Hypoxic-Ischaemic Encephalopathy

Question 1

What is HIE?

Why is it important?

Answer 1

Hypoxic ischaemic encephalopathy (HIE) 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

When should HIE be suspected in neonates?

Answer 2

Suspect HIE in 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 later) or evidence of multi organ failure.

Question 3

Causes of HIE?

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

Grading of HIE?

Answer 4

Sarnat Staging

Question 5

Management of HIE?

Answer 5

Management will be coordinated by specialists in neonatology, on the neonatal unit. This involves supportive care with neonatal resuscitation and ongoing optimal ventilation, circulatory support, nutrition, acid base balance and treatment of seizures. Therapeutic hypothermia is an option in certain circumstances to help protect the brain from hypoxic injury.

Children will need to be followed up by a paediatrician and the multidisciplinary team to assess their development and support any lasting disability.

Question 6

Therapeutic hypothermia for HIE?

Answer 6

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.