General anesthesia for dental treatment in a Williams syndrome patient with severe aortic and pulmonary valve stenosis: suspected episode of postoperatively malignant hyperthermia

A 28-month-old boy (height, 76 cm; weight, 9.4 kg) diagnosed as having Williams syndrome presented for dental care. We report a case of postoperatively suspected malignant hyperthermia after the administration of general anesthesia for dental treatment in this patient with severe supravalvular aortic stenosis and pulmonary artery hypoplasia. Anesthesia was maintained through the inhalation of nitrous oxide and sevoflurane with oxygen. The patient was hemodynamically stable and no other abnormalities were observed. After the completion of the dental treatment, he was transferred to the pediatric ward. On arrival at the ward, the patient’s core temperature increased to 39.5°C and tachypnea (RR, 30 breaths/min) was observed. The SPO2 during inhalation was slightly low (92%-93%). Serum biochemistry revealed an elevated CK level (1345 U/L) but no other abnormal findings. Twelve hours after the dental treatment, the patient’s core temperature fell to 37.4°C. After hospitalization for 4 days, the patient was discharged in good condition. In the present case, general anesthesia was employed for dental treatment despite severe supravalvular aortic stenosis and peripheral pulmonary artery hypoplasia, because conventional dental therapy was very difficult as a result of the patient’s mental retardation and hyperkinesia. The present case suggests that the use of volatile agents that could trigger malignant hyperthermia should be avoided wherever possible.