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Intraosseous access



It is 15.50 hrs on a Tuesday when the call comes in. A 3-year-old female is in cardiac arrest.

When it is an adult patient, we can manage this without even breaking stride…but as you begin to formulate your action plan, your brain now needs to focus on areas that you don’t tend to dwell on when it comes to a grown-up patient – How will I gain access? What are my medication doses? What are those novel airway features again?

While we are more confident and experienced in managing adult patients in cardiac arrest, it is important to remember that – “Familiarity Breeds Contempt”, – and this is different.

We are weaving in and out of rush hour traffic while deriving our WETFAG when we get updated information that an FBAO* may have led to this arrest.

*EM/prehospital speak for foreign body airway obstruction

My colleague and I discuss a plan of action:  we allocate roles, make a difficult airway plan, and agree to ensure that exceptional, high-quality Basic Life Support is delivered in the first instance.

We discuss access options:

  • Intravenous (IV) – but will it be possible?
  • Intraosseous (IO) – we know this is possible and effective.

On arrival, we find a 3-year-old girl lying in a playroom. She is being tended to by a crew of firefighter paramedics who have arrived just ahead of us.

I can see she is unresponsive but breathing. Her breathing does not look normal. She looks very unwell.

I get a handover from those on the scene while Simon gets to work with airway assessment.

We voice our plan to the team

The decision to proceed with vascular access in paediatric patients is not an easy (or common) one to make for pre-hospital practitioners. Knowing that this patient was “Big Sick” makes the decision somewhat easier, but not so the challenge.  

When to go intraosseous (IO)?

Intraosseous (IO) is a rapid and effective method for accessing non-collapsible marrow veins without sacrificing pharmacokinetics.

Any delay in establishing vascular access can be potentially life-threatening.

The Royal Children’s Hospital Melbourne states, In decompensated shock IO access should be established if IV failed or is going to be longer than 90 seconds”.

The decision to gain IO access should be considered in the following scenarios.

Where should you place the IO needle?

Is the case medical or trauma? If it is a trauma, where are the injuries? Fractures at or above the insertion site can compromise the integrity of the underlying anatomic structures. What sites are practical and accessible to me in this case right now?

Having never attempted IO access on a paediatric patient before, I stuck with what I had done most frequently in training. I decided on the “proximal tibia” as my site for IO insertion.

“In the pre-hospital environment, it is sometimes as important to know when not to do something as it is to know when to do something.”

Justification for tibial IO access in this not-arrested patient was based on the following case elements for me:

  • IV access had failed.
  • I had a small child, obtunded and unresponsive, requiring airway and breathing support, tachycardic, tachypnoeic, and hypoxic. Big Sick.
  • Activities “up top” were very busy – although the airway did not appear to have an FBAO, it required my colleague to maintain a good seal. I did not feel positioning for humeral IO was viable at this moment.
  • This was a medical case with no apparent lower limb or pelvic trauma.

Of course, one must always consider contraindications before proceeding with IO access.

What are the contraindications to IO access?

  • Fractures at (or above) the insertion site
  • Crush Injuries
  • Ipsilateral vascular injury
  • Illness or anomalies to the underlying bone, e.g. osteomyelitis, osteogenesis imperfecta, osteoporosis.
  • Previous failed IO attempts at this location
  • Overlying skin infection
  • Pain associated with infusion may be considered a reason not to continue using the line if it cannot be controlled.

What are the anatomical landmarks for IO access?

I considered all potential options for IO insertion before choosing the site most familiar to me– the proximal tibia. Other possible sites included:

  • Distal tibia
  • Distal femur
  • Humeral head
Intraosseous insertion sites

Anatomical landmarks for the insertion site depend on whether you can palpate the tibial tuberosity. The tibial tuberosity does not develop until around two years of age. If you cannot feel the tibial tuberosity in the smaller child, palpate two fingerbreadths down from the inferior border of the patella, then one finger breath medial to this point. Where the tuberosity is palpable, go one fingerbreadth medial to it.

Target flat bone and pinch the tibia (especially in the very young patient) to reduce bone mobility and to prevent the skin from rotating with the driver before starting needle insertion.

Surface anatomy for insertion around knee
Landmarks for proximal tibial insertion

This is a small child. While it might seem like there is no time to hesitate, training, planning, awareness, and observation are vital. I recalled the phrase “Power and Pressure”. This would not require as much force as I usually use in adult IO insertion. “Let the driver do the work”, and be careful not to overshoot through the bone.

Placing the needle over the landmark site at 90 degrees, I visualised the line I wanted to drill. After careful but firm passing of the needle through the skin, I pressed the trigger. After the first pop, I was careful not to overshoot. Anticipation here is key, so avoid putting too much pressure on the driver. Similarly, be careful to avoid excessive recoil when you feel you have reached the medullary space, as this can result in the dislodgement of the needle.

How do you know if the IO is in the right place?

