What every Intensivist should know about the role of ammonia in liver failure

Purpose: Acute liver failure (ALF) or acute-on-chronic liver failure (ACLF) patients have high short-term mortality and morbidity. In the context of liver failure, increased serum ammonia is associated with worse neurological outcomes, including high-grade hepatic encephalopathy (HE), cerebral edema, and intracranial hypertension. Besides its neurotoxicity, hyperammonemia may contribute to immune dysfunction and the risk of infection, a frequent trigger for multi-organ failure in these patients. Material and methods: We performed a literature-based narrative review. Publications available in PubMed® up to June 2023 were considered. Results: In the ICU management of liver failure patients, serum ammonia may play an important role. Accordingly, in this review, we focus on recent insights about ammonia metabolism, serum ammonia measurement strategies, hyperammonemia prognostic value, and ammonia-targeted therapeutic strategies. Conclusions: Serum ammonia may have prognostic value in liver failure. Effective ammonia targeted therapeutic strategies are available, such as laxatives, rifaximin, L-ornithine-L-aspartate, and continuous renal replacement therapy.