Factors predicting atracurium reversal time

Background: To identify individual factors and combination of factors predi ctive of reversal time (defined as time from neostigmine administration to train-of-four (TOF) ratio 0.70) from atracurium-induced neuromuscular block , the present study tested the following variables as possible predictors o f reversal time: 1) degree of block at the time of antagonism as quantified by first response to TOF or double-burst stimulation (DBS); 2) time from l ast supplemental dose of atracurium to administration of neostigmine (pre-r eversal time); and 3) time from administration of initial atracurium dose t o T1 (the magnitude of the first twitch in TOF) recovered to 10% (duration of action of the initial dose of atracurium). Methods: The study population comprised 83 female patients, ASA physical st atus 1 or 2, anaesthetized with fentanyl, thiopental, halothane and nitrous oxide. Initial and supplemental doses of atracurium were 0.5 mg . kg(-1) a nd 0.15 mg . kg(-1), respectively. Evoked responses to TOF or DBS were reco rded mechanomyographically. Neuromuscular block was antagonized with neosti gmine, 0.07 mg . kg(-1), at varying time intervals (6-50 min) after the fin al atracurium dose. Results: Multiple linear regression analyses testing T1, D1 (the magnitude of the first twitch in DBS), pre-reversal time and duration of action of th e initial dose of atracurium, demonstrated that with superficial block, T1 >15%, T1 is the only significant Predictor for reversal time. With moderate block, 0< T1 less than or equal to 15%, both T1 and duration of action of the initial atracurium dose are significant predictors for reversal time. W ith profound block, T1=0, duration of action of the initial dose and pre-re versal time are significant predictors for reversal time. Conclusion: 1) T1 is a mere important predictor for reversal time from atra curium-induced neuromuscular block than D1; 2) predictors differ with the d egree of block: with T1 >15%, T1 is the only significant predictor; with 0< T1 less than or equal to 15%, the duration of action of the initial dose a nd T1 are predictors for reversal time; with T1=0, the duration of action o f the initial dose and pre-reversal time predict reversal time.