Malignant hyperthermia (MH) is among the most feared complications of general anesthesia. As the name implies, malignant hyperthermia patients get very, very hot. The hotter they get, the more likely they are to die. Does inadequate temperature monitoring contribute to patient mortality? Dr. Marilyn Green Larach, The North American Malignant Hyperthermia Registry of the Malignant Hyperthermia Association of the United States, Pittsburgh, Pennsylvania, and the Department of Anesthesiology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, and colleagues from Olympia Anesthesia Associates, Olympia, Washington, the Department of Anesthesiology and Pain Medicine, University of California at Davis, Davis, California, and the Department of Public Health Sciences, Penn State College of Medicine, Hershey, Pennsylvania, evaluated adverse metabolic or muscle reaction to anesthesia (AMRA) reports received by The North American Malignant Hyperthermia Registry (Registry) of the Malignant Hyperthermia Association of the United States (MHAUS) between January 1, 2007, through December 31, 2012, to see whether inadequate temperature monitoring was associated with an increased risk of dying from an episode of MH. The results of this analysis are published in this month’s issue of Anesthesia and Analgesia and summarized in the article titled “Malignant Hyperthermia Deaths Related to Inadequate Temperature Monitoring 2007-2012: A Report from The North American Malignant Hyperthermia Registry of the Malignant Hyperthermia Association of the United States.”
Reports of 189 AMRA episodes came from the United States and Canada, but only 84 met study inclusion criteria. The first sign of fatal MH events occurred >30 minutes after anesthesia induction. Deaths occurred in patients whose peak temperature was ≥38.9°C. Of the 9 patients whose temperature was >41°C, only 2 had core temperature monitoring, and both of those patients survived. Core temperature monitoring significantly contributed to survival: 30% of patients whose temperature was not monitored died from an MH episode, 21% died if only their skin temperature was monitored, but only 2% (1 patient) died when core temperature was monitored.
The study analysis concludes that widespread use of core temperature monitors for patients under general anesthesia would increase survival rates from an MH episode. Though temperature elevation might be a late sign on the cellular level, temperature elevation better separated patients who would live and die than other findings like heart rate or CO2. The American Society of Anesthesiologists states that every patient receiving anesthesia shall have temperature monitored when clinically significant changes in body temperature are intended, anticipated or suspected. Based on the findings of an earlier study, the MHAUS recommends that an electronic temperature probe should be used for all patients whose anesthetic duration exceeds 30 minutes. Because of the study being published this month, MHAUS is reformulating its temperature monitoring policy to call for core electronic temperature monitoring for all general anesthetics lasting more than 30 minutes in duration. This reformulation has not been officially adopted as yet.
Dr. Steven L. Shafer, Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, California, and colleagues from the Department of Anesthesia, University of Iowa, Iowa City, Iowa, and the Department of Anesthesiology, Mayo Clinic College of Medicine, Jacksonville, Florida, note in “Deadly Heat: Economics of Continuous Temperature Monitoring During General Anesthesia,” the accompanying editorial, that electronic temperature probes cost about $6.00. Even though MH is rare, at $6.00 per patient it makes economic sense, as well as medical sense, to routinely monitor all patients electronically. “If you don’t monitor core temperature routinely, start today. Do it right, with a continuous electronic measurement of core temperature. Tell risk management at your facility that every patient deserves the benefits of continuous core temperature monitoring, and that the economic risks of not monitoring are easily outweighed by the economic benefit in lives saved. This is better than explaining to patients, parents, or the next of kin, why you chose to save $6.”