Anaes · Critical incidents
Malignant hyperthermia
Also known as MH · MH crisis · Malignant hyperpyrexia · Anaesthesia-induced rhabdomyolysis · Dantrolene
Exam-exhaustive malignant hyperthermia: RYR1 calcium storm, absolute trigger list, early ETCO2/masseter signs, EMHG/MHAUS crisis bundle, exact dantrolene dosing, cooling and hyperkalaemia/DIC management, trigger-free technique, and family counselling with MH unit referral for ANZCA Final and equivalents.
Checked against its sources on 1 Oct 2026
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Target exams
Red flags
- Unexplained rising ETCO2 that will not fall with increased ventilation is the sentinel sign — fever is late; waiting for fever kills.
- Dantrolene 2.5 mg/kg IV immediately, repeated until hypermetabolism controlled (commonly up to 10 mg/kg total) — do not wait for a perfect diagnosis.
- Never give verapamil or other calcium-channel blockers with dantrolene — severe hyperkalaemia and cardiovascular collapse.
- Masseter rigidity after suxamethonium is a warning shot: stop triggers, watch metabolism, treat early.
- Known MH susceptibility = TIVA, vapour-free machine, no suxamethonium, dantrolene in the room, family/MH unit follow-up.
Meet the patient
A 24-year-old man having a knee arthroscopy is forty minutes into a sevoflurane anaesthetic when the end-tidal carbon dioxide climbs from 4.5 to 9 kPa despite a doubling of the minute ventilation. His heart rate is 140, his jaw is tight after the suxamethonium you gave at induction, and the soda lime is warm. The temperature probe reads 38.4 degrees and is still rising.[2]
The two questions that decide his next ten minutes are the two that decide every hyperthermia crisis: is the carbon dioxide rising against ventilation? and has he been exposed to a trigger? Answer yes to both and you do not wait for a temperature — you open the dantrolene drawer now.[2]
References9ShowHide
- [1]Glahn KPE, Girard T, Hellblom A, et al. Recognition and management of a malignant hyperthermia crisis: updated 2024 guideline from the European Malignant Hyperthermia Group Br J Anaesth, 2025.PMID 39482150
- [2]Larach MG, Gronert GA, Allen GC, et al. Clinical presentation, treatment, and complications of malignant hyperthermia in North America from 1987 to 2006 Anesth Analg, 2010.PMID 20081135
- [3]Rosenberg H, Pollock N, Schiemann A, et al. Malignant hyperthermia: a review Orphanet J Rare Dis, 2015.PMID 26238698
- [4]Krause T, Gerbershagen MU, Fiege M, et al. Dantrolene--a review of its pharmacology, therapeutic use and new developments Anaesthesia, 2004.PMID 15023108
- [6]Schuster F, Johannsen S, et al. [Pharmacological Treatment of Malignant Hyperthermia: Update 2019]. Anasthesiol Intensivmed Notfallmed Schmerzther, 2019.PMID 31525788
- [7]Rüffert H, Bastian B, Bendixen D, et al. Consensus guidelines on perioperative management of malignant hyperthermia suspected or susceptible patients from the European Malignant Hyperthermia Group Br J Anaesth, 2021.PMID 33131754
- [8]Riazi S, Biesecker LG, Rosenberg H, Dirksen RT Nonsyndromic Malignant Hyperthermia Susceptibility GeneReviews (NCBI Bookshelf), 1993.PMID 20301325
- [9]Larach MG, Brandom BW, Allen GC, Gronert GA, Lehman EB. Cardiac arrests and deaths associated with malignant hyperthermia in north america from 1987 to 2006 Anesthesiology, 2008.PMID 18362591
- [10]Allen GC, Larach MG, Kunselman AR. The sensitivity and specificity of the caffeine-halothane contracture test: a report from the North American Malignant Hyperthermia Registry of MHAUS. Anesthesiology, 1998.PMID 9523799