Train-of-4 quantitation of competitive neuromuscular block.

Thumb twitch in response to "train-of-4" nerve stimulation was observed in 34 anesthetized patients receiving d-tubocurarine. Over the range of 75 to 100 percent block of the 1st twitch in the train, the 4th, 3rd, 2nd, and 1st twitch become undetectable, in that order. The reappearance of twitch by spontaneous recovery also occurs predictably, following the reverse order. Counting the number of visible twitches remaining in the train (0 to 4) permits quantitative assessment of the competitive neuromuscular block 75 to 100 percent, thereby facilitates provision of profound relaxation and safeguards reversibility.