Asymptomatic methaemoglobinaemia and its implications.

Anaesthetists are well trained to detect subtle skin signs of life-threatening situations such as cyanosis in hypoxia. However, cyanosis resulting from drug-induced, asymptomatic methaemoglobinaemia is rare and is likely to go undetected preoperatively. Patients presenting with asymptomatic methaemoglobinaemia may, therefore, offer a dramatic challenge to the unprepared anaesthetist. We report a case of methaemoglobinaemia secondary to dapsone ingestion that was diagnosed intraoperatively.