparable to that of the adult population, estimated at 70/100000/year. The incidence of in-hospital paediatric arrests is much higher, with a nearly one-hundred-fold increase, compared to the out-of-hospital incidence for the <16’s. 

Survival, and especially a “good” survival from a neurological perspective still remain poor. Out of hospital survival rates are estimated to be 5 – 12%. Only 0.3 to 4% of those that survive have no long-term neurological insult.

Children have cardiac arrests due to severe respiratory insult or circulatory collapse, in the main. Either can lead to a respiratory arrest coupled with hypoxia, which then results in a cardiac arrest. The overwhelming majority of cardiac arrests present with a non-shockable rhythm.  It is also worth noting that almost half of the paediatric population that have a cardiac arrest have other chronic comorbidities such as respiratory conditions e.g. asthma, congenital cardiac disorders, or neurodisability. 

In the adult population, cardiac arrest is more likely due to long-term comorbidities such as ischaemic heart disease. This contributes to the development of an acute myocardial insult and (usually) a shockable rhythm. Understanding the difference in pathology leading to a cardiac arrest between adults and children is vital. Reversing the cause of the respiratory compromise can make the impalpable pulse palpable, allowing us to perfuse our patient once again. 

The recommended CPR ratio of 15:2 for children aims to provide adequate ventilation for oxygenation as well as satisfactory cardiac compressions to maintain sufficient perfusion of the coronary and cerebral circulation. Adult studies looking at compression-only CPR in patients with VF arrest have shown that success in achieving ROSC is due to pre-existing pre-arrest aortic blood oxygen and pulmonary oxygen stores.  As a mere 14% of cardiac arrests are due to a shockable rhythm, combining ventilation and compressions is vital. 

What is the Post Cardiac Arrest Syndrome (PCAS)? 

PCAS describes the period in which our patients are at the highest risk of developing ventricular arrhythmias and reperfusion injuries after ROSC. This is secondary to prolonged ischaemia then reperfusion of vital organs, primarily the myocardium and central nervous system. Its systemic effects are not dissimilar to those encountered in severe sepsis. There are four stages to PCAS:

  • Immediate post-arrest – First 20 minutes. 
  • Early post-arrest – 20 minutes to 6-12 hours. 
  • Intermediate phase – 6-12 hours up to 72 hours.
  • Recovery phase – From 72h onwards. 

Neuroprotection

Even high-quality closed-chest CPR can only achieve 50% of normal cerebral blood flow at best. It is not a secret that the brain does not tolerate hypoxia or ischaemia, the effects on both of these processes are exponential during a cardiac arrest, the longer the downtime, the worse the neurological hit

The pathophysiological cascade for neurodegeneration following cardiac arrest is complex and multi-factorial. Following a hypoxic or ischaemic period the brain develops cerebral oedema and cerebral hyperaemia. There is impaired cerebral vascular reactivity and like any other organ trying to reperfuse, the post-ischaemic biochemical cascade is activated. All these factors contribute to a secondary brain injury. Of course, the duration of hypoxia will in large part dictate how severe the primary brain injury is and whether the patient is likely to survive or not. Brain injury can manifest as myoclonus, stroke, seizures, coma, or brain death. 

We can minimize the extent of secondary brain injury with simple proactive, neuroprotective measures:

  • Strict normothermia
  • Aggressive seizure prophylaxis
  • Avoiding hypoxia and hyperoxia
  • Tight circulatory monitoring and support
  • Patient position
  • Eucapnia and normoventilation
  • Vigilant glucose monitoring
  • Frequent neurological assessment, especially before the administration of anaesthetic agents and paralysis

Strict normothermia

Therapeutic hypothermia following a cardiac arrest during the intermediate phase (after VF in adults), as well as newborns with birth asphyxia, has shown some correlation with better neurological outcomes and reduced neurodisability.  Similarly, there is strong evidence linking core temperature above 38° with worse neurological outcomes in patients following cardiac arrest. There is a wide variation in practice in relation to therapeutic hypothermia.  Mild hypothermia after paediatric cardiac arrest is in the policy of some PICU’s. Patients are cooled to 33-34°C for 1 – 2 days and are then gradually rewarmed. Paralysis can be used as an adjunct to stop shivering. Temperatures below 32°C should be avoided as they are associated with worse survival, immunosuppression, arrhythmias, coagulopathies, and infections.  The decision to “cool” must be made early and in conjunction with your critical care transport team. You have many tools at your disposal to achieve this such as cold IV fluids, cooling blankets, and catheters. 

What is, and should be, more aggressively targeted is strict normothermia (temperatures between 36-37°C), and depending on local practice hypothermia can be targeted to 33-36°C. Avoidance of pyrexia is crucial. Fever can result in an increased metabolic demand of the brain. This contributes to more ischemic injury and more infarcts as the threshold for ischemia in the injured brain is lower than that of the normal brain. The brain can no longer auto-regulate the mismatch between cerebral blood flow and metabolic demand.

Aggressive seizure prophylaxis

Seizures after paediatric cardiac arrest can occur in up to 47% of cases. 35% of these can lead to refractory status epilepticus.  Whilst CFAM/EEG monitoring is unlikely to be available in your local PED, it is important to have a low threshold to administer a long-acting anti-epileptic or a continuous infusion of a short-acting medicine to prevent/avoid this from happening. Ideally, a continuous infusion of midazolam +/- levetiracetam (less arrhythmogenic than phenytoin but both will work) and standard national guidelines should be followed. 

Clues as to whether a patient is still fitting include:

  • Unexpected changes in the pupillary size (beware of the child that had atropine on induction with the “fixed dilated pupils”).
  • Sudden changes in BP or heart rate.  

If you have given a paralytic for intubation, do not fall into the trap of thinking that the patient is not seizing, only an EEG or CFAM can tell you that. It is better to err on the side of caution.

Avoiding hypoxia and hyperoxia

Avoiding hypoxia and hyperoxia are also key components in minimizing secondary brain injury.  Whilst hypoxia will further exacerbate secondary brain injury, hyperoxia  (PaO2 > 40 kPa) is also be associated with worse survival due to oxygen free-radical formation that can inactivate intracellular enzymes, damage DNA, and destroy lipid membranes. It is reasonable to have high concentration oxygen therapy during the low-flow resuscitation and early post-resuscitation phases (as the commonest causes are respiratory). In the subsequent phases, we should target oxygen saturations between 94 and 96% and be proactive in how we reduce the FiO2 whilst avoiding hypoxia. There is a caveat in cases of severe anaemia or carbon monoxide poisoning. Then it is clinically appropriate for the highest concentration of oxygen to be administered.

Tight circulatory monitoring and support

Inotropic support may also be needed early. A degree of myocardial dysfunction/stunning is expected following CPR. To ensure adequate cerebral perfusion we need to target an age-specific, physiologically normal blood pressure. Both hypo and hypertension can exacerbate secondary brain injury. Because of this, monitoring the blood pressure through an arterial line is preferred. If the local set-up or skillset does not allow for arterial line placement, especially in smaller children, having non invasive blood pressure on 1-2 minute cycles can be a useful proxy.  

The paediatric myocardium is much more resilient than its adult counterpart.  If the arrest is not secondary to congenital heart disease the paediatric heart can regain normal function within 12-24 hours.  During the first 20 minutes following ROSC poor cardiac function is due to profound systemic vasoconstriction and cellular acidosis. We can support the myocardium by supplying adequate fluid resuscitation, targeting normal (age-appropriate) blood pressure and inotropic support. Point of care ultrasound, CVP monitoring, or assessing for hepatomegaly/rales if there is no access to the former, can help us prevent fluid overload

Inotrope choice is usually made with the help of the critical care team and depends on the balance between the need for inotropy and vasoconstriction.  Adrenaline is preferred for inotropy, noradrenaline for vasoconstriction.  Be aware that severe acidosis can cause catecholamine resistance, so giving some bicarbonate if the pH <7 may help your inotropes work better. Routine administration of bicarbonate has not been shown to improve clinical outcomes. There are some special circumstances in which we should consider its use such as cases of hyperkalaemia or hypermagnesaemia and arrests due to tricyclic antidepressant overdose. 

Patient position

The patient position that can achieve optimum cerebral perfusion is with the patient semi-sat up at a 30-45 degree angle.

Eucapnia and normoventilation

Avoidance of hypercapnia or hypocapnia is important in preventing secondary brain injury. It is, therefore, recommended that eucapnia is achieved by targeting a PaCO2 between 4.5 and 5.5 kPa. Hyperventilation can cause hypoxia and increase intracranial pressure due to hyperaemia, it can also cause further cerebral ischemia. As the intrathoracic pressures increase, cardiac venous return is impaired. Since the myocardium is already injured this can have catastrophic effects causing the BP to plummet and subsequently impair cerebral perfusion.

Vigilant glucose monitoring 

Following ROSC, children are also at risk of developing hypoglycemia (glucose <3 mmol/L). There is good evidence to suggest that hypoglycaemia negatively impacts neurological outcome and cause hypoglycaemic seizures, especially in the younger ages. Vigilant glucose monitoring and correction as per APLS guidelines is important. If regular dextrose boluses are needed, consider a continuous glucose infusion. If the patient mounts an adequate stress response, they may become hyperglycaemic.  There is no evidence to suggest that aggressive glucose control with insulin in the non-diabetic patient is beneficial; wait with watchful deliberation and the glucose will usually return to normal levels with no intervention.

Frequent neurological assessment

It is important to frequently assess neurological status frequently after ROSC as this can help us prognosticate. Take the time to do a very quick assessment ideally before the administration of anaesthetic agents and paralysis. Document clearly pupillary size/reactivity, GCS (and its break down) and any respiratory effort or gasping. 

Adjunctive investigations

Following ROSC a number of investigations will be needed to guide diagnosis and therapy. Routine bloods such as renal function, electrolytes, liver function tests, full blood count, and clotting are a basic standard. In cases of lactaemia and/or severe metabolic acidosis ammonia and toxicology is useful. Arterial blood sampling is invaluable to allow quick correction of any electrolyte abnormalities and help titrate ventilation settings and (in part) guide inotropic support. Arterial samples will also help uncover any exposure to carbon monoxide, especially in burns cases. 

From an imaging perspective, a chest X-ray is vital in ascertaining tube positioning and lung pathology as well as cardiac contours in case a congenital or acquired heart disease is suspected. Head CT is obviously useful in cases in keeping with traumatic arrest and NAI but timing of the CT and whether it should take place pre-departure to PICU or after depends largely on local trauma network protocols so should ideally be discussed with the regional trauma team lead and paediatric critical care transport team. 

Children that die or arrest unexpectedly in the UK are subject to a sudden unexpected death in infancy investigation (SUDI) so the appropriate referrals need to be made to the child protection team, police and social care. It is important to clarify that even near-miss cases merit triggering the same SUDI process to ensure that any NAI cases don’t slip through the net. 

Transport pearls

After ROSC the patients will need stabilisation and transfer to PICU for on-going management. Depending on the geographical location of your hospital and the availability of a critical care retrieval service you may have to transfer the patient yourselves or look after them until he/she is retrieved by transport team. A good transport and adequate neuroprotection can be achieved by applying these simple pearls: 

  1. Aggressive temperature monitoring and control between 33°C and 37°C.
  2. Monitor for seizures and pre-empt with long-acting antiepileptic accordingly.
  3. Correct electrolytes and hypoglycaemia and monitor frequently.
  4. Nurse the patient a 45° degree angle.
  5. Aim for a higher end of normal BP and use inotropes to achieve this. If you can’t insert an arterial line, have the NIVBP cycle every couple of minutes. 
  6. In cases of trauma, blood products should be used for volume. In an atraumatic arrest, balanced solution boluses are less harmful than 0.9% saline; don’t forget that you are still likely to need blood products. 
  7. Aim for a pCO2 of 4.5-5.5 kPa; use your continuous EtCO2 monitor to titrate ventilation. 
  8. Vigilant and through history/examination to rule out NAI. Free up a member of the team to do a thorough history from the family, always suspect NAI until proven otherwise especially in children under 6 months. 
  9. Know your anaesthetic drug side-effects (atropine dilates pupils for example so impairs our ability to monitor for seizures). Primum non nocere. 
  10. Intraosseous access can be used instead of a central line, have a low threshold to insert one and do it early.
  11. Have a member of the team check-in with the family every 10-15 minutes to explain what is happening, this is a bad day at work for you but probably the worst day of their lives. 

