Characteristics and outcomes of critically ill patients with severe hyperammonemia

PurposeTo determine the etiology and outcomes of critically ill patients with severe hyperammonemia.Materials and methodsRetrospective observational study of adults (18 years or older) admitted to a MICU from 2007 to 2016 who had a serum ammonia level >180 μmol/L (3 times the upper limit of normal).ResultsThe 78 patients (45 male, 32 female) had a median age of 52 (interquartile range [IQR] 46–58) years. Hyperammonemia occurred most often with acute-on-chronic liver failure (ACLF) (49 %) or decompensated cirrhosis (27 %) and less often as a consequence of prior gastric bypass (9%), acute hepatic failure (6%), or valproic acid (3%). Median serum ammonia level was 201 μmol/L (IQR 126–265, range 18–736) on admission, with peak value of 245 μmol/L (IQR 205–336, range 185–842). Fifty (64%) patients died during the hospitalization. Cerebral edema was documented in 8 (10%) patients, only one of whom survived. Six of the 8 patients with cerebral edema had hyperammonemia related to ACLF, giving an incidence of 14% in this subset of patients. Neither mortality nor cerebral edema was associated with peak ammonia level.ConclusionsCritically ill patients with severe hyperammonemia have a high mortality rate and are at risk of developing cerebral edema.