Malignant Hyperthermia
From Holoprosencephaly
Malignant Hyperthermia
Malignant hyperthermia MH or MHS for "malignant hyperthermia syndrome", or "malignant hyperpyrexia due to anesthesia" is a rare life-threatening condition that is triggered by exposure to drugs used for general anesthesia, such as volatile anesthetics or the depolarizing muscle relaxant suxamethonium chloride. In susceptible individuals, these drugs can induce a drastic and uncontrolled increase in skeletal muscle oxidative metabolism which overwhelms the body's capacity to supply oxygen, remove carbon dioxide, and regulate body temperature, eventually leading to circulatory collapse and death if untreated.
Signs/Symptoms
The phenomenon presents with muscular rigidity, followed by a hypermetabolic state with increased oxygen consumption, increased carbon dioxide production, metabolic acidosis, tachycardia, and an increase in body temperature (hyperthermia) at a rate of up to ~2°C per hour. This is followed by a breakdown of muscle cells, which release their contents such as myoglobin, creatine kinase (CK/CPK) and potassium, into the bloodstream.
Treatment
The current treatment of choice is the intravenous administration of dantrolene, discontinuation of triggering agents, and supportive therapy directed at correcting hyperthermia, acidosis, and organ dysfunction. Treatment must be instituted rapidly on clinical suspicion of the onset of malignant hyperthermia. Dantrolene is a muscle relaxant that works directly on the ryanodine receptor to prevent the release of calcium. Pretreatment with dantrolene has been advocated in the past to prevent MH, but this is probably unreliable, and the long half-life of the drug may leave patients weak for extended periods. The only sure way to prevent MH is avoid the use of triggering agents in patients known or suspected of being susceptible to MH.
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