Conclusion

Achieving ROSC is an important step to give our patients a shot at survival. In some cases, achieving ROSC can only give us enough time to prognosticate and understand that survival is not possible. In some other cases ROSC can be the stepping-stone for a good, meaningful survival with a good quality of life. To achieve that, we must be able to apply good quality post–ROSC care and aggressive, pre-emptive neuroprotection. Learn the PCAS disease process to beat the PCAS disease process.  The APLS algorithm has become the bread and butter of anyone that is involved in paediatric care. Understanding and applying the principles of post-cardiac arrest syndrome is equally vital in improving survival outcomes for our patients. Learn the pearls, use them, teach them and I guarantee that it will make a difference.

Haemolytic Uraemic Syndrome

Cite this article as:
Jennifer Watt. Haemolytic Uraemic Syndrome, Don't Forget the Bubbles, 2020. Available at:
https://doi.org/10.31440/DFTB.26233

What is HUS?

Haemolytic Uraemic Syndrome is a combination of findings which involves the triad of:

  • Microangiopathic haemolytic anaemia with red blood cell fragmentation on blood film
  • Acute renal failure
  • Thrombocytopenia

 What causes HUS?

About 90% of cases follow an infection, most commonly with entero-haemorrhagic E. Coli (EHEC). Other infective causes to be considered include Shigella and Streptococcus pneumoniae.

These infections are commonly contracted by the ingestion of contaminated food or water sources. In the US and UK, E. Coli 0.157 forms part of the natural intestinal microflora of cattle and sheep, therefore infection can be caused by direct contact with animal faeces. This can take place at farms or petting zoos, or via undercooked contaminated meat or dairy products.

The other 10-15% of cases represent atypical HUS and are due to a variety of causes, which will not be discussed here.

How do children present?

In children infected with EHEC about 10-15% of them will go on to develop HUS.

The common presentation includes bloody diarrhoea +/- cramping abdominal pain, fever and/or vomiting. The average onset of HUS after development of diarrhoea is about 7-10 days, with children under the age of 5 at highest risk.

Dependent on the extent of HUS progression, children may present with pallor, oedema, lethargy, or reduced urine output.

How to approach the examination

As with any unwell child, an A to E assessment is critical to rule out any immediate, life threatening complications.

Specific attention should be paid to assessing their fluid status, especially for evidence of dehydration.

*Although they may be oedematous, it is important to assess if they are intra-vascularly dry.

Things to examine for:

  • Prolonged capillary refill time
  • Observations: Tachycardia; hypotension or hypertension
  • Are they are cool peripherally?
  • Assess fontanelle tension (if applicable)
  • Dry mucus membranes/reduced skin turgor
  • Oedema (common locations in children include lower limbs, sacral and peri-orbital)

Is there evidence of neurological sequelae?

  • Irritable/restlessness
  • Confusion
  • Reduced GCS

Key investigations to perform

A. Initial blood samples:

  • Full blood count with blood film to assess for RBC fragmentation
  • Coagulation
  • Group and Save +/- cross match if haemoglobin low
  • Biochemistry: U&Es, calcium, phosphate, magnesium, bicarbonate
  • Glucose
  • CRP
  • Liver function including albumin
  • Amylase/Lipase (hospital dependent)
  • LDH
  • Blood gas
  • Blood cultures

B. Stool MC&S + E. Coli PCR

C. Urinalysis + MC&S

How to approach the management of HUS

Management should always be discussed with your local paediatric nephrologist in order to individualise/optimise management.

This is a generalised framework for the approach to management. Treatment involves supportive therapy to allow time for the infection to clear and the HUS process to cease.

1. Fluid Management:

  • IV access
  • Assess fluid status
  • Monitor for electrolyte disturbances and correct as per local guidelines
  • Daily weight, In/Out fluid balance, close monitoring of patient observations

*Fluid rehydration should be administered cautiously and in the setting of oliguria/anuria and oedema, fluids given should not exceed insensible loss + urine output.

*Evidence has shown that children presenting to hospital with dehydration in the prodromal phase of EHEC-induced HUS have a higher risk of developing an oliguric AKI and the requirement for dialysis. The administration of isotonic fluid in this phase has shown to be nephroprotective. 

2. Hypertension:

  • Can be secondary to fluid overload or as a result of the HUS process
  • Trial of diuretics or if receiving dialysis, fluid can be offloaded
  • If unresponsive to diuretics, consider a vasodilator (For example, amlodipine/ nifedipine *hospital dependent)

3. Anaemia:

  • Target Haemoglobin: 70-100g/L
  • Avoid excessive transfusion due to the associated risk of development of hyperkalaemia or fluid overload

4. Thrombocytopenia:

  • Consideration for platelet transfusion if platelets <10 x109
  • If undergoing surgery may require platelets > 50 x 109

5. Abdominal pain/vomiting:

  • Secondary to colitis
  • Regular paracetamol for pain relief
  • Avoid opiates if possible due to constipating side effects

*NSAIDS like Ibuprofen should not be prescribed*

6. Nutrition:

  • All patients should be reviewed by a dietician
  • NG tube and feeding regime

7. Dialysis (Peritoneal Dialysis or Haemodialysis) Indications:

  • Intractable acidosis
  • Diuretic resistant fluid overload
  • Electrolyte abnormalities Hyperkalaemia
  • Symptoms of uraemia

In children with HUS, peritoneal dialysis is the preferred treatment option as it is a gentler form of dialysis.

Haemodialysis is indicated for children with severe colitis, severe electrolyte abnormalities and those with neurological complications.

 HUS Complications

  • AKI:  Oliguria/anuria; hyperkalaemia; hypertension
  • Neurological: Irritable, confusion, seizures
  • Bleeding Risk
  • Cardiac: Hypertensive cardiomyopathy/myocarditis
  • Gastrointestinal: Severe colitis with bleeding/perforation
  • Pancreatitis
  • Pulmonary oedema

Selected references

Mayer CL, Leibowitz CS, Kurosawa S and Stearns-Kurosawa DJ. Shiga Toxins and the Pathophysiology of Hemolytic Uremic Syndrome in Humans and Animals. Toxins (Basel). Nov 2012. [Cited June 2020]; 4 (11): 1261-1287. doi: 10.3390/toxins4111261

Kausman. J 517 Haemolytic uraemia syndrome. Royal Hospital for Children- Nephrology. Dec 2013. [Cited June 2020]; Available from:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3509707/

Hughes D. Management and investigation of bloody diarrhoea and haemolytic uraemic syndrome [draft].  GG&C Paediatric Guidelines- Kidney Diseases. Oct 30 2019. [Cited June 2020]; Available from: https://www.clinicalguidelines.scot.nhs.uk/ggc-paediatric-guidelines/ggc-guidelines/kidney-diseases/management-and-investigation-of-bloody-diarrhoea-and-haemolytic-uraemic-syndrome-draft/

Balestracci A et al. Dehydration at admission increased the need for dialysis in hemolytic uremic syndrome children. Pediatr Nephrol. 2012. [ Cited June 2020];27: 1407-1410. Doi: 10.1007/s00467-012-2158-0

Scheiring J. Andreoli SP. Zimmerhackl LB. Treatment and outcome of Shiga-toxin-associated hemolytic uremic syndrome (HUS). Ped Neprhrol. 2008. [Cited June 2020]; 23: 1749-1760. Doi: 10.1007/s00467-008-0935-6

Grisaru Silviu. Management of hemolytic-uremic syndrome in children. Int J Nephrol Renovasc Dis. 2014 [Cited June 2020]; 7: 231-239. Doi: 10.2147/IJNRD.S41837.

Metabolic presentations part 1: neonates

Cite this article as:
Taciane Alegra. Metabolic presentations part 1: neonates, Don't Forget the Bubbles, 2020. Available at:
https://doi.org/10.31440/DFTB.28423

You are working in the Paediatric Emergency Department and are called in to see a neonate with a history of irritability and seizures. You enter the room and are told the following: “Emma is a 3 day old, term baby who has been refusing feeds and crying excessively. Her mother says she has been irritable since birth. There has been no history of fever or cough. At home she had seizure-like activity with tonic posturing”. When you examine her, you find an awake, extremely irritable baby with flexed upper limbs flexed, extended lower limbs and global hyperreflexia. She is not dysmorphic and has no cardiac murmurs, respiratory distress or abdominal organomegaly.

Babies cry (a lot!) and we all know that, however Emma is presenting some red flags: she’s irritable and has an acute onset of seizures, without any obvious trigger.

The basics

In this post we will discuss some acute metabolic presentations in the neonatal period, how to identify potential problems and emergency treatment in the ED. You don’t need to make a diagnosis (bonus points if you do) but do need to remember that spotting the zebra will lead to more favourable outcomes. Metabolic diseases / disorders are also called inborn errors of metabolism (IEM).

How common are metabolic conditions?

Individually, metabolic conditions are rare, most having an incidence of less than 1 per 100,000 births. However, when considered collectively, the incidence may reach 1 in 800 to 1 in 2500 births (Applegarth et. al, 2000; Sanderson et.al, 2006). 

Remember: some symptoms can be unspecific and can mimic sepsis; or a child with an undiagnosed metabolic condition can decompensate with an intercurrent infection. 

An easy-to-understand classification by Saudubray divides the IEM in three groups of disorders, depending on how they present. 

Intoxication disorders

An acute or progressive intoxication from the accumulation of toxic compounds, usually small molecules. 

These usually present with a symptom-free interval and clinical signs of ‘intoxication’, which may be acute, although can be intermittent.

  • disorders of amino acid catabolism: e.g. phenylketonuria, maple syrup urine disease, homocystinuria, tyrosinemia 
  • most organic acidurias: e.g. methylmalonic, propionic, isovaleric acidaemia
  • urea cycle defects: e.g. Ornithine transcarbamylase deficiency (OTC deficiency), Citrullinemia type I (ASS1 deficiency).
  • sugar intolerances: galactosemia
  • metals: Wilson’s, Menkes, hemochromatosis
  • porphyrias

Disorders involving energy metabolism

A deficiency in energy production or utilization, within the liver, myocardium, muscle, brain or other tissues. 

Common symptoms include hypoglycemia, hyperlactatemia, hepatomegaly, failure to thrive and cardiac failure. 

  • Mitochondrial defects: congenital lactic acidemias (defects of pyruvate transporter, pyruvate carboxylase, pyruvate dehydrogenase, and the Krebs cycle), mitochondrial respiratory chain disorders and the fatty acid oxidation defects (MCAD deficiency).
  • Cytoplasmic energy defects: disorders of glycogen metabolism (collectively known as glycogen storage diseases), hyperinsulinism.  

Complex molecules disorders

Problems in the synthesis or catabolism of complex molecules, leading to storage of big molecules. 

Symptoms are chronic, progressive and independent of intercurrent events or food intake. 

  • Mucopolysaccharidosis (I-IV, VI and VII). The eponymous names are used less frequently now, particularly in the literature, but you might come across them in clinical practice (MPS I, Hurler’s Syndrome; MPS II, Hunter’s Syndrome; MPS VI, Maroteaux- Lamy) 
  • Gaucher disease
  • Peroxisomal disorders: e.g. X-linked adrenoleukodystrophy (X-ALD) and Zellweger’s Syndrome.

Treatment strategies

Remember your biochemistry: a substrate is transformed by an enzyme into a product .

If there is a problem with the enzyme, the substrate will accumulate. If this substrate accumulation is a problem, we eliminate it, like avoiding protein in the diet or removing toxins with treatments such as ammonia scavengers.  If a lack of the product is the problem, we can supplement it (for example the administration of carbohydrate in glycogen storage disease). And for some diseases the  enzyme can be “corrected” with organ transplantation or enzyme replacement therapy.

