Malignant hyperthermia is disease passed down through families that causes a fast rise in body temperature (fever) and severe muscle contractions when the affected person gets 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 occur with muscle diseases such as multiminicore myopathy and central core disease.

Symptoms include:

• Bleeding
• Dark brown urine
• Muscle ache without an obvious cause, such as exercise or injury
• Muscle rigidity and stiffness
• Quick rise in body temperature to 105 degrees F or higher

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

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

The person may have a fast 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
• Urine myoglobin (muscle protein) determination

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.

To preserve kidney function during an episode, you must get fluids through a vein and by mouth, as well as certain medications.

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

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

• Amputation
• Breakdown of muscle tissue (rhabdomyolysis)
• Compartment syndrome (swelling of the hands and feet and problems with blood flow and nerve function)
• Death
• Disseminating intravascular coagulation (abnormal blood clotting and bleeding)
• Heart rhythm problems
• Kidney failure
• Metabolic acidosis
• Respiratory dysfunction (fluid buildup in the lungs)
• Weak muscles (myopathy) or muscular dystrophy (deformity)

Tell 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 anesthesia. Using certain medications can prevent the complications of malignant hyperthermia during surgery.

Avoid stimulant drugs such as cocaine, amphetamine (speed), and ecstasy. These drugs may cause problems similar to malignant hyperthermia in people who are prone to this condition.

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.

Schmidt EW, Nichols CG. Heart-related illness. In: Wolfson AB, Hendey GW, Ling LJ, et al, eds. Harwood-Nuss' Clinical Practice of Emergency Medicine. 5th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2009:chap 346.

Steele MT. Rhabdomyolysis. In: Wolfson AB, Hendey GW, Ling LJ, et al, eds. Harwood-Nuss' Clinical Practice of Emergency Medicine. 5th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2009:chap 211.