Malignant hyperthermia in the ambulatory surgery center: how should we prepare?

1306 June 2014 M hyperthermia (MH) occurs when a patient who has inherited a causative mutation (usually in RYR1, the gene on chromosome 19 that encodes for the ryanodine receptor) is exposed to one or both anesthetic-triggering agents (i.e., volatile anesthetics and succinylcholine).1 MH is just as likely to occur in a healthy patient who receives anesthesia in a freestanding ambulatory surgery center (ASC) as in a medically complex inpatient. The Malignant Hyperthermia Association of the United States recommends that an MH “cart” be stocked with drugs and equipment used to manage MH, and that it be immediately available to any anesthetizing location where triggering anesthetics are used. The most important ingredient on this cart is dantrolene, the essential treatment of MH. For approximately 4 decades, dantrolene has been known to reverse the symptoms and reduce mortality from acute MH. Thus, dantrolene has become as essential a fixture in the operating room environment as a defibrillator. This issue of ANeSTHeSIoLoGy contains an insightful look at the cost effectiveness of stocking dantrolene in ASCs.2 This analysis revealed that the cost of stocking dantrolene would be less than the costs incurred by a patient’s death as a result of supportive care only. The authors performed a simulation study to bias the results against the recommendation of stocking dantrolene by increasing the effectiveness of supportive care alone and reducing the effectiveness of prompt administration of dantrolene. even with these unlikely scenarios, the argument for cost effectiveness of dantrolene is strong. The Malignant Hyperthermia Association of the United States recommends that the MH cart contains a minimum of 36 vials of dantrolene. This is because some patients may require up to 10 mg/kg of dantrolene for initial stabilization (calculation based on the standard 20-mg dantrolene vial and a mean average patient weight of 70 kg).3 However, some might argue that ASCs could stock a smaller starting dose of dantrolene in anticipation of the patient being transferred to a major medical center soon after recognition of the MH event. But, the cost of delaying dantrolene administration, either in inadequate dosage (if a limited supply is available) or no administration (if it is not stocked) is significant, because larger initial doses are often needed to control the acute life-threatening complications of MH that may occur in some patients, such as hyperkalemia and severe hyperthermia. The results of this rigorous study allow us to move from the controversy of stocking dantrolene to the larger issue of preventing MH-related deaths in ASCs. A study that assessed the trends and outcomes of MH in the United States found that its incidence is increasing and that there are geographic differences in the mortality rate.4 of importance, mortality was higher when patients were transferred from other hospitals or other healthcare facilities (e.g., ASCs). Therefore, it is essential that all anesthetizing facilities, especially ASCs, prepare for the eventuality of an acute lifethreatening MH event. All facilities should perform annually Malignant Hyperthermia in the Ambulatory Surgery Center