A bonus on smells

Due to accumulation of “unusual” products in their body fluids, people with certain metabolic conditions have distinctive odours (better observed in urine, for practical reasons):

  • Maple syrup, burnt sugar, curry: Maple syrup urine disease
  • Sweaty feet: glutaric aciduria type II, isovaleric acidaemia
  • Cabbage: tyrosinemia
  • Mousy, musty: phenylketonuria
  • Rotting fish: trimethylaminuria
  • Swimming pool: Hawkinsinuria 

Back to Emma. You explain to Emma’s mother that there are lots of things that could be making her unwell so you’re going to send some tests to help work out what the problem is. You put in a cannula, take a gas, send some bloods to the lab and set her and her mother up to collect a urine.

Seeing that Emma has a metabolic acidosis on her gas you send a metabolic screen: plasma amino acids, urine organic acids, acylcarnitine profile. Her urine dip has some ketones but is otherwise unremarkable, except for a strange smell of sweaty feet…

Remembering a fabulous infographic about the importance of calculating the anion gap in children with a metabolic acidosis (and how to interpret them!), you get out your pen and paper and do the following calculations: 

Just as you’re pondering the causes of a raised anion gap, the lab phones with Emma’s blood results… Her ammonia is 184!

Emma has an acute neurological presentation, with metabolic acidosis, increased anion gap and mildly elevated ammonia, suggestive of an organic acidaemiaIn the context of a sick neonate with a raised anion gap, a normal lactate and normal ketones, think organic acids.

Are you familiar with ammonia?

A normal ammonia level is <50 mol/l but mildly raised values are common, up to 80 mol/l.

In neonates, any illness may be responsible for values up to 180 mol/l.

Artifactually high values can be caused by muscle activity, haemolysis or delay in separating the sample. Capillary samples are often haemolysed or contaminated and therefore should not be used.

There’s debate as to whether a level of >100 or 200 should be discussed with a metabolic specialist, but if in doubt, follow the RCPCH DeCon guideline and seek advice for any patient presenting with a level >100 mmol/l.

Urine organic acids and blood acylcarnitines will also be sent as part of this baby’s metabolic work-up. Although the results won’t be available in ED, the urine organic acid profile will confirm a diagnosis of an organic acidaemia, while the blood acylcarnitine profile will support the diagnosis as the organic acids conjugate with carnitines creating compounds such as isovalerylcarnitine.

The emergency treatment of suspected organic acidaemias

It’s important to think about your differentials. Sepsis is the most common – these conditions can mimic sepsis, or decompensation can be triggered by an infection, always cover with broad spectrum antibiotics. But don’t forget non-accidental injury and other differentials – the baby is likely to need a CT head if presenting encephalopathic or with seizures. If she continues to seize, load with an anticonvulsant.

 Specific emergency treatment of her metabolic presentation requires:

  • stopping sources of protein (milk)
  • avoiding catabolism (by giving glucose IV – 2mL/kg 10% glucose) 
  • rehydration (IV fluids resuscitation and maintenance)

What about that urine?

The “sweaty feet” smell of the urine points towards the diagnosis of Isovaleric Acidaemia. Remember that this condition can be part of the Newborn Screening in some countries (Ireland, UK, Australia, New Zealand).

Isovaleric acidaemia is a type of organic acidemia, inherited in an autosomal recessive way. It is caused by a problem with the enzyme that usually breaks down the amino acid leucine. This amino acid accumulates and is toxic at high levels, causing an ‘intoxication’ encephalopathy. The sweaty feet smell is stronger without treatment or  during acute exacerbations.

Maple Syrup Urine Disease (MSUD) is another organic acidaemia, associated with sweet smelling urine during decompensation. These children cannot break down leucine, valine and isoleucine. They may not have hypoglycaemia, hyperammonemia or acidosis and, if not picked up on newborn screening, can be diagnosed late, resulting in neurological sequelae.

Organic acidaemias: the take homes

  • Always measure the anion gap and send an ammonia sample in any sick neonate.
  • Sick neonates with metabolic acidosis, increased anion gap and mildly elevated ammonia may have an organic acidemia.
  • Treatment is to stop feeds, prevent catabolism with 10% dextrose (and standard electrolytes for IV maintenance) and cover for sepsis with IV antibiotics, whilst considering other differentials.

The next case feels like déjà vu…

The next baby you see is remarkably like Emma but with a subtle difference. Lucy is a 3 day old baby, presenting with poor feeding, irritability and seizures at home. There has been no fever, cough, coryza, or sick contacts. On examination she’s awake, extremely irritable, with upper limbs, extended lower limbs extended and global hyperreflexia. She has no dysmorphic features, cardiac murmur or abdominal organomegaly. You notice that she seems tachypnoeic at 70, although her lungs are clear. The rest of her observations are normal. 

The key differences between Emma and Lucy’s presentations is that Lucy is tachypnoeic and has a respiratory alkalosis; this should make you suspicious of hyperventilation. Always check an ammonia level in sick babies, but particularly in this case as hyperammonemia stimulates the brain stem respiratory centre, causing hyperventilation and, as consequence, respiratory alkalosis. 

The lab phones you with Lucy’s ammonia result…

Acute neurological presentations, with respiratory alkalosis and extremely elevated ammonia point towards a urea cycle disorder. Respiratory alkalosis is a common early finding caused by hyperventilation secondary to the effect of hyperammonemia on the brain stem, although later the respiratory rate slows as cerebral oedema develops and an acidosis is seen. Lucy also has a low urea and mildly deranged liver enzymes and INR, all of which support the diagnosis of a urea cycle disorder.

The emergency treatment of suspected urea cycle disorders

Overall the acute treatment is similar to the first case: cover for sepsis, manage seizures and consider differentials.

And as in the first suspected metabolic case:

  • stop sources of protein – stop feeds 
  • avoid catabolism – giving glucose IV – 2mL/kg 10% glucose 
  • rehydrate – IV fluids resuscitation and maintenance

In urea cycle disorders, the toxic metabolite is ammonia, so ammonia scavengers are used, all given intravenously:

  • sodium benzoate
  • phenylbutyrate 
  • arginine

A nice guideline on the management of hyperammonemia secondary to an undiagnosed cause can be found on the British Inherited and Metabolic Disease Group website.

Urea cycle disorders are autosomal recessive inborn errors of metabolism. A defect in one of the enzymes of the urea cycle, which is responsible for the metabolism of nitrogen waste from the breakdown of proteins, leads to an accumulation of ammonia as it cannot be metabolised to urea. The urea cycle is also the only endogenous source of the amino acids arginine, ornithine and citrulline.   The most common urea cycle disorder is Ornithine Transcarbamylase (OTC) deficiency. Unlike the other urea cycle disorders (which are autosomal recessive), OTC deficiency is x-linked recessive, meaning most cases occur in male infants. Female carriers tend to be asymptomatic.

CPSI: Carbomoyl Phosphate Synthetase; OTC: Ornithine Transcarbamylase; ASS: Arginosuccinate Acid Synthase; ASL: Arginosuccinate; ARG: Arginase

Classically, urea cycle disorders present in the neonatal period with vomiting, anorexia and lethargy that rapidly progresses to encephalopathy, coma and death if untreated. In these circumstances, ammonia accumulates leading to a very high plasma ammonia. 

Children presenting in infancy generally have less acute and more variable symptoms than in the neonatal period and include anorexia, lethargy, vomiting and failure to thrive, with poor developmental progress. Irritability and behavioural problems are also common. The liver is often enlarged but, as the symptoms are rarely specific, the illness is initially attributed to many different causes that include gastrointestinal disorders. The correct diagnosis is often only established when the patient develops a more obvious encephalopathy with changes in consciousness level and neurological signs. 

Adolescents and adults can present with encephalopathy and or chronic neurological signs. 

What are ammonia scavengers?

In urea cycle defects, ammonia cannot be converted to urea so instead is converted to glutamine and glycine. 

Ammonia scavengers phenylbutyrate and sodium benzoate offer alternative pathways for ammonia excretion through urinary pathways.

Phenylglutamine and hippurate are produced and are excreted in urine.

Urea cycle disorders: the take homes

  • Always measure the anion gap and send an ammonia sample in any sick neonate.
  • Sick neonates with respiratory alkalosis, normal anion gap and very elevated ammonia may have a urea cycle defect. 
  • Emergency treatment of urea cycle disorders is the same as for an organic acidaemia (stopping feeds, starting dextrose and rehydrating) PLUS intravenous ammonia scavengers.

Thank you to Dr Roshni Vara, Consultant in Paediatric Inherited Metabolic Disease at the Evelina London Children’s Hospital for her help with this post.

References

Adam , HH. Ardinger, RA. Pagon, S. E. Wallis, L. J. H. Bean, K. Stephens, & A. Amemiya (Eds.), GeneReviews® [online book].

Applegarth DA, Toone JR, Lowry RB. Incidence of inborn errors of metabolism in British Columbia, 1969-1996. Pediatrics. 2000 Jan;105(1):e10.

Sanderson S, Green A, Preece MA, Burton H. The incidence of inherited metabolic disorders in the West Midlands, UK.Arch Dis Child. 2006 Nov;91(11):896-9. 

Saudubray J-M, Baumgartner MR, Walter JH. (editors) Inborn Metabolic Diseases. Diagnosis and treatment. 6th Edition. Springer 2016. 

Neonatal ventilation basics

Cite this article as:
Jasmine Antoine. Neonatal ventilation basics, Don't Forget the Bubbles, 2020. Available at:
https://doi.org/10.31440/DFTB.19875

A term infant is admitted to the intensive care nursery with severe respiratory distress. They are currently on CPAP 8cm H2O and FiO2 0.50  with no signs of improvement. You begin preparing for intubation. The nurse looking after the baby is setting up the ventilator. “What ventilator setting would you like, doctor”?

 

Before listing off some ventilator settings, there are several decisions that we need to make. What type of ventilation should we be using for this baby? What settings will we start them on? What do we need to do post ventilation? This post will begin to answer some of these questions, but as always, it is advisable to be guided by your unit policies and senior staff members.

 

Ventilation modes

This post will discuss the basics of conventional ventilation. High-frequency oscillatory ventilation (HFOV) is also commonly used in the nursery, particularly for extremely preterm infants or those with persistent pulmonary hypertension. Stay tuned for an upcoming post on HFOV.

Synchronized intermittent mandatory ventilation (SIMV)

This type of ventilation administers a set amount of mechanical breaths that are synchronized with the patient’s own inspiration. When the infant breaths above the set ventilator respiratory rate, these additional breaths do not receive a ventilator breath. This mode can be useful when weaning ventilation.

Synchronized intermittent positive pressure ventilation (SIPPV) or patient triggered ventilation (PTV) or Assist Control (AC)

This form of ventilation confusingly has many different names. It supports every breath the infant makes. The set ventilator respiratory rate is the backup number of breaths that will be mechanically administered if the infant makes no spontaneous breaths. Each mechanical breath is synchronized with the patient’s own inspiration.

Pressure support ventilation (PSV)

Similar to SIPPV in that every breath is supported with mechanical ventilation. However, the inspiratory time is limited depending on the infant’s own inflation. The infant sets their own mechanical breath rate and inspiratory time.

Volume controlled (VC) or volume guarantee

This mode of ventilation can be used with SIMV or SIPPV. The ventilator aims to deliver tidal volumes (VT) set by the clinician. A maximum peak inspiratory pressure (PIP) is set, the ventilator’s PIP will vary to reach the target volume.

 

So, which is better for our infant?

There have been no large prospective trials that have determined if SIMV or SIPPV is the superior format of ventilation. The choice of ventilation will largely depend on unit preference. Studies have illustrated that volume-controlled ventilation reduces the duration of ventilation, risk of pneumothorax, grade 3/4 intraventricular haemorrhage, and chronic neonatal lung disease.

 

So what’s on your ventilator screen?

Peak end expiratory pressure (PEEP):

The maximum pressure that provides continuous distension of the lungs. Usually between 6-8cmH20

Peak inspiratory pressure (PIP):

Maximum pressure used during inspiration. Consider the tidal volumes achieved to determine a suitable PIP. VT are usually around 4-5ml/kg.

