Hyperammonemia in the Critically Ill

• Patients with acute hyperammonemia have significant morbidity and mortality 
• Fulminant hepatic failure is the most common cause of acute hyperammonemia in adult ICUs
• Other causes include TPN, GI hemorrhage, steroid use, trauma, multiple myeloma, infection with urease-splitting organisms, and drugs (salicylates, valproate) 
• Cerebral edema, intracranial hypertension, seizures, and herniation are the most significant effects
• Initial management should focus on treating intracranial hypertension - mannitol, hypothermia, N-acetylcysteine have been used
• Lactulose has not been shown to reduce mortality in acute hyperammonemia but is unlikely to be harmful

Clay AS, Hainline BE. Hyperammonemia in the ICU. Chest 2007;132:1368-1378.