Edrophonium antagonism of intense mivacurium-induced neuromuscular block in children

We have studied the time course of recovery after administration ofedrophonium during intense mivacurium block in children aged 2-10 yr, usingthumb acceleration in response to train-of-four (TOF) stimulation.Forty-three children receiving alfentanil, propofol, nitrous oxide,isoflurane anaesthesia and mivacurium 0.2 mg kg-1 were allocated randomlyto one of three groups. Patients in group 1 (n = 15) received edrophonium 1mg kg-1, 2 min after maximum block (intense block group). At the time ofadministration of edrophonium in this group, there was no response to TOFstimulation (100% block) and the post-tetanic count was 10.7 (range 0-20).Patients in group 2 received the same dose of edrophonium after 10%recovery of the first twitch (T1) in the TOF (conventional reversal).Patients in group 3 (n = 13) recovered spontaneously. All patientsdeveloped complete suppression of twitch height in response to the bolusdose of mivacurium. All recovery times were measured from the point ofmaximum block after mivacurium. Mean time for 25% recovery of T1 (clinicalduration) was 3.8 (SD 1.1) min in the intense block group. This wassignificantly shorter than the conventional reversal (8.3 (2.4) min) andspontaneous recovery (9.2 (3.5) min) groups (P < 0.001). The times for75% and 90% recovery of T1 were shorter in the intense block group (9.4(2.8), 12.3 (4.2) min) compared with the conventional (13.1 (3.8), 17.3(4.8) min) and spontaneous recovery (14.9 (4.5), 17.9 (5.2) min) groups (P< 0.01). Total recovery time required for 70% recovery of the TOF ratio(T4/T1) was 8.8 (2.4) min in the intense block group. This wassignificantly shorter than the conventional reversal (11.9 (3.2) min) (P< 0.05) and spontaneous recovery (17.1 (4.0) min) groups (P < 0.001).Conventional reversal was associated with a shorter total recovery timecompared with spontaneous recovery (P < 0.01). The recovery index (timeinterval between T1 25% and 75%) was comparable in groups 1-3 (5.5 (2.0),4.8 (2.1) and 5.7 (1.4) min respectively). Ten minutes after development ofmaximum block, the numbers of patients who recovered adequately (TOF ratio70% or more) were, respectively, 12 (80%), 8 (53%) and 1 (8%) in groups1-3. We conclude that edrophonium antagonized intense (no response to TOFstimulation) mivacurium-induced block in children, with significantreduction in the recovery times of T1 and TOF ratio compared withconventional reversal and spontaneous recovery.