New genetic test may detect risk of malignant hyperthermia (MH) from anesthesia

A rare but potentially life-threatening inherited condition called malignant hyperthermia (MH) may strike surgical patients who receive common drugs for general anesthesia.

Usually there is no outward sign of a problem before the drugs are given, but the drugs may trigger abnormal metabolic responses, such as a rapid rise in body temperature, muscle rigidity and other complications that may constitute a medical emergency.

Approximately one in 10,000 persons have a susceptibility to MH; most will not know this unless they receive general anesthesia. Currently, the only test for MH susceptibility requires a muscle biopsy done at a few specialized diagnostic centers. However, a newly offered genetic test requires only a blood sample from a patient suspected to be at risk for MH. The test detects 25 to 50 percent of the mutations known to make one susceptible to the condition. If physicians know that a patient has this genetic susceptibility, they can substitute other anesthesia drugs when surgery is required.

Ronald S. Litman, D.O., a pediatric anesthesiologist at The Children's Hospital of Philadelphia, is the lead author of a review article on MH in the June 15 Journal of the American Medical Association. That article summarizes current knowledge of MH and describes the new genetic test, which is expected to increase in accuracy over time. (The journal's patient page in the same issue provides a brief overview of MH.)

Dr. Litman is a nationally recognized expert on MH, having chaired panels on the topic at anesthesiology conferences. He also serves on a national emergency hotline for physicians, sponsored by the Malignant Hyperthermia Association of the United States.