Hypoxic Ischaemic Encephalopathy (N)

Question 1

What are the causes of HIE?

Answer 1

1. Placental = abruption, insufficiency, antepartum haemorrhage
2. Umbilical = cord compression, prolapse
3. Materno-placental = any cause of maternal hypoxia/hypotension
4. Neonatal = difficult delivery (e.g. shoulder dystocia), inadequate resus (failure of breathing at birth), IEM,
   evidence of fetal distress: Poor CTG, acidic FBS, meconium-stained liquor
5. Peripartum = Low APGAR score, depressed condition (neonatal abstinence syndrome)
6. Other = IUGR, anaemia, failure to breathe at birth, kernicterus

Question 2

What are the features of HIE?

Answer 2

Mild
(Alert baby)
Increased tone and reflexes
Irritable, responds excessively to stimulation, staring of eyes, hyperventilation, hypertonia, impaired feeding
Transient behavioural changes that resolves in 24h
Complete recovery expected

Moderate
(Lethargic, obtunded)
Hypotonic, sluggish (weak or absent) reflexes, occasional apnoea
Seizures common; strong tonic neck, pupil miosis, bradycardia
May recover in 1-2 weeks
If neurological examination normal and feeding normal by 2 weeks age = good long term prognosis. If not full recovery unlikely

Severe
(All reflexes absent)
Stupor, coma, hypotonia, irregular breathing
Fixed dilated pupils; Irregular HR/ BP
Seizures subside as disease progresses
40% mortality
80% neurodevelopmental disability if not cooled e.g. cerebral palsy

Question 3

What investigations are carried out for HIE?

Answer 3

• Amplitude integrated electroencephalogram (aEEG, cerebral function monitor)
  Detects abnormal background brain activity
• MRI brain at 5-15 days (in term infant)
  Abnormal white signal in basal ganglia and thalamus
  Absent signal in internal capsule = high risk of cerebral palsy

Question 4

What is the management for HIE?

Answer 4

1. Therapeutic hypothermia (active cooling) improve survival and neurodevelopment in neonates with
   moderate to severe HIE
   Consider in infants meeting criteria:
   A) ≥36+0 admitted to NNU with at least one of following:
   - Apgar score of ≤5 at 10 min after birth
   - Continued need for resuscitation, incl. endotracheal or mask ventilation, at 10 min after birth
   - Acidosis within 60min of birth (def: any occurrence of umbilical cord or arterial or capillary pH <7.00)
   - Base deficit ≥16mmol/L within 60 min of birth in umbilical cord or any blood sample (arterial/venous/
   capillary)
   Infants that meet criteria A should be assessed for whether they meet the criteria (B):
   B) Seizures or moderate to severe encephalopathy, consisting of:
   - Altered state of consciousness (lethargy, stupor, coma) AND
   - Abnormal tone (focal or general hypotonia, or flaccid) AND
   - Abnormal primitive reflexes (weak or absent suck or Moro response)
   IF meet criteria A and B = consider Tx with cooling

C/I (not appropriate)

1) Likely need surgery within 1st 3D after birth
2) Poor LT outcome
3) Futile Px

STEP 2: Rewarming = start after completing 72 hours of therapeutic hypothermia, over 12 hours
Aim: Increase core temp by 0.5°C every 2 hours + maintain normoglycemia + RV aEEG/CFM every 2 hours
- Cx: In cooled HIE neonates, 50% seizures start after first 24 hours, aEEG monitor for duration of cooling
and rewarming,

• Supportive Mx of all other organs
  Abnormal LFT, oliguria, NEC, hypotensive, metabolic acidosis, DIC - all complications
• Respiratory support
• Anticonvulsants 🡪 clinical seizures
• Fluid restriction 🡪 for transient renal impairment
• Volume and inotrope support 🡪for hypotension