TY - JOUR T1 - Metabolic encephalopathy caused by nitrous oxide (‘laughing gas’) induced hyperammonaemia JF - BMJ Case Reports JO - BMJ Case Reports DO - 10.1136/bcr-2019-232163 VL - 12 IS - 11 SP - e232163 AU - Marissa Ginette Danielle Vive AU - Galia Valentinova Anguelova AU - Sjoerd Duim AU - Herman Marcel André Hofstee Y1 - 2019/11/01 UR - http://casereports.bmj.com/content/12/11/e232163.abstract N2 - 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. ER -