RECOVERY CHARACTERISTICS AFTER EARLY ADMINISTRATION OF ANTICHOLINESTERASES DURING INTENSE MIVACURIUM-INDUCED NEUROMUSCULAR BLOCK

The time course of recovery after early administration of anticholines terases during intense mivacurium-induced block was evaluated by recor ding the mechanomyographic response of the adductor pollicis to post-t etanic count (PTC) and train-of-four (TOF) ulnar nerve stimulation. Se venty-two adult patients receiving thiopentone, fentanyl, nitrous oxid e, isoflurane anaesthesia and mivacurium 0.15 mg kg(-1) were allocated randomly to one of six equal groups according to the type of antichol inesterase and intensity of block at which antagonism was attempted. G roups 1, 3 and 5 received neostigmine 0.07 mg kg(-1), while groups 2, 4 and 6 received edrophonium 1 mg kg(-1). At the time of administratio n of antagonist there was no response to PTC in groups 1 and 2, a PTC of 1 or more was detectable in groups 3 and 4 and the first twitch of the TOF (T1) had recovered to 10% in the conventional antagonism group s (5 and 6). The longest clinical duration (CD) values (time from admi nistration of mivacurium to T1 25%) were encountered in groups 1, 5 an d 6 and were 17.4 (7.9), 19.7 (3.4) and 21.4 (4.8) min, respectively. CD was reduced significantly in groups 2, 3 and 4 and values were 13.9 (3.5), 13.7 (3.5) and 13.8 (3.3) min, respectively. Recovery indices (RI) (time interval between T1 25% and 75%) were 13.8 (7.3), 6.3 (1.4) , 4.6 (1.8), 6.0 (2.1), 3.7 (2.2) and 4.8 (3.1) min in groups 1-6, res pectively and was prolonged with neostigmine antagonism at PTC 0 (grou p 1). Reversal time (RT) (time between administration of antagonist an d TOF 0.70) was 34.9 (16.6) min in group 1 who received neostigmine at PTC 0 and was prolonged markedly compared with all other groups. Anta gonism with edrophonium at PTC 0 (group 2) was associated with an RT o f 16.7 (5.1) min and was significantly longer compared with the conven tional antagonism groups only. Reversal times were similar in groups 3 -6. Total recovery times (TRT) (time between administration of mivacur ium and TOF 0.70) were 41.5 (16.6), 23.2 (5.2), 23.2 (5.3), 24.1(4.5), 26.8 (4.8) and 28.5 (9.1) min in groups 1-6, respectively, and was ma rkedly prolonged in group 1 only. In summary, administration of neosti gmine during intense mivacurium block, not responsive to TOF and PTC s timulation was associated with marked delay in recovery, possibly beca use of inhibition of plasma cholinesterase. At this intensity of block , edrophonium was preferable. It is advisable to wait for a detectable PTC before attempting antagonism of an intense mivacurium block. Afte r detection of PTC, neostigmine or edrophonium antagonism reduced the clinical duration but not the total recovery time compared with conven tional reversal administered at T1 10%.