Malignant Hyperthermia Care in PACU

Malignant hyperthermia is a condition that happens when the body has a severe reaction to certain anesthetic agents. During malignant hyperthermia, the body releases calcium into cells which leads to dangerous problems with metabolism. Only those with an underlying genetic abnormality are susceptible. Malignant hyperthermia is treatable, and people can be screened with genetic testing to find out whether they are at risk.

Definition

• Malignant hyperthermia is a severe reaction to generalized anesthesia. The most common symptoms are very high fevers, high heart rate, high breathing rate, muscle breakdown, and abnormal levels of oxygen, carbon dioxide and acids in the bloodstream. Because it is a reaction to anesthesia, malignant hyperthermia most often occurs in the operating room or right after a surgery when someone is in the postanesthesia care unit.

Causes

• Malignant hyperthermia happens as a result of a genetic mutation that an affected person will pass it to half of their children, on average. It is triggered by giving certain anesthetic gases, including halothane, sevoflurane, ethane, isoflurane and desflurane, or the muscle relaxant succinylcholine to those with the genetic abnormality. For unclear reasons, these medicines cause large stores of calcium to be released inside the cells of those with the malignant hyperthermia gene, which leads to severe abnormalities in cell metabolism and causes the symptoms of malignant hyperthermia.

Treatment

• Malignant hyperthermia is a medical emergency. The patient must be rapidly cooled to bring down the temperature. Dantrolene, a muscle relaxant, is the primary treatment. Dantrolene works by stopping the release of calcium that causes malignant hyperthermia. Those who experience malignant hyperthermia are typically treated with an intravenous infusion of dantrolene for a day and a half and are then switched to oral medication. Dantrolene should only be taken under a doctor's supervision.

Testing and Screening

• Once a person is suspected to have malignant hyperthermia due to a reaction to anesthesia, they can be tested by the in vitro contracture test. A small biopsy is taken of a muscle in the leg. This muscle tissue is then exposed to both caffeine and halothane, and the muscle contraction is measured. Contraction in response to both caffeine and halothane is considered a positive result. If a person has a positive test result, genetic polymerase chain reaction tests can then be done to look for the specific gene mutation. If a mutation is identified, other members of the family can also be screened for the potential to develop malignant hyperthermia.