Respiratory rate (RR):

Set number of mechanical breaths administered in a minute. Usually between 40-60. In SIMV the set RR is both the maximum and minimum rate while in SIPPV the RR is the minimum but not the maximum rate.

Inspiratory time (Ti):

Set time for inspiration during a breath. Usually between 0.3-0.5s

Patient Circuit Flow Rate or Rise Time or Rise Slope:

Depending on the manufacturer or the unit policy, one of these options will be available. If only the patient circuit flow rate is available then this is set 6 – 10 L/min. If rise time or slope is available then this is set to 30 – 50% of the Ti.

Pmax:

In the volume-controlled mode this is the maximum peak inspiratory pressure you wish the ventilator to administer to reach target tidal volumes. Usually set 5 cmH2O higher than the average PIP used to achieve the set tidal volume.

FiO2:

The amount of supplementary oxygen. Target saturations will depend on the gestational age and the underlying condition affecting the infant. Your unit’s policy on SpO2 targets should guide the FiO2 setting.

Many other ventilators exist

 

What are the ventilator measurements we should be aware of?

Minute volume (MV):

Amount of gaseous exchange in one minute. MV= VT x RR

Tidal volume (VT):

The amount of gas in an expiration. Usually around 4-5ml/kg.

Leak:

Traditionally in neonates, uncuffed tubes are used for intubation due to concerns regarding subglottic stenosis and pressure necrosis. As a result, most infants will have a percentage of leak. It will change during an infant’s respiratory cycle, it is usually greater in inspiration.

 

What do we need to do next?

After attaching our infant to the ventilator, clinical checks should once again be undertaken to ensure adequate ventilation. Review the infant, is there misting of ETT, equal air entry by auscultation, symmetrical chest rise, stable observations and adequate tidal volumes being achieved.

A post-intubation chest x-ray should be taken as early as possible to check the placement of the endotracheal tube. The ideal placement is between T1-3,  just above the carina.

An arterial gas should be undertaken post-intubation to check adequate ventilation, within an hour. The timing of the next gas will depend on the results, clinical condition and how old the patient is. Your boss will be able to give you some guidance.

 

Take-home messages

  • Avoiding mechanical ventilation using early continuous positive airway pressure (CPAP) with, or without, surfactant administration is the most effective way to reduce the risk of lung injury.
  • Using volume-controlled ventilation reduces the risk of chronic neonatal lung disease.
  • If you’re not sure where to start or how to alter ventilation, ask for your boss’ help.

 

Resources

Keszler M. State of the art in conventional mechanical ventilation. Journal of Perinatology. 2009 Apr;29(4):262.

Mechanical ventilation of the premature neonate. Respir Care. 2011 Sep;56(9):1298-311; discussion 1311-3. doi: 10.4187/respcare.01429

Aerosol Generating Procedures

Cite this article as:
Tagg, A. Aerosol Generating Procedures, Don't Forget the Bubbles, 2020. Available at:
https://dontforgetthebubbles.com/aerosol-generating-procedures/

As more cases of Covid19 present to health care facilities across the world, there seems to be some confusion as to what is an aerosol-generating procedure. Turning up to work is not without risk with a large number of healthcare workers in Italy and Ireland. diagnosed with COVID19. There is a case report of asymptomatic carriage lasting up to 16 days so we need to be careful whether the child in front of us has been diagnosed with COVID19 or not.

A lot of the data we have comes from the 2003 SARS epidemic and the H5N1 influenza outbreaks. There are always going to be a number of confounding variables when looking at these reports – whether the HCW was wearing appropriate PPE (or had access to it), how good their hand-washing was, how close together patients are – but nosocomial infections do occur.

First off,  we are going to take a look at what an aerosol is, then how aerosols and droplets relate to some common, and uncommon, things we do in paediatrics.

 

Aerosol or droplet?

Let’s define some terms before we get started – not as easy as it sounds, it turns out.

A  respiratory droplet is a fluid bundle of infectious particles that travels from the respiratory tract of the infected individual onto the mucosal surface of another, rather than floating down the respiratory tract. Small droplets are between 5-20μm and tend to hang up around the glottis. Large droplets are > 20μm and are probably too big to follow airflow. They tend to obey the laws of gravity and so settle on nearby surfaces when you sneeze. If you inadvertently touch the same surface then touch your face you can potentially transmit the infection. This is why we wash our hands. In healthcare, droplet precautions include a surgical mask, eyewear, disposable gown, and gloves. The surgical mask acts as a physical barrier to droplets that are too large to be inhaled.

A droplet nucleus is what is left once the liquid rapidly evaporates from a droplet. They are in the order of 10μm in diameter and are in the respirable range. This is generally defined as any particle less than 10μm. The inspirable range is defined as anything between 10 – 100μm in size.

An aerosol is a liquid (or solid) suspended in the air – think mist and fog. These small particles are less than 5μm and so are in the respirable range (rather than the inspirable range like droplets) and can enter the lower respiratory tract. They are affected by diffusion rather than gravity so tend to hang around for a while.  Measles is one such airborne disease. A recent letter in the NEJM suggests that SARS-CoV-2 can remain viable in aerosols for at least 3 hours, though the WHO’s guidance is clear that it should be managed with droplet and contact precautions UNLESS you are performing an aerosolising procedure.

Consider them on the continuum of aerosol -> small droplets -> large droplets -> puddles. Aerosols and small droplets have the ability to travel fair distances, especially if powered by a blast of oxygen or expired air. Larger droplets tend to obey the laws of gravity and settle on surfaces.

 

Just breathing, coughing and sneezing

But even putting an oxygen mask on the patient may not protect you. Hui et al. (2006) used fancy laser beams and smoke to detect just how far a single breath might travel.  With a standard oxygen mask on the patient and a flow rate of 4l/min, a tidal volume of 500mls, and 12 breaths a minute the smoke plume traveled approximately 0.45m. In most experiments, scientists use smoke as a stand-in for the more nebulous breath of air. Non-biological aerosols will behave differently depending on the airflow and ventilation in the room and have a constant density. Mathematical modelling would suggest that the further from the source a sample is taken then the lower the potential infectivity until a state of equilibrium is reached. Fortunately, the air is exchanged in most hospital rooms on a regular basis.

A patient that is coughing and sneezing can produce large, short-range droplets and small, long-range aerosols. The aerosols produced by coughing are heavier than the smoke used in experiments so hopefully, they may not be able to travel as far. Experimental data will tend to over-estimate the spread of droplets.

Thompson et al (2013) took 99 air samples around presumptive AGPs. 26.1% of them contained viral RNA. But the baseline level of contamination, when no AGPs (as defined by WHO 2009) were performed was 10.5%. Just because a procedure might generate an aerosol, it does not hold true that the aerosol can cause an infection.

Most of the data we have comes from the fast SARS-CoV epidemic in 2002-2003. Tran et al. tried to find all of the papers related to HCW infection and aerosol-generating procedures. They found 10 – 5 non-randomized cohort studies and 5 retrospective cohort studies. They then created pooled estimates of odds ratios.

Judson and Munster usefully categorized AGPs into those that mechanically create and disperse aerosols and those that make the patient wriggle and cough. Or you could think of them, as suggested by Brewster et al. (2020) as those procedures that require gas flow and those that require no extrinsic gas flow.

 

 

Bag-valve-mask ventilation and CPR

High risk 

A paediatric cardiac arrest is uncommon. When it occurs your first move* should be to open the airway and provide rescue breaths. In this time of COVID19, I doubt anyone is going to be doing mouth-to-mouth/nose ventilation. They are going to reach for an appropriately sized bag-valve-mask. Just like when placing a standard oxygen mask, there is a transverse movement of droplets even with a reasonable seal. The addition of an HME filter does appear to attenuate some of this, as demonstrated by Chan et al.(2018).

Adapted from Chan MT, Chow BK, Lo T, Ko FW, Ng SS, Gin T, Hui DS. Exhaled air dispersion during bag-mask ventilation and sputum suctioning-Implications for infection control. Scientific reports. 2018 Jan 9;8(1):1-8.

 

Adult CPR guidelines are advocating for chest compression-only CPR in the community and rapid intubation pre-compressions if circumstances allow. There has been little guidance on paediatric CPR from the ALSG but a number of enterprising teams are looking at it.

Possible cases of SARS transmission by CPR have been reported (Christian et al. 2004) but BVM ventilation took place during the cases and this may be the most important factor for possible viral transmission.

 

Intubation

High risk 

Anything, where the clinician is inches away from the respiratory tract of the patient, is going to be a high-risk procedure. There have been huge collaborative efforts worldwide creating COVID intubation algorithms. They share a lot of commonalities.

  • The most experienced operator performs the procedure – this is not a time for learning
  • No bag-valve-mask ventilation prior to intubation
  • Use of videolaryngoscopy to maximize the distance between intubator and patient
  • Minimum number of staff present

This is my favourite paediatric intubation resource from Queensland Children’s Hospital.

 

Nebulizing a medication

High risk / Unclear evidence

There are few indications for nebulizing medication. Bronchodilators are best delivered by MDI and spacer when possible but in cases of severe asthma or perhaps, more commonly, in croup, a nebulizer chamber may be the way to go. The UK guidelines do not consider the delivery of nebulized medications as an AGP. The rationale behind this is that the aerosol is derived from a non-patient source. Even if they do have the disease the medication sticks to the mucus membranes and so will not get released into the general environs. There seems to be a lack of global consensus on this.

Nebulizers generate small particles, between 1-5microns in diameter, in order to get down into the bronchioles and not just be deposited in the oropharynx. Viable COVID19 viral RNA has been detected in aerosol form 3 hours after delivery by nebulizer in experimental conditions but this does not prove infectivity, just infectious potential.

In 2009 O’Neill et al. performed air sampling studies for common patient activities, including making the bed and providing nebulized therapy, as well as some more invasive treatments (bronchoscopy and suctioning). Although small numbers they found an increase in influenza particle numbers (from baseline) of up to 70,000/cm³.

 

High Flow Nasal Cannula

High risk 

In adult practice, high flow oxygen delivery is anything over 6l/min. In paediatrics, it is 2l/kg/min up to the adult maximum of 60l/min. In one of my favourite studies to date (and certainly in keeping with the DFTB ethos) five anaesthetists gargled 10mls of red food dye, inhaled to their vital capacity and then coughed. They then repeated the experiment using blue food dye and HFNC at 60l/min and compared the distance traveled. They showed a baseline cough distance of 2.48m increasing up to 2.91m with high flow. Of course, children have a much smaller vital capacity.

This is in contradiction to the data from Hui et al. (2019). They used a human-patient-simulator (as opposed to humans in the above study), smoke and lasers. With a properly fitted mask flow forward flow was increased to ~26 cm with 5cm of CPAP and to around 33cm with 20cm of CPAP. With HFNC the exhalation distance increased from 6.5cm (10l/min) to ~17cm (60l/min). When the mask became loose or disconnected smoke was detected up to ~62cm laterally.  So why the big difference in the studies? It is the cough that causes the problem.

This video from Sick Kids in Toronto says more than any words ever could.

Whether you believe in the benefits of high-flow or not, pushing oxygen through the nose at 2l/kg/min and out through the mouth can create an aerosol spread of snot and virus. We would advise that it is only be used in cases where low flow oxygen therapy has failed. It also makes sense then, that it should only be started in the place where the patient is going to end up. It would not be wise to start a patient on HFNCO2 then wheel them through the hospital leaving a cloud of viral particles in their wake like some overactive Bisto Kid. And if you are going to do it with a coughing patient then it would be sensible to put a standard face mask on first.

 

Non-invasive ventilation (CPAP or BiPAP)

High risk 

High flow nasal cannula seems to have superseded non-invasive ventilation in many cases, though CPAP is regularly used in neonatal practice. There is very little evidence for maternal transmission of COVID19 and one might suppose that full PPE is then not warranted. However, you need to consider where the baby has come from.

