Recovery of mivacurium block with or without anticholinesterases following administration by continuous infusion.

Thirty patients received a bolus dose of 0.2 mg.kg-1 of mivacurium followed by an infusion during anaesthesia with thiopentone, fentanyl and halothane. Neuromuscular block was monitored using train-of-four stimulation and mechanomyography and the block maintained to keep the first response in the train-of-four (T1) at 10% of control. At the end of surgery the patients were randomly allocated to reversal with neostigmine or edrophonium or to spontaneous recovery. The mean dosage of mivacurium for maintaining the T1 at 10% was 5.7 micrograms.kg-1.min-1. There was a significant (r = -0.81, p < 0.001) negative correlation between time to recovery of T1 to 10% after the bolus dose and infusion rate. The times taken for T1 to reach 25, 75 and 90% of control and for the train-of-four ratio to reach 0.7 were significantly shorter (p < 0.05 to 0.001) with neostigmine and edrophonium compared to the spontaneously recovering group. The average (SD) times for attaining the train-of-four ratio of 0.7 were 7.0 (1.2), 6.8 (1.4) and 13.5 (2.3) min respectively for neostigmine, edrophonium and spontaneously recovering groups. There were no differences between endrophonium and neostigmine in any of the recovery times.