Edrophonium antagonism of vecuronium at varying degrees of fourth twitch recovery.

The purpose of this study was to determine the optimal dose of edrophonium needed for successful antagonism (train-of-four ratio, or T4/T1 > 0.7) of vecuronium-induced blockade when all four twitches were visible in response to indirect train-of-four (TOF) stimulation. Forty patients, scheduled for elective surgical procedures not exceeding 120 min, received vecuronium, 0.08 mg.kg-1, during thiopentone-N2O-isoflurane anaesthesia. Train-of-four stimulation was applied every 20 sec and the force of contraction of the adductor pollicis muscle was recorded. Increments of vecuronium, 0.015 mg.kg-1, were given as required. At the end of surgery, and provided that neuro-muscular activity had recovered to four visible twitches, edrophonium, 0.1 mg.kg-1, was given. Two minutes later, edrophonium, 0.1 mg.kg-1, was given if T4/T1 did not reach 0.7. After another two minutes, edrophonium, 0.2 mg.kg-1, was given if T4/T1 did not reach 0.7 or more. Finally, if T4/T1 was still < 0.7, a dose of 0.4 mg.kg-1 was given. Seventeen patients (42.5%) required 0.1 mg.kg-1 of edrophonium for successful reversal, sixteen patients (40%) needed a cumulative dose of 0.2 mg.kg-1 and six patients (15%) required 0.4 mg.kg-1. Only one patient received 0.8 mg.kg-1. There was a good correlation between T4/T1 two minutes after the first dose of edrophonium and pre-reversal T4/T1 (r = 0.6; P = 0.00014). All patients with pre-reversal T4/T1 > 0.23 required at most 0.2 mg.kg-1 of edrophonium for successful reversal.(ABSTRACT TRUNCATED AT 250 WORDS)