Open suctioning and chest physiotherapy

High risk 

Removal of nasal foreign body

Medium to high risk

There are lots of ways to remove a nasal foreign body but all of them will generate snot. The old standby – the mother’s kiss – is, realistically, no more dangerous for the parent than living in close proximity. If your pre-encounter probability of infection with SARS-CoV-2 is low, i.e. there is little community transmission, then the risk to the provider is probably low.

Nitrous oxide

Medium to high risk 

Respiratory illness is a contra-indication to nitrous sedation but given that there is a degree of asymptomatic carriage it is not impossible that we might need to use it. With children not going to school and being told to stay away from their friends, there is going to be a spike in trampoline and bunk-bed related injuries. Again consideration should be made as to the possibility of community transmission. Logically holding a continuous flow mask on an uncooperative toddler would expose a HCW to higher risk than being a room Sith a cooperative patient using a demand system with appropriately attached to suction.

Examining the throat

Medium to high risk 

In normal times, no paediatric examination is complete without looking in the ears, nose, and throat, no matter how hard it might be. You can argue that looking at tonsils might not be overly helpful, given that the inter-rate variability is pretty high but there are other things to look for too – emerging teeth, Koplik spots, ulcers. But does a look in the throat put us at risk?

The Royal College of Paediatric and Child Health concurs, and in a statement put out on the 24th of March suggest that we only look in the throat if it is essential. If we have to do it we should be wearing appropriate protection (glove, gown, surgical face mask). If a child is at particularly high risk then they recommend empiric antibiotics.

Even ENT experts, like Eric Levi, recognize the unique risks that fiddling around near the upper respiratory tract hold.

Inserting a nasogastric tube

Medium to high risk

The combined Colleges of Surgeons of Great Britain and Ireland suggest that insertion of a nasogastric tube in an adult is an AGP, probably as it may induce coughing.

Taking a nasopharyngeal swab

Low to moderate risk 

The CDC state that collecting a nasopharyngeal swab doesn’t need to take place in an isolation room but should at least be performed in a single room with a closed door. The health care practitioner should wear an N95 mask or equivalent, coupled with eye protection, gloves, and gown. Given how far the swab has to travel up the nasopharynx nobody should be surprised that it might make someone sneeze.

The current Australian guidance contains slightly different advice.

 

We can also add things like IV access, suprapubic aspiration and performance of a lumbar puncture to this list of LOW-risk procedures.

And let’s not forget our surgical and dental colleagues

Surgical procedures

Clearly, some surgical procedures are more dangerous than others. Eric Levi. advocates for a risk assessment before any procedure takes place, starting with ‘Does it need to be done now?” Take a look at his post on how he is modifying his operative technique in order to reduce risk to himself and his colleagues.

On the 25th of March, the combined Colleges of Surgeons of Great Britain and Ireland recommended against laparoscopic surgery due to the potential for aerosol formation. Endoscopy, at either end, also has the potential for the creation of fomites and aerosolizing droplets and so should be carried out with extreme caution.

Dental procedures

There are very few dental procedures that need to be performed as an emergency but given that high-speed drills can lead to aerosolization have a care for our dental colleagues that may also be exposed in the course of duty.

The guidance for these procedures is common sense. Don’t perform them if you don’t have to. This is not the time for some minor dental procedures. If they have to be carried out then it should happen in the appropriate space with the appropriate staff. This means in a single room (ideally) with the minimum number of staff wearing appropriate PPE.

 

These are our thoughts, based on the current evidence, and we’d love you to persuade us otherwise in the comments below.

*Clearly the first step of the algorithm is D for Danger. That means putting on your PPE.

Selected references

Bourouiba L. Turbulent Gas Clouds and Respiratory Pathogen Emissions: Potential Implications for Reducing Transmission of COVID-19. JAMA. 2020 Mar 26.

Brewster DJ, Chrimes NC, Do TB, Fraser K, Groombridge CJ, Higgs A, Humar MJ, Leeuwenburg TJ, McGloughlin S, Newman FG, Nickson CP. Consensus statement: Safe Airway Society principles of airway management and tracheal intubation specific to the COVID-19 adult patient group.

Brown JS, Gordon T, Price O, Asgharian B. Thoracic and respirable particle definitions for human health risk assessment. Particle and fibre toxicology. 2013 Dec 1;10(1):12.

Davies A, Thompson G, Walker J, Bennett A. A review of the risks and disease transmission associated with aerosol generating medical procedures. J Infect Prev 2009; 10:122–6.

van Doremalen N, Bushmaker T, Morris D, Holbrook M, Gamble A, Williamson B, Tamin A, Harcourt J, Thornburg N, Gerber S, Lloyd-Smith J. Aerosol and surface stability of HCoV-19 (SARS-CoV-2) compared to SARS-CoV-1. medRxiv. 2020 Jan 1.

Hui DS, Ng SS. Recommended hospital preparations for future cases and outbreaks of novel influenza viruses. Expert Review of Respiratory Medicine. 2020 Jan 2;14(1):41-50.

Hui DS, Ip M, Tang JW, Wong AL, Chan MT, Hall SD, Chan PK, Sung JJ. Airflows around oxygen masks: A potential source of infection. Chest. 2006 Sep 1;130(3):822-6.

Judson SD, Munster VJ. Nosocomial Transmission of Emerging Viruses via Aerosol-Generating Medical Procedures. Viruses. 2019 Oct;11(10):940.

Kam KQ, Yung CF, Cui L, Lin Tzer Pin R, Mak TM, Maiwald M, Li J, Chong CY, Nadua K, Tan NW, Thoon KC. A well infant with coronavirus disease 2019 (COVID-19) with high viral load. Clinical Infectious Diseases. 2020 Feb 28.

Liu Y, Ning Z, Chen Y, Guo M, Liu Y, Gali NK, Sun L, Duan Y, Cai J, Westerdahl D, Liu X. Aerodynamic Characteristics and RNA Concentration of SARS-CoV-2 Aerosol in Wuhan Hospitals during COVID-19 Outbreak. bioRxiv. 2020 Jan 1

Macintyre CR, Seale H, Yang P, Zhang Y, Shi W, Almatroudi A, Moa A, Wang X, Li X, Pang X, Wang Q. Quantifying the risk of respiratory infection in healthcare workers performing high-risk procedures. Epidemiology & Infection. 2014 Sep;142(9):1802-8.

Noti JD, Lindsley WG, Blachere FM, Cao G, Kashon ML, Thewlis RE, McMillen CM, King WP, Szalajda JV, Beezhold DH. Detection of infectious influenza virus in cough aerosols generated in a simulated patient examination room. Clinical Infectious Diseases. 2012 Jun 1;54(11):1569-77.

Seto WH. Airborne transmission and precautions: facts and myths. Journal of Hospital Infection. 2015 Apr 1;89(4):225-8.

Shiu EY, Leung NH, Cowling BJ. Controversy around airborne versus droplet transmission of respiratory viruses: implication for infection prevention. Current opinion in infectious diseases. 2019 Aug 1;32(4):372-9.

Somogyi R, Vesely AE, Azami T, Preiss D, Fisher J, Correia J, Fowler RA. Dispersal of respiratory droplets with open vs closed oxygen delivery masks: implications for the transmission of severe acute respiratory syndrome. Chest. 2004 Mar 1;125(3):1155-7.

Tang JW, Li Y, Eames I, Chan PKS, Ridgway GL. Factors involved in the aerosol transmission of infection and control of ventilation in healthcare premises. J Hosp Infect 2006;64:100-14.

Tellier, R., Li, Y., Cowling, B.J. et al. Recognition of aerosol transmission of infectious agents: a commentary. BMC Infect Dis 19, 101 (2019). https://doi.org/10.1186/s12879-019-3707-y

Thompson KAPappachan JVBennett AM, et al. EASE study consortium. Influenza aerosols in UK hospitals during the H1N1 (2009) pandemic–the risk of aerosol generation during medical procedures. PLoS One. 2013;8:e56278.

Tran K, Cimon K, Severn M, Pessoa-Silva CL, Conly J. Aerosol generating procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review. PloS one. 2012;7(4).

World Health Organization. Infection prevention and control during health care when novel coronavirus (‎‎‎ nCoV)‎‎‎ infection is suspected: interim guidance, January 2020. World Health Organization; 2020

Intubation

Cheung JC, Ho LT, Cheng JV, Cham EY, Lam KN. Staff safety during emergency airway management for COVID-19 in Hong Kong. The Lancet Respiratory Medicine. 2020 Feb 24.

Nebulizing a medication

O’Neil CA, Li J, Leavey A, Wang Y, Hink M, Wallace M, Biswas P, Burnham CA, Babcock HM. Characterization of aerosols generated during patient care activities. Clinical Infectious Diseases. 2017 Oct 1.

Amirav I, Newhouse MT. RE: Transmission of Corona Virus by Nebulizer-a serious, underappreciated risk!.

High Flow Nasal Cannula

Hui DS, Chow BK, Lo T, Tsang OT, Ko FW, Ng SS, Gin T, Chan MT. Exhaled air dispersion during high-flow nasal cannula therapy versus CPAP via different masks. European Respiratory Journal. 2019 Apr 1;53(4):1802339.

Leung CCJoynt GMGomersall CD, et al. Comparison of high-flow nasal cannula versus oxygen face mask for environmental bacterial contamination in critically ill pneumonia patients: a randomized controlled crossover trial. J Hosp Infect. 2019;101(1):8487.

Loh NH, Tan Y, Taculod J, Gorospe B, Teope AS, Somani J, Tan AY. The impact of high-flow nasal cannula (HFNC) on coughing distance: implications on its use during the novel coronavirus disease outbreak. Canadian Journal of Anesthesia/Journal canadien d’anesthésie. 2020 Mar 18:1-2.

Non-invasive ventilation

Singh A, Sterk PJ. Noninvasive ventilation and the potential risk of transmission of infection. European Respiratory Journal. 2008 Sep 1;32(3):816-.

Bag-Valve-Mask Ventilation

Chan MT, Chow BK, Lo T, Ko FW, Ng SS, Gin T, Hui DS. Exhaled air dispersion during bag-mask ventilation and sputum suctioning-Implications for infection control. Scientific reports. 2018 Jan 9;8(1):1-8.

Christian MD, Loutfy M, McDonald LC, Martinez KF, Ofner M, Wong T, Wallington T, Gold WL, Mederski B, Green K, Low DE. Possible SARS coronavirus transmission during cardiopulmonary resuscitation. Emerging infectious diseases. 2004 Feb;10(2):287.

Suctioning

Inserting a nasogastric tube

Nitrous oxide

Taking a naso-pharyngeal swab

Examining the throat

Lu D, Wang H, Yu R, Zhao Y. Integrated infection control strategy to minimize nosocomial infection of corona virus disease 2019 among ENT healthcare workers. Journal of Hospital Infection. 2020 Feb 27.

Tang JW, Nicolle AD, Klettner CA, Pantelic J, Wang L, Suhaimi AB, Tan AY, Ong GW, Su R, Sekhar C, Cheong DD. Airflow dynamics of human jets: sneezing and breathing-potential sources of infectious aerosols. PLoS One. 2013;8(4).

Removal of foreign bodies

Surgical spread

Ong J, Cross GB, Dan YY. The prevention of nosocomial SARS-CoV2 transmission in endoscopy: a systematic review of recommendations within gastroenterology to identify best practice. medRxiv. 2020 Jan 1.

Dental spread

Divya R, Senthilnathan KP, Kumar MP, Murugan PS. Evaluation of aerosol and splatter contamination during minor oral surgical procedures. Drug Invention Today. 2019 Sep 1;12(9).

Sabino-Silva R, Jardim AC, Siqueira WL. Coronavirus COVID-19 impacts to dentistry and potential salivary diagnosis. Clinical Oral Investigations. 2020 Feb 20:1-3.

Prepare for transport: Costas Kanaris at DFTB19

Cite this article as:
Team DFTB. Prepare for transport: Costas Kanaris at DFTB19, Don't Forget the Bubbles, 2020. Available at:
https://doi.org/10.31440/DFTB.22605

Costas Kanaris is a paediatric intensivist working in Manchester. He is also internet-famous for his challenging #fridayquiz in which he presents a case, drip-feeding information, as the Twitter audience figure out the diagnosis and the best way to treat the patient in front of them.

