Malignant hyperthermia (MH) is a hypermetabolic reaction occurring during general anaesthesia in response to specific triggering agents. If MH is not recognised and treated appropriately, it can be fatal.
Malignant hyperthermia susceptibility is not usually associated with any symptoms during every-day life. Occasionally persons with malignant hyperthermia susceptibility have muscle symptoms which may need to be investigated further.
The triggering drugs are the potent inhalational anaesthetics (isoflurane, sevoflurane, desflurane, etc.) and the depolarising neuromuscular blocking drug suxamethonium.
Potent inhalational anaesthetics are used by the majority of anaesthetists for most surgical procedures. MH susceptible patients should not receive the MH triggering drugs.
Alternative anaesthetic agents are available and anaesthesia for MH susceptible individuals is of equivalent risk to the general population when triggering agents are avoided. This is why it is important to clarify MH susceptibility status for individuals and their family.
Diagnosis of MH
Muscle biopsy testing
Definitive diagnosis requires an open muscle biopsy and contracture study known as the in vitro contracture test (IVCT). This can only be done in specialised laboratories as it relies on the testing of freshly excised muscle samples.
There are 3 laboratories where IVCT is performed in Australia and 1 in New Zealand.
Genetic screening
Genetic Screening can identify 35 to 40% of true MH cases but it cannot be used to exclude MH susceptibility. In most cases it is used in conjunction with invasive muscle biopsy testing after referral to an MH diagnostic centre. Genetic screening should only be undertaken in conjunction with appropriate genetic counselling which can be accessed via the MH diagnostic unit.
Patient referral information
If one of your patients’ needs referring to an MH unit because of a family history of malignant hyperthermia please fill in the following form and the information will be received by the appropriate Diagnostic Unit who will contact the patient directly.