The Effect Of Epidural Anesthesia On Vecuronium-induced Neuromuscular Block

OBJECTIVE To study the effect of epidural anesthesia on vecuronium-induced neuromuscular block by observing the time-course of vecuronium on thumb and toe under general anesthesia (GA) or combined general and epidural anesthesia (cGEA).METHODS Forty patients, ASAⅠ～Ⅱ, scheduled for abdominal total hysterectomy, were assigned to Group GA and Group cGEA(n=20, each group). Patients in Group cGEA underwent epidural puncture at L₁-L₂, and local anesthetics were administered 10 minutes after tracheal intubation. General anesthesia was induced with midazolam 2 mg, fentanyl 0.1-0.15mg and propofol given by target-controlled infusion (TCI) at a concentration of 2.5-3μg·ml^-1 in effect compartment. With the TOF-WATCH SX acceleromyograph, ulnar nerve and tibial nerve were stimulated respectively; TOFR and T1 were measured simultaneously. After calibration and single twitch height was stabilized, vecuronium 0.1 mg·kg^-1 was administered to facilitate tracheal intubation. Anesthesia was maintained with propofol 3-5μg·ml^-1 by TCI, fentanyl given by IV injection and nitrous oxide 50% in oxygen. Repetitive vecuronium was given when TOFR at the thumb recovered to 25%. Onset times and the times to reappearance of T1, T2 and T4, and the times of TOFR=25%, 50%, 75% and 90% were recorded. T1 was recorded every 5 minutes. When patients in Group cGEA were transferred to PACU, modified Bromage score was evaluated.RESULTS (1)In Group GA, lag time and onset time were shorter at the thumb than that at the toe (25.7±7.2 s vs 33.9±7.6 s,92.6±19.4 s vs 113.6±23.9 s). The time to reappearance of T1, T2 and T4 after every administration of vecuronium were shorter at the thumb than those at the toe. The duration of action was similar at the thumb and toe(47.9±13.2 min vs 48.0±11.1 min), and the spontaneous recovery time was longer at the thumb than that at the toe(48.6±10.0 min vs 35.3±17.1 min).(2)In Group cGEA, the times to reappearace of T1, T2 and T4 after every administration were shorter at the thumb than those at the toe. The durations of action was similar at the thumb and toe (57.1±11.9 min vs 53.7±15.6 min), and the spontaneous recovery time was longer at the thumb than that at the to(e56.6±18.5 min vs 47.3±20.5 min).(3)Compared with Group GA, the times to reappearace of T1, T2 and T4 and duration of action after first repeated administration of vecuronium were longer at the thumb in Group cGEA, while there was no difference at the toe. The times to reappearace of T1, T2 and T4, and the times of TOFR recovering to 25% and 90% were longer at the thumb in Group cGEA than in Group GA. And in both muscle groups, TOFR and T1 were always smaller in Group cGEA than in Group GA .CONCLUSIONS (1)The neuromuscular block of vecuronium in the toe appears slower onset and faster recovery in both Group cGEA and Group GA, compared with those at the thumb.(2)Epidural anesthesia can accelerate the onset, and delay the recovery of neuromuscular block of vecuronium, but cannot change the relationship of neuromuscular effect between thumb and toe.