Attempt to aspirate marrow from your line (though it might not always be present). Flushing saline through with little to no resistance is very reassuring. No Flush = No Flow!

The line needs to be secured, and the extension tubing is attached properly with no identifiable leak points. What we give through the line should generate a physiological response – if it does not, always consider if the line has become displaced.

The proximal tibial site may not always be an option, so where else can we go?

Medial view of ankle
Landmarks for distal tibial insertion

Distal Tibia

Place one finger directly over the medial malleolus; move approximately 3 cm or two fingerbreadths proximal and palpate the anterior and posterior borders of the tibia to ensure that your insertion site is on the flat centre aspect of the bone. 

Distal femur surface anatomy
Landmarks for the distal femoral site of insertion

Distal Femur

Midline, 2-3 cm above the external condyle or two fingerbreadths above the superior border of the patella. This is often an accessible site due to children having less muscle bulk. To ensure you avoid the growth plate, the leg should be outstretched when performing your landmarking above and aim about 15 degrees cephalad too.

Landmarks of the humeral head for IO insertion
Landmarks for insertion in the proximal humerus

Humeral Head:

The humeral head represents an excellent access point for large proximal vasculature (which lies closer to the heart). Flow rates may be higher here, too, due to lower intramedullary pressures. The greater tuberosity secondary ossification centre doesn’t appear until about five years of age, making the palpation of this landmark more of a challenge in the younger child.  For this reason, it is more often used in older children, typically over seven years of age or only in those in whom the anatomy can be readily identified.

You may need to consider using a longer needle here due to the larger amount of soft tissue over this axillary area.

The insertion site is located directly on the most prominent aspect of the greater tubercle, 1 cm above the surgical neck. The surgical neck is where the bone juts out slightly – you will find this by running a thumb up the anterior aspect of the humerus until you feel a prominence. This is the greater tuberosity. The insertion site is approximately 1cm above this.

It is important to position the arm correctly.

hand on belly or thumb to bum position for humeral IO
Positioning the arm for humeral IO

Humeral IO placement techniques:

  • Thumb to Bum – Move the patient’s hand (on the targeted arm) so that the patient’s thumb and dorsal aspect of the hand rest against the hip (“thumb-to-bum”).
  • Palm to umbilicus – Move the patient’s hand (on the targeted arm) so that the palm rests over the umbilicus while maintaining the elbow close to the body.

Site versus flow

As mentioned above, the proximal humerus is very close to the heart. This, coupled with seemingly lower intramedullary pressures, lends itself to higher flow rates when compared to the lower limb sites.

Important to note, however, that any abduction or external rotation of the arm during resuscitative efforts (easy to picture this happening when moving your patient from scene to ambulance!) can lead to dislodgment of your IO. Nice and easy, does it.

Can you place an IO in an awake patient?

The sound of the driver buzzing brings back dentist chair memories for all of us, no less so for your patient who, if conscious during the insertion, will be particularly anxious and upset. Anticipate this and control anxiety with reassurance, distraction, and parental explanation if possible.

Pain in the conscious patient with an IO in situ can be from the area around the insertion site and the volume expansion caused by infusion. A small volume of 2% lidocaine can be given through the line before commencing the infusion to help with pain – this is slowly infused over 120 seconds, left for 60 seconds, and then flushed with 2-5ml of saline.

Consider line dislodgment or compartment syndrome with gross discomfort and inspect/flush the line to ensure it still functions adequately.

What about the gear itself?

The EZ-IO 10 driver and needle Set is a semi-automatic intraosseous placement device commonly found in our EDs. All needle catheters are 15 gauge, giving gravity flow rates of approximately 60-100ml/min. The use of pressure bags can greatly increase these rates. You must pre-flush the connector set to ensure no residual air can be injected after attachment.

Fail to Prepare, Prepare to Fail”. Practice makes perfect, so frequent familiarisation sessions are encouraged to get used to the IO equipment and identify the various access sites and their relevant anatomy.

A recent study by Mori et al. (2020) showed a highly successful placement rate of 92.7%. This paper also described the complications encountered with using EZ-IO in a paediatric population in a paediatric ED. The complication rate seems to be consistent across all needle sizes at around 21%. Complications (particularly the more commonly occurring extravasation and skin) are important considerations for PEM IO training programmes.

What size IO needle should we use?

Size of IO – credit to Tim Horeczko

These are the manufacturer recommendations, but are they right?

In our clinical experience, a red (15 mm) IO cannula placed into the distal tibia of a typical chubby one-year-old tends to be too short because of the amount of pretibial fat. The needle tip may reach the medullary cavity, but minimal movement can cause dislodgement and extravasation (with consequences).

The manufacturer advises that before activating the driver, you should push the needle through the skin against the bone, ensuring that at least one 5mm mark is visible above the skin. 

However, this would mean that a longer needle set has to be opened should this test fail. 

Let’s see what the literature says.

