Seizures, neonatal

P90

DESCRIPTION

Neonatal seizures are usually secondary to a serum biochemical disorder or an underlying brain disturbance/injury/malformation. Seizures may be subtle due to the relatively underdeveloped cortex. Seizures persist when limbs are flexed (as opposed to jitteriness).

The most likely causes are:

  • perinatal asphyxia,
  • hypocalcaemia,
  • birth trauma,
  • hypomagnesaemia,
  • intracranial haemorrhage,
  • hyponatraemia,
  • meningitis,
  • hypoglycaemia,
  • narcotic or alcohol withdrawal syndrome,
  • inborn errors of metabolism,
  • pyridoxine deficiency,
  • CNS developmental abnormalities.

DIAGNOSTIC CRITERIA

Categories of convulsions

  • Subtle seizures:
    • tonic deviation of the eyes,
    • ‘swimming’ movements of the arms,
    • fluttering of the eyelids,
    • ‘cycling’ movements of the legs,
    • sucking and chewing movements,
    • apnoea,
    • vasomotor changes.
  • Tonic clonic movements.
  • Focal clonic movements.
  • Myoclonic movements.
  • Tonic movements/posturing.

GENERAL AND SUPPORTIVE MEASURES

  • Identify and treat the underlying cause, e.g. meningitis and hypoxic-ischaemic encephalopathy.
  • Ensure an open airway and administer oxygen, if necessary.
  • Nurse in neutral thermal environment.
  • Ensure adequate nutrition and hydration.
  • Monitor and maintain within accepted physiological range:
    • respiration,
    • acid-base status,
    • heart rate,
    • electrolytes,
    • blood pressure,
    • minerals,
    • blood gases,
    • blood glucose,
    • SaO₂,
    • haematocrit,
    • body temperature.

MEDICINE TREATMENT

Seizure Control

Administer anticonvulsants with monitoring of cardiorespiratory function.

Phenobarbitone

  • Phenobarbitone, IV.
    • Loading dose: 20 mg/kg administered over 10 minutes.
    • Refractory seizures: Additional 10 mg/kg/dose up to 40 mg/kg.

Maintenance:

  • Phenobarbitone, IV or oral
    • 4 mg/kg/day beginning 12–24 hours after the loading dose.

Seizures refractory to phenobarbitone, should be admitted to a high or intensive care unit.

Cardiorespiratory support is usually required in this category of infants.

For seizures refractory to phenobarbitone use:
Lignocaine (lidocaine)

For term normothermic neonates:

  • Lignocaine (lidocaine), IV.
    • Loading dose: 2 mg/kg administered over 10 minutes.
    • Follow with a continuous infusion of:
      6 mg/kg/hour for 6 hours, then,
      4 mg/ kg/hour for 12 hours, then,
      2 mg/kg for 12 hours.
    • If seizures are well controlled, slow taper lignocaine (lidocaine) over 12 hours.

For preterm neonates:

A safe dose of lignocaine (lidocaine) in preterm neonates has not been established but the following dosing schedule has been used.

  • Lignocaine (lidocaine), IV.
    • Loading dose: 2 mg/kg administered over 10 minutes.
    • Follow with a continuous infusion of 3 mg/kg/hour for 3 days.
    • Gradually taper lidocaine over next 2 days.

Do not use lidocaine if phenytoin was given.
Do not use lidocaine for seizures in newborns with congenital heart disease, dysrhythmias, acute heart failure and shock.
  • A safe lignocaine (lidocaine) dosing regimen for term infants undergoing hypothermia treatment for hypoxic ischaemic encephalopathy has not been established.
  • Clearance of lignocaine (lidocaine) is slower in hypothermic neonates and preterm infants. There is a risk of accumulation.
  • Start tapering earlier than 3 days if seizures are well controlled.
  • Continuous monitoring of ECG, heart rate and blood pressure is mandatory if lignocaine (lidocaine) is used.
  • Dysrhythmias and bradycardia are the main side effects of lignocaine (lidocaine). Life threatening dysrhythmias may indicate lignocaine (lidocaine) toxicity.

Lignocaine (lidocaine) toxicity:

  • Lipid emulsion 20%, IV, 1.5 mg/kg administered over 1 minute.
    • Follow with a continuous infusion of 0.25 mL/kg/minute for 30 minutes. (See Referral section.)

Pyridoxine deficiency:

  • Pyridoxine, IV/IM, 20 mg/kg.

Maintenance anticonvulsant therapy

Maintenance anticonvulsant therapy is usually considered for neonates with underlying brain damage due to hypoxic ischaemic encephalopathy, meningitis, intracranial haemorrhage or birth trauma.
Continue until neonate is seizure-free for 2 weeks, then slowly taper to stop.
If seizures recur during tapering of anticonvulsant therapy, continue with maintenance therapy.
Follow-up by medical practitioner or at clinic/hospital after discharge

Note:
Patients with head or whole body cooling should have an adjustment of the anticonvulsant doses.

Hypocalcaemia

Serum total calcium ≤ 1.8 mmol/L, or ionized calcium < 0.7 mmol/L.

  • Calcium gluconate 10%, IV, 100–200 mg/kg/dose administered over 10 minutes.
    • Dilute 1:4 with dextrose 5% water.
    • Administer under ECG monitoring over 5 minutes (preferred) or until seizure ceases. Repeat if necessary.
      (1 mL of 10% calcium gluconate = 100 mg calcium gluconate)

Hypoglycaemia

Serum glucose < 2.6 mmol/L.

  • Dextrose, IV as bolus, 250–500 mg/kg.
    • Follow with 6–12 mg/kg/minute or more until blood glucose is within the physiological range. (10% Dextrose = 10g dextrose/100mL).

Hypomagnesaemia

Serum magnesium < 0.6 mmol/L.

  • Magnesium sulphate 50%, IV, 0.25 mL/kg administered slowly over 3 minutes as a single dose.

REFERRAL

  • Seizures not responding to adequate therapy.
  • Seizures where the underlying cause is unclear.
  • Refractory cases for further treatment and aEEG monitoring.
  • Lidocaine toxicity.