Residual Block after Mivacurium with or without Edrophonium Reversal in Adults and Children

Background: The rapid recovery from mivacurium-induced neuromuscular block has encouraged omission of its reversal. The purpose of this study was to determine, in children and in adults, whether failure to reverse mivacurium neuromuscular block was associated with residual neuromuscular block on arrival in the postanesthesia care unit.

Methods: In 50 children, aged 2-12 yr, and 50 adults, aged 20-60 yr, anesthesia was induced and maintained with propofol and fentanyl, and neuromuscular block was achieved by an infusion of mivacurium, to maintain one or two visible responses to train-of-four (TOF) stimulation of the ulnar nerve. At the end of surgery, mivacurium infusion was stopped, and 10 min later, reversal was attempted with saline or 0.5 mg *symbol* kg sup -1 edrophonium by random allocation. On arrival in the postanesthesia care unit, a blinded observer assessed patients clinically and by stimulation of the ulnar nerve with a Datex electromyogram in the uncalibrated TOF mode.

Results: Children arrived in the postanesthesia care unit 8.2 +/-3.4 min after reversal of neuromuscular block and showed no sign of weakness, either clinically or by TOF stimulation. Although TOF ratio was greater in children who had received edrophonium (1.00 +/-0.05 vs. 0.93+/-0.01, P < 0.01), TOF was > 0.7 in all children. Adults arrived in the postanesthesia care unit 12.9+/- 5.3 min after reversal of neuromuscular block (P < 0.01 vs. children). Six in the saline group demonstrated weakness (two required immediate reversal of neuromuscular block, and TOF was < 0.7 in four others), compared with TOF < 0.7 in only one of the edrophonium group (P < 0.05).