Malignant Hyperthermia

Malignant Hyperthermia is a rare and potentially life threatening genetically inherited condition that can be triggered by drugs commonly used in anaesthesia. If it is not recognised and treated in its early stages, MH can be fatal.

In 1962, Denborough and colleagues reported that 10 members of a Melbourne family had previously died during or shortly after having general anaesthesia. Over time it was identified that the cause was due to an inherited pharmacogenetic disorder - Malignant Hyperthermia (MH).

Malignant Hyperthermia is a rare and potentially life threatening genetically inherited condition that can be triggered by drugs commonly used in anaesthesia.  The most common triggering agents are volatile anaesthetic agents, such as sevoflurane, desflurane, isoflurane, and depolarizing muscle relaxants such as succinylcholine. In MH susceptible individuals other less common causes  include heat stress, and extreme exercise.

MH has an estimated incidence of <0.02%(2), occurring between 1:5,000-1:10,000 procedures involving general anaesthesia(3)

In the 1970s, mortality was greater than 80%; however with current management strategies, mortality is less than 5%(3).  

The disorder has been reported worldwide, affecting all racial groups. The highest incidence of MH in the world is found in the Manawatu region of New Zealand, with up to 1:200 people identified with the condition(4).

There is no cure for the autosomal dominant genetic predisposition to MH. It is hereditary being passed from parent to child. There is a 50% occurrence that a person with MH will pass the gene onto each child they have.  

An In Vitro Contracture test (IVCT) test is currently the only definitive test for MH.  The group Malignant Hyperthermia Australia & New Zealand have identified 4 locations for MH testing across Australia & New Zealand.  

If it is not recognised and treated in its early stages, MH can be fatal. General anaesthesia can be achieved avoiding triggering agents if patients are known or suspected to have MH. Clinicians involved in general anaesthesia must be aware of the signs and symptoms of Malignant hyperthermia and in order to quickly identify and effectively manage patients who develop this condition.  

If patients show signs and symptoms of MH, a rapid response is essential, all triggering agents must be discontinued, and attention focused on clinical deterioration including correcting hyperthermia, acidosis, hypercarbia, muscle rigidity, rhabdomyolysis, and organ dysfunction. Intravenous administration of Dantrolene (Dantrolene™, Ryanodex™) is the primary treatment, and the only known antidote in conjunction with other supportive measures.  

The Malignant Hyperthermia Australia and New Zealand, MH Resource Kit (published August, 2018 and endorsed by ANZCA Council in September 2018) is a comprehensive kit that can be downloaded and used by facilities using MH triggering agents on patients undergoing general anaesthesia www.malignanthyperthermia.org.au

If you are interested in gaining more knowledge on this topic and others relating to Anaesthetics & PACU nursing,  you can enrol in our live virtual classroom via the link below.

https://medcast.com.au/education/anaesthesia-pacu-nursing

For other courses relating to Anaesthetic & PACU nursing, and a full list of events and courses visit https://medcast.com.au/critical-care

Authors: Danielle Grace and Ken Hambrecht for Critical Care Education Services

References:

The New England Journal of Medicine. Date accessed: 14/10/2020.

Science Direct Date accessed 14/10/2020.

[2] Rosenberg H, Sambuughin N, Riazi S, Dirksen R. Malignant Hyperthermia Susceptibility. In: Pagon RA, Adam MP, Ardinger HH, Bird TD, Dolan CR, Fong CT, et al., editors. Gene Reviews. Seattle (WA)1993.

(3) Rosenberg H, Davis M, James D, Pollock N, Stowell K (April 2007). "Malignant hyperthermia". Orphanet Journal of Rare Diseases. 2: 21. Wikipedia - DOI, DOI, Wikipedia - PMC, NCBI, Wikipedia - PMID, Pubmed

(4) Rosenberg, Henry; Pollock, Neil; Schiemann, Anja; Bulger, Terasa; Stowell, Kathryn (4 August 2015). "Malignant hyperthermia: a review". Orphanet Journal of Rare Diseases. 10 (1): 93. Wikipedia - DOI, DOI, Wikipedia - PMC, NCBI, Wikipedia - PMID, Pubmed

Halsall PJ, Hopkins PM; Hopkins (2003). "Malignant hyperthermia". Continuing Education in Anaesthesia, Critical Care and Pain. 3 (1): 5–9. Wikipedia - DOI, DOI, Archived from the original on 2006-10-03.Malignangt Hyperthermia Australia & New Zealand 

Clinical Anesthesiology 3rd Edition.  International Edition.  2002.  p869-873.  Morgan, Mikhail, Murray, with Larson. Published by Lange Medical Books/McGraw-Hill.

Rosenberg H, Davis M, James D, Pollock N, Stowell K (April 2007). "Malignant hyperthermia". Orphanet Journal of Rare Diseases. 2: 21. Wikipedia - DOI, DOI, Wikipedia - PMC, NCBI, Wikipedia - PMID, Pubmed

Australian and New Zealand College of Anaesthetics.  Malignant Hyperthermia Malignant Hyperthermia  Site accessed 25/9/2020 

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Danielle Grace

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