Duration of action of vecuronium after an intubating dose of rapacuronium,vecuronium, or succinylcholine

Rapacuronium (RAP) is a new, rapid-onset, short-duration, nondepolarizing n euromuscular blocker. Lf RAP is used to facilitate endotracheal intubation, what will the duration of a subsequent maintenance dose of vecuronium (VEC ) be? We investigated the duration of action of a maintenance dose of VEC a fter intubation with RAP, VEC, or succinylcholine (SUC). Adult surgical pat ients under general anesthesia were randomly allocated to receive a trachea l intubating dose of RAP 1.5 mg/kg, VEC 0.1 mg/kg, or SUC 1 mg/kg. The anes thetic was induced with propofol and maintained with propofol, nitrous oxid e, and oxygen. Neuromuscular function was monitored with electromyography. Recovery of the intubating dose of neuromuscular blocker was allowed to occ ur spontaneously until the first twitch of the train-of-four (T1) reached 5 0% of baseline, and then VEC 0.025 mg/kg (0.5 x 95% effective dose [ED95]) was administered. The onset, duration, and recovery to T1 = 25% and 50% wer e recorded. The durations of action (recovery of T1 25%) after intubating d oses of RAP, VEC, and SUC were 13.7 +/- 5.3, 43.2 +/- 13.2, and 9.2 +/- 3.7 min (mean +/- so), respectively (P < 0.0001). The times to maximum depress ion of T1 after a maintenance dose of VEC (0.5 x ED95) were 5.4 <plus/minus > 2.9, 5.1 +/- 2.5, and 5.3 +/- 2.8 min (mean +/- so) for the RAP,VEC, and SUC groups, respectively. Recoveries to T1 25% after VEC for the RAP, VEC, and SUC groups were 18.9 +/- 11.5, 21.5 +/- 8.03, and 12.8 +/- 8.4 min,and at TI 50% they were 21.5 +/- 9.1, 30.8 +/- 9.5, and 15.5 +/- 9.7 min (mean +/- so), respectively (P < 0.001, RAP and VEC versus SUC). The duration of action of a maintenance dose of VEC was similar after an intubating dose of RAP or VEC but was shortened when preceded by an intubating dose of SUC.