Hyperammonaemia / metabolic crisis

Paediatric emergency management · Metabolic · Emergency

Suspect an inborn error of metabolism in a neonate or child with encephalopathy, vomiting, tachypnoea (respiratory alkalosis) or unexplained coma. Send an urgent free-flowing ammonia on ice, plus gas, glucose, lactate and ketones.

Immediate — stop protein, reverse catabolism

• Stop all protein and enteral feeds.
• Start a high-rate 10% dextrose infusion (aim glucose delivery 8–10 mg/kg/min), add insulin if hyperglycaemic, to switch off catabolism.
• Support the airway and treat cerebral oedema.

• Give ammonia-scavenging drugs (sodium benzoate with or without sodium phenylacetate, plus arginine) as directed by the metabolic team.
• Add L-carnitine if an organic acidaemia is suspected.

Escalate

• Ammonia above about 400–500 micromol/L, or rising, or coma → urgent haemodialysis (clears ammonia far faster than scavengers); haemofiltration if dialysis is not available.
• Contact the metabolic team and a dialysis-capable centre early.