See also:            Seizure guideline                Body cooling            Metabolic Disease

Background

Neonatal Encephalopathy (NE) is “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” ¹. NE occurs in approximately 3.5 - 6/1000 live births and usually affects the full term infant. The terminology NE is preferred to Hypoxic Ischemic Encephalopathy (HIE) as it is not always possible to document a significant hypoxic-ischemic insult ²and there are potentially several other aetiologies ^{3, 4}. Specifically, it is important to exclude metabolic disease, infection, drug exposure, nervous system malformation and neonatal stroke as possible causes of the encephalopathy. The requirement for investigation to exclude these possibilities will depend on the presentation, history and clinical features of the individual case.

Three clinical stages of encephalopathy are described.

• Stage 3 or persistence of stage 2 for more than seven days or failure of the EEG to revert to normal is associated with neurodevelopmental impairment or death ⁵.
• Full-term infants who develop long-term neurologic sequelae from intrapartum asphyxia may not have low Apgar scores but will demonstrate neurological dysfunction within 48 hours.

Initial Management

1. Adequate resuscitation should be promptly instituted at birth. Aim to keep oxygen saturation > 95% in term infants.
2. Cord gases should be collected
3. Apgar scores : a low Apgar score indicates an abnormal condition at birth but it is not exclusive to asphyxia and drug exposure, trauma, hypovolemia, infection, or congenital anomalies should be excluded.
4. A note should be made of
   • the time for respiration to be established, and
   • the return of tone as this may help indicate the severity of the insult.
   • Also slow recovery of the heart rate despite adequate resuscitation may indicate a severe insult and meconium staining of umbilical cord and skin suggests prolonged exposure to meconium (> 3 hrs).

Ongoing Management

Once oxygenation is established management is supportive.
Note:  If the clincal course is not typical of a hypoxic-ischaemic insult, consider other causes (possible other causes include [but are not limited to] metabolic disease, infection, drug exposure, CNS malformation, or neonatal stroke)

1. Monitor blood gases, glucose, urea & electrolytes, creatinine and fluid balance.
2. If metabolic acidosis is severe or persistent then sodium bicarbonate may be used but caution is advised as rapid infusion increases serum osmolality and alkalisation may decrease cerebral blood flow.
3. Inotropes and volume expansion may be cautiously used to maintain blood pressure and renal blood flow. Hypotension and low cerebral flow may be associated with adverse neurologic outcome but the loss of cerebral autoregulation makes hypertension equally hazardous.
4. Acute tubular necrosis or the presence of inappropriate ADH secretion affect fluid output and thus fluid overload is a distinct but avoidable hazard. Urine output must be carefully measured and urinary cateterisation should be considered.
5. Other organ impairments such as persistent fetal circulation require specific measures. Echocardiogram will help to rule out structural cardiac disease and will assist with assessment of cardiac function.
6. Seizures require prompt treatment as cerebral oxygen use is increased almost fivefold during a seizure.
7. The use of mannitol or steroids for either the early cerebral oedema or increased intracerebral pressure is not supported by any controlled studies.
8. All infants should have serial clinical neurologic assessment.
9. For infants with Stage 2 or Stage 3 NE, further investigations should be performed to assist with prognosis. Every attempt should be made to co-ordinate appointments.
   • Where possible an EEG should be performed at approximately 7 days of age (Auckland Hospital ext. 7524).
   • Imaging ⁶  should be performed to assist with exclusion of haemorrhage and other intracerebral abnormalities.
   • Cerebral ultrasound scans provide little additional information regarding prognosis.  Doppler studies suggest that a resistive index of less than 0.5-0.6 is consistent with the diagnosis of HIE.
   • CT scanning may be useful to exclude haemorrhage and may assist with prognosis.  Ring Starship Hospital CT scanning on ext. 25132.
   • MRI may provide prognostic information.  Abnormalities of the thalami and basal ganglia are associated with an increased risk of subsequent abnormal developmental outcome.  Discuss with the on-duty paediatric radiologist at Starship Hospital.
     • Because MR demonstrates findings similar to CT and has greater inter-observer agreement, it appears that MR is a superior test to CT in determining brain abnormalities in the term neonate ⁷.
     • Furthermore, since MR eliminates the use of ionizing radiation, a putative cause of malignancy, it should be the standard in neonatal brain imaging.
10. Recruitment to the Selective Head Cooling Study has now been completed and results are awaited.

Long term follow up and audit of Perinatal Asphyxia outcome of at NWH

Full term infants who suffer from Grade 2 or 3 encephalopathy are known to have a high incidence of neurologic damage. A systematic follow up of these infants born at NWH is necessary to feed back to those involved with the initial care. In order to obtain this information ALL TERM AND POST TERM INFANTS WITH CLINICAL SEIZURES OR STAGE 3 encephalopathy should have a psychometric assessment at 18 months in the Child Development Unit at NWH.

This definition is clear cut and has the advantage of simplicity. Most of the infants with seizures will have had moderate-to-severe NE. Seizures due to metabolic problems or meningitis are rare - but these infants also frequently have an adverse outcome.

The parents of all term infants who have had clinical seizures should have a follow up process defined, preferably at a discharge planning meeting. Dependent on the clinical state and consultant decision these infants should have a psychometric assessment at 18 months of age, in the Child Development Unit at NWH. Referrals should be sent to Dr A Dezoete after the discharge planning meeting, with the name, address and telephone number of the infant's parents and a contact person (usually grandparent). If the paediatrician following these infants is not from NWH they should be notified of the provision of such an assessment and be told that this is done for audit purposes.

A neurological examination should be done at 12 months of age, either by the paediatrician who provided care in the neonatal period or the paediatrician providing care at 12 months of age. A copy of this neurologic examination should be sent to the Director of the Child Development Unit for inclusion in the annual report.

References