Malignant hyperthermia (MH) is a rare, potentially lethal, clinically and genetically heterogeneous
pharmacogenic myopathy, which during or after
general anesthesia manifests as MH crisis (MHC) in genetically predisposed, but otherwise mostly normal, individuals (MH susceptibles) in response to
anesthetic-triggering agents. MHC can also occur in patients with
central core disease. MCH-like crises have been reported in those with
Duchenne/Becker muscular dystrophy,
myotonic dystrophy, mitochondriopathy, and various other conditions. MH susceptibility is diagnosed if there is an MHC in the individual or family history or by the in vitro
caffeine-
halothane contracture test. Although screening for mutations in the ryanodine-receptor-1 gene and the
dihydropyridine-receptor gene, respectively, could further substantiate the diagnosis, the
caffeine-
halothane-
contracture test still remains the gold standard for diagnosing MH susceptibility. The most well-known triggers of an MHC are
depolarizing muscle relaxants and volatile
anesthetics.
Therapy of an MHC comprises discontinuation of triggering agents, oxygenation, and correction of the
acidosis and
electrolyte disturbances, treatment of arrhythmias, cooling, and
dantrolene. If MH susceptibility is not known preoperatively and an MHC unexpectedly interrupts
anesthesia, consultation by a specialist in MH susceptibility after
anesthesia is essential to investigate the patient for MH susceptibility or subclinical
myopathy, guide laboratory investigations, manage
therapy, and counsel the family on further risk. To further reduce morbidity and mortality of those with MHC, anesthesiologists and neurologists should be well educated and should strengthen their clinical vigilance. Research should be intensified and extended with regard to the development of new in vitro tests to further elucidate the heterogeneous genetic background of MH susceptibility.