Malignant Hyperthermia

Malignant hyperthermia is a rare condition that causes a fast rise in body temperature when someone with the disease receives general anesthesia.

Malignant hyperthermia (MH) is a rare, inherited condition that causes muscle rigidity, high fever, fast heart rate, and abnormal muscle contractions when someone with the disease receives general anesthesia. These complications can include or lead to rhabdomyolysis, high blood potassium, and death. MH has a low incidence and high mortality rate.

Hyperthermia means high body temperature, but this condition is not the same as hyperthermia from other medical emergencies such as heat stroke or infection.

Patients with MH can experience life-threatening complications, called a MH crisis, if they are exposed to trigger agents, such as certain anesthetics that are used to put patients to sleep for surgery.

Trigger agents currently in use in the United States include most of the inhalational anesthetic gases and the muscle relaxant, Succinylcholine. These agents do not necessarily trigger a crisis every time a susceptible patient comes in contact with them. That means an uneventful anesthetic in the past does not rule out MH-susceptibility.

Recent evidence indicates that individuals with MH-susceptibility may develop MH with exercise or heat exposure.

Malignant Hyperthermia Symptoms

A MH crisis can occur when a susceptible patient is exposed to triggering agents.

This exposure can lead to muscle rigidity, very high fever, failure of other organs (kidney, lung), abnormal blood clotting and other life-threatening complications.

If treatment is not started promptly, up to 7 out of 10 patients may die from a MH crisis and its complications.

Malignant Hyperthermia Diagnosis

In general, testing for MH-susceptibility is recommended in 2 groups of patients:

Anyone who experienced a MH crisis or questionable MH crisis during anesthesia that involved trigger agents.
Anyone with a close relative who tested positive for MH or who experienced a MH crisis. Children of an affected person have a 50 percent chance of inheriting MH from their parents.

Tests may include:

Blood clotting studies
Blood work
Genetic testing
Muscle biopsy

Muscle Biopsy for Malignant Hyperthermia

Watch a video on muscle biopsy and caffeine halothane contracture testing (CHCT) performed at Wake Forest Baptist Medical Center.

Our Malignant Hyperthermia Team

Thomas Pranikoff, MD

Alan Woodruff, MD

Marina R Lin, MS, Biochemist

Malignant Hyperthermia Crisis Management

Preventing a MH crisis is the key. If you are MH-susceptible, safe anesthesia agents will be used and the risk of a MH crisis can be avoided.

If you experience a MH crisis, there is treatment available – a drug called dantrolene. However, effectiveness is greatest when given early. Dantrolene is given through an intravenous line and is thought to reverse the effects of triggering agents on muscle function. If dantrolene is started promptly in a MH crisis, together with rapid cooling, discontinuing triggering agent, and hyperventilating with oxygen, the risk of complications or death is substantially reduced.

Life with Malignant Hyperthermia

Individuals known to be susceptible to MH can safely undergo anesthesia for any type of surgical or dental procedure as long as trigger agents are avoided. Below are some frequently asked questions for individuals who may be MH-susceptible.

What precautions should I take?

The most important thing is to inform all your health care providers and especially your anesthesiologist if you are going to have any type of surgery. Worldwide not a single patient has died from MH when his or her condition was previously known to the medical team and appropriate precautions were taken.

Should I wear any kind of identification bracelet?

Yes. If you are MH-susceptible it is strongly advised that you wear an identification bracelet at all times so that any health care professional will be alerted to your condition.

Identification bracelets are available through the Malignant Hyperthermia Association of the United States (MHAUS).

Do I need to take any medications, follow a special diet or change my lifestyle?

No. If you are MH-susceptible you don't require any form of medication, diet or particular precautions for your daily life. However, if you are undergoing any type of surgical or dental procedure requiring the use of anesthetics, certain precautions need to be taken by your health care provider to avoid complications. Therefore, it is most important to inform your health care provider about your MH-susceptibility.

Can I donate blood with this condition?

Yes. MH-susceptibility is not blood borne and cannot be transmitted through blood or blood products.

Will I pass this condition on to my children?

MH is inherited. Only one parent has to carry the defected RYR1 gene (ryanodine receptor of skeletal muscle) for a child to inherit the condition. Therefore if a person is MH-susceptible, each of his or her children have a 50 percent chance of inheriting this condition. Because of this, muscle biopsy testing is advised in all children of a parent known to be MH-susceptible. Currently there are 5 biopsy and testing centers in North America and Wake Forest Baptist Health is one of them.

Molecular genetic testing is now available to look for defects in the RYR1 gene but may not identify certain cases of MH-susceptibility. Muscle biopsy and CHCT remain the gold standard test for diagnosis.

Can malignant hyperthermia be dangerous in my pregnancy?

If a woman is MH-susceptible she can safely become pregnant.

The risk of anesthesia complications from MH is the same in pregnant and non-pregnant patients; therefore, the same precautions as in any other MH-susceptible patients must be followed (e.g., in the case of a cesarean section under general anesthesia).

Can I safely travel with this condition?

In general, travel within North America, Western Europe, Australia, New Zealand, and Japan can be considered safe. In the case of an emergency, health care professionals in these countries can be assumed to be aware of MH and its implications and also to be trained and equipped to treat possible complications. Wearing an identification bracelet is strongly recommended.

For other countries, especially developing countries, it is difficult to predict the level of alertness and ability to diagnose and treat MH and its complications. We would therefore strongly suggest that travelers contact either MHAUS or any of the institutions performing muscle biopsies for individualized advice.

MyAtriumHealth