Page 27 - CASA Bulletin of Anesthesiology 2022, Vol 9, No 1 (1)

Vol. 9, No 1, 2022

MALIGNANT HYPERTHERMIA

Mohammad Yousef, MD, Associate Research Physician
Andrew Mannes, Chief, Senior Research Physician
Department of perioperative medicine
Clinical Center, NIH

Epidemiology Dr. Mohannad Yousef

Malignant hyperthermia (MH) manifests clinically as a
hypermetabolic crisis when an MH-susceptible (MHS) individual
is exposed to a certain anesthetic trigger leading to a result of
calcium overload within the skeletal muscle cell that leads to
sustained muscular contraction and breakdown (rhabdomyolysis),
cellular hypermetabolism, anaerobic metabolism, acidosis, and
their sequelae.
The exact incidence of Malignant Hyperthermia is unknown,
but the incidence varies depending on the concentration of MH
families in a given geographic area. For example, high incidence
areas in the United States include Wisconsin, Nebraska, West Virginia and Michigan. MH cases
have been reported ranging from 1/5,000 – 1/100,000 anesthetics, which vary regionally and are
highest in children and young adults.

The prevalence of genetic change that predisposes to MH is much higher, where roughly one
in 2,000 patients harbor a genetic change that makes them susceptible to MH, and there are over
80 known genetic defects associated with MH. MH susceptibility is inherited with an autosomal
dominant inheritance pattern. This means that children and siblings of a patient with MH
susceptibility usually have a 50% chance of inheriting a gene defect for MH, and hence would
also be MH susceptible and may develop an MH reaction upon exposure to triggers. MH-
susceptible persons have a mutation that results in the presence of abnormal proteins in the
muscle cells of their body. Mutations encoding for abnormal Ryanodine receptors (RYR1) or
Dihydropyridine (DHP) receptors have been found in a majority of MHS patients.

MH occurs in all ethnic groups in all parts of the world. Reactions occur more frequently in
males than females (2:1). Children under 19 years account for 45 to 52 percent of reported
events.

Estimates of mortality from MH have come from data derived from the National Inpatient
Sample, and from reports submitted to the North American Malignant Hyperthermia Registry
(NAMHR). Mortality from MH has declined significantly with the routine use of end-tidal
carbon dioxide (ETCO2) monitoring and availability of dantrolene, and is reported to be between
6 and 10 percent.

In an analysis of suspected MH reports submitted to Malignant Hyperthermia Association of
the United States (MHAUS) between 1987 and 2006, there were 84 cases of likely MH, and 8

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