This time he tries it in front of a live studio audience. Here is a teaser to tickle your brain.

 

This talk was recorded live at DFTB19 in London, England. With the theme of  “The Journey” we wanted to consider the journeys our patients and their families go on, both metaphorical and literal.

If you want our podcasts delivered straight to your listening device then subscribe to our iTunes feed or check out the RSS feed. If you are more a fan of the visual medium then subscribe to our YouTube channel. Please embrace the spirit of FOAMed and spread the word.

iTunes Button
 

 

Surviving Sepsis Campaign International Guidelines

Cite this article as:
Damian Roland. Surviving Sepsis Campaign International Guidelines, Don't Forget the Bubbles, 2020. Available at:
https://doi.org/10.31440/DFTB.23460

The lens with which you view sepsis is dependent on the environment and emotion in which you associate the term. For a parent, this may be the spectrum from having never heard the term before “Your child is well enough to go home, we’ve ruled out sepsis and other serious conditions” to the anguish of being told, “I’m afraid your child died of sepsis“. This spectrum remains equally wide for health care professionals. A family doctor or general practitioner may never see a case of confirmed sepsis, and an emergency clinician can potentially go years between seeing a truly shocked child. An intensivist, however, may deal with the consequences on a weekly basis. Even in the last month, we have seen two papers from the same publishing group; one highlighting the global burden of sepsis and the other challenging the current hype surrounding its recognition and management.

Regardless of your viewpoint, the publication of the Surviving Sepsis campaign’s international guidance will have been of interest.

 

Weiss, S.L., Peters, M.J., Alhazzani, W. et al. Surviving sepsis campaign international guidelines for the management of septic shock and sepsis-associated organ dysfunction in children. Intensive Care Med 46, 10–67 (2020). https://doi.org/10.1007/s00134-019-05878-6

 

It is important to recognize two features of this publication which should carry an important health warning in its interpretation.

The first is that the authors are clear that they are focusing on severe sepsis or septic shock. While in adult practice definitions have changed, these have not been formalized or ratified for children:

 

“For the purposes of these guidelines, we define septic shock in children as severe infection leading to cardiovascular dysfunction (including hypotension, need for treatment with a vasoactive medication, or impaired perfusion) and “sepsis-associated organ dysfunction” in children as severe infection leading to cardiovascular and/or non-cardiovascular organ dysfunction.”

 

The authors clearly recognize that the absence of a clear definition of paediatric sepsis is challenging health care providers and organizations. The group has steered away from suggesting management options in the ‘pre-sepsis’ group i.e. those children with potential infections that may result in sepsis and have physiological instability but without organ dysfunction. They suggest that management practices for this group aren’t radically different, however:

 

Even though these guidelines are not intended to address the management of infection with or without SIRS when there is not associated acute organ dysfunction, we recognize that sepsis exists as a spectrum and some children without known acute organ dysfunction may still benefit from similar therapies as those with known organ dysfunction

 

The second is that this is a consensus document. It is neither a systematic review nor a clinical practice guideline (in a local hospital sense). It comprises the opinions of an expert group of clinicians (49 in fact) from a variety of international settings using the best available evidence. The publication is essentially a list of recommendations. This approach is valid in situations where evidence may be heterogeneous and that randomized controlled trials can not be performed for all possible permutations of clinical practice. As with all things in science, however robust the data is, it still needs interpreting and that interpretation is subject to all manner of explicit and implicit bias.

 

The panel supports that these guidelines should constitute a general scheme of “best practice,” but that translation to treatment algorithms or bundles and standards of care will need to account for variation in the availability of local healthcare resources.

 

Without becoming meta it’s important that this blog itself needs a health warning. It’s an interpretation of an interpretation of evidence.

So the big-ticket items

1. A child was defined as beyond 37 weeks gestation and up to 18 years old.

2. They apply to children with severe sepsis or septic shock as defined by the 2005 International Pediatric Sepsis Consensus Conference or inclusive of severe infection leading to life-threatening organ dysfunction.

2005 definition:

  • greater than or equal to two age-based systemic inflammatory response syndrome (SIRS) criteria
  • confirmed or suspected invasive infection, and cardiovascular dysfunction
  • acute respiratory distress syndrome (ARDS), or greater than or equal to two non-cardiovascular organ system dysfunctions

Septic shock was defined as the subset with cardiovascular dysfunction, which included hypotension, treatment with a vasoactive medication, or impaired perfusion.

3. Panel members were selected through recommendations from chairs and vice-chairs of the 12 worldwide member organizations. Each panel member was required to be a practicing healthcare professional with a focus on the acute and/or emergent care of critically ill children with septic shock or other sepsis-associated acute organ dysfunction. There was lay representation and the final membership was felt to be demographically diverse with regard to sex, race, and geography.

4. The panel was assisted by various methodological experts and split into six groups

  • recognition and management of infection
  • hemodynamics and resuscitation
  • ventilation
  • endocrine and metabolic therapies
  • adjunctive therapies
  • review research priorities in pediatric sepsis

5. A list of critical questions was developed in the PICO format (Population, Intervention, Control, and Outcome) which was then rigorously searched for by a specialist medical librarian and the resulting literature assessed according to GRADE criteria a well-recognized methodology for systemically presenting summaries of evidence.

6. Following discussion and debate recommendations would be made:

 

We classified recommendations as strong or weak using the language “We recommend…” or “We suggest…” respectively. We judged a strong recommendation in favor of an intervention to have desirable effects of adherence that will clearly outweigh the undesirable effects. We judged a weak recommendation in favor of an intervention to have desirable consequences of adherence that will probably outweigh the undesirable consequences, but confidence is diminished either because the quality of evidence was low or the benefits and risks were closely balanced.

 

The paper goes into considerable detail (which is why it is 55 pages long) into the rationale behind the recommendations. They are all summarised in the appendix (commencing page e102). It is beyond the scope of this blog to explore all the recommendations in detail, and it is important that health care providers read the paper itself. The following highlights some of the areas which may prompt debate or query.

 

‘Screening’ remains in

For those in emergency and acute care, this recommendation may have come as a surprise given a large amount of anecdotal feedback and experience suggesting that current screening mechanisms for the un-differentiated child are neither specific nor sensitive. It is worth nothing again the panel was looking at severe sepsis or shock and the evidence for ‘bundles’ of care i.e. targeted or mandated treatments once recognized is relatively robust. There is a further section on protocols/guidelines for treatment but it may have been useful to separate the afferent limb (recognition) from the efferent limb (response) in relation to collated evidence. This is important as the evidence for ‘bundles’ is cited under screening, with minimal evidence of screening approaches alone put forward (or to be fair to the panel perhaps of insufficient quality to make a judgment on).

Although subtle I think the panel recognized how important local buy-in is in relation to quality improvement. Of note, there is nothing on national guidance for recognizing sepsis. They also highlight how blindly integrating screening with any other scoring system may not be as beneficial as believed.

Ultimately no one particular screening system is recommended.

 

There is no target lactate

There appears to be a palpable sense of regret that the evidence didn’t support any particular threshold for lactate. Despite evidence of rising mortality with increasing lactate, the panel was not able to determine a specific level.

However, no RCTs have tested whether initial or serial measurement of blood lactate directly informs evaluation and/or management in children. Lactate levels should, therefore, be interpreted as a part of a more comprehensive assessment of clinical status and perfusion.

 

Take blood cultures but don’t delay treatment to obtain them

Appreciating this isn’t a particularly scientific response, but well, duh.

 

One hour time to treatment for those in shock but up to three hours without it. 

This is the potential game-changer from this body of work. While the evidence shows a temporal relationship between the administration of antibiotics and outcome in severe sepsis some pooled data demonstrated that it was unlikely the hour alone made the difference. Given the numerous papers showing a linear relationship between time to administration and outcome the ‘golden hour” was maintained. In the absence of shock, the panel felt, based on data showing a three-hour threshold effect, this would be a reasonable time point. This will be a welcome relief for those working in areas where there are associated penalties for not reaching the hour window and hopefully will remove some of the gaming associated with this target.

 

Broad spectrums antibiotics, but narrow when pathogens available

Little controversy here. The panel highlight that 48 hours should be the maximum time that is allowed to pass before re-evaluation in the absence of culture growth rather than a standard time to elapse.

If no pathogen is identified, we recommend narrowing or stopping empiric antimicrobial therapy according to clinical presentation, site of infection, host risk factors, and adequacy of clinical improvement in discussion with infectious disease and/or microbiological expert advice.

There are a number of recommendations on immunocompromised children and source control which appear pragmatic.

 

Bolus if intensive care available, if not then don’t unless documented hypotension

In units with access to intensive care, 40-60ml/kg bolus fluid (10-20ml/kg per bolus) over the first hour is recommended. With no intensive care, and in the absence of hypotension, then avoiding bolus and just commencing maintenance is recommended. It is not clear how long access to intensive care has to be to switch from fluid liberal to restrictive.

**Post-publication note (13/02/20): A more correct description of no intensive care would be “in health systems with no access to intensive care”. The guidance states, “For children with septic shock without signs of fluid overload in low-resource settings where advanced supportive and intensive care is not available, the panel recommends against bolus fluid administration,”. This question is raised in the comments section below as for units in without intensive care on site but it will resourced health systems then ‘access’ to intensive care should be assumed**

For purposes of this weak recommendation, hypotension can be defined as:

 

The panel suggests crystalloids, rather than albumin, and balanced/buffered crystalloids rather than 0.9% saline. They recommend against using starches or gelatin.

 

Use advanced haemodynamic variables, not bedside clinical signs in isolation

The evidence didn’t support a target mean arterial blood pressure but suggested avoiding using clinical signs to differentiate into cold and warm shock. No one monitoring approach was advised but included cardiac output, cardiac index, systemic vascular resistance, and central venous oxygen saturation.

 

Intensive care vasoactive and ventilation management is given but acknowledged as weak recommendations 

There is a list of suggestions regarding vasoactive infusion and ventilatory strategies that are very specific to intensive care management. While a number of recommendations are given (epinephrine rather than dopamine for septic shock for example) these are generally based on the panels summation of weak evidence.

There are further suggestions on corticosteroid management, nutrition, and blood products which will be of interest to those in intensive care and anaesthetic settings.

 

Summary

This is a very rich piece of work that is well structured and easy to read (even if you are not an expert on a particular field of practice). For most paediatricians there is unlikely to be an immediate change in practice but the softening of antibiotic time to delivery in the non-shocked child and emphasis of local review of sepsis incidence and performance will be welcome. How these filter into national guidance will be determined country by country but it is unlikely that radically different views can be drawn from the available evidence. What is still sorely needed is a working definition for the non-hypotensive child with sepsis (or an acknowledgment that perhaps this isn’t really a clinical entity…)

 

Diabetic Ketoacidosis

Cite this article as:
Dani Hall. Diabetic Ketoacidosis, Don't Forget the Bubbles, 2020. Available at:
https://doi.org/10.31440/DFTB.22689

Maisie is 2 years old. Apart from a few coughs and colds, she is usually a very well, happy little girl. She’s been a bit poorly for the last 48 hours – a bit off colour, off her food, lethargic and just not her usual cheeky self.

She’s been drinking though and has had good wet nappies. In triage she has a runny nose and slight cough. She is pretty tachycardic and tachypnoeic and doesn’t look well and so she’s moved to majors.

Maisie is put on a monitor and immediately you can see that her respiratory rate is elevated at 40 breaths per minute with saturations of 97% in air. Her heart rate is also elevated at 150 beats per minute with a normal blood pressure of 105/65. Her capillary refill time is 3 seconds peripherally and she is afebrile.

Her heart sounds are normal, her chest is clear and her abdomen is soft although mildly tender throughout.

The only objective thing you have is the tachypnoea with a bit of a runny nose. You wonder if she has viral induced wheeze and is just too tight for the wheeze to be audible so you prescribe salbutamol and review after 10 minutes. But that’s made no difference to her respiratory rate, and her chest is still completely clear.

