SPONTANEOUS VERSUS EDROPHONIUM-INDUCED RECOVERY FROM PARALYSIS WITH MIVACURIUM

This study compared spontaneous with edrophonium-induced recovery of n euromuscular transmission (NMT) after mivacurium infusion. During nitr ous oxide-narcotic-propofol anesthesia, the electromyogram (EMG) of th e adductor pollicis (AP) was recorded and the movement of the first to e in response to stimulation of the posterior tibial nerve was noted. Mivacurium infusion was titrated to produce a posttetanic count of 1-5 at the toe and absence of NMT at the AP. Thirty children were assigne d to three groups on the basis of age. Edrophonium, 1 mg/kg, with atro pine 10 mu g/kg, was given after the mivacurium infusion when NMT of t he AP was 1% or 10% of baseline. In the third group, spontaneous recov ery was observed. Edrophonium given when NMT was 11% +/- 1% SEM produc ed the most rapid recovery, 7.5 +/- 0.6 min to a train-of-four (TOF) r atio (T4/T1) of 0.9 and the shortest interval from T4/T1 of 0.4-0.9, w hen residual block was likely to be underestimated, 4.8 +/- 0.6 min. E drophonium given when block was greater produced recovery of the T4/T1 to 0.4 in 2.8 +/- 0.7 min, but the time from then to T4/T1 = 0.9 was 7.9 +/- 1.1 min, as long as during spontaneous recovery. Spontaneous r ecovery to T4/T1 = 0.9 occurred 12.9 +/- 0.7 min after the first measu rable AP EMG. There was no significant relationship between duration o f infusion, which ranged from 16 to 135 min, and time to appearance of AP EMG after the infusion, which averaged 3.1 +/- 0.5 min. We recomme nd that administration of edrophonium to induce reversal of mivacurium be delayed until two responses to a TOF stimuli are observed because this will produce the most rapid recovery and decrease the interval in which residual block may be underestimated.