Pretreatment with non-depolarizing muscle relaxants: the influence on neuromuscular transmission and pulmonary function.

The influence of pretreatment with non-depolarizing muscle relaxants on the neuromuscular transmission was evaluated in 40 healthy, awake, non-premedicated volunteers using train-of-four (TOF) nerve stimulation and measurement of vital capacity (VC), inspiratory force (IF), peak expiratory flow (PEF), and forced expiratory volume in the first second (FEV1). The subjects were randomly allocated to one of four groups: group I received pancuronium 0.01 mg/kg; group II pancuronium 0.015 mg/kg; group III gallamine 0.3 mg/kg, and group IV gallamine 0.4 mg/kg intravenously. TOF ratio decreased significantly in groups II, III and IV but not in group I following precurarization. Median (25 and 75 percentiles) TOF ratios after pretreatment wer 94(92-96), 89 (86-93), 92 (89-93), and 93 (87-96), respectively. Overall there were decreases in VC, IF, and PEF, but only the decrease in PEF was statistically significant in all four groups. FEV1 was unchanged. The most pronounced decrease in VC, IF, and PEF (11, 29, and 29%, respectively) was seen one subject in group II with a TOF-ratio of 63 following precurarization. Four subjects (20%) in groups II and IV experienced difficulty in breathing. All subjects were, however, able to maintain head lift for more than 10 s, and none needed respiratory support. Seventy percent of all subjects had various minor complaints as, for instance, blurred vision and difficulty in swallowing. It is concluded that the higher doses of pancuronium 90.015 mg/kg) and gallamine (0.4 mg/kg) cannot be recommended for routine precurarization.