Overview
Also known as anoxic encephalopathy, neonatal hypoxic-ischaemic encephalopathy (HIE) describes brain ischaemia due to interrupted blood flow or gas exchange immediately before, during, or after birth.
Neonatal HIE is commonly caused by perinatal asphyxia, which describes oxygen deprivation significant to cause physical damage.
Epidemiology
- HIE affects around 2.8 per 1000 births in the UK each year
Causes
Causes may include:
- Antepartum causes:
- Maternal hypoxia (e.g. respiratory failure, infection)
- Maternal haemodynamic compromise (e.g. amniotic fluid embolus)
- Placental abruption
- Intrapartum causes:
- Prolonged labour
- Shoulder dystocia
- Umbilical cord compression
- Umbilical cord knots
- Intrapartum infection
- Uterine rupture
- Haemorrhage
Presentation
Overview
The Sarnat staging can be used to assess HIE’s features and severity:
| Feature | Stage I | Stage II | Stage III |
| Consciousness | Hyperalert and irritable | Lethargy, reduced alertness | Comatose |
| Pupils | Dilated | Constricted | Dilated |
| Tone | Normal tone | Hypotonia | Flaccid |
| Reflexes | Normal/increased | Reduced | Absent |
| Seizures | No seizures and symptoms resolve in <24 hours | Seizures common | Frequent seizures that are more resistant to treatment |
| Electroencephalogram (EEG) | Normal | Abnormal | Abnormal with decreased background activity |
| Apgar score | 5-7 | 3-4 | 1-2 |
Diagnosis and Management
Neonates with suspected HIE are treated in intensive care with supportive management and therapeutic hypothermia depending on the severity of HIE. Supportive treatment involves airway, respiratory, and cardiovascular support, managing seizures, treating infection, correcting fluid electrolyte abnormalities etc.
Prognosis
- In the short-term, mortality rates of birth asphyxia can be as high as 30%
- Long-term consequences of HIE can include cerebral palsy, neurodevelopmental delays, seizures, blindness, and hearing impairment.
