[Effects of succinylcholine on neuromuscular transmission during recovery from vecuronium]

Effects of succinylcholine (SCC), 1 mg.kg-1, given following incomplete recovery from muscle paralysis induced by vecuronium were investigated in 27 female patients undergoing elective surgery, which was performed under epidural anesthesia. Anesthesia was induced with thiamylal 5 mg.kg-1 followed by SCC to facilitate orotracheal intubation. Vecuronium bromide 0.08 mg.kg-1 was given and the lungs were ventilated with 67% N2O in O2 and 0.6% sevoflurane. Neuromuscular function was monitored by means of the induced EMG. The ulnar nerve was stimulated at the wrist. Supramaximal trains of four stimuli (2 Hz for 2 s: pulse width 0.2 ms) were administered every 20 s. The effect of SCC varied depending upon the degree of recovery from vecuronium. At the 25% recovery point, the response to SCC was biphasic, showing an initial reversal followed by an increase of the partial vecuronium block which recovered showing a fade phenomenon on train-of-four stimulation. At the 50% recovery point, an initial reversal was slight. Administered at 75% recovery from vecuronium, SCC produced total neuromuscular blockade without initial recovery. The overall duration of the SCC effect (time from the administration to 90% recovery) was 7-18 min. No prolonged paralysis from SCC occurred.