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Hypoxic Ischaemic Encephalopathy


It’s 2 a.m., and you are called to the birth suite. The expectant mother has been pushing for over an hour, and your Obstetric colleague has called for a vacuum after a post-date induction. The CTG is “a bit iffy” according to the midwife who hands it over to you. There has been an otherwise unremarkable antenatal course with normal scans.

You crack on and check the trolley, mentally rehearsing your resus. You talk through the resus plan with your assistant.

It’s clearly a tense situation, and with the third pull, the head is delivered. There’s a minute before the rest of the baby is born, and she comes out looking marbled, apnoeic, hypotonic and meconium stained. The child is brought to the trolley within 30 seconds of delivery.

Bottom Line

Consider hypoxic ischaemic encephalopathy early.

Cooling improves mortality rates without additional adverse neurodevelopmental outcomes at 18 months.

If the child fits the FEAST criteria during or soon after resus, they may be a candidate for cooling.

Neonates must only be actively cooled in a tertiary neonatal centre.

Use your local guidelines and discuss with a neonatologist early

Your resuscitation unfolds. You suction their oropharynx and nares. Their airway is clear, but as their pulse is less than 60 bpm, you commence IPPV via Neopuff. She is hard to ventilate initially, but there is rise and fall of the chest.

The pulse is still less than 60 bpm, so you start chest compressions. As it reaches 90 bpm, you cease compressions and continue IPPV as she is apneoic and floppy. The sats probe reads 80% at 4 minutes.

You examine the vacuum site. It’s boggy but doesn’t cross the suture lines. You think that it’s a chignon and does not examine as a subgaleal haemorrhage.

The birth suite nurse returns with the cord gases:

pH 6.95

CO2 70

BE -17

Lactate 13

A few minutes later, the child begins to breathe spontaneously, at a rate of 80-90, with plenty of work. This looks like hypoxic ischaemic encephalopathy.

What is Hypoxic Ischaemic Encephalopathy?

Hypoxic ischaemic encephalopathy is just that: injury to the nervous system as a result of a hypoxic and consequent ischaemic event. Injury to nerves occurs in three phases: latent (30 mins to 6-12 hrs), secondary (6-12 hrs to 72 hrs) and tertiary (72 hrs+). During the latent phase, hypoxia and subsequent reperfusion have triggered cell death via apoptosis and other mechanisms.

After the first draft of this article, a succinct review was published in JAMA Pediatrics; I’ve adapted their figure.

From JAMA Paediatrics 2014

Most departments will have a protocol around cooling for hypoxic ischaemic encephalopathy. There are a few links below to guidelines for particular hospitals/areas, each with slightly varying details around particular parameters. Here in Queensland, our guideline is freely available online and was the basis for a ‘rough and ready’ cognitive framework (and mnemonic) I use in a resus situation to trigger the consideration of cooling;


Flat APGAR less than or equal to 5 for up to 10 minutes. If I’m at less than 5 @ 5mins, I think pretty hard about this one.

Encephalopathic As per Sarnat below, a child may be clearly encephalopathic during the resuscitation.

Acidotic Cord or venous gas in the first hour of life pH <7.00 or base deficit >12.

Sentinel events Include severe fetal bradycardia (? +/- from a vacuum or forceps, slow descent), placental abruption, ruptured uterus, cord prolapse, amniotic fluid embolus, fetal exsanguination from vasa praevia.

Term At least 35+0/40. 

Notably, for most of the unit protocols I’ve seen, there are additional inclusion and exclusion criteria that must be filled in to identify the child as appropriate for cooling; the above is a strictly cognitive framework to trigger the thought about hypoxic ischaemic encephalopathy and cooling.

Additional criteria include a minimum weight limit, no severe congenital abnormality and that the infant not be moribund and with plans for full care. These are based on the large trial data, as discussed below. Some infants might be very close to fitting the facility’s criteria; it’s very reasonable to discuss the child with the tertiary neonatologist on call if you’re not sure. There are limited data below the ages and weights described, but the intervention may still be appropriate.

Sarnat and Sarnat

The first published staging system for hypoxic ischaemic encephalopathy was produced by the Western Australian duo Sarnat and Sarnat in 1976. The introduction is particularly elegantly written; the whole paper merits a read. Particularly, in their initial publication, more than half of the neonates in the series had ‘Stage 2’ encephalopathy at birth; that is, they fit the criteria above.

Sarnat, H.B. and Sarnat, M.S., 1976. Neonatal encephalopathy following fetal distress: a clinical and electroencephalographic study. Archives of neurology33(10), pp.696-705.


