"Train-of-four" fade during clinical nondepolarizing neuromuscular block

Previous clinical studies on the train-of-four (TOF) fade have used different recording techniques, anesthesia agents and muscles for measurement, thus comparison of the results has become difficult. On 49 surgical patients divided into 6 groups, we compared: 1) The TOF fade ratios (T4/T1) produced by d-tubocurarine (dTc), pancuronium (P), atracurium (A), and vecuronium (V) and 2) the influence of previously given suxamethonium on TOF ratios (dTc and P). Neuromuscular block (NMB) was monitored simultaneously by electromyography (EMG) and by mechanomyography (MMG). Differences between the TOF fade ratios of different groups were determined and statistically analyzed by ANOVA of repeated measures, 1) at onset, as compared to spontaneous recovery with the same agent, 2) between NMB agents at (a) onset and (b) during recovery.

TOF fade was significantly more pronounced during spontaneous recovery than during onset of NMB: a) with all NMB agents, b) with both EMG and MMG responses, with bolus dose administration of the agents, c) the degrees of TOF fade significantly differed between NMB agents during onset, d) the degrees of TOF fade (MMG) were more pronounced during onset when the agents were given in incremental doses following succinylcholine as compared to degrees of fade following single bolus doses in the absence of succinylcholine. During recovery, there was also difference in the TOF fade ratios among the agents: dTc and P produced more fade than A and V.(ABSTRACT TRUNCATED AT 250 WORDS)