Neonatal hyperammonaemia — RACP Paediatrics MCQ

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HardNeonatalNeonatal hyperammonaemiaRACP Paediatrics

A term neonate on day 3 develops poor feeding, lethargy, and seizures. Blood gas shows severe metabolic acidosis with high anion gap. Ammonia is 800 µmol/L (normal <80). Glucose is normal. What is the most important immediate step?

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Correct answer: D — Stop feeds + IV dextrose + ammonia level

Severe hyperammonaemia (>200 µmol/L) in a neonate is a metabolic emergency. Immediate management includes stopping all protein intake, providing IV dextrose (to suppress catabolism), and measuring ammonia levels. Sodium benzoate and/or sodium phenylbutyrate (nitrogen scavengers) should be given. Haemodialysis/haemofiltration is indicated if ammonia >500 µmol/L or rising despite medical management.

Reference: RCH Melbourne – 2023 – Metabolic Emergency CPG; RACP Paediatric Curriculum – Metabolic