Malignant hyperthermia

Malignant hyperthermia (MH) was first described by Denborough in 1962 when deaths were occurring during and immediately (within 24 hours) following the administration of anesthesia medications. The common denominator in these patients was sudden and critical increases in body temperature. These occurrences were quick to reveal that MH is passed down through families (Denborough, Forster, Lovell, Maplestone, & Villiers, 1962).

Half of the patients who have an MH crisis have had prior exposure to anesthesia agents known to trigger a crisis without any such reaction. Males have a higher incidence than females, and patients less than the age of 50 are more likely to have MH. Pediatric patients are most frequently affected. Pediatric patients with a history of rheumatoid arthritis have the highest incidence of anesthesia-induced malignant hyperthermia (Butterworth, Mackey, & Wasnick, 2013).

Although the most common patients are surgical patients, MH has also been reported after anesthesia medications are used for sedation in surgeon’s offices, intensive care units, dental offices, and emergency departments (National Institute of Arthritis and Musculoskeletal and Skin Diseases, 2018).

The most common medications administered prior to an MH event include: succinylcholine, sevoflurane, desfluane, isoflurane, and halothane. Some non-triggering anesthetic agents that are recommended for patients with a previous diagnosis of MH include: thiopental sodium and pancuronium, droperidol, benzodiazepines, and ester-type local anesthetics.

If appropriately treated, the mortality rate is less than 10%. If not recognized and treated, the mortality rate can be expected to be as high as 80%. Most professionals believe that this could be much lower with proper preparedness for rapid recognition and treatment of malignant hyperthermia (McCarthy, 2004). One of the ways that the surgical team can better prepare is by maintaining an emergency cart dedicated to the treatment of malignant hyperthermia. The recommended contents of such a cart is found at the end of this article.

The following treatment protocol is published by the Malignant Hyperthermia Association of the United States (MHAUS) (Malignant Hyperthermia Association of the United States, n.d). Although written in a specific order, many of the following interventions should be done simultaneously. Early diagnosis and treatment are essential to limit mortality. Treatment

Muscle cells are destroyed during an MH crisis and the myoglobin that is released accumulates in the kidneys, obstructing urinary flow, referred to as myoglobinuria. Diuretics are given IV to promote and maintain urinary flow in order to prevent renal damage. Mannitol 0.25 g/kg IV; furosemide 1 mg/kg IV up to four doses each. Urinary output of 2 ml/kg/hr or higher must be maintained to prevent renal failure.

Dantrolene, a skeletal muscle relaxant specifically developed for the treatment of MH, is the backbone of the treatment regimen. Administration is every 6–8 hours for 24–72 hours after the initial episode. The dose is 1 mg/kg. The standard dose is based on an adult that weights 70 kg; thirty-six 20 mg vials of dantrolene will be needed to stabilize the patient. Rarely does the total required dosage exceed 10 mg/kg. A common complication of dantrolene is phlebitis; therefore, it is recommended that it be given via a central line (Butterworth, 2013).