The condition is thought to be due to a loss of the normal control of calcium homeostasis in skeletal muscle when exposed to these agents. This results in marked metabolic stimulation which in turn produces the clinical signs of an MH reaction, one of which is a rapid rise in temperature, hence its name.
When first identified, malignant hyperthermia (MH) was known as malignant hyperpyrexia. First described in Australia, MH is an inherited condition in which susceptible patients can develop a potentially fatal reaction to certain anaesthetic agents.
What are the causes?
How is it diagnosed?
The clinical diagnosis needs to be confirmed by laboratory testing of living muscle tissue, a muscle biopsy. If the test is positive the patient is provided with full information about MH and the family is offered screening based on the autosomal dominant pattern of inheritance, that is parents, siblings and children of the patient in the first instance. About 40 per cent of families carry one of the 29 RYR1 diagnostic mutations associated with MH. Genetic testing using DNA from blood samples has recently become available as a preliminary screen for suitable families but this will still need to be coordinated through a MH centre.
Patients known to be susceptible to MH or who have a family history of MH must inform any anaesthetist treating them about their condition who can then arrange safe alternative anaesthesia. Advice can be obtained from the MH centre.
The condition does not affect the general health of the patient and previous uneventful general anaesthesia does not exclude MH.
How is it treated?
Originally, mortality was 70 to 80 per cent but this is now significantly reduced to two to three per cent due to the improved monitoring facilities in the operating theatre and the availability of dantrolene, the only specific treatment, enabling the reaction to be detected much earlier and successfully treated.
The UK MH referral centre and National MH register is at St James's University Hospital, Leeds; Tel: 01132 065274/0 (medical emergencies only) or Tel: 0113 2433133 ask for the MH consultant on call.
There is also a European European Malignant Hyperthermia Group (EMHG) composed of 23 MH centres throughout Europe - see their website for details.
Is there support?
There is currently no support group for Malignant Hyperthermia in the UK.
Families can use Contact a Family's freephone helpline for advice, information and, where possible, links to other families. Contact a Family also has a web-based linking service at community.cafamily.org.uk