Diagnosis and early management of acute hyperammonaemia

Abstract

Acute hyperammonaemia is a consequence of inborn defects of urea cycle or acute liver damage. Clinical presentation varies considerably with the age of the af ected individual and includes nausea, vomiting, neuro-psychiatric symptoms, convulsions and progressive lethargy with a deepening coma. Ammonia concentration above 200 μM is a medical emergency and requires prompt treatment, regardless of its aetiology. h e acute management includes restriction of protein intake, glucose infusion sui cient to maintain anabolic state, administration of ammonia scavengers (sodium benzoate, sodium phenylacetate, sodium phenylbutyrate), administration of urea cycle substrates and haemodialysis when the concentration of ammonia is exceedingly high or does not respond promptly to the medical treatment. Elevated ammonia concentration is neurotoxic and causes irreversible glial and neuronal damage resulting in cerebral oedema with poor outcome. Early diagnosis and prompt treatment are crucial and may considerably improve the clinical course.