Last reviewed:September 2019
Last updated:January  2018



History and exam

Key diagnostic factors

  • presence of risk factors
  • increased minute ventilation
  • elevated core temperature
  • muscle rigidity

Other diagnostic factors

  • tachycardia
  • decreased urine output
  • excessive sweating with exercise
  • muscle cramps
  • spontaneous episodes of severe muscle stiffness

Risk factors

  • exposure to potent inhalation anaesthetic and/or succinylcholine (suxamethonium)
  • susceptibility to MH
  • previous MH episode
  • positive family history
  • exposure to illicit or designer drugs
  • exertional heat illness

Diagnostic investigations

1st investigations to order

  • discontinuation of inhalation anaesthetic
  • exhaled carbon dioxide, oxygen consumption (inspired-expired oxygen concentration difference)
  • venous blood gases
  • serum electrolytes
  • serum creatinine
  • therapeutic trial of intravenous dantrolene
  • creatine kinase
  • urinalysis
  • urine myoglobin
  • platelets
  • prothrombin time
Full details

Investigations to consider

  • caffeine halothane contracture test (CHCT)
  • in vitro contracture test (IVCT)
  • genetic testing
  • screen for muscle enzyme deficiencies
Full details

Treatment algorithm


Professor and Chair

Department of Anesthesiology

University of Florida at Gainesville




NG declares that he has no competing interests.

Retired Professor

Department of Anesthesiology

University of Pittsburgh School of Medicine




BWB has been reimbursed by the not-for-profit sponsor of the North American MH Registry (NAMHR), the Malignant Hyperthermia Association of the United States (MHAUS) for attending meetings related to the management of the NAMHR. For the past 16 years, BWB received grants from MHAUS to maintain the NAMHR. BWB has given lectures and prepared educational materials for her previous employer, the Department of Anesthesiology in the University of Pittsburgh. As of 1 July, 2016, BWB retired from that employment. BWB has published papers and prepared educational materials for MHAUS, with the help of other volunteers for MHAUS. BWB sponsored LM for an award granted by the American Society of Anesthesiologists. This award allowed LM to travel to several medical centers that were active in the diagnosis of MH, as well as to the NAMHR to improve her understanding of this syndrome. This is part of BWB's mentoring of younger anesthesiologists. BWB is also an author of a number of references cited in this topic.

Professors Nikolaus Gravenstein and Barbara W. Brandom would like to gratefully acknowledge Dr Lena Mayes, a previous contributor to this topic. LM declares that she has no competing interests.

Peer reviewersVIEW ALL


Department of Medical Education and Clinical Research

Saint Barnabas Medical Center




HR declares that he has no competing interests.

Professor of Anesthesia

University of Leeds

Academic Unit of Anesthesia

St James's University Hospital




PH is an author of a number of references cited in this monograph.

Associate Professor

Perioperative Patient Safety

Department of Biomedicine

University Hospital Basel




TG declares that he has no competing interests.

Professor and Chairman

Department of Anesthesiology

Wake Forest University School of Medicine




JT is an author of a number of references cited in this monograph.

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