Information for Anaesthetists
Definitions
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 as 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 is caused primarily by excess calcium availability in the skeletal muscle cytoplasm resulting in excessive muscle contraction and hypermetabolism.
This 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.
History
Malignant hyperthermia was first described as genetically inherited entity in a letter to the editor of the Lancet in 1960 penned by Michael Denborough and Richard Lovell1 and in a follow up article in 1962 in the British Journal of Anaesthesia2.
The family described showed an autosomal dominant pattern of inheritance for this reaction to anaesthesia. The original letter called for others to share experiences with this type of reaction and the term malignant (