HIE and neurological problems

Question 1

What is neonatal encephalopathy?

causes?

Answer 1

“A clinically defined syndrome of disturbed neurological function in the earliest days of life in the term infant, manifested by difficulty with initiating and maintaining respiration, depression of tone and reflexes, sub normal level of consciousness and often seizures”. Can be mild, moderate or severe.

Causes:

• birth asphyxia
• transfer of maternal anaesthetic agents,
• cerebral malformations,
• metabolic disorders (hypoglycaemia, hyponatraemia, hypocalcaemia)
• infection,
• hyperbiirubinaemia,
• neonatal withdrawal,
• intracranial haemorrhage or infarction.

Question 2

What are the causes of birth asphyxia?

Answer 2

• Maternal, via impaired oxygenation (asthma, PE, pneumonia) and/or inadequate perfusion of the maternal placenta (cardiac arrest, maternal hypotension)
• Placental (placental insufficiency, abruptio placenta, uterine rupture)
• Cord (tight nuchal cord, cord prolapse, cord compression, true knot)
• Fetal, via impaired fetal oxygenation/perfusion (FMH, fetal thrombosis)

Question 3

What are the causes and management of neonatal seizures?

Answer 3

• HIE
• ICH
• Infection
• Metabolic (hypoglycaemia, hypocalcaemia)
• Kernicterus
• Drug withdrawal
• Developmental brain abnormalities
• Idiopathic

Investigations:
•	BSL, EUCs, Ca, Mg, blood gases
•	Cranial USS, 
•	Urine analysis, LP, blood cultures and viral investigations
•	Metabolic screen
•	Consider cranial CT/MRI/EEG

Management:
• NICU, ventilation, BP control, fluid and electrolyte balance
• AED IV - Phenobarbitone, phenytoin, midazolam

Question 4

How does asphyxia cause HIE?

Answer 4

Compromise in gas exchange (either pulmonary or placental) leading to hypoxia, hypercarbia and metabolic acidosis.

Compromised cardiac output leads to decreased cerebral perfusion and subsequent hypoxic injury.

Origin may be antenatal, during labour/delivery or postnatal.

Question 5

What are the markers of asphyxia or HIE?

Answer 5

In HIE as opposed to other forms of encephalopathy there is:
• Significant hypoxic event immediately before or during labour and delivery
• Pathological CTG prior to delivery suggestive of acute hypoxia
• Apgar <5 at 5 and 10 minutes
• Multisystem organ failure
• Fetal umbilical artery acidaemia - cord pH<7.0, base deficit >12.
• Neuroimaging evidence of acute brain injury

Incidence in HIC of 0.5-1/1,000. 0.3/1000 will have neurological disability.

Question 6

Define HIE.

Answer 6

A type of neonatal encephalopathy as the result of antepartum or intrapartum asphyxia.

Question 7

What are the criteria for asphyxia?

Answer 7

All 4 must be met:

• profound acidemia (pH <7) on an umbilical cord artery sample, if obtained 
• Apgar score <5 at 5 and 10 minutes
• multi-system organ dysfunction
• intracranial imaging suggestive of acute hypoxic-ischemia

Question 8

How do you grade HIE?

Answer 8

• Sarnat and Sarnat system
• grade 1 / mild = irritable (usually good long term outcome)
• grade 2 / /mod = drowsy/obtunded, seizures common (increased risk for cerebral palsy)
• grade 3 / severe = coma, seizures unlikely (75% mortality, >80% significant disability)

Question 9

What are the investigations for HIE?

Answer 9

• Cord blood gases for pH, lact, BE
• Cerebral USS - for haemorrhage, anatomy, oedema, blood flow in MCA
• MRI - Imaging of choice. Best done around 10 days of life for prognosis. Allows early recognition of bilateral basal ganglia injury, internal capsule, white matter and cortical injury, focal cerebral infarction, haemorrhage and malformations.
• EEG - seizures and periodic or isoelectric output are bad prognostic signs.
• Brain function testing
• Brainstem auditory evoked responses (test brainstem auditory conduction)