A: A rare, inherited muscle disorder, malignant hyperthermia can be chemically induced by inhalation anesthetics, such as halothane and enflurane, or muscle relaxants, such as succinylcholine. The triggering agent increases oxygen consumption and raises lactate and heat production, leading to hypermetabolism. This alters calcium function at the cellular level, causing increased muscle contraction (rigidity), hyperthermia, and subsequent damage to the central nervous system. Stress and some medications, such as epinephrine, theophylline, aminophylline, atropine, and cardiac glycosides, can induce or intensify this reaction.
Identification of patients at risk for malignant hyperthermia is key. Susceptible patients include those with strong and bulky muscles, a history of muscle cramps or muscle weakness and unexplained temperature elevation, and an unexplained death of a family member during surgery that was accompanied by a febrile response.
Malignant hyperthermia usually manifests about 10 to 20 minutes after induction of anesthesia, but be aware that it may occur at any time during the first 24 hours after surgery. Initial symptoms are related to cardiovascular and musculoskeletal activity. Tachycardia is often the earliest sign. In addition, sympathetic nervous stimulation leads to ventricular dysrhythmia, hypotension, decreased cardiac output, oliguria, and cardiac arrest. With the abnormal transport of calcium, rigidity or tetanus-like movements occur, often in the jaw. The increase in body temperature is actually a late sign that develops rapidly; temperature can increase 2[masculine ordinal indicator] to 4[masculine ordinal indicator] F (1[masculine ordinal indicator] to 2[masculine ordinal indicator] C) every 5 minutes. Core body temperature can reach or exceed 104[masculine ordinal indicator] F (40[masculine ordinal indicator] C) in a very short time and must be properly monitored and recorded during surgery.
Recognizing symptoms early and discontinuing anesthesia promptly are imperative. Goals of treatment are to decrease metabolism, reverse metabolic and respiratory acidosis, correct dysrhythmias, decrease body temperature, provide oxygen and nutrition to tissues, and correct electrolyte imbalance. The Malignant Hyperthermia Association of the United States publishes a treatment protocol that should be posted in the OR and be readily available on a malignant hyperthermia cart.
As soon as the diagnosis is made, anesthesia and surgery are halted and the patient is hyperventilated with 100% oxygen. Dantrolene, a skeletal muscle relaxant, and sodium bicarbonate are administered immediately. Continue to monitor the patient.
Although malignant hyperthermia is uncommon, you must know how to identify patients at risk, recognize its signs and symptoms, and be knowledgeable about the protocol to follow.
Malignant hyperthermia kit: cheat sheet
A malignant hyperthermia kit includes:
* dantrolene 20 mg (36 vials)
* sterile water for drug dilution
* dextrose 50%
* furosemide
* calcium gluconate
* sodium bicarbonate
* regular insulin
* mannitol
* methylprednisolone
* procainamide
* I.V. cannulas (assorted sizes)
* I.V. administration sets
* three-way stopcocks
* central venous pressure sets
* blood collection tubes
* oxygen tubing and delivery devices
* arterial blood gas kit
* nasogastric tubes
* indwelling urinary catheter tray normal saline irrigation solution and I.V. fluids (normal saline solution), which are removed from the kit and kept refrigerated.
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