Train-of-four ratio after antagonism of atracurium with edrophonium: influence of different priming doses of edrophonium.

This study was designed to investigate the effect of different priming doses of edrophonium on the relationship between the the recovery of the first twitch of the train-of-four (T1) and train-of-four (TOF) ratio. This relationship was studied after the administration of the full dose of the antagonist in all groups. Edrophonium 1.0 mg.kg-1 was administered either in a single bolus dose (Group I, controls) or in an initial dose of 0.05, 0.1, 0.15 or 0.2 mg.kg-1 followed one minute later by the remainder of the 1.0 mg.kg-1 dose in Groups II to V. Reversal was attempted at the ten per cent spontaneous recovery of twitch height (T1) from atracurium-induced neuromuscular blockade. Of all the groups studied, Group V had a significantly greater recovery in the TOF ratio at any given T1 value. When first twitch tension (T1) had recovered to 100 per cent of the control, it was found for the same tension that the TOF ratio was greater in Group V, being 0.75 compared to 0.63, 0.65, 0.65 and 0.64 in Groups I to IV respectively. The implication is that this differential ability to reverse fade (or prejunctional activity) may be involved in the acceleration of recovery.