Things just don’t add up. She’s holding her tummy – perhaps her tachypnoea and tachycardia are secondary to pain. Her abdomen remains soft with no guarding, but she doesn’t like you palpating it. Could this be appendicitis? Or even worse an intussusception? You speak to the paediatric surgeon who asks you to cannulate Maisie and send some blood. They’ll be down to review her shortly.

You cannulate Maisie and take a venous gas. The results seem to take an age. And your heart sinks when you see them…

She’s acidotic at 7.15 and it looks metabolic with a bicarbonate of 13.9 and base deficit of minus 8.7. Her lactate is 2.9 and her glucose is very high at 29.5. You run a drop of Maisie’s blood through the bedside ketone monitor. Her blood beta-hydroxybutyrate is. 5.1.

This is diabetic ketoacidosis.

 

DKA can be really difficult to diagnose in toddlers

Classically children with DKA present with polyuria and polydipsia with abdominal pain, nausea, and vomiting. This can progress to dehydration, weakness, and in severe cases, they may be lethargic. Blood tests show a raised white cell count as a physiological response to the raised stress hormones, cortisol and catecholamines, and so are not a reliable indicator of infection. But, and this is a big but, an infection can precipitate DKA so it is important it is considered.

Although ketoacidosis may result in a classic ‘pear drop/acetone’ smell to the breath, not everyone has the chemoreceptors to detect it.

Common misdiagnoses include dehydration secondary to infection or respiratory presentations. Ketoacids stimulate the respiratory centre resulting in rapid fast breathing – Kussmaul breathing – blowing off carbon dioxide to compensate for the metabolic acidosis. It may also present as an acute abdomen as abdominal pain and ileus can result from hypokalaemia, acidosis, and poor gut perfusion. If opioids are given for pain this can suppress the Kussmaul breathing leading to worsening acidosis

The BSPED (2020), and ISPAD definitions of DKA are:

acidotic with a bicarbonate of <15 mmol/l or a pH <7.3 and ketones of >3.0 mmol per litre

However… just when you starting thinking it was easy… children with known diabetes may develop DKA with normal glucose and so you must keep a high index of suspicion and check pH and ketones in an unwell child with diabetes.

Lack of insulin leads to rising blood glucose levels in the bloodstream. However, this glucose is not transported into the cells and so the body needs to produce an alternative energy source for cellular activity. Three processes occur:

  • muscle is broken down to mobilise amino acids which are then used to create glucose (catabolism)
  • fat is broken down to produce glycol and ketones (lipolysis)
  • the liver uses lactate, glycol and amino acids to create more glucose (gluconeogenesis)

High ketone levels lead to metabolic acidosis.

Hyperglycaemia leads to glucose spilling into the urine (glycosuria). These glucose molecules exert an osmotic pull, dragging water, cations, and anions such as phosphate, potassium, and sodium into the urine (osmotic diuresis). The child becomes dehydrated with physiologically low levels of potassium and phosphate. Ketones also spill into the urine (ketonuria) in preference to chloride, which is retained in the plasma, leading to a worsening chloride-driven acidosis.

Maisie is dehydrated because of the osmotic diuresis exerted by the glucose in her urine. And she’s acidotic because of the ketones circulating in her bloodstream. The question is, what are we going to do about this?

The complications of DKA have incredibly high mortality and morbidity, so we’re going to start here.

Cerebral oedema

Cerebral oedema occurs in approximately 1% of children with DKA. While relatively rare, it can have devastating consequences with mortality of approximately 25%. In fact, more than half of all diabetes-related deaths in children are caused by cerebral injury.

Cerebral oedema usually occurs within the first four to 12 hours of starting treatment for DKA, suggesting that it’s the treatment itself that precipitates cerebral oedema.

Risk factors for cerebral oedema in DKA can be split into two groups.

The first group is characterised by children who have a longer duration of symptoms and are therefore more severely dehydrated at presentation. Younger children, particularly toddlers, and children who present in DKA without a previous diagnosis of diabetes mellitus, fall into this group, most likely because they have been in DKA for a long period of time before the diagnosis is made.

The second group is children who develop cerebral oedema because of the treatment they have received. Giving insulin within the first hour of treatment increases the risk of cerebral oedema – the theory is that the usually inactive sodium-hydrogen ion exchange pump is activated by the double hit of high intracellular hydrogen ions early in treatment while children are more acidotic plus insulin crossing the leaky blood-brain-barrier. The exchange pump transports sodium into the intracellular fluid, which then drags water with it due to its osmotic effect, leading to cerebral oedema.

Giving bicarbonate also increases the risk of cerebral oedema. The physiological mechanism of this is unclear but there is some thought that giving bicarbonate to correct acidosis can worsen tissue hypoxia due to effects on 2,3-DPG in erythrocytes (remember acidosis shifts the oxygen dissociation curve to the right, increasing the affinity of haemoglobin and oxygen) or that giving bicarbonate may lead to preferential movement of carbon dioxide across the blood-brain barrier, both of which will promote acidosis and poor oxygen offload in the CSF. However, whatever the cause, it is clear from a systematic review published in 2011 by Chua et al that giving bicarbonate to children with DKA is linked with increased rates of cerebral oedema. The guidance, therefore, mandates that bicarbonate should not be used routinely to correct acidosis. Fluids and insulin will do that by improving skin perfusion and reducing ketosis. Only give bicarbonate if the acidosis is resulting in reduced cardiac function, and then give very carefully…

So, with that in mind, how are we going to treat Maisie?

ABC resuscitation

The initial management of a child with DKA follows the principles laid out in APLS: ABC resuscitation.

If a child is obtunded and not protecting their own airway then they should be intubated because of the risk of airway obstruction. However, intubation in DKA is risky… both sedation and the resultant hypercarbia can cause cerebral herniation. Central lines are also risky in these children because of the increased risk of thrombosis. Only use them if absolutely necessary and remove them as soon as possible.

Luckily, Maisie is maintaining her own airway, her GCS is 15 and she is not obtunded. The airway is not a problem for her.

After managing the airway and breathing we move onto circulation. So the question is: should we give Maisie a fluid bolus?

This is a big question.  We are taught that children with cardiovascular compromise should receive fluid boluses to support their circulation.  But assessing cardiovascular compromise in children with DKA can be very challenging. Clinical evaluation of hydration and shock is very difficult in children with DKA. Acidosis drives tachycardia and reduces peripheral skin perfusion.

Koves et al set out to look at this by studying a group of 37 children under 18 presenting with DKA.

Emergency Department doctors recorded heart rate, respiratory rate, blood pressure, cool peripheries, capillary refill time, skin turgor, the presence or absence of sunken eyes and dry mucous membranes to provide a clinical estimate of dehydration. A second emergency department doctor, blinded to the clinical interpretations of the primary doctor, was asked to review the patient before treatment and record their assessment of the same clinical variables. There was a good clinical correlation between the two assessments. Following admission, the children’s weights were measured daily until discharge and percentage dehydration was calculated from the weight gain from admission to discharge.

There was no agreement between assessed and measured dehydration. There was a tendency to overestimate dehydration in children with <6% measured dehydration and underestimate in children >6% dehydrated.

It’s a tricky business and these same parameters clearly won’t be of use in estimating shock in these children.

A true assessment of shock in DKA should rely on assessment on blood pressure measurements and peripheral pulse volume. So that doesn’t really help us. Maisie’s blood pressure and pulse volumes are normal so she’s not shocked. But she clearly is dehydrated. 

BSPED (2020) uses pH and bicarbonate to classify the severity of DKA:

  • pH 7.2–7.29 or bicarbonate <15 mmol/l is mild DKA with 5% dehydration
  • pH 7.1–7.19 or bicarbonate <10 mmol/l is moderate DKA with 7% dehydration
  • pH < 7.1 or bicarbonate <5 mmol/l is severe DKA with 10% dehydration

So, are we going to give her a fluid bolus?  Let’s turn to the guidelines…

BSPED 2020 states:

Any child in DKA presenting with shock (as per the APLS definition of tachycardia and prolonged capillary refill time) should receive a 20 ml/kg bolus of 0.9% saline over 15 minutes. Let’s call this a ‘resuscitation bolus’.

Further 10 ml/kg boluses may be given if required up to a total of 40 ml/kg. Then add inotropes if the child remains shocked.

Boluses given to treat shock should NOT be subtracted from the calculated fluid deficit.

All children with DKA, whether mild, moderate or severe, who require IV fluids should receive an initial 10 ml/kg bolus over 60 minutes. Let’s call this a ‘rehydration bolus’. This bolus SHOULD be subtracted from the calculated fluid deficit.

The American Academy of Pediatrics, agrees that all children with DKA should have a bolus of 10ml/kg over 30 minutes to an hour. If a child is critically unwell with hypovolaemic shock, then additional boluses of 20ml/kg of 0.9% saline should be given.

Australian guidelines vary depending on region – from no routine fluid boluses to 10-20 ml/kg 0.9% saline for the sickest. Some say subtract fluid boluses from rehydration calculations, others don’t. There is no clear consensus.

So why is there so much international variation?

Traditionally, we have been warned about the danger of causing cerebral oedema in children with DKA by giving them too much fluid, reducing serum osmolality and literally flooding the brain. This is based, on the most part, by an old paper that showed an association between large volume fluid resuscitation in DKA and cerebral oedema. Note the word association, not causation.

Fluid management in DKA

Dogma has been to restrict fluids in paediatric DKA. It is widely thought that the rapid administration of intravenous fluids reduces serum osmolality, resulting in cerebral oedema. Guidelines traditionally have, therefore, advised slow fluid replacement using isotonic fluids as using hypotonic fluids was thought to cause further drops in osmolality. 

And the evidence seemed to support this.  Retrospective reviews showed better outcomes in children with DKA who received less fluid.

But…

  • only an association had been demonstrated, not causality.
  • and it is reasonable to suspect a confounder in that those with more severe DKA could be expected to be both at higher risk of cerebral oedema and more likely to receive large volumes of fluid resuscitation based on their clinical presentation.

And then along came this paper by Kupperman et al published in the New England Journal of Medicine in 2018, which has shifted thinking a bit, as well as causing some controversy…

Lead authors Nate Kupperman and Nicole Glaser suggested the causal effect of fluid resuscitation and cerebral oedema was a myth in Glaser’s 2001 retrospective case-control study that gave us the list of risk factors for cerebral oedema in DKA.

Kupperman’s team wanted to look specifically at the relationship between fluids and cerebral oedema (defined in the study as a drop in GCS, or longer-term evidence of neurological injury defined as a drop in IQ or short-term memory difficulties 2-6 months later) in DKA in children. They looked at 1255 children with DKA presenting to 13 hospitals in the States over a 9 year period, which, because 101 children presented twice, equated to 1389 episodes of DKA. Children were excluded if their GCS was less than 12, or if they had already received significant DKA management prior to assessment. 289 were withdrawn by the treating physician. The mean age was 11. It’s important to think about all of this as these exclusion criteria mean that the very sick and the very young, two groups who are at significantly increased risk of cerebral oedema, were probably lost in this cohort.

Children were randomized into 4 groups. All patients in both groups received IV insulin at 0.1u/kg/hr. Dextrose was added to the saline solution when blood glucose dropped to 11.1 to 16.7 mmol/l.

Children were randomized into 4 groups:

  • FAST rehydration with 0.45% sodium chloride
  • FAST rehydration with 0.9% sodium chloride
  • SLOW rehydration with 0.45% sodium chloride
  • SLOW rehydration with 0.9% sodium chloride

In short, Kupperman’s team found no difference between the groups. There was no significant difference in GCS, or longer-term evidence of neurological injury. The endpoint that many of us are most concerned about, clinically apparent brain injury (deterioration in neurological status requiring hyperosmolar therapy or endotracheal intubation or resulting in death) was a secondary outcome, presumably due to its rarity and hence difficulty in showing statistically significant differences between groups. But again, there was no significant difference between groups.

