Malignant hyperthermia in a patient with Graves' disease during subtotal thyroidectomy

We report the case of a 31-year-old man with Graves' disease who manifested malignant hyperthermia during subtotal thyroidectomy. His past medical his tory and family history were unremarkable. Before surgery, his condition wa s well controlled with propylthiouracil, beta -adrenergic blocker and iodin e. During the operation, anesthesia was induced by intravenous injection of vecuronium and thiopental, followed by suxamethonium for endotracheal intu bation. Anesthesia was maintained with nitrous oxide and sevoflurane. One h our after induction of anesthesia, his end tidal carbon dioxide concentrati on (ETCO2) increased from 40 to 50 mmHg, heart rate increased from 90 to 10 0 beats per min and body temperature began to rise at a rate of 0.3 degrees C per 15 min. Suspecting thyroid storm, propranolol 0.4 mg and methylpredui solone 1,500 mg were administered, which, however, had little effect. Despi te the lack of muscular rigidity, the diagnosis of malignant hyperthermia w as made based on respiratory acidosis. Sevoflurane was discontinued and dan trolene was given by intravenous bolus. Soon after the treatment, ETCO2, he art rate and body temperature started to fall to normal levels. His laborat ory findings showed abnormally elevated serum creatine phosphokinase and my oglobin but normal thyroid hormone levels. Since dantrolene is efficacious in thyrotoxic crisis and malignant hyperthermia, an immediate intravenous a dministration of dantrolene should be considered when a hypermetabolic stat e occurs during anesthesia in surgical treatment for a patient with Graves' disease.