Test for malignant hyperthermia?
A healthy 8-year-old boy needs elective oral surgery for excision of an extra tooth. His paternal great-great-uncle died of suspected malignant hyperthermia (MH). The boy's mother has had two cesarean sections and his father has had oral surgery several times, all without incident. When the patient's younger brother had a tooth removed at the age of 3 years because of a dental abscess, he was sedated with chloral hydrate. Since MH is inherited as an autosomal dominant disorder and neither parent has had a problem with anesthesia, is it safe to conclude that the 8-year-old does not have the trait? Would you test this patient for MH via muscle biopsy or encourage the oral surgeon to use conscious sedation with chloral hydrate?—Nathalie May, MD, Narberth, Pa.
This patient should not be tested, as he has a very low likelihood of susceptibility to MH. The absence of other cases in the family is reassuring given that, as stated, MH is inherited as an autosomal dominant disorder. Furthermore, it is impossible to know if the great-great-uncle truly had MH or died of other causes of hyperpyrexia, such as sepsis, or other complications of anesthesia. Testing by muscle biopsy with the caffeine-halothane contracture test (CHCT) would be indicated if a close relative has had MH or is susceptible based on testing. The biopsy and testing would need to be done at an approved research center, of which there are only four in the United States.
It should be noted that even a patient who is susceptible to MH could safely have oral surgery with local anesthesia or general anesthesia using nontriggering anesthetics, such as IV medications and nitrous oxide. The Malignant Hyperthermia Association of the United States has a Web site (www.mhaus.org) with a registry, answers to frequently asked questions, and helpful recommendations.—Susan Kashaf, MD, MPH (137-6)