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What to Know About Malignant Hyperthermia

Medically reviewed by Darragh O'Carroll, MD — By Catherine Crider on September 29, 2022A major risk of common anesthesia is malignant hyperthermia, which is a severe reaction to some of the drugs that healthcare professionals may administer to put you to sleep before surgery. This article will provide information about malignant hyperthermia, what causes this severe drug reaction, and who is most at risk. This will help guide you in discussing this possible risk with your doctor or anesthesiologist before going into any surgical procedure.

What is malignant hyperthermia

Malignant hyperthermia is a severe reaction to some anesthesia drugs commonly used during surgery. It affects some individuals who have a genetic predisposition to it. People who experience this reaction may have a rapid increase in heart rate and body temperature when exposed to certain anesthesia drugs. Their breathing rate may increase, and they may experience a breakdown of muscle fibers and an increase in acid levels in their blood. Even when treated properly, malignant hyperthermia can cause death. It’s important to take this risk seriously.

What causes malignant hyperthermia

Malignant hyperthermia has been associated with a variety of genetic changes. One of the more commonly affected genes is RYR1. CACNA1S and STAC3 are affected less often. In most cases, people inherit the gene for malignant hyperthermia susceptibility (MHS). However, it can sometimes be the result of a random genetic change. MHS is passed down through dominant inheritance, which means that children of adults with a gene pattern for MHS have a 50% chance of inheriting it. If a person has not previously developed symptoms while under anesthesia, their relatives may not be aware of the risk.

What drugs can trigger malignant hyperthermia

The following types of anesthesia drugs can trigger malignant hyperthermia:inhaled general anestheticshalothanedesfluraneenfluraneetherisofluranesevofluranesuccinylcholine You can consult with your doctor, surgeon, and anesthesiologist about any concerns you may have before a surgical procedure.

What are the early symptoms of malignant hyperthermia

Most of the time, no signs or symptoms of malignant hyperthermia occur until a person receives certain anesthesia drugs. Once a person has ingested the drugs (and for a short time afterward), the following symptoms may indicate malignant hyperthermia:increased heart rateIncreased carbon dioxide production muscle rigidity rapid increase in body temperature However, symptoms of malignant hyperthermia may not occur with every exposure to triggering drugs.

Are there later signs of malignant hyperthermia

Without immediate treatment, malignant hyperthermia can lead to more serious complications such as:muscle breakdown cardiac arrestbrain damage internal bleedingfailure of other body systemsseizurescoma

How is malignant hyperthermia diagnosed

Genetic testing can determine whether you have MHS. Individuals with a family history of malignant hyperthermia may wish to have genetic testing before undergoing anesthesia. A select few laboratories can perform a caffeine halothane contracture test, which involves a muscle biopsy. Laboratory staff will expose the live muscle sample to halothane and caffeine to analyze its reaction to anesthesia gas. In many cases, there are no indicators of malignant hyperthermia before it occurs. Monitoring during and after surgery can help surgical staff identify signs of malignant hyperthermia so that they can treat it immediately. Even if you have not experienced malignant hyperthermia during past surgeries, you may be at risk. You may not receive a diagnosis until you’ve had several surgeries and symptoms finally appear.

How is this different from neuroleptic malignant syndrome

At first glance, malignant hyperthermia and neuroleptic malignant syndrome might seem similar. They share some symptoms, such as changes in body temperature and rigid muscles, and treatment for either condition requires stopping the triggering medication. However, there are several large differences between them. The two conditions are triggered by different drugs. While some anesthesia drugs can trigger malignant hyperthermia, neuroleptic medications bring on neuroleptic malignant syndrome. Healthcare professionals most commonly prescribe these to treat schizophrenia and other neurological, psychological, or emotional disorders. Additionally, neuroleptic malignant syndrome tends to appear slowly over several days, while malignant hyperthermia comes on more quickly. The appropriate medications to treat the two conditions also differ.

How do you treat malignant hyperthermia

Being vigilant is key to treating malignant hyperthermia. Without prompt treatment, complications from malignant hyperthermia can be life threatening. If signs of malignant hyperthermia begin while you are under anesthesia, your surgical team will immediately administer the drug dantrolene and stop any drugs that are triggering the reaction. The surgeon will attempt to end the surgery as quickly as possible. Any symptoms or side effects due to malignant hyperthermia should also be addressed immediately. This could involve using any of the following:ice packscold fluid IVs to cool your bodyextra oxygen through a maskmedications to address an irregular heartbeat Once healthcare professionals have stabilized your condition, you will usually need to spend a day or more in the intensive care unit for monitoring.

Takeaway

Malignant hyperthermia is a potentially life threatening reaction to some anesthesia drugs. To help prevent malignant hyperthermia, it’s important to let your doctor know if you have a family history of this condition or a history of negative reactions to anesthesia medication. If you believe you may have a genetic predisposition to malignant hyperthermia, genetic testing is available to find out. It’s important to raise any questions or concerns you have about surgical procedures with your surgeon or anesthesiologist. They can advise you on any potential risks. Last medically reviewed on September 29, 2022

How we vetted this article

SourcesHistoryHealthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.Allen GC, et al. (1998). The sensitivity and specificity of the caffeine-halothane contracture test: A report from the North American Malignant Hyperthermia Registry. The North American Malignant Hyperthermia Registry of MHAUS.
pubs.asahq.org/anesthesiology/article/88/3/579/36600/The-Sensitivity-and-Specificity-of-the-CaffeineAmeer MA, et al. (2022). Neuroleptic medications.
ncbi.nlm.nih.gov/books/NBK459150/Chung E, et al. (2022). Enflurane.
ncbi.nlm.nih.gov/books/NBK554595/Dobson GP. (2020). Trauma of major surgery: A global problem that is not going away.
ncbi.nlm.nih.gov/pmc/articles/PMC7388795/Edgington T, et al. (2022). Sevoflurane.
ncbi.nlm.nih.gov/books/NBK534781/Hager H, et al. (2022). Succinylcholine chloride.
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brighamandwomens.org/neurology/critical-care-neurology/neuroloptic-malignant-syndrome-nmsRatto D, et al. (2022). Dantrolene.
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ncbi.nlm.nih.gov/books/NBK482282/Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available. Current Version Sep 29, 2022 By Catherine Crider Edited By Mike Hoskins Medically Reviewed By Darragh O'Carroll, MD Copy Edited By Jill Campbell Share this articleMedically reviewed by Darragh O'Carroll, MD — By Catherine Crider on September 29, 2022

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