You’ve called for your consultant; this is a baby needing senior review.

So, what happens next?

  • Transfer the neonate to the Special Care Nursery.
  • IV access
  • Blood culture, FBC, Repeat VBG, BSL
  • Start IV fluids & IV antibiotics
  • Check the blood pressure
  • Given ongoing respiratory distress, continue CPAP 8cm, FiO2 to keep SaO2 in the normal range
  • Via facemask/snorkel
  • OGT placed, CXR
  • NBM
  • Monitor in and out/weigh nappies, consider?IDC

Results: BSL is 8 pH is now 7.06 @ 20mins of life CO2 60 BE -10 Lactate 7

Obs: HR 150, RR 80, Sao2 94% in air, temp 37.2degC BP 65/55 (57)

Baby is still working hard to breathe but hasn’t moved much otherwise. She’s really grunting away on the CPAP.

You discuss the baby with the tertiary centre for retrieval and consideration of cooling.

The neonatologist advises turning off the overhead heater.

What’s the evidence for cooling?

A 2007 Cochrane review found that, when started within 6 hours of birth, 72 hours of moderate hypothermia reduced the rate of death and disability at 18 months of age for neonates with moderate to severe HIE. At that stage, the data was considered inadequate and incomplete with respect to data or neurodevelopment outcomes in survivors. The question also remained whether the benefits of hypothermia were attenuated by the severity of encephalopathy.

This was further updated in Edwards et al.’s 2010 meta-analysis in the BMJ. Their total analysis included ten trials (~1300 patients) for mortality and a subset of 767 patients for whom neurodevelopmental outcomes at 18 months were available. This subset comprised three large trials completed after the 2007 meta-analysis.

With regard to the primary outcome of neurodevelopment, the analysis was strongly in favour of cooling to prevent death or disability by 18 months, with an NNT of 9.

Note well that cooling (aka therapeutic hypothermia) needs tertiary-level care; a good example of this is a small study from Uganda (included in the Edwards et al. meta-analysis), in which the outcomes for cooled babies with HIE were significantly worse than those not cooled. The implication is that without adequate monitoring, experienced personnel and appropriate equipment, any benefit of therapeutic hypothermia is rapidly lost.

The new Dad has been by his baby daughter’s side through all of this, and soon after your call with the NICU Team, Mum arrives.

What do you tell them?

The BeBoP group provides a nice printout for parents, available here.

Some of the good explanations I’ve heard are short and simple. It’s good to start right back at the start. Both BeBoP and the Queensland Maternity and Neonatal Guidelines program recommend the explainers below:

CriteriaAdvice for parents
ConsequencesThis can result in brain damage from direct injury and also from ongoing changes that begin around six hours after the injury. These secondary changes are known to increase the amount of brain injury that occurs.
IncidenceAbout 1-3 in 1000 newborn babies suffer from the effects of reduced blood flow or oxygen supply to their brain around the time of birth.
ResuscitationYour baby needed significant resuscitation at birth to help him/her breathe. He/she appears to have suffered from the effects of lack of oxygen and blood supply to the brain.
What does the treatment entail?Your baby will receive cooling therapy in addition to standard intensive care support. Your baby's temperature will be slowly lowered and kept between 33 to 34u00b0C for 72 hours. Cooling will be achieved by exposing your baby to the ambient air temperature and subsequently by specialised cooling equipment. Your babyu2019s temperature and other vital signs will be closely monitored throughout the process. If your baby shows any signs of discomfort during cooling he/she will be prescribed medication to reduce this. After 72 hours of cooling, your baby will be gradually rewarmed to a temperature of 37C.
TreatmentIn the past there were no treatments to reduce the severity of brain injury in these newborn babies. Recent research has shown that cooling these babies reduces the secondary brain injury, increases the chances of survival and reduces the severity of possible long-term disability.
PrognosisApproximately 30 to 60% of those babies who survive after this degree of damage to their brain may develop long-term disabilities. These disabilities include cerebral palsy and severe learning difficulties.

More recently, I’ve begun to mention a protocol. The idea that this is common enough and that there’s been some forethought and research in the area can provide another kind of reassurance to parents. It helps set expectations and frame your decision-making, in the subacute phase.

Whilst waiting for the retrieval team, the baby has 5 minutes of cycling movements of both legs. You think it’s a seizure.

