Summary
We examined the effect of milrinone, a phosphodiesterase III inhibitor, on neuromuscular block induced by vecuronium. Thirty adult patients were randomly assigned to one of two equal groups: the milrinone group and the control group. Subjects in the milrinone group received an intravenous loading dose of milrinone 5βΞΌg.kg^β1^.min^β1^ for 10βmin, followed by an infusion at a rate of 0.5βΞΌg.kg^β1^.min^β1^. Subjects in the control group received normal saline at a rate of 0.1βml.kg^β1^.h^β1^. Thirty minutes after the beginning of the infusion of milrinone, anaesthesia was induced with intravenous thiopental 4βmg.kg^β1^ and fentanyl 2βΞΌg.kg^β1^, and was maintained with isoflurane in oxygen and nitrous oxide. Neuromuscular blockade was monitored electromyographically at the adductor pollicis muscle. The times from the administration of vecuronium 0.1βmg.kg^β1^ to the onset of neuromuscular block and the return of the first, second, third, and fourth response of the trainβofβfour were compared between the two groups. Times to the recovery of the ratio of the first twitch to the control twitch to 25%, 50% and 75%, and times to the recovery of trainβofβfour ratio to 25%, 50% and 75% were also compared between the two groups. The onset of neuromuscular block in the milrinone group was significantly slower than in the control group. The times to the returns of the four twitches of the trainβofβfour, times to recovery of the ratio of the first twitch to the control twitch to 25% and 50%, and the times to the recovery of the trainβofβfour ratio to 25% and 50% were significantly shorter in the milrinone group than in the control group. We conclude that milrinone delays the onset of neuromuscular blockade but hastens its recovery in anaesthetised patients receiving vecuronium.