Malignant hyperthermia

Last reviewed:September 2019

Last updated:January 2018

Summary

A potentially lethal syndrome usually triggered by inhalation anaesthetics or suxamethonium.

The underlying genetic susceptibility is most often due to a range of autosomal-dominant mutations in RYR1.

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 metabolic 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. Muscle contracture testing can be used to exclude susceptibility to MH.

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

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

If the diagnosis is confirmed, first-degree relatives must be contacted and tested.

Definition

Malignant hyperthermia (MH) is a syndrome that typically follows exposure to potent inhalation anaesthetics and/or succinylcholine (suxamethonium) in susceptible individuals.[1] This exposure produces a dramatic increase in metabolism, which leads to critical temperature elevation and rhabdomyolysis with potential hyperkalaemia. In the absence of central core disease, susceptibility to MH is a sub-clinical condition. However, some MH-susceptible people may feel uncomfortable exercising in the heat, and complaints of muscle cramps are not uncommon.[2]

History and exam

Key diagnostic factors

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

Full details

Other diagnostic factors

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

Full details

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

Full details

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

ACUTE

inhalation anaesthetic-induced

exercise- or heat-induced

Contributors

AuthorsVIEW ALL 

Nikolaus Gravenstein, MD

Professor and Chair

Department of Anesthesiology

University of Florida at Gainesville

Gainesville

Disclosures

NG declares that he has no competing interests.

Barbara W. Brandom, MD

Retired Professor

Department of Anesthesiology

University of Pittsburgh School of Medicine

Pittsburgh

Disclosures

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.

Acknowledgements

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 

Henry Rosenberg, MD

Director

Department of Medical Education and Clinical Research

Saint Barnabas Medical Center

Livingstone

Disclosures

HR declares that he has no competing interests.

Philip Hopkins, MD

Professor of Anesthesia

University of Leeds

Academic Unit of Anesthesia

St James's University Hospital

Leeds

Disclosures

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

Thierry Girard, MD

Associate Professor

Perioperative Patient Safety

Department of Biomedicine

University Hospital Basel

Basel

Switzerland

Disclosures

TG declares that he has no competing interests.

Joseph Tobin, MD, FAAP, FCCM

Professor and Chairman

Department of Anesthesiology

Wake Forest University School of Medicine

Winston-Salem

Disclosures

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

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Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic investigations

1st investigations to order

Investigations to consider

Treatment algorithm

inhalation anaesthetic-induced

exercise- or heat-induced

Contributors

AuthorsVIEW ALL 

Nikolaus Gravenstein, MD

Disclosures

Barbara W. Brandom, MD

Disclosures

Acknowledgements

Peer reviewersVIEW ALL 

Henry Rosenberg, MD

Disclosures

Philip Hopkins, MD

Disclosures

Thierry Girard, MD

Disclosures

Joseph Tobin, MD, FAAP, FCCM

Disclosures

Differentials

Guidelines

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