Henry Goldstein. Induced Hypothermia for Hypoxic-Ischaemic Encephalopathy – Part 1, Don't Forget the Bubbles, 2015. Available at:
https://doi.org/10.31440/DFTB.7015
Bottom Line:
- Consider and identify 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 might 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
It’s 2am and you (the Paeds Reg), 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-dates induction. The CTG is “a bit iffy” according to the midwife who hands 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 marbelled, apnoeic, hypotonic and meconium stained. The child is brought to the trolley within 30 seconds of delivery.
Your resuscitation unfolds, thus:
- You suction the child’s oropharynx & nares, observing the airway is normal & clear
- HR is <60
- You commence IPPV via Neopuff
- The child is hard to ventilate initially, but there is improving rise and fall of the chest
- HR check is still <60
- Chest compressions for 30 sec, with IPPV ongoing (FiO2 to 1.00)
- HR 90; cease compressions
- There’s adequate air entry bilaterally, with equal rise & fall of the chest
- IPPV ongoing as child remains apnoeic
- Tone remains very low
- HR is now 130
- You attach an SaO2 probe, which reads 80% at 4 minutes
- The SaO2 remain normal for age
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 child remains floppy and apnoeic at 8 minutes; the Birth Suite nurse returns with the cord gases, which show:
pH 6.95
CO2 70
BE -17
Lactate 13
A few minutes later, the child begins to breath spontaneously, at a rate of 80-90, with plenty of work.
This looks like hypoxic ischaemic encephalopathy. What is HIE?
Defining HIE
Hypoxic-ischaemic encephalopathy is just that; the injury to the nervous system as a result of a hypoxic and consequent ischaemic event. The 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 has triggered cell death via apoptosis & other mechanisms, concurrently, oxidative stress, inflammation and excitotoxicity lead to
After the first draft of this article, a succinct review was published in JAMA Pediatrics; I’ve adapted their figure.
Most departments will have a protocol around cooling for HIE. There’re 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 & ready’ cognitive framework (and mnemonic) I use in a resus situation to trigger the consideration of cooling;
‘FEAST’
Notably, for most of the unit protocols I’ve seen, there are additional inclusion and exclusion criteria that must be filled to identify the child as appropriate for cooling; the above is a strictly cognitive framework to trigger the thought about HIE & 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’s limited data below the ages and weights described, but the intervention may still be appropriate. Sarnat & Sarnat The first published Staging system for hypoxic-ischaemic encephalopathy was produced by Western Australian duo Sarnat & Sarnat in 1976. The introduction is particularly elegantly written; the whole paper merits a read. Particularly, in their initial publication, that more than half of the neonates in the series had ‘Stage 2’ encephalopathy at birth; that is, they fit the criteria above. You’ve called for your consultant; this is a baby needing senior review. 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 tertiary centre for retrieval & consideration of cooling. The neonatologist advises to turn off the overhead heater. … Part 2. Summary HIE is a poorly understood pathophysiologic process, that can lead to long term disability or death. Identifying the features of HIE early in the piece (either during resuscitation, but specifically within 6 hours) can be important to facilitating cooling. When there’s a long neonatal resus for a flat baby, make sure you think of HIE and the FEAST. References: 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 https://www.bmj.com/content/340/bmj.c363 Walston, F et al East of England Perinatal Networks: Guidelines for Management of Infants with Suspected Hypoxic Ischaemic Encephalopathy (HIE). Published 28/2/2012. 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) 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. https://apps.who.int/rhl/newborn/cd003311_ballotde_com/en/ Flat
Encephalopathic
Acidotic
Sentinel event
Term
So, what happens next?
A Paediatric Trainee based in Queensland, Australia, Henry is passionate about Adolescent Medicine & General Paediatrics, with a strong interest in Medical Education & Clinical Teaching. An admitted nerd & ironman with a penchant for Rubik's Cubes & 'Dad jokes'.
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