These authors from Switzerland and Canada examined lower leg radiographs (0-16 months) and extrapolated the measured distances to intraosseous needle placements. Using the suggested needle length, 10.5-18.5% of needles (depending on puncture level) wouldn’t even reach the medullary cavity. The opposite cortical wall was touched or penetrated in 16%-25% of cases, mostly in very small babies. Puncture level and needle length influence potential needle tip positions, so care must be taken to avoid too deep or too shallow insertions.

This other study also used a radiographic approach to determine the appropriate needle length in the distal femur and proximal tibia insertion sites below the age of 2 years. Based on their measurements for the tibia site, using a 25 mm instead of a 15 mm EZ-IO needle would mean an 81-91.1% reduction in malposition risk among 6-24-month-old children.  

Based on our clinical experience and these two articles, we changed our policy regarding EZ-IO needle selection during pre- and intrahospital emergencies in children:

What are the complications of IO access?

  • Extravasation or subperiosteal infusion – the highest reported complication in the Mori paper was 17% of all IO insertions. This occurs if you fail to enter the bone marrow or happen to go through the entire bone itself and overshoot the medullary canal. Dislodgement of a well-placed IO line during resuscitation can also lead to this.
  • Dermal abrasion4% in Mori study. A more recently described complication of using the semi-automatic IO approach, these injuries can occur due to friction from the rotating plastic base surrounding the EZ-IO needle. While these all seemed to settle with conservative treatment, it is important to watch out for this during insertion.
  • Compartment syndrome – is rare…but the smaller the patient, the higher the risk.
  • Fracture or physeal plate injury.
  • Osteomyelitis is rare, reported as 0.6% (Rosetti et al.).
  • Fat embolus

The use of POCUS to rapidly confirm intraosseous line placement and reduce the risk of misplacement with extravasation has been discussed in recent times. This paper by Tsung et al. in 2009 comments on its feasibility and describes using a colour Doppler signal with a saline flush to identify flow in the bone around the IO to confirm placement. Misplacement may also be identified if flow is seen in the soft tissues rather than bone.  

The Super Smallies

Achieving safe and reliable intraosseous access in neonates or infants can be challenging as they have smaller medullary canal diameters. Higher risks of misplacement and extravasation also put this group at risk of compartment syndrome. Case reports of limb amputation secondary to iatrogenic compartment syndrome from IO misplacement are almost exclusively in neonates and small infants.

A case report by Suominen et al. 2015 described proximal tibia mean medullary diameters on X-ray as 7mm in neonates, 10mm in 1-12-month infants, and 12mm in 3-4-year-old children. The EZ-IO needle set for this group is 15mm in length and 12mm in length once the needle stylet is removed. This leaves a narrow margin of safety for the correct positioning and avoiding dislodgement of the IO needle.

With the measurements above, it makes sense that one would need to stop a few mm short to avoid through-and-through insertion and subsequent extravasation. Stopping short like this could make the line more difficult to protect…Scott Wingart and Rebecca Engelman outline some neat tricks to “SEAL THE HECK OUT OF…” these delicate lines here.

The systematic review by Scrivens et al. in 2019 describes IO as an important consideration for timely access in neonatal resuscitation practice. They comment on the importance of incorporating IO insertion techniques into neonatology training. While a more recent study of IO access in neonatal resuscitation by Mileder et al. reports lower success rates for insertion at 75%, further studies are needed to scrutinise this access modality in neonates and whether it can be considered a standard, reliable and fast alternative to umbilical vein access in a time-critical scenario.

What are the take-homes?

  • Have a vascular access plan before arriving at the scene for every paediatric patient – consider adding this to the end of your WETFLAG.
  • There are clinical scenarios outside of the patient in cardiac arrest where IO placement may be necessary – the decision to IO after a failed IV should be rapid in the shocked child.
  • Familiarise yourself with the equipment, needle sizes and gauge, and be aware of the age-related anatomical considerations when landmarking sites for IO insertion.
  • Let the driver do the work – nice and easy does it!
  • Complications can occur and are not always rare – extravasation from dislodgement or misplacement and skin abrasions are well reported.
  • The smaller the patient, the higher the risk of through-and-through misplacement – these “super smallies” are at a greater risk of compartment syndrome. 
  • Keep it simple….“No Flush = No Flow!”. POCUS may be used to confirm satisfactory line placement, too.


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Intraosseous (IO) – Salford Royal NHS Foundation Trust.

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  • Gavin Hoey is a Firefighter and Advanced Paramedic with Dublin Fire Brigade, working in the Prehospital environment for past 12 years. Loves to learn and develop new skills. Interested in Trauma and Paediatric emergencies. Big football fan. Owen Keane is an Advanced Specialist Trainee in Emergency Medicine in Ireland with an interest in PEM, Education, and Trauma / Pre-Hospital Care Systems. Keen fan of caffeine, beaches, and oval ball watching

  • Gyula Tovishazi is a paediatric anaesthetist in Semmelweis University, Budapest, Hungary and medical director of Szent Marton paediatric transport service. He loves playing basketball and spending time with family.


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