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Malignant Hyperthermia and Other Anesthetic-Induced Myodystrophies


Acknowledgement

The authors are grateful to Henry Rosenberg, MD, who authored the previous edition of this chapter. It has served as a framework for this updated edition.

Risk

  • Incidence of MH impossible to know because of lack of reporting mechanisms; Malignant Hyperthermia Association of the US hears of approximately 1–2 cases per week in North America.

  • More common in males (approximately 2:1).

  • Family Hx of MH or unexplained death during surgery associated with MH occurrence.

Perioperative Risks

  • Mortality with MH unknown. Malignant Hyperthermia Association of the US hears of approximately 1–2 deaths directly related to MH every 1–2 years.

  • Occurrence of MH reduced by avoidance of triggering agents in MH susceptible individuals, and use of succinylcholine only when indicated.

  • Immediate availability of dantrolene has greatly reduced morbidity and mortality from MH.

  • Myopathies associated with MH are those associated with mutations in RYR1; most common is central core disease.

  • Some obscure myopathies associated with risk of MH when caused by mutations in RYR1, STAC3, or CACNL1A3 genes. These include King-Denborough syndrome (RYR1), multiminicore disease (RYR1), congenital myopathy with cores and rods (RYR1), congenital fiber type disproportion (RYR1), Native American myopathy (STAC3), and hypokalemic periodic paralysis (CACNL1A3).

  • Pts with unexpected severity of rhabdomyolysis in response to hot environment, exercise, or statin administration may have increased chance of MH susceptibility. These occurrences probably unmask RYR1 inheritance.

  • Myopathies associated with hyperkalemic cardiac arrest following administration of succinylcholine: Duchenne and Becker muscular dystrophies; also reports of arrest with volatile agents only.

  • Other neuromuscular diseases not associated with MH susceptibility include mitochondrial myopathies, Noonan syndrome, Freeman-Sheldon syndrome, and osteogenesis imperfecta.

  • Muscle rigidity can be seen in all myotonias following succinylcholine administration.

Worry About

  • Unexplained increase in PETCO 2 , hyperthermia, tachycardia, or tachypnea (if spontaneous breathing) during GA with triggering agents

  • Generalized muscle rigidity with or without trismus sensitive indicator for development of MH

  • Recrudescence of MH in 25% of cases despite treatment

Overview

Malignant Hyperthermia

  • No phenotypic signs predict MH susceptibility other than previous Hx of MH or family Hx or unexplained elevated CK.

  • Hypermetabolic disorder manifested by increased CO 2 production and O 2 consumption, acidosis, hyperkalemia, myoglobinuria/myoglobinemia, rhabdomyolysis, tachycardia, tachypnea, increased ETCO 2 , and hyperthermia (if severe leads to DIC).

  • Dx by CHCT of biopsied muscle is most sensitive and specific. Sensitivity is approximately 80%; specificity close to 100%.

  • DNA testing available in USA and in many centers in Europe. Sensitivity is approximately 50%, specificity close to 100%.

  • Information for provider and pt available through the Malignant Hyperthermia Association of the US, Sherburne NY ( www.mhaus.org , 607-674-7901).

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