Hypoxic Ischaemic Encephalopathy (HIE)
Definition
HIE is a specific type of neonatal encephalopathy caused by acute oxygen and blood flow deprivation (hypoxia-ischaemia) that occurred around the time of birth.
Neonatal encephalopathy is a clinical syndrome of disrupted neurologic function in the early neonatal period (first few days of life), in infants born ≥35 weeks of gestation. [Ref]
Causes and Risk Factors
HIE develops following an acute reduction in fetal oxygen delivery and cerebral perfusion, causing hypoxic-ischaemic brain injury, most commonly around the time of labour and delivery [Ref1][Ref2]
| Fetal / placental / umbilical factors |
|
| Maternal / obstetric factors |
|
Less commonly, postnatal causes: [Ref]
- Severe neonatal respiratory failure (e.g. meconium aspiration syndrome, neonatal respiratory distress syndrome)
- Severe congenital heart disease
Predisposing antenatal risk factors (that make the fetus more susceptible to hypoxic-ischaemic injury) [Ref1][Ref2]
- Small for gestational age / fetal growth restriction
- Hypertensive disorder of pregnancy (gestational hypertension, pre-eclampsia, HELLP syndrome) → placental insufficiency
- Genetic susceptibility and congenital anomalies
- Maternal infection
Clinical Features and Diagnosis
HIE can be diagnosed when BOTH of the following are present: [Ref]
- Neonatal encephalopathy
- Evidence of acute peripartum hypoxic-ischaemic insult as the cause of neonatal encephalopathy
| Diagnostic domain | Description / details |
|---|---|
| Neonatal encephalopathy | 3 clinical hallmarks of neonatal encephalopathy: [Ref]
EEG can provide objective evidence of encephalopathy [Ref] |
| Evidence of peripartum hypoxic-ischaemic insult | Clinical indicators: [Ref]
Objective tests: [Ref]
|
Complications
HIE remains a major leading cause of infant death
Short-term complications: [Ref]
- Seizures
- Dysglycaemia (both hypoglycaemia and hyperglycaemia)
- Intracranial haemorrhage
- Systemic multi-organ dysfunction
Long-term complications: [Ref]
- Cerebral palsy – primary long-term complication
- Epilepsy – major cause of post-neonatal epilepsy and persistent seizure disorders
- Cognitive and intellectual problems
- Speech and communication problems
Management
Mainstay of management involves: [Ref]
| Supportive management |
|
| Therapeutic hypothermia | Therapeutic hypothermia is the main established neuroprotective treatment for moderate-to-severe HIE:
Rationale: after the initial hypoxic-ischaemic insult, there is a short latent phase, followed by secondary energy failure, seizures, cytotoxic oedema and mitochondrial dysfunction. Cooling during this early therapeutic window reduces secondary neuronal injury. There is currently no additional neuroprotective drug routinely recommended to improve outcomes when added to therapeutic hypothermia. |
Ongoing assessment and follow-up: [Ref]
- MRI to assess the pattern and extent of brain injury + provide prognostic information
- Long-term neurodevelopmental follow-up due to the risk of complications