Hypoxic Ischaemic Encephalopathy

Question 1

What is Hypoxic ischaemic encephalopathy?

Answer 1

occurs in neonates as a result of hypoxia during birth. Hypoxia is a lack of oxygen, ischaemia refers to a restriction in blood flow to the brain and encephalopathy refers to malfunctioning of the brain. Some hypoxia is normal during birth, however prolonged or severe hypoxia leads to ischaemic brain damage. HIE can lead to permanent damage to the brain, causing cerebral palsy. Severe HIE can result in death.

Question 2

Suspect HIE in neonates when?

Answer 2

neonates when there are events that could lead to hypoxia during the perinatal or intrapartum period, acidosis (pH < 7) on the umbilical artery blood gas, poor Apgar scores, features of mild, moderate or severe HIE (see below) or evidence of multi organ failure.

Question 3

Causes of HIE in Neonates?

Answer 3

Anything that leads to asphyxia (deprivation of oxygen) to the brain can cause HIE. For example:

Maternal shock
Intrapartum haemorrhage
Prolapsed cord, causing compression of the cord during birth
Nuchal cord, where the cord is wrapped around the neck of the baby

Question 4

How to stage HIE?

Answer 4

Sarnat Staging

Mild
Poor feeding, generally irritability and hyper-alert
Resolves within 24 hours
Normal prognosis

Mod
Poor feeding, lethargic, hypotonic and seizures
Can take weeks to resolve
Up to 40% develop cerebral palsy

Severe
Reduced consciousness, apnoeas, flaccid and reduced or absent reflexes
Up to 50% mortality
Up to 90% develop cerebral palsy

Question 5

Treating HIE

Answer 5

Babies near or at term considered to have HIE can benefit from therapeutic hypothermia. Therapeutic hypothermia involves actively cooling the core temperature of the baby according to a strict protocol. The baby is transferred to neonatal ICU and actively cooled using cooling blankets and a cooling hat. The temperature is carefully monitored with a target of between 33 and 34°C, measured using a rectal probe. This is continued for 72 hours, after which the baby is gradually warmed to a normal temperature over 6 hours.

The intention of therapeutic hypothermia is to reduce the inflammation and neurone loss after the acute hypoxic injury. It reduces the risk of cerebral palsy, developmental delay, learning disability, blindness and death.