Myasthenia gravis and pipecuronium--report of two cases.

The use of pipecuronium in two patients with myasthenia gravis undergoing thymectomy is described. Neuromuscular function was monitored throughout using the train-of-four (TOF) mechanical twitch response. The cumulative dose-response to pipecuronium was determined in both patients during nitrous oxide-oxygen-narcotic anaesthesia. Both patients were sensitive to pipecuronium. The ED50 doses of pipecuronium were 11.6 and 11.1 micrograms.kg-1 and the ED95 doses were 35 and 33.3 micrograms.kg-1 in patients #1 and 2 respectively. Edrophonium 1 mg.kg-1 and neostigmine 0.06 mg.kg-1 were administered to patients #1 and 2 respectively for antagonism of residual neuromuscular blockade at 25 per cent spontaneous recovery of first twitch (T1) of the TOF stimulation. As with other non-depolarizing muscle relaxants pipecuronium in reduced dosage and with careful neuromuscular monitoring can be used to provide surgical relaxation safely in patients with controlled myasthenia gravis.