The implications of myasthenia gravis for the anaesthesiologist

Myasthenia gravis is an autoimmune disease in which antibodies which are generated to the acetylcholine nicotinic receptors at the motor end plate cause skeletal muscle weakness.(1) There appears to be an association with the thymus gland, where T cells generate antibodies after being sensitised to a protein similar to the acetylcholine receptor.(1) Historically, myasthenia gravis was classified into five classes by Osserman, ranging from eye involvement alone, to mild, moderate or severe weakness, and the need for intubation and ventilation.(1) Patients with myasthenia gravis are commonly treated with the acetylcholinesterase inhibitor, pyrodistigmine, glucocorticosteroids, other immune suppressants, as well as plasma exchange and intravenous immunoglobulins. Patients with generalised disease may present for surgery to remove the thymus gland, after which approximately 75% of patients enter remission.(1) In the perioperative period, the nuances of the disease process must be appreciated in order to provide the most beneficent care. Neuromuscular blockade should be avoided unless absolutely necessary, and when non-depolarising agents are used, they must always be accompanied by monitoring of the neuromuscular junction and appropriately reduced doses, due to the increased sensitivity to these agents. Sugammadex should also be available. These patients are relatively resistant to succinylcholine, and an increased dose should be used with the knowledge that prolonged blockade may ensue.(1)