Sevoflurane-induced malignant hyperthermia during cardiopulmonary bypass and moderate hypothermia.

A 56-year old man was admitted for elective mitral valve repair and coronary artery bypass surgery due to mitral valve leakage and unstable angina. After induction of anaesthesia he developed a combined metabolic and respiratory acidosis. Different diagnosis were considered and we decided to treat the patient with dantrolene due to suspicion of malignant hyperthermia (MH). The patient received one dose of dantrolene 2,5 mg/kg during cardiopulmonary bypass (CPB) and a second dose of dantrolene 2,5 mg/kg during weaning from CPB. The first arterial blood gas sample taken in the intensive care unit showed relapse of the acidosis and we administered an infusion of 150 mg dantrolene over 3 hours. The patient gradually recovered without sequel and MH was verified by muscle biopsy testing.