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

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

Malignant hyperthermia is often noted for the first time after a patient is given anesthetic drugs during a surgical procedure. The anesthetized patient quickly develops muscle rigidity. Body temperature rapidly rises to 105 degrees F or higher. During these episodes, muscle tissue is destroyed and, eventually, kidney failure may result. Urine may turn a dark color (see rhabdomyolysis).

Malignant hyperthermia is an autosomal dominant trait, meaning it requires only one parent carrying the disease for a child to inherit the condition. It may be associated with muscular diseases such as multiminicore myopathy and central core disease.

The condition requires immediate treatment.

• Rapid rise in temperature after general anesthesia is given
• Muscle rigidity and stiffness after general anesthesia is given
• Dark brown urine
• Muscle ache without obvious exercise to explain sore muscles
• Family history of malignant hyperthermia or unexplained death during anesthesia

• Blood chemistry ( chem-20 ) shows increased blood levels of creatine phosphokinase (CPK ), potassium, uric acid, phosphate.
• Myoglobin in the urine is elevated.
• Muscle biopsy may show abnormal results in response to certain drugs such as caffeine and halothane (an anesthetic) and abnormal muscle fibers.
• Genetic testing such as ryanodine receptor (RYR1) may show gene abnormalities.
• Phosphorus magnetic resonance spectroscopy, a research test, may show abnormal muscle function.

The best course of action for this condition is prevention. The use of appropriate anesthetic medication can prevent the complications of malignant hyperthermia during surgery. If you or other members of your family have a history of anesthesia-related problems, you must inform your surgeon and anesthesiologist.

For an episode of malignant hyperthermia, fever-reducing medicines (antipyretics) such as acetaminophen and a cooling blanket can help reduce fever. The use of a drug called dantrolene during episodes of malignant hyperthermia has greatly reduced the number of deaths.

Fluids given by IV and 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.

• Rhabdomyolysis, a kidney injury caused by excess myoglobin
• Renal failure
• Myopathy (weak muscles) or muscular dystrophy
• Death

If you know that you or a member of your family has had problems with general anesthesia, or if you know you have a family history of malignant hyperthermia, be sure to notify both the surgeon and the anesthesiologist before having any surgery.

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.

It is important to avoid stimulant drugs such as cocaine, amphetamine (speed) and ecstasy (an amphetamine derivative) as they may produce malignant hyperthermia-like problems in susceptible individuals.

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

Marx J. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 5th ed. St. Louis, Mo: Mosby; 2002:2000.