MH is a hit or miss condition, a person may have been exposed to a triggering agent multiple times without any difficulty and then the next time an agent is used MH is triggered. The first signs to indicate MH has been activated are an increase in end-tidal carbon dioxide, tachycardia, muscle rigidity, tachypnea, and hyperkalemia. Most people associate fever with MH, however fever is a later sign.
Malignant Hyperthermia (MH) is an autosomal dominate muscle disorder that requires immediate treatment. When triggered it causes a hyper-metabolic state within muscle cells. MH is a life threatening condition that is sparked by use of inhaled volatile gasses or succinylcholine. After administration of a triggering agent specific receptors, most commonly the RYR1 receptor, allows too much calcium into the muscle cell. The influx of calcium results in hyper-metabolism causing an increase in carbon dioxide, increased oxygen use, hyperkalemia, heat production, metabolic and respiratory acidosis, rhabdomyolysis, and activation of the sympathetic nervous system. Disseminated intravascular coagulation and multi-organ failure can soon follow.
A MH cart should be within easy access whenever triggering agents are used. Dantrolene vials contain 20mg of freeze dried agent and must be mixed with 60mls of sterile water (without preservatives). The suggested number of vials to have on hand is 36. A newer formulation of dantrolene sodium takes significantly less time to mix and prepare for administration. Dantrolene should be administered as a 2.5-mg/kg bolus and repeated until MH reaction has subsided or 10 mg/kg has been administered. If no change is seen with 10 mg/kg other causes of reaction should be considered.
References Chapin, J. w. (2013, February). Malignant hyperthermia. In Medscape. Retrieved October 4, 2014, from Managing a MH crisis. (n.d.). In Malignant Hyperthermia Association of the United States. Retrieved October 4, 2014, from
MH may occur during anesthesia or after, the treatment will correspond accordingly. There are several things to do in treating MH, however the only agent to interrupt the calcium release is Dantrolene sodium 2.5 mg/kg. Extra staff will be needed to assist in the many tasks. If possible stop surgery immediately and turn off the noxious stimuli. If surgery must continue another anesthetic agent will be needed such as propofol. Hyperventilate with 100% 02 Use end tidal CO2 and blood gasses to adjust ventilation Give Dantrolene Monitor blood gasses, electrolytes, creatine kinase, myoglobin and lactate Cool patient through ice water lavage, cooling blankets, or ice packs Diuresis Other medications for treating hyperkalemia, acidosis and arrhythmias include: Calcium Chloride Sodium bicarbonate Glucose/insulin Antiarrhythmics except calcium channel blockers
Malignant Hyperthermia Association of the United States (MHAUS) is available 24-hour per day. They have experts on call to assist in diagnosis and treatment of MH. MHAUS has a very nice website for patients and professionals with current and ongoing literature and research. 24-HOUR MH HOTLINE800-644-9737