Extending a pipecuronium neuromuscular block. Increments of atracurium or vecuronium as an alternative to pipecuronium.

Ten patients received increasing doses of pipecuronium at induction of anaesthesia. A dose response relationship was then constructed from which ED90 and ED95 values were measured as 43.4 micrograms.kg-1 and 50.5 micrograms.kg-1 respectively. A further 30 patients received pipecuronium in a dose sufficient to produce greater than 90% neuromuscular block. When the first contraction of the train-of-four had returned to 10% of control, a small increment of atracurium (1.1 mg), vercuronium (0.25 mg) or pipecuronium (0.21 mg) was administered, and this was repeated subsequently using the same criterion of recovery on each occasion. The duration and intensity of the block with pipecuronium increments remained constant. The duration of the block following atracurium or vecuronium was progressively less with subsequent increments until steady state was reached. The final mean durations at steady state were pipecuronium 7.37 min, atracurium 6.99 min, and vecuronium 5.15 min.