Pretreatment with Non-Depolarizing Muscle Relaxants: The Influence on Neuromuscular Transmission and Pulmonary Function

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Abstract
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-4 (TOF) nerve stimulation and measurement of vital capacity (VC), inspiratory force (IF), peak expiratory flow (PEF) and forced expiratory volume in the 1st s (FEV1). The subjects were randomly allocated to 1 of 4 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 i.v. 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 were 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 4 groups. FEV1 was unchanged. The most pronounced decrease in VC, IF and PEF (11, 29 and 29%, respectively) was seen in 1 subject in group II with a TOF-ratio of 63 following precurarization. Subjects (4, 20%) in groups II and IV experienced difficulty in breathing. All subjects were able to maintain head lift > 10 s and none needed respiratory support. Of all subjects, 70% had various minor complaints, i.e., blurred vision and difficulty in swallowing. The higher doses of pancuronium (0.015 mg/kg) and gallamine (0.4 mg/kg) cannot be recommended for routine precurarization.