THE EFFECT OF SUCCINYLCHOLINE ON ATRACURIUM-INDUCED NEUROMUSCULAR BLOCK

Background: The interaction between prior succinylcholine and atracuri um has been found only after full recovery of succinylcholine block. W e investigated whether the effect of succinylcholine on atracurium blo ck may depend on the level of recovery from succinylcholine. Methods: Fifty patients in 4 groups received atracurium 0.2 mg/kg when first re sponse (T1) in train-of-four (TOF) after succinylcholine 1 mg/kg had r ecovered to 5%, 25%, 75% or 100%. A control group received only atracu rium. The following indices were compared: the time from injection of atracurium to maximum block (onset time) and to return of T1 to 25% (d uration 25%), maximal depression of T1, time from 25% to 75% recovery of T1 (interval 25-75%) and time from injection of atracurium to a TOF ratio of 0.75 (duration TOF 0.75). Results: Onset time was shorter, m ax T1 depression was greater and duration 25% increased the more succi nylcholine recovery progressed. Neither interval 25-75% nor duration T OF 0.75 varied with the level of recovery from succinylcholine. The co ntrol group showed a shorter latency and onset time compared to the ea rly (5%) recovery group and a longer onset time and less depressed T1 compared to the late (100%) recovery group. There was no difference be tween the control group and the early or late recovery groups, respect ively for duration 25% or duration TOF 0.75. Conclusion: The effect of prior administration of succinylcholine on atracurium block depends o n the state of recovery from succinylcholine and concerns both its pot ency, onset and duration characteristics.