[A case of malignant hyperthermia with evident symptoms in the postoperative period]

A 36-year-old man (185 cm tall, weighing 85 kg) was scheduled for fixation of a right carpal bone fracture. He had no operative history, and his preoperative laboratory data were normal. A laryngeal mask was inserted after intravenous propofol and fentanyl administration without a muscle relaxant. Anesthesia was maintained by sevoflurane in a mixture of air and oxygen. A tourniquet was placed on the right upper arm. One hour after the operation, his heart rate increased to 90-100 beats x min(-1) from 70-80 beats x min(-1) at the start of the operation, and tachycardic continued, even after release of the tourniquet. Although end-tidal CO2 was 50-60 mmHg, his body temperature remained 37.6 degrees C, and neither muscle stiffness nor brown urine was observed. The duration of the operation and the duration of anesthesia were 2 hours 40 min and 4 hours, respectively. The patient went back to the ward without myalgia after removal of the laryngeal mask. On the postoperative day one, the patient had brown urine. On the postoperative day 2, he experienced myalgia of the upper and lower extremities and masseter muscle. On the postoperative day 3, myoglobinuria was detected. As in this case, although evident symptoms of malignant hyperthermia are not always observed during operations, some cases show obvious symptoms during the postoperative period. Thus, it is important to be aware of the symptoms of malignant hyperthermia postoperatively for early diagnosis and treatment.