Malignant hyperthermia (MH) is a rare genetic condition that can occur after general anesthesia, causing symptoms such as an elevated heartbeat, muscle stiffness, and discolored urine. It can lead to organ failure and death if left untreated. Treatment focuses on relieving symptoms and preventing complications, and individuals with a family history of the disorder should inform their doctor to prevent episodes. Safe anesthetic drugs are available for those with MH.
Malignant hyperthermia (MH), also known as malignant hyperthermia syndrome (MHS), is a rare genetic condition that occurs following the administration of a general anesthetic. Treatment for this life-threatening condition focuses on immediate relief of breakthrough symptoms to prevent complications that can include organ damage and impaired brain function. If left untreated, malignant hyperthermia can lead to organ failure and premature death.
Individuals with malignant hyperthermia experience an adverse physiological reaction to the administration of certain general anesthetic drugs, such as desflurane, methoxyflurane, and sevoflurane. Generally administered as inhalants, such anesthetics can induce an elevated or irregular heartbeat once the drugs enter an individual’s system. In most cases, the adverse reaction is discovered only after the anesthetic has been administered. Some individuals with malignant hyperthermia may develop an extremely high temperature following anesthetic administration requiring immediate application of cooling materials to lower fever and prevent brain damage. Additional signs of HD include stiff muscles and discolored urine resulting from impaired kidney function.
Many who develop this serious condition have a family history of the disorder or anesthetic-induced death. Those diagnosed with MHS usually have at least one parent who is a carrier of the disease. Individuals with HD possess a genetic cellular mutation that triggers the uncontrolled release of calcium and potassium when exposed to certain anesthetic drugs or, in some cases, to physiological stress induced by extreme temperatures or extreme physical exertion.
The rapid release of calcium from the muscles during an HD episode essentially causes muscle convulsions and stiffening while depleting the energy needed for proper muscle function. The lost cellular energy triggers the onset of muscle wasting and the unregulated release of potassium into the bloodstream. The introduction of potassium is further aggravated by the loss of myoglobin pigmentation released from decaying muscle tissues. The combination of the two adversely affects cardiovascular and kidney function.
If an individual is suspected of having the genetic mutation responsible for malignant hyperthermia or is aware of a family history, they may undergo genetic testing to check for the presence of the ryanodine receptor 1 (RYR1) gene responsible for presenting HD. Although the condition is most often diagnosed following the administration of an anesthetic drug, there are tests that can be administered to assess an individual’s condition following their HD episode. A urine myoglobin test may be performed to evaluate the condition of the muscles and check for deterioration as indicated by the presence of myoglobin in the urine. Additionally, a metabolic panel may be conducted to evaluate the individual’s liver and kidney function.
Treatment for HD depends entirely on the presentation and severity of symptoms. Most individuals have an extremely high temperature that requires immediate measures to reduce it to prevent permanent organ damage. In such cases, a cool towel or blanket may be placed over the individual to help lower their body temperature. Muscle relaxant and nerve blocking drugs, such as dantrolene and beta-blockers, can be given to relieve muscle spasms and regulate an individual’s heart rhythm. Additional fluids may be given intravenously to prevent dehydration and support proper organ function.
Episodes of malignant hyperthermia can be prevented by being aware of one’s family medical history. Those who have relatives who have been diagnosed with MHS or have died from complications associated with this disorder should inform their doctor. There are anesthetic drugs that can be given in the presence of malignant hyperthermia that are completely safe and do not trigger an HD episode, such as vecuronium, nitrous oxide and propofol.
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