[Neuromuscular inhibitory effects of propofol evaluated by cat's evoked EMG]

Neuromuscular inhibitory effects of propofol were investigated in 7 cats using muscular compound action potential (mCAP) elicited from the gastrocnemius muscle by sciatic nerve stimulation. A rectangular pulse of supramaximal strength and duration of 0.2 msec was applied serially to the sciatic nerve at 0.1 Hz during the experiments, and mCAPs obtained from the gastrocnemius muscle were recorded. After obtaining a constant mCAP amplitude, a series of 8 consecutive mCAPs (M 1-8) evoked by repetitive stimulation at 100 Hz was recorded, and M 8/M 1 amplitude ratio (M 8 amplitude/M 1 amplitude.100%) was calculated as the control value. After control variables had been obtained, initial dose of 2.5 mg.kg-1 of propofol was administered intravenously followed by continuous infusion with incremental dosages of 10, 20, 50 and 100 mg.kg-1.hr-1 of each 30 minute duration. The effects on mCAPs evoked by single and 8 consecutive repetitive stimulation were observed in each period. The depression of single mCAP amplitudes and fading responses in the M 8/M 1 amplitude ratios were not observed at any infusion rate. Our results suggest that propofol has no influence on neuromuscular transmission in cats when administered intravenously at 10 times of human clinical infusion doses.