Seizures and other complications

Apnoea, lip smacking, rowing of the arms or cycling of the legs can be subtle signs of seizures in neonates. It’s important to have a low threshold for suspicion of seizures and an experienced nurse keeping an eye on the baby. A full description of the management of seizures associated with HIE is (just) outside the scope of this post, but they can be notoriously hard to control.

It’s also worth considering some of the other complications of delivery that may arise concurrently with a hypoxic ischaemic-type presentation; urgent delivery may be facilitated by vacuum extraction, with an increased risk of subgaleal haematoma.

What’s the best available evidence for cooling in HIE?

The most recent meta-analysis of the evidence for induced hypothermia is Jacobs et al., 2013. This post finely examines the results of this analysis. You can read the original review here:

Jacobs SE, Berg M, Hunt R, Tarnow-Mordi WO, Inder TE, Davis PG. Cooling for newborns with hypoxic ischaemic encephalopathy. Cochrane Database of Systematic Reviews 2013, Issue 1. Art. No.: CD003311. DOI: 10.1002/14651858.CD003311.pub3.

I’ve given some opinions and thoughts in the last two posts, so today, I’ll mostly just let the numbers do the talking. The review’s introduction outlines what we already know: HIE occurs in 0.5-1/10000 live births. Of these infants, between 10 and 60% will die.

 25% will have long-term neurodevelopment sequelae.

Between 0-6 hours post-insult, secondary neuronal death occurs via several mechanisms. This 0-6 hours time period is, therefore, a ‘therapeutic window of opportunity’.





One of the great things about this review is that the numbers are given as NNT (to benefit). So there’s not a whole lot of explaining to do, as they speak for themselves.

Tangible resultsPositive

Tangible results – Negative

What next?

Jacobs et al. note that there are some studies in the works looking at early (<6 hours) vs late (6 – ~10 hours) start of cooling.

Additionally, several parameters of the cooling therapy would benefit from clarification. These include:

  • Duration of cooling (~48 to ~72 hrs)
  • Target temperature (~32.5 to ~35.0oC)
  • Total body vs head-only cooling. However, the difference in overall mortality seems to lean the evidence towards total body cooling at present.
  • Whether to cool infants aged 32-35 weeks gestation
  • Infants on ECMO
  • The usage and utility of adjuncts, including xenon, levetiracetam, melatonin, n-acetylcysteine, or topiramate


The current evidence is that therapeutic cooling for moderate to severe HIE suggests that mortality is reduced without increasing major disability in survivors.

Cooling should be undertaken under the supervision of a neonatologist at a centre of excellence. Some aspects of the therapy need further refining, as does clarification around the utility of certain adjuncts.

Selected References

Hypoxic-Ischemic Encephalopathy; A Review for the Clinician Escobar, et al. JAMA Pediatr. 2015;169(4):397-403. doi:10.1001/jamapediatrics.2014.3269.

Edwards, D et al. Neurological outcomes at 18 months of age after moderate hypothermia for perinatal hypoxic ischaemic encephalopathy: synthesis and meta-analysis of trial data. BMJ 2010;340:c363 doi:10.1136/bmj.c363

Queensland Maternity and Neonatal Clinical Guidelines Program

.Hypoxic-ischaemic encephalopathy. Published May 2010.

Sarnat, H & Sarnat M. “Neonatal Encephalopathy Following Fetal Distress – A Clincal and Electroencephalographic study. Arch Neuol 33 Oct 1976, 696-705.

Walston, F et al East of England Perinatal Networks: Guidelines for Management of Infants with Suspected Hypoxic Ischaemic Encephalopathy (HIE). Published 28/2/2012.

BeBoP (Baby Brain Protection); East of England Neuroprotection Team, Cambridge University Hospitals NHS Foundations Trust.

De Paoli A (Ed.) Royal Hobart Hospital Clinical Guidelines – Cooling for Neonatal Hypoxic Ischaemic Encephalopathy (HIE) – Guideline.

Davies, Cartwright & Inglis. “Pocket notes on Neonatology 2E.” 2008.  Elsevier. (3rd Ed available as iPhone application)

Ambalavanan, N & Carlo, W A. (Chapter Authors) 93.5 Hypoxic-Ischemic Encephalopathy; Nelson’s Textbook of Pediatrics 18th Edition.

Battin, M. Auckland District Health Board Newborn Services Clinical Guideline – Cooling Overview. Feb 2010.

Ballot DE. Cooling for newborns with hypoxic ischaemic encephalopathy: RHL commentary (last revised: 1 October 2010). The WHO Reproductive Health Library; Geneva: World Health Organization.



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