Malignant hyperthermia (MH) is a potentially fatal health crisis triggered by certain anesthetics in patients with a genetic abnormality. It causes sustained muscle contractions, rapid muscle cell death, and organ failure. Susceptibility is heritable, and preventive measures can be taken if known. MH is triggered by a class of gaseous anesthetics, and non-polarizing anesthetics can be used as an alternative. The exact incidence is unknown, but patients with a family history of MH should inform their anesthetist before surgery.
Malignant hypothermia (MH) is a common misspelling of malignant hyperthermia, a potentially fatal health crisis that can arise when a surgical patient with a certain type of genetic abnormality is prepped for surgery with a particular type of anesthetic. Using the wrong class of anesthetic can trigger a life-threatening chemical reaction in the body due to the genetic defect. HD can also occur if, unbeknownst to doctors, a patient has muscular dystrophy, as the onset of HD begins with a reaction in skeletal muscles. Susceptibility to HD is genetically heritable. Preventive measures can be taken if treatment providers are aware of any history of HD in the patient or in his family.
A genetic mutation in susceptible HD patients causes abnormal proteins to be found in the body’s muscle cells. While generally not of any medical concern in daily activities, the introduction of some anesthetics into skeletal muscle tissue causes extremely high levels of calcium to be released into the muscle cells. This triggers sustained muscle contractions, causing muscle cells to die rapidly. The resulting release of potassium into the bloodstream as cells die causes rapid damage to the body’s organ systems, including the brain, and possibly fatal organ failure.
There are more than 80 genetic defects associated with malignant hyperthermia. Susceptibility to HD has been determined to be inherited in what is termed an autosomal dominance pattern. Children and siblings of a person susceptible to HD would therefore have a 50% chance of inheriting a genetic defect that would also make them susceptible to HD. Estimates of the incidence of HD range from one in 65,000 administrations of anesthetics to one in 5,000. In the US, Midwestern states have a higher incidence of HD cases.
The specific anesthetics that trigger malignant hyperthermia have been identified. They are a class of gaseous anesthetics that are inhaled before surgery. They include all depolarizing muscle relaxants, especially sucinicoline, known as Anectin, a numbing agent. Non-polarizing anesthetics such as nitrous oxide and some narcotics and barbiturates can be used as an alternative to anesthetics that pose a threat to HD. It is important for healthcare professionals to know in advance of any possibility that a patient is susceptible to HD so that preventive measures can be taken.
The exact incidence of malignant hyperthermia is not known. In the United States, the Malignant Hyperthermia Association of the United States (MHAUS) recommends that anyone with a family history of HD inform their anesthetist before any surgery. MH susceptibility can also be registered with the MHAUS North American Registry.
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