Birth Asphyxia / hypoxic ischaemic encephalopathy

Question 1

What is hypoxic ischaemic encephalopathy / birth asphyxia?

Answer 1

Hypoxic ischaemic encephalopathy is a clinical syndrome of brain injury secondary to hypoxic ischaemic insults.

The lack of oxygen in the foetal circulation results in poor supply of oxygen to the brain. This ischaemia results in irreversible brain damage, both from primary neuronal death (immediate) and secondary reperfusion injury (delayed).
This can develop ante-natal, intrapartum or post-partum.

In mild to moderate cases, children may recover completely.

In severe case, there may be permanent disability i.e. developmental delay, cerebral palsy (motor impairment), epilepsy or cognitive impairment.

If blood/oxygen supply to the brain has been impaired, the rest of the body may also be hypoxic => organ damage inc. heart, liver, kidneys, bowels

Question 2

What are the causes of hypoxic ischaemic encephalopathy?

Answer 2

Any event causing poor oxygenation:

=> Maternal antepartum haemorrhage due to placental abruption, uterine rupture, placenta previa (low lying placenta right on top of cervix)

=> Difficult extraction i.e. shoulder dystocia, breech, forceps converted to c-section

=> Umbilical cord prolapse (occurs when umbilical cord leaves the cervix before the baby)

=> Compression of the umbilical cord

=> Meconium aspiration syndrome (occurs when baby inhales a mixture of amniotic fluid and meconium)

=> Premature birth (<37 weeks) and inadequate postnatal cardiopulmonary circulation

=> Amniotic fluid embolism to the mother

=> Congenital foetal infection during labour

=> Prolonged / difficult labour

=> Preeclampsia

=> High / low blood pressure in pregnancy, maternal diabetes with vascular disease

=> Severe foetal anaemia

=> Maternal hypoxia

Question 3

What are the risk factors for hypoxic ischaemic encephalopathy?

Answer 3

=> Maternal age between 20-25 years

=> Multiple births i.e. delivering twins or triplets

=> Not attending prenatal care

=> Low birth weight

=> Abnoraml position of foetus during delivery

=> Preeclampsia / eclampsia

=> Hx of birth asphyxia in a previous birth

Question 4

What are the signs and symptoms of hypoxic ischaemic encephalopathy?

pH soon after birth = <7.0
Base excess worse than -12
*encephalopathy develops within 24h of birth

Answer 4

Signs & symptoms can occur before, during or after birth.

Before birth, foetus might have abnormal heart rate, low blood pH levels which indicates excess acid.

Signs post birth can indicate lack of oxygen or blood flow and is categorised as mild, moderate and severe:

Mild:
=> Irritability
=> Hyperalert
=> Mild hypotonia 
=> Poor sucking

Moderate:
=> Lethargy
=> Seizures
=> Marked abnormalities of tone
=> Need for NG feeding

Severe:
=> Coma
=> Prolonged seizures
=> Severe hypotonia
=> Failure to maintain spontaneous respiration

• generally condition worsens and gradually improves.
• severe HIE may lead to permanent problems and ~80% of severe HIE baby die

Question 5

What is APGAR score?

Answer 5

APGAR score - rating system to measure newborn health

A = appearance 
P = pulse
G = grimace
A = activity 
R = respiration 

*clinicians rate from 0-10 depending on skin colour, heart rate, muscle tone, reflexes and breathing .

Low APGAR score (between 0-3) that lasts for more than 5 minutes can indicate birth asphyxia.

Question 6

What are the short & long term effects of hypoxic ischaemic encephalopathy?

Answer 6

Short term:
=> Acidosis

=> Respiratory distress

=> Hypertension

=> Blood clotting problems

=> Kidney injury

Long term:
=> Hyperactivity

=> Autism spectrum disorder

=> Attention deficit

=> Low intelligence quotient score

=> Schizophrenia

=> Psychotic disorders in adulthood

Severe asphyxia:

=> Intellectual disability
=> Cerebral palsy
=> Epilepsy
=> Sight / hearing impairment

Question 7

How is hypoxic ischaemic encephalopathy treated?

Answer 7

Immediate treatment:

=> Extra oxygen to mother if birth asphyxia prior to delivery

=> Emergency c-section

=> Suctioning fluid away from the airways in case of meconium aspiration syndrome

=> Newborn on respirator for resuscitation (Intermittent positive-pressure ventilation)

For severe cases of hypoxic ischaemic encephalopathy:

=> Place baby in a hyperbaric oxygen tank which supplies 100% oxygen to baby

=> Induced mild hypothermia to cool body down for 33-34 degrees over 72 hours and prevent brain damage (avoid hyperthermia) to prevent reperfusion injury

=> Dialysis to support kidneys and remove excess waste

=> Meds to control BP and seizures

=> IV nutrition - careful fluid balance, electrolyte monitoring and inotropes

=> Breathing tube to supply nitric oxide

=> Life support with heart and lung pump

Question 8

How is hypoxic ischaemic encephalopathy investigated?

Answer 8

EEG

Question 9

What is the management criteria for hypoxic ischaemic encephalopathy?

Answer 9

TOBY criteria for therapeutic cooling

Babies >36 weeks to neonatal unit:

Criteria A (perinatal factors):
=> Apgar <5 @ 10mins
=> Resus >10 mins 
=> pH <7.0
=> BD >16

Criteria B (encephalopathy):
=> Altered consciousness
=> Abnormal tone
=> Abnormal primitive reflexes

*Cooling a baby reduces metabolism of the brain to reduce further damage

Question 10

Why is hypothermia induced as a management of hypoxic ischaemic encephalopathy?

Answer 10

It slows down cerebral metabolism to limit release of neurotransmitters (glutamine) and oxygen free radicals.