Frequency of train-of-four stimulation influences neuromuscular response

We have compared the effects of two different frequencies oftrain-of-four stimulation of the ulnar nerve (2-Hz stimulationonce every 10 or 20 s) on onset time and potency of atracurium,vecuronium and mivacurium during balanced anaesthesia. The adductorpollicis EMG was recorded simultaneously in both hands of 24children aged 2–12 yr. After administration of an ED₅₀dose of each blocker, onset times were mean 21 (SEM 10) s shorter(P<0.05) and decreases in neuromuscular function were 22(3)% greater (P<0.001) in the hand which was stimulated onceevery 10 s. We conclude that it is not possible to compare potencyestimates of neuromuscular blocking agents if different stimulationpatterns have been used.