Comparative fading responses induced by mivacurium, XXXX , and @entity2899 in the evoked muscular compound action potentials of the cat.

@entity4094 @entity24818 @entity3370 @entity468 @entity2899 @entity2897
PURPOSE: It has been suggested that the different degrees of fade induced by nondepolarizing neuromuscular blocking agents in repetitive muscular contractions may be due to the varying affinities or binding kinetics of presynaptic nicotinic receptors. We compared the degree of fade induced by mivacurium, @entity2897 , and @entity2899 in the cat muscular compound action potential ( @entity24818 ). METHODS: In 21 @entity468 , mCAPs of the gastrocnemius muscle were evoked by paired (conditioning and test stimuli) and 2 Hz @entity3370 ( @entity3370 ) sciatic nerve stimulation. The interval between the paired stimuli was changed stepwise from 7 to 1000 ms. The ratios of the amplitude evoked by test stimulus to that evoked by the conditioning stimulus (M2/M1 ratios) and @entity3370 ratios were measured. After baseline variables had been obtained, the cat received either mivacurium (0.08 mg x kg(-1), n = 7), @entity2897 (0.05 mg x kg(-1), n = 7), or @entity2899 (0.5 mg x kg(-1), n = 7). A series of M2/M1 ratios and @entity3370 ratios were measured at various levels of partial block during recovery. RESULTS: At 10% of baseline amplitude, all agents significantly depressed the M2/M1 ratios (i.e., fade) at relatively longer intervals of paired stimuli (mivacurium, > or = 100 ms; @entity2897 . > or = 40 ms; and @entity2899 , > or = 20 ms), when compared with baseline. The order of activity to produce fade was mivacurium < @entity2897 < @entity2899 . A similar result was obtained in @entity3370 ratios measured at various levels of @entity4094 . CONCLUSION: Our results suggest that mivacurium shows a lesser degree of fade during partial @entity4094 than @entity2897 and @entity2899 .
