Hypoxic-ischaemic encephalopathy — Rapid

Synopsis

Recognise neonatal encephalopathy after perinatal compromise, stabilise physiology, determine therapeutic-hypothermia eligibility within 6 hours, monitor seizures and multiorgan injury, and communicate prognosis using serial multimodal assessment.

Neonatal encephalopathy is abnormal neurological function; HIE is the subset attributable to impaired oxygen delivery and perfusion around birth after alternative causes are considered.
Assess biological evidence of perinatal compromise and neurological evidence of moderate or severe encephalopathy; neither an isolated low pH nor a difficult birth alone proves HIE.
Stabilise effective ventilation, oxygenation and circulation while avoiding hyperoxia, hypocarbia, hyperthermia, hypoglycaemia, marked hyperglycaemia and hypotension.
First-line disease-modifying treatment for eligible moderate or severe HIE is controlled therapeutic hypothermia started as soon as possible and within 6 hours.
UK standard pathways usually apply to babies at least 36 weeks, using whole-body cooling to about 33.5°C for 72 hours followed by slow controlled rewarming.
Use a regional eligibility protocol incorporating acute event, cord or early gas, 10-minute Apgar or continued ventilation, neurological examination and aEEG or EEG; exact entry criteria vary.
Do not delay referral while waiting for aEEG when clinical and biological criteria strongly suggest eligibility; start controlled thermal management with the cooling centre.
Continuous multichannel EEG is the reference standard for seizure detection. aEEG provides useful bedside trending but can miss brief, focal or low-amplitude seizures.
Treat electrographic seizures that are prolonged or frequent. Phenobarbital remains common first-line neonatal antiseizure therapy, adjusted for organ dysfunction and specialist protocol.
Monitor renal, hepatic, cardiac, coagulation, glucose and electrolyte function because HIE is a multiorgan disease and cooling changes pharmacokinetics.
Brain MRI with diffusion and spectroscopy after the acute phase supports injury definition and prognosis; timing follows the neonatal neurology pathway.
Prognosis must integrate serial examination, EEG background and seizures, MRI, organ course and development; avoid a definitive prediction from one early measure.

Key red flags

Apgar score 5 or lower at 10 minutes, ventilation still needed at 10 minutes, severe early acidosis or a documented acute perinatal event triggers urgent encephalopathy assessment.

Reduced alertness, abnormal tone, weak or absent suck or Moro reflex, abnormal pupils, apnoea or seizures indicates moderate or severe encephalopathy.

Subtle repetitive eye deviation, cycling, chewing, tonic posturing or autonomic change may be neonatal seizures and needs EEG correlation.

Hypotension, oliguria, bleeding, transaminitis, persistent lactate or myocardial dysfunction marks multiorgan hypoxic-ischaemic injury and modifies drug and fluid treatment.

Temperature above 37.5°C after hypoxic-ischaemic injury is harmful; uncontrolled cooling below the target also causes arrhythmia, coagulopathy and instability.

A baby below 36 weeks should not enter routine term cooling criteria automatically; current BAPM advice requires specialist individual decision because evidence of benefit is lacking and harm is possible.

Investigation priorities

First-line: cord or early blood gas and serial lactateFirst stepFirst line

Document biological evidence of impaired gas exchange and track perfusion recovery.

Reference standard: continuous multichannel EEGReference standard

Detect, quantify and guide treatment of neonatal seizures and assess background recovery.

Management branches

First 6 hoursIdentify and cool

Perinatal compromise is followed by abnormal neurological function.

Stabilise physiology, avoid hyperthermia and gather cord gas, early gas, Apgar and resuscitation data.
Grade encephalopathy and start aEEG/EEG; contact the regional cooling centre immediately.
If eligible, begin controlled cooling as soon as possible within 6 hours and organise intensive-care transfer.

After acute careDefine injury and support development

The baby is physiologically stable after cooling or encephalopathy care.

Arrange protocol-timed MRI and formal hearing assessment and integrate findings in a family meeting.
Establish neonatal neurology, therapy and developmental surveillance before discharge.
Provide seizure, feeding and tone safety-netting and support parental mental health and bereavement needs when relevant.

Key medicines

Phenobarbital intravenousCommon first-line neonatal seizure loading is 20 mg/kg IV with cardiorespiratory monitoring; if electrographic seizures continue, specialists may give additional 10 mg/kg loads to a usual cumulative maximum of 40 mg/kg under the neonatal formulary. Maintenance is individualised.Can cause respiratory depression, hypotension and sedation that obscures examination. Cooling and hepatic or renal injury delay clearance; use levels and specialist dose intervals, and support ventilation when required.

Open full textbook →Answer 2 questions