Rate of onset of good intubating conditions, respiratory depression and hand muscle paralysis after vecuronium.

The development of neuromuscular blockade of the adductor pollicis muscle following vecuronium 0.1, 0.15 and 0.2 mg kg-1, was compared with the development of intubating conditions and respiratory paralysis. From this relationship, the optimal time after injection required for ideal tracheal intubation was calculated for the three doses of vecuronium. The effects of these doses of vecuronium on the onset, the duration of action and rate of recovery were studied. Vecuronium and "light" thiopentone anaesthesia produced ideal intubation conditions only when complete neuromuscular blockade had been established for at least 30 s. Intubation could be carried out with minimal reaction 3.5 and 2.5 min after the injection of vecuronium 0.1 mg kg-1 and 0.2 mg kg-1, respectively. Pancuronium 0.1 mg kg-1 produced good conditions about 3.8 min after injection. Suxamethonium 1.5 mg kg-1 (preceded by gallamine 20 mg 2 min earlier), produced excellent conditions in under 1 min. Hypopnoea occurred when the peripheral neuromuscular blockade was about 20-40% established with vecuronium or 50% established with pancuronium. Increasing the dose of vecuronium from 0.1 mg kg-1 to 0.2 mg kg-1 prolonged significantly the duration of action (from 21 to 48 min) but did not shorten significantly the onset time nor prolong the rate of recovery.