Neuromuscular effects of vecuronium and neostigmine in Montreal and Paris

The potency of vecuronium was reported to be greater in Montréal than in Paris. This study was designed to determine whether there were differences in onset, duration, and reversibility with neostigmine between both centres. Twenty ASA I or II adults (ten men, ten women), aged 18-65 yr were studied in each of the two cities, during a standard thiopentone-fentanyl-nitrous oxide (60-70%) - isoflurane 0.5% end-tidal anaesthetic. Train-of-four stimulation was applied every 20 sec to the ulnar nerve at the wrist and the force of contraction of the adductor pollicis muscle was measured. Vecuronium, 0.1 mg.kg-1, was given as a bolus, and neostigmine, 0.04 mg.kg-1, was administered, with atropine 0.02 mg.kg-1, at 25% first twitch height recovery. Onset time to maximum blockade was (mean +/- SD) 3.9 +/- 1.3 min in Paris vs 4.5 +/- 1.3 min in Montréal (NS). Duration from injection to 25% first twitch recovery was shorter (28.5 +/- 6.8 min) in Paris than in Montréal (39.1 +/- 7.3 min) (P < 0.0001). Time from injection of neostigmine to a train-of-four ratio of 70% was not different in Paris (6.3 +/- 2.2 min) from Montréal (5.6 +/- 1.9 min). It is concluded that the duration of an "intubating" dose of vecuronium is longer in Montréal, but, when given at 25% first twitch recovery, neostigmine has the same efficacy in Montréal as in Paris.