There was a 0.9% rate of brain injury overall and it didn’t matter which type of fluids or how fast. Patients were more likely to get hyperchloraemic acidosis in the 0.9% NaCl group but this is of debatable clinical significance.

The evidence does not seem to support our traditionally cautious approach to DKA. The speed of IV fluids does not seem to be the cause of brain injury in DKA. But… and this is a big but… don’t forget the youngest and sickest patients weren’t included. All we can probably really conclude is that children who are not in the at-risk group for cerebral oedema are probably more resilient to higher volumes of fluids delivered at faster rates.

Ok… back to Maisie. How are we going to manage her fluids

Well, again it depends where in the world Maisie presents. 

BSPED 2020 advises to calculate maintenance fluids the same way as they’re normally calculated for children in the UK:

  • 100 ml/kg/day for the first 10kg
  • plus 50ml/kg/day for each kg between 10 and 20kg
  • plus 20ml/kg/day for each kg above 20kg

(A maximum weight of 80kg should be used for fluid calculations)

The International Society for Pediatric and Adolescent Diabetes guidance is as follows:

ISPAD says

  • Shock is rare in DKA but if present should be treated with 20ml/kg fluid boluses, repeated as necessary to achieve tissue perfusion.
  • Give all children a 10ml/kg bolus over an hour to rehydrate them.
  • Calculate maintenance fluids in the normal way using the simplified Holliday-Segar formula.
  • Replace rehydration fluids over 24-48 hours, using clinical signs of dehydration to estimate the degree of dehydration. 2 or 3 signs would constitute to 5% dehydration, more signs would equate to 7% dehydration and weak pulses, hypotension or oliguria would indicate the child is 10% dehydrated.

Managing electrolytes

Once you’ve navigated the quagmire of fluid management in DKA, you need to think about adding electrolytes. Remember, glucose molecules in the urine exert an osmotic pull, dragging water, cations, and anions such as phosphate, potassium, and sodium into the urine: the child becomes dehydrated with physiologically low levels of the electrolytes potassium and phosphate.

Always assume whole body potassium depletion in DKA. This is compounded by the treatment you give which causes potassium to move intracellularly. Replace potassium as soon as the patient has urine outpatient and labs confirm the child is not hyperkalaemic.

An ECG will give you clues about clinically significant hypokalaemia:

  • Prominent U waves (an extra positive deflection at the end of the T wave)
  • Flat or biphasic T waves
  • ST-segment depression
  • Prolonged PR interval

Although phosphate is lost in the urine as part of the osmotic diuresis in DKA, prospective studies involving relatively small numbers of subjects and with limited statistical power have not shown clinical benefit from phosphate replacement. Administrating phosphate can be dangerous, by causing calcium levels to drop. However, symptomatic severe hypophosphataemia, when serum phosphate levels drop below 1 mg/dL with an ensuing metabolic encephalopathy or depressed cardiorespiratory function, can be dangerous, albeit very rare. A sensible approach is to monitor phosphate levels alongside regular potassium level checks and, if a child is hypophosphataemic and symptomatic, replace phosphate whilst carefully monitoring serum calcium levels.

Back to Maisie. We’ve managed her fluids according to our local guidelines. But how can we tell if we’ve got the balance right?

We can’t monitor urine output as Maisie is going to be polyuric anyway because of the osmotic effect of glycosuria. Her capillary refill time will be prolonged because she’s acidotic and therefore skin perfusion will be reduced.

And her serum sodium and osmolality won’t be reliable indicators of fluid balance because of the effect of plasma glucose on her electrolytes. On top of this, her kidneys will preferentially excrete chloride from any saline and potassium chloride over ketones so there’s limited value to monitoring the anion gap because it doesn’t differentiate between hyperchloraemia or ketones. Instead, we should measure Maisie’s corrected sodium.

Because of its osmotic effect, glucose drags water with it into the intravascular compartment diluting the other osmols – 1mmol rise in glucose will drop sodium and chloride by 1mmol/L.  If Maisie’s glucose goes up by 1 the other osmols will go down by 1.  If glucose goes down by 1 the other osmols will go up by 1.

The corrected sodium must rise with therapy at a rate of 0.5-1 mmol/h

  • Falling corrected sodium means too much water gain: we’ve been overzealous the fluids.
  • A rapidly rising corrected sodium means too much water loss: we’ve been too fluid restrictive.

The Evelina London South Thames Retrieval Service has a great corrected sodium calculator on their website. You plug in her numbers – her initial sodium was 148 with glucose of 29.5, giving her a corrected sodium of 157.6. A couple of hours have passed and her latest gas shows that her glucose has come down to 24.5 – great – and her sodium has improved slightly to 144. You press calculate…

… and your heart sinks as you see her second corrected sodium has fallen by 6 points to 151.6 as you know that the corrected sodium must rise with treatment.

You go back to Maisie’s bedside to review her.

Maisie has dropped her GCS to 12 (E3, V4, M5).  This is incredibly worrying – her GCS was 15 when you last checked on her.  You move her round to resus and ask your nurse to grab some hypertonic saline.

Clinical features of cerebral oedema

  • Headache
  • Slowing heart rate
  • Rising blood pressure
  • Focal neurology such as cranial nerve palsies
  • Falling oxygen saturations
  • Change in neurological status including restlessness, irritability, drowsiness, confusion, incontinence

Treat cerebral oedema with either hypertonic saline or mannitol.

Calculate your dose of hypertonic saline or mannitol before you need it and know where it’s kept. If a child has an acute deterioration, treat it.

Mannitol is an osmotic diuretic and can be given at 0.5 – 1 g/kg over 10-15 minutes. The effects should be apparent after 15 minutes. Mannitol lasts about 2 hours and can be repeated at this point if needed.

Hypertonic saline is a good alternative to mannitol or can be used after mannitol if a second agent is needed.

Don’t forget other neuroprotective measures like elevating the head of the bed to 30 degrees and intubation if concern regarding airway protection.

If there’s no improvement in GCS, do a CT, but not until the child is stable. CT is used to identify any potential lesion that would warrant neurosurgery – intracranial haemorrhage, or a lesion that would warrant anticoagulation such as thrombosis.

Hypertonic saline or mannitol?

DeCourcey et al (2013) conducted a retrospective cohort study over a 10 year period to see whether the increase in the use of hypertonic saline had had any effect on mortality in DKA. They looked at over 43,000 children under the age of 19 with DKA presenting to 41 children’s hospitals in America and found that the use of hypertonic saline replaced mannitol as the most commonly used agent in many of the participating hospitals. Controversially, their data suggested that hypertonic saline may not have benefits over mannitol and may be associated with a higher mortality rate.

However, this does remain controversial, with a counter-argument published as a letter to the editor a few months later arguing that (1) the fact that mortality from cerebral oedema in DKA had decreased by 83% over the same time period that use of hypertonic saline had increased, along with (2) the fact that DeCourcey’s paper only found a statistically significant difference in mortality between hypertonic saline and mannitol once age and race were removed from analyses (two factors that, themselves, have a significant influence on mortality in DKA-related cerebral oedema), meant that we shouldn’t be rushing to conclude that hypertonic saline is less safe than mannitol in the treatment of cerebral oedema.

No guidelines are yet to recommend mannitol over hypertonic saline. This seems to be one of those situations where a prospective study is needed to really answer the question of whether mannitol is superior, or at least non-inferior to hypertonic saline.

Back to Maisie. You give Maisie 3ml / kg 3% saline over 15 minutes and are relieved to see her wake up.  You decrease her fluid prescription and thankfully from that point on her corrected sodium starts to slowly rise.

Insulin

Finally, you’re ready to give Maisie some insulin. Insulin will control Maisie’s glucose and switch off ketosis, therefore improving her acidosis.  Some departments use 0.1 units/kg/hr and some use 0.05 units/kg/hr.  The question is, what is the optimal dose? 

Nasllasamy’s team set out to compare the efficacy and safety of low-dose and standard-dose insulin infusions. They randomized 50 children under the age of 13 with DKA presenting over a 12 month period to receive insulin infused at either 0.05 units/kg/hr or 0.1 units/kg/h. They found that the rate of decrease in blood glucose and time to resolution of acidosis were similar in each group. There was no statistical difference in complication rates of hypokalaemia, hypoglycaemia or cerebral oedema.

This study suggests that low dose insulin is non-inferior to standard-dose insulin in managing children with DKA.  It’s important to note that this was a non-inferiority trial and a larger study, powered to show superiority would be helpful. However, many units have been using lower doses of insulin at 0.05 units/kg/hr safely for some time and this study supports the use of lower dose insulin.

BSPED 2020 states:

Insulin can be given at 0.05units/kg/hr or 0.1 units/kg/hr, although ‘0.05 units/kg/hr would probably be sufficient in most cases except perhaps severe DKA’.

Children under 5 years should be given 0.05 units/kg/hr.

And so, as Maisie is young and therefore in the higher risk group of children with DKA, you opt to start her on insulin at 0.05 units/kg/hr.

In children who are already on long-acting insulin, BSPED 2020 states that it should be continued, or if they are newly diagnosed, they advise to consider starting long-acting subcutaneous insulin alongside intravenous insulin.<

 

Manage high-risk children in PICU

  • pH <7.1
  • young (under 2s or under 5s depending which guideline you read)
  • cardiovascular shock
  • corrected sodium >150 or <130
  • hyper or hypokalaemia
  • altered conscious state
  • glucose >50

Maisie has multiple risk factors: she’s young and she developed clinically apparent cerebral oedema.  You admit her to PICU where she makes stable progress and is discharged home 4 days later on a subcutaneous insulin regime.

Selected references

Take a read of Chris Gray’s take for St Emlyns here

Lawrence SE, Cummings EA, Gaboury I, Daneman D. Population-based study of incidence and risk factors for cerebral edema in pediatric diabetic ketoacidosis. J Pediatr 2005; 146:688

Glaser N, Barnett P, McCaslin I, et al. Risk factors for cerebral edema in children with diabetic ketoacidosis. The Pediatric Emergency Medicine Collaborative Research Committee of the American Academy of Pediatrics. N Engl J Med 2001; 344:264

Edge JA, Jakes RW, Roy Y, et al. The UK case-control study of cerebral oedema complicating diabetic ketoacidosis in children. Diabetologia 2006; 49:2002

Marcin JP, Glaser N, Barnett P, et al. Factors associated with adverse outcomes in children with diabetic ketoacidosis-related cerebral edema. J Pediatr 2002; 141:793

Scibilia J, Finegold D, Dorman J, et al. Why do children with diabetes die? Acta Endocrinol Suppl (Copenh) 1986; 279:326

Edge JA, Hawkins MM, Winter DL, Dunger DB. The risk and outcome of cerebral oedema developing during diabetic ketoacidosis. Arch Dis Child 2001; 85:16

Chua HR, Schneider A and Bellomo R. Bicarbonate in diabetic ketoacidosis – a systematic review. Ann Intensive Care. 2011; 1:23

Koves IH et al. The Accuracy of Clinical Assessment of Dehydration During Diabetic Ketoacidosis in Childhood. Diabetes Care 2004:27(10);2485-2487

Kuppermann N et al. Clinical Trial of Fluid Infusion Rates  for Pediatric Diabetic Ketoacidosis. N Engl J Med. 2018;378:2275-87

DeCourcey et al. Increasing use of hypertonic saline over mannitol in the treatment of symptomatic cerebral edema in pediatric diabetic ketoacidosis: an 11-year retrospective analysis of mortality. Pediatr Crit Care Med. 2013; 14(7):694-700

Tasker RC, Burns J. Hypertonic saline therapy for cerebral edema in diabetic ketoacidosis: no change yet, please. Pediatr Crit Care Med. 2014;15(3):284-285

Nallasamy K et al. Low-Dose vs Standard-Dose Insulin in Pediatric Diabetic Ketoacidosis. A Randomized Clinical Trial. JAMA Pediatr. 2014; 168(11): 999 – 1005

ISPAD Clinical Practice Consensus Guidelines 2018: Diabetic ketoacidodis and the hyperglycaemic hyperosmlar state. Pediatric Diabetes 2018; 19 (Suppl. 27): 155–177