Malignant Hyperthermia

What is Malignant Hyperthermia?

Malignant hyperthermia is a very rare but life-threatening reaction to anesthetics that can make otherwise minor surgery deadly. There are 80 distinct genetic patterns known to predispose patients to this condition, so it’s possible to test patients for the condition. About 50% of the children or siblings of a person confirmed to have malignant hyperthermia will also have it.

Only certain anesthetics and drugs trigger a reaction, so patients can still work with an experienced anesthesiologist to make surgery safer. The biggest danger comes when a patient goes in for an emergency procedure without being able to notify the healthcare professionals of their condition.

What are the Symptoms of Malignant Hyperthermia?

A patient with malignant hyperthermia will have no signs or symptoms of the condition until a critical reaction occurs upon exposure to an inhaled anesthetic or the muscle relaxant known as succinylcholine.

Symptoms associated with the reaction are:

  • A sudden rise in body temperature to 105 degrees F or higher (40.5 °C)
  • Stiffness and rigidity through the muscle groups
  • Achiness and tenderness of the muscles if the patient is awake
  • Internal bleeding and rarely external bleeding from the nose
  • Cardiac arrest and brain damage when emergency treatment is not given.

Malignant Hyperthermia Causes

The causes of malignant hyperthermia are connected to a genetic defect that is inherited. It is called a pharmacogenetic disorder because the reaction is caused by specific drugs. Those with a parent, child, or sibling with malignant hyperthermia, have a 50% chance of developing this condition at some point. Close relatives like uncles, aunts, and grandchildren, typically have a 25% chance of developing malignant hyperthermia. Also, men are typically more likely to have an episode of malignant hyperthermia than women. Children are more likely to suffer reactions during surgery. A malignant hyperthermia reaction might not be triggered during someone’s first surgery, but the risk of reaction remains possible during future surgeries. In some rare cases, those with malignant hyperthermia have exhibited signs of a reaction after undertaking intense physical exercise and activity.

How is Malignant Hyperthermia Treated?

Since many cases are not discovered until a reaction interrupts surgery or recovery, immediate treatment is essential. Emergency cooling measures like ice baths and cold irrigation are started first, followed by medications to control heart rate and supplemental oxygen as needed. Intravenous fluids prevent organ damage.

The symptoms must be waited out and the focus should be on minimizing damage. Once a patient knows they have malignant hyperthermia, they should invest in a medical alert bracelet or an implanted chip to notify emergency responders of their reaction.

Malignant Hyperthermia Prevention

Genetic testing makes it possible to reveal whether a person possesses MH mutations helping to prevent future reactions and those at risk of having a reaction can be given safer medications. An awareness of susceptibility is an essential factor in avoiding the mortality/morbidity that comes with MH. Susceptibility is determined by DNA testing or a muscle biopsy test, with the muscle biopsy test being more sensitive than the DNA test. The advantages of DNA testing are its low cost and the lack of a need to travel. Additionally, DNA testing has the advantage of identifying the causative mutation and then allowing family members to be tested with more ease than a muscle biopsy test. Avoidance of the triggering agents seems to be one of the most effective means of preventing MH. Also, although it is somewhat more expensive and difficult to administer, alternative anesthetics can be made available for patients who are at risk for MH. Among those medicines are Sodium dantrolene, which is known as an effective antidote to triggering agents.

Last Reviewed:
October 07, 2016
Last Updated:
March 02, 2018