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Malignant Hyperthermia in the Operating Room

Practice Essentials

Malignant hyperthermia (MH) is a rare, inherited disorder of skeletal muscle that presents as a hypermetabolic response triggered by halogenated anesthetics, succinylcholine, or both. The incidence of MH reactions ranges from 1 in 10,000 to 1 in 250,000 anesthetic exposures.
 It is possible that an anesthesiologist may practice for an entire career without encountering a single case.
 Nevertheless, given the seriousness of the condition, it is important that anesthesiologists be able to recognize MH promptly and treat it effectively.

Common symptoms of MH include hypercarbia, muscle rigidity, masseter muscle spasm, sinus tachycardia, arrhythmias, hyperthermia, and cyanosis. MH can be rapidly fatal; however, with current treatment, including the use of intravenous (IV) dantrolene, mortality from MH has been reduced from 80% to 1.4% percent in North America.

Management of an MH crisis includes the following steps

Discontinue the potent Inhaled anesthetic agents – Turn the vaporizers off, and insert activated charcoal filters into the circuit if available

If succinylcholine has been given, do not readminister it 

Call for help

Stop surgery as soon as possible

Switch to total IV anesthesia to complete the surgical procedure if it cannot be stopped

Increase the minute ventilation to decrease end-tidal carbon dioxide (EtCO

Increase fresh gas flow with 100% oxygen to 10 L/min

Administer IV dantrolene – Initial dose of 2.5 mg/kg, then 2.5 mg/kg every 5-10 minutes until acidosis, pyrexia, and muscular rigidity are resolving

Cool patient with IV sodium chloride 0.9% at 4ºC, ice packs, and gastric lavage; stop cooling at 38.5ºC to prevent rebound hypothermia

Obtain values for arterial blood gases (ABG), electrolytes, creatine kinase, and blood and urine myoglobin

Treat arrhythmias and hyperkalemia – Do not use calcium-channel blockers

Observe the patient in the intensive care unit (ICU) for 24 hours

Ensure urine output of 2 mL/kg/hr with
furosemide, or fluids as needed

Continue dantrolene 2.5 mg/kg if signs or symptoms recur

Refer the patient and family for MH testing

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