Triad of hyperthermia, muscle rigidity, and metabolic acidosis
– Occurs in genetically susceptible individuals (both autosomal dominant and recessive inheritance patterns)
– Triggered by general anaesthetics (volatile gases, succinylcholine)
– Hypermetabolic state induced in skeletal muscle
– Mortality decreased from 90% to 7 % with appropriate treatment
– Muscle biopsies can be used to test for susceptibility
– Disordered calcium regulation in skeletal muscle fibres may play a role in the pathophysiology of MH. There is decreased ability to retain and regulate calcium in the sarcoplasmic reticulum.
Increased intacellular calcium may lead to excessive and prolonged muscle contraction with resulting excessive heat production
Increased calcium also uncouples oxidative phosphorylation
MH is resistant to neuromuscular blockers
Dantrolene is a direct skeletal muscle relaxant which blocks calcium release from the sarcoplasmic reticulum
Dose is 2 mg/kg iv q5min until resolution
Procainamide has similar action to dantrolene and is the drug of choice for MH associated dysrhythmias
Associated with depolarizing neuromuscular blocking agents or volatile general anesthetics in genetically susceptible individuals
Treatment: withdrawal of inciting agent, supportive care, and dantrolene administration.