Use of atracurium or vecuronium to prolong the action of tubocurarine.

Forty patients received tubocurarine in a dose greater than ED90. When neuromuscular function had recovered to amplitude of the first contraction of the train-of-four equals 10% of control, a small increment of atracurium or vecuronium was administered, repeating the same increment at each subsequent recovery to 10%. The intensity and duration of the neuromuscular block following the first increment was always greater than that of subsequent increments. The duration and intensity of the block was progressively reduced with subsequent increments until the responses to further increments were unchanged. These final means at steady state were: group 1 (atracurium 1.1 mg) 6.4 (0.3) min; group 2 (atracurium 2.0 mg) 8.2 (0.9) min; group 3 (vecuronium 0.25 mg) 5.8 (0.4) min; group 4 (vecuronium 0.5 mg) 13.2 (0.4) min.