Suxamethonium block in the myasthenic patient. Correlation with plasma cholinesterase.

The neuromuscular block of suxamethonium 1.5 mg.kg-1 was investigated in three myasthenic patients (Class IIA), undergoing thymectomy. Two of the patients were receiving pre-operative pyridostigmine therapy. In the three patients, plasma cholinesterase activity was determined on the morning of surgery and was correlated with the neuromuscular response to suxamethonium as monitored by electromyography. The results suggest that the response to suxamethonium in the myasthenic patients can show wide variations according to the level of their plasma cholinesterase activity. The degree and duration of suxamethonium block is inversely related to the plasma cholinesterase activity.