Fade Profiles During Spontaneous Offset of Neuromuscular Blockade: Vecuronium and Gallamine Compared

Abstract

The characteristics of the train-of-four (TOF) response have been studied electromyographically during the onset and the spontaneous offset of neuromuscular blockade induced with vecuronium or gallamine. During the onset of blockade, at 75% depression of initial twitch height, gallamine was associated with significantly more TOF fade than vecuronium. Both agents were associated with significantly less fade during onset than during spontaneous offset. When the two neuromuscular blocking drugs were compared during spontaneous offset they showed a similar degree of fade during early offset (up to 50% recovery of initial twitch height). However, during late spontaneous offset, when the initial twitch height had recovered to 75% of control values, vecuronium was associated with more fade than gallamine.

The relationship between twitch depression and twitch fade during neuromuscular block produced by vecuronium: correlation with the release of acetylcholine

“…This finding is also consistent with the results from other investigations [14,15]. During the offset of NMB, the pooled T 4 /T 1 -T 1 data pairs from all subjects (Figure 2) are similar to those reported by other investigators using vecuronium as well as other neuromuscular blocking drugs [12-16]. …”

“…Our finding that vecuronium produces less fade for any given twitch depression during the onset compared to the offset of NMB (Figure 2) is consistent with the findings reported by other investigators [12-16]. We have also found that, during the onset and at similar T 1 , larger doses of vecuronium produce less fade than smaller doses (Figure 2).…”

Train-of-four fade and neuromuscular block in rats: a comparison between pancuronium, vecuronium, and rocuronium

“…In previous studies in humans, it was noted that TOF fade depends not only on the drug but also on the size of a single bolus dose. 3,12 To exclude this dose-dependent effect, we collected data in vivoduring recovery from a uniform degree of neuromuscular block. Given that the T 1 block was stable for at least 30 min prior to data collection, a pseudo-steady-state for drug distribution between plasma and muscle is assumed to have been reached.…”

“…, all NBAs used clinically show less TOF fade during onset than during recovery. 3,10,12,23 Bartkowski et al 24 have explained this difference based on pharmacokinetic differences between muscle compartments. Generally a muscle is composed of several compartments with regard to the rate of drug distribution and elimination.…”

“…Although it is generally accepted that the relationship between the TOF fade and neuromuscular block is constant, 1,2 previous clinical reports have shown differences in the magnitude of the TOF fade during the recovery phase for different NBA at the same level of neuromuscular block. [3][4][5][6] While nondepolarizing NBAs act mainly at the postjunctional site, some investigators have suggested that they also have a prejunctional effect that is responsible for the TOF fade. [7][8][9][10][11] Consequently, drug-dependent differences in TOF fade are believed to be a function of their prejunctional potency.…”