A 26-year-old man presented at the emergency department with confusion and decreased consciousness after several days of vomiting. In the preceding 6 months, he had used a 2-litre tank of nitrous oxide (N2O) weekly. His metabolic encephalopathy was caused by hyperammonaemia which probably resulted from interference of N2O-induced vitamin B12 deficiency with ammonia degradation. A catabolic state might have contributed to the hyperammonaemia in this case. After treatment with vitamin B12 and lactulose, both his consciousness and hyperammonaemia improved. He reported no residual complaints after 3 months of follow-up. Since N2O is increasingly used as a recreational drug, we recommend considering hyperammonaemia as a cause of metabolic encephalopathy in cases of N2O use and altered mental status.
Brain Diseases, Metabolic/chemically induced , Confusion/diagnosis , Consciousness Disorders/diagnosis , Hyperammonemia/chemically induced , Nitrous Oxide/adverse effects , Adult , Brain Diseases, Metabolic/drug therapy , Confusion/etiology , Consciousness Disorders/etiology , Diagnosis, Differential , Gastrointestinal Agents/administration & dosage , Gastrointestinal Agents/therapeutic use , Humans , Hyperammonemia/complications , Lactulose/administration & dosage , Lactulose/therapeutic use , Male , Treatment Outcome , Vitamin B 12/administration & dosage , Vitamin B 12/therapeutic use , Vitamin B 12 Deficiency/complications , Vitamin B Complex/administration & dosage , Vitamin B Complex/therapeutic use , Vomiting/diagnosis
