Malignant hyperthermia is diagnosed based on signs and symptoms, monitoring during and immediately after anesthesia, and lab tests to identify complications.

Susceptibility testing

Testing to find out if you're at increased risk of malignant hyperthermia (susceptibility testing) may be recommended if you have risk factors. Testing may include genetic testing or a muscle biopsy test.

  • Genetic testing. The gene change (mutation) that makes you susceptible to malignant hyperthermia is identified using genetic testing. A sample of your blood is collected and sent to a lab for analysis. Genetic testing can identify the gene change that shows you have the genetic disorder called malignant hyperthermia susceptibility (MHS).
  • Muscle biopsy (contracture test). In some cases, your health care provider may recommend a muscle biopsy if you're at risk of malignant hyperthermia. During this test, a small piece of muscle tissue is surgically removed for lab analysis. In the lab, the specimen is exposed to triggering chemicals for malignant hyperthermia to determine how the muscle contracts. Because this test must be done on muscle tissue immediately after removing it, travel to a specialized muscle biopsy center is necessary.


If you or someone in your family has malignant hyperthermia susceptibility (MHS) or you think you may be at risk of malignant hyperthermia, it's important to tell your health care provider and anesthesiologist before you get anesthesia. Drugs that do not trigger malignant hyperthermia may be used as part of your anesthesia.

Immediate treatment of malignant hyperthermia includes:

  • Medication. A drug called dantrolene (Dantrium, Revonto, Ryanodex) is used to treat the reaction by stopping the release of calcium into muscles. Other medications may be given to correct problems with a balance of the body's chemicals (metabolic imbalance) and treat complications.
  • Oxygen. You may have oxygen through a face mask. In most cases, oxygen is given through a tube placed in the windpipe (trachea).
  • Body cooling. Ice packs, cooling blankets, a fan with cool mist and chilled intravenous (IV) fluids may be used to help reduce body temperature.
  • Extra fluids. You may also get extra fluids through an intravenous (IV) line.
  • Supportive care. You may need to stay in the hospital in intensive care for a day or two to monitor your temperature, blood pressure, heart rate, breathing and response to treatment. Several lab tests will be done frequently to check the extent of any muscle breakdown and possible kidney damage. A stay in the hospital is usually needed until lab test results start to return to a standard range.

With treatment, malignant hyperthermia usually resolves within a few days.

Follow-up care

If you've experienced malignant hyperthermia due to certain anesthesia drugs, exercising during excessive heat and humidity could trigger another reaction. Talk to your health care provider about any precautions you should take.

Also, check with your health care provider to see if you should have genetic testing to determine if you have a genetic disorder that puts you at risk of malignant hyperthermia. Ask if close family members should also consider genetic testing.

If you have the genetic disorder MHS that puts you at risk of malignant hyperthermia, wear a medical alert bracelet or necklace. This lets health care providers know of your risk, especially in an emergency, when you may not be able to talk.

May 13, 2022

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