| Malignant Hyperthermia
What Is Malignant Hyperthermia? MH Reporting Form (Download PDF)
Malignant Hyperthermia (MH) is an acute pharmacogenetic (autosomal dominant) disorder, which develops during or immediately after the application of general anaesthesia involving volatile agents and/or depolarising muscle relaxants.
The disorder is likely to be a result of a defect in calcium channel regulation in the muscle cell. Volatile anaesthetic agents and depolarising muscle relaxants interact with the calcium channel resulting in the clinical crisis.
The classic MH crisis consists of a hyper-metabolic state caused primarily by continued contraction of the skeletal muscles, which leads to massive CO2 production, skeletal muscle rigidity, tachyarrhythmias, unstable haemodynamics, respiratory acidosis, cyanosis, hyperkalaemia, lactic acidosis, fever, and eventually (if untreated) death. MH can present with a few or all of these features.
How do we test for it?
In Vitro Contracture Test
Survivors of an MH crisis and their family members can be tested for susceptibility to MH with an in vitro contracture test (IVCT), which exposes excised live muscle to increasing concentrations of caffeine and halothane. The test involves an open muscle biopsy, anaesthesia and specialised laboratory equipment and expertise. This test is only performed in 4 sites in Australia and New Zealand. These are the Royal Melbourne Hospital (Victoria), The Royal Perth Hospital (Western Australia), Westmead Children’s Hospital (New South Wales) and Palmerston North Hospital (New Zealand).
Some genetic testing is available in Australia and New Zealand for MH diagnosis. Simple screening of the population is not practical or useful.
Genetic testing is directed at tracking a specific mutation through a family after having determined that mutation in a known IVCT positive family member. Up to 50% of persons with a positive muscle biopsy will have a mutation identified. Genetic testing cannot yet be used to prove that a person does not have MH.