Assessment of masseter spasm complicated by a faulty temperature probe.

During palatoplasty on a 9-year-old girl with no personal or familial history of malignant hyperthermia, the temperature monitor reported an increase in temperature. Additionally, the surgeon thought the patient's jaw muscle was in spasm. While preparations were made for treatment of malignant hyperthermia, the temperature probe was tested and found to be defective. When it was replaced, the patient's temperature was within normal range. When the temperature probe was tested 6 days later, it was working properly. The cause of the problem may have been moisture in the connection between the probe and the exterior cable, which eventually evaporated. Decision algorithms can assist in such situations to distinguish between a medical problem and a mechanical problem with the monitor.