What Is Malignant Hyperthermia?
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Malignant Hyperthermia - Risk Factors, Symptoms, and Treatment

Published on Dec 16, 2022 and last reviewed on Jul 14, 2023   -  4 min read


Drugs taken for various purposes may sometime cause serious reactions. One such is malignant hyperthermia; read the article to know more about it.


Medications are prescribed and used by doctors to treat and manage several conditions. Before surgical procedures, specific medications are indulged in providing general anesthesia. This article describes a serious condition called malignant hyperthermia that occurs as a result of severe drug reactions.

What Is Malignant Hyperthermia?

Malignant hyperthermia is considered to be a genetic disorder, and it is characterized by severe reactions to specific drugs used for general anesthesia. The affected individual may have sudden muscle spasms, an increase in body temperature, etc.

Studies show that about one in every 30,000 adults who undergo surgical procedures under general anesthesia are affected by malignant hyperthermia. In addition, individuals of a young age are more commonly affected.

How Does Malignant Hyperthermia Occur?

Malignant hyperthermia mainly occurs due to changes or alterations in genes such as RYR1 (most common), CACNA1S, and STAC3. Mutation (change) in the RYR1 (type 1 ryanodine receptor) present on chromosome 19 usually results in 50 percent of cases of malignant hyperthermia. In addition, a person can inherit malignant hyperthermia from the affected parents, or it can arise due to genetic changes in that individual. Studies also show that men and women are equally affected by this condition.

What Is the Underlying Pathophysiology?

A person with an altered RYR1 gene may live everyday life without any signs of malignant hyperthermia. However, when this person is administered specific medications used for general anesthesia (anesthetics), then severe reactions happen. It is because a mutation in the RYR1 gene is responsible for causing excess production of calcium by the muscle cells.

The excess calcium loss from muscle cells results in abnormal muscle contractions, a rise in body temperature, and increased metabolism. Even worse complications may occur when muscle cells die and release potassium into circulating blood.

What Are the Risk Factors for Malignant Hyperthermia?

The following factors may put one at risk for malignant hyperthermia:

What Symptoms Indicate Malignant Hyperthermia?

The symptoms may vary in each individual and may arise during or after the procedure under general anesthesia. It includes:

  • A rise in heart rate.

  • Severe muscle spasms (contractions).

  • Rapid breathing.

  • Low oxygen and high carbon-dioxide levels in the body.

  • Abnormal heart rhythm.

Overtime, the following severe signs may occur:

How Does the Doctor Diagnose Malignant Hyperthermia?

If the affected individual does not inform before the procedure, it is difficult for the doctor to diagnose such conditions. Only after administering anesthetics do symptoms appear, and the doctor may suspect the individual to be affected by malignant hyperthermia.

On the other hand, if a patient priorly informs of any previous or family history and the doctor suspects malignant hyperthermia, they might advise the following tests to diagnose such conditions:

1. Genetic Testing - To check for any mutations or alterations in the genes (RYR1, CACNA1S, and STAC3) responsible for causing malignant hyperthermia, the healthcare specialist may draw blood from the suspected person’s vein in the arm and then sends the blood sample for further investigations.

2. Contracture Testing - These tests involve the evaluation of a sample of muscle tissue obtained from the suspected individual. The muscle sample under examination may be exposed to anesthetic agents or the chemicals present to determine any abnormal reaction or contraction happening in the sample. It includes:

  • Caffeine Halothane Contracture Test (CHCT) - In this method, caffeine and halothane is used to test the muscle sample.

What Are the Related Disorders?

Many conditions may resemble the symptoms of malignant hyperthermia, and it includes:

  • Exertional Rhabdomyolysis - It is a rare disorder characterized by skeletal muscle damage. It also causes excess creatinine kinase (CK) levels in the blood. Athletes and bodybuilders are at increased risk of exertional rhabdomyolysis. The central core disease mainly affects the skeletal muscles, causing pain and extreme weakness. In severe cases, facial muscles and muscles of the eyes may be involved, and the affected individual may have low muscle tone also.

  • Exertional Heat-Illness - The disorder affects the central nervous system and other organs of the body. In addition, multiple organ failures may occur with raised body temperature.

What Are the Complications?

If malignant hyperthermia is not treated immediately, it may result in the following:

  • Severe kidney damage or failure.

  • Severe bleeding.

  • Breakdown of muscle cells.

  • Liver failure.

  • Death.

How Is Malignant Hyperthermia Treated?

1) Dantrolene - If symptoms appear during the surgical procedure, the doctor might immediately use the classic drug of choice (Dantrolene) to treat malignant hyperthermia. Dantrolene is administered immediately to control the symptoms and to complete the surgical procedure.

2) Supportive Care - Other procedures followed to control the symptoms of malignant hyperthermia are:

  • Oxygen support through face masks or tracheostomy.

  • Ice packs or chilled fluids through IV (intravenous) to decrease the raised body temperature.

  • In addition, monitoring breathing, heart rate, and other vital signs are also responsible.

  • Avoiding strenuous physical activity and exposure to excessive heat is essential to prevent another malignant hyperthermia reaction.

How to Prevent Malignant Hyperthermia?

It is not possible to prevent genetic mutations. However, severe drug reactions can be prevented by informing the doctor before any surgical procedures. Therefore, an individual with a family history of malignant hyperthermia should tell the specialist about it. Doing so will allow the healthcare specialist to assess the individual’s health status and will look for alternative drugs and treatments. In addition, the doctor may avoid triggering medications such as Cocaine or Amphetamine during such surgical procedures.


A genetic condition, namely malignant hyperthermia, seems challenging for specialists. Diagnostic tests for these disorders are expensive and not available. An individual should notify the doctor of any family history or previous drug reactions. The doctor may also use non-triggering anesthetics for a suspected individual to avoid complications.

Last reviewed at:
14 Jul 2023  -  4 min read




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