Edrophonium antagonism of intense mivacurium-induced neuromuscular block in children.

We have studied the time course of recovery after administration of edrophonium during intense mivacurium block in children aged 2-10 yr, using thumb 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 randomly to one of three groups. Patients in group 1 (n = 15) received edrophonium 1 mg kg-1, 2 min after maximum block (intense block group). At the time of administration of edrophonium in this group, there was no response to TOF stimulation (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 patients developed complete suppression of twitch height in response to the bolus dose of mivacurium. All recovery times were measured from the point of maximum block after mivacurium. Mean time for 25% recovery of T1 (clinical duration) was 3.8 (SD 1.1) min in the intense block group. This was significantly shorter than the conventional reversal (8.3 (2.4) min) and spontaneous recovery (9.2 (3.5) min) groups (P < 0.001). The times for 75% 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 was significantly 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 time compared with spontaneous recovery (P < 0.01). The recovery index (time interval 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 of maximum block, the numbers of patients who recovered adequately (TOF ratio 70% or more) were, respectively, 12 (80%), 8 (53%) and 1 (8%) in groups 1-3. We conclude that edrophonium antagonized intense (no response to TOF stimulation) mivacurium-induced block in children, with significant reduction in the recovery times of T1 and TOF ratio compared with conventional reversal and spontaneous recovery.