Malignant hyperthermia

Malignant hyperthermia (MH) is a potentially lethal syndrome usually triggered by inhalation anesthetics and/or succinylcholine.

The underlying genetic susceptibility is most often due to a range of autosomal dominant mutations in RYR1, although CACNA1S and STAC3 are also implicated.

Caused by an increase in metabolic rate driven by an increase in intracellular calcium levels in muscle.

Presents with increased carbon dioxide production, muscle rigidity, tachycardia, hyperthermia, and mixed metabolic and respiratory acidosis.

A definitive diagnosis requires testing after the acute episode has resolved. Genetic testing may be the first test performed in selected patients; it may form part of the autopsy if MH is suspected as the cause of death. A muscle biopsy contracture test can be used to exclude susceptibility to MH.

The mainstay of treatment includes discontinuation of the triggering agent, administration of intravenous dantrolene, and restoration/maintenance of normal core temperature.

Rhabdomyolysis, acute kidney injury, hyperkalemia, and disseminated intravascular coagulation are frequently seen.

If the diagnosis is confirmed, all blood relatives should be contacted since the disease is autosomal dominant with variable penetrance and testing for the condition may be indicated.

MH is a syndrome that typically follows exposure to potent inhalation anesthetics and/or succinylcholine in susceptible individuals.[1]Hopkins PM, Girard T, Dalay S, et al. Malignant hyperthermia 2020: guideline from the Association of Anaesthetists. Anaesthesia. 2021 May;76(5):655-64. https://www.doi.org/10.1111/anae.15317 http://www.ncbi.nlm.nih.gov/pubmed/33399225?tool=bestpractice.com [2]Larach MG, Dirksen SJ, Belani KG, et al; Society for Ambulatory Anesthesiology; Malignant Hyperthermia Association of the United States; Ambulatory Surgery Foundation; Society for Academic Emergency Medicine; National Association of Emergency Medical Technicians. Special article: creation of a guide for the transfer of care of the malignant hyperthermia patient from ambulatory surgery centers to receiving hospital facilities. Anesth Analg. 2012 Jan;114(1):94-100. http://journals.lww.com/anesthesia-analgesia/Fulltext/2012/01000/Creation_of_a_Guide_for_the_Transfer_of_Care_of.12.aspx http://www.ncbi.nlm.nih.gov/pubmed/22052978?tool=bestpractice.com In MH susceptible patients this exposure may produce a clinical MH episode: a dramatic increase in metabolism, which leads to critical temperature elevation and rhabdomyolysis with potential hyperkalemia. In the absence of central core disease, susceptibility to MH is a subclinical condition. However, some MH-susceptible people may feel uncomfortable exercising in the heat, and complaints of muscle cramps are not uncommon.[3]Sagui E, Montigon C, Abriat A, et al. Is there a link between exertional heat stroke and susceptibility to malignant hyperthermia? PLoS One. 2015 Aug 10;10(8):e0135496. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4530942 http://www.ncbi.nlm.nih.gov/pubmed/26258863?tool=bestpractice.com