New Guidance Focused on Genetic Testing for Malignant Hyperthermia, a Potentially Fatal Anesthesia Reaction

CHICAGO – Guided by a few simple screening questions, genetic testing can play a key role in identifying patients at risk of malignant hyperthermia (MH): a rare, potentially life-threatening reaction to inhaled anesthetics. An expert panel outlines an updated approach to assessing MH risk in North American patients, according to a special article in the April 2026 issue of Anesthesiology, the peer-reviewed medical journal of the American Society of Anesthesiologists (ASA). The article is being co-published in the Canadian Journal of Anesthesia/Journal canadien d’anesthésie.

"Identifying patients potentially at risk for MH is a critical priority for anesthesiologists, but challenging to diagnose,” said study lead author Sheila Riazi, M.D., University Health Network and the University of Toronto. "We outline a stepwise approach to identifying patients and families who might be at risk, highlighting the use of genetic testing to identify MH-causing mutations."

Patients with MH have genetic mutations affecting muscle metabolism, leading to dangerously high body temperature and other serious reactions when exposed to certain anesthesia drugs – including widely used inhaled anesthetics. Although effective treatments are available, MH can be fatal – making it essential to identify patients who are MH-susceptible (MHS). Most MHS patients can safely undergo surgery with the use of alternative approaches, such as total intravenous anesthesia. It is estimated that the prevalence of MH ranges from 1 in 2,000 and 1 in 3,000 to as high as 1 in 800.

Assessment of MH risk is challenging. Accurate tests of the muscle dysfunction are available but invasive, expensive, and – in North America – available at only a few specialized centers. Genetic testing may provide an alternative approach to identifying MHS patients, according to the new guidance.

Dr. Riazi and coauthors outline a practical approach to identifying patients who should be targeted for genetic testing. The decision depends on the anesthesiologist asking three simple questions:

• "Do you have MHS or have you had an MH reaction?"
• "Does someone in your family have MHS or have they had an MH reaction?"
• "Have you or a family member undergone genetic testing for MHS? If yes, what were the test results?"

The answers will guide the anesthesiologist's decision-making as to next steps. Patients with past episodes of MH reactions "should be managed as if they are MHS" and should undergo surgery with the use of "non-triggering" anesthetics. Patients with any personal or family history of MH may also undergo genetic testing for MH-related genes. If testing detects an MH gene variant, family members should also be tested.

The authors’ recommendation reflects the fact that "genetic testing is becoming so inexpensive that it is increasingly affordable to do the testing as a screening tool rather than just as a diagnostic tool," they wrote. However, they note that the rate of MH after a positive genetic test can be "surprisingly low" in patients with no other history or risk factors.

In some situations, further evaluation for definitive diagnosis of MH may be considered. The article provides anesthesiologists with a detailed decision tree to guide patient evaluation and management. The article also discusses other scenarios, such as delivery of an infant with possible MHS. If one parent has an MHS-causing gene, there is a 50% chance that the infant may have the same mutation.

"Even with increased emphasis on safety, it is critical to recognize that risk can never be reduced to zero," Dr. Riazi said. The authors’ intent is that their proposed approach will help anesthesiologists clarify their clinical decision-making and appropriately balance the risks and benefits of inhaled anesthetics to support surgery.

The Malignant Hyperthermia Association of the United States (www.mhaus.org) provides further information and education on MH and related disorders.

THE AMERICAN SOCIETY OF ANESTHESIOLOGISTS
Founded in 1905, the American Society of Anesthesiologists (ASA) is an educational, research and scientific society with more than 60,000 members organized to advance the medical practice of anesthesiology and secure its future. ASA is committed to ensuring anesthesiologists evaluate and supervise the medical care of all patients before, during, and after surgery. ASA members also lead the care of critically ill patients in intensive care units, as well as treat pain in both acute and chronic settings.

For more information on the field of anesthesiology, visit the American Society of Anesthesiologists online at asahq.org. To learn more about how anesthesiologists help ensure patient safety, visit asahq.org/madeforthismoment. Follow ASA on Facebook, X, Instagram, Bluesky, and LinkedIn.

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