Malignant hyperthermia is an inherited disease that causes a rapid rise in body temperature (fever) and severe muscle contractions when the affected person receives general anesthesia.

This condition is not the same as hyperthermia that is due to medical emergencies such as heat stroke or infection.

Hyperthermia - malignant; Hyperpyrexia - malignant

Malignant hyperthermia is inherited. Only one parent has to carry the disease for a child to inherit the condition. It may be associated with muscular diseases such as multiminicore myopathy and central core disease.

Symptoms include:

• Rapid rise in temperature to 105 degrees F or higher
• Muscle rigidity and stiffness
• Dark brown urine
• Muscle ache without obvious exercise to explain sore muscles
• Bleeding

Malignant hyperthermia is often discovered after a patient is given anesthesia during a surgical procedure.

There may be a family history of malignant hyperthermia or unexplained death during anesthesia.

The person may have a rapid and often irregular heart rate.

Tests that may be done include:

• Chem-20
• Genetic testing to look for defects in the RYR1 gene
• Muscle biopsy
• Myoglobin in the urine

During an episode of malignant hyperthermia, wrapping the patient in a cooling blanket can help reduce fever and the risk of serious complications. Drugs such as dantrolene, lidocaine, or a beta-blocker drug can help with heart rhythm problems.

Fluids given by through a vein and by mouth, as well as certain medications, are essential for maintaining kidney function during an acute episode.

Malignant Hyperthermia Association of the United States - www.mhaus.org

Repeated episodes or untreated episodes can cause kidney failure. Untreated episodes can be fatal.

• Breakdown of muscle tissue (rhabdomyolysis)
• Weak muscles (myopathy) or muscular dystrophy
• Kidney failure
• Metabolic acidosis
• Death

Notify both the surgeon and anesthesiologist before having any surgery if:

• You know that you or a member of your family has had problems with general anesthesia
• You know you have a family history of malignant hyperthermia

If you or anyone in your family has malignant hyperthermia it is very important to tell your doctor, especially before having surgery with general anesthetic. The use of appropriate medications can prevent the complications of malignant hyperthermia during surgery.

It is important to avoid stimulant drugs such as cocaine, amphetamine (speed), and ecstasy. They may produce malignant hyperthermia-like problems in people who are susceptible.

Genetic counseling is recommended for anyone with a family history of myopathy, muscular dystrophy, or malignant hyperthermia.

Vicario S. Heat illness. In: Marx J, ed. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 6th ed. St. Louis, Mo: Mosby; 2006:chap 139.

Dinarello CA, Porat R. Fever and hyperthermia. In: Fauci A, Kasper D, Longo DL, et al, eds. Harrison's Principles of Internal Medicine. 17th ed. [online version]. New York, NY:McGraw Hill;2008:chap 17.