Comparative neuromuscular inhibitory effects of volatile anesthetics

Abstract

Neuromuscular inhibitory effects of three volatile anesthetics were compared using muscular compound action potential (CAP) which was elicited from gastrocnemius muscle by sciatic nerve stimulation in cats. The amplitude of CAP evoked by 0.1 Hz single stimulation and eight repetitive stimulation (RS8) with frequencies ranged from 2 to 100 Hz were recorded as control values. After obtaining the control values, 0.5, 1, 1.5 and 2 MAC of halothane (n=5), isoflurane (n=7) or sevoflurane (n=10) were administered respectively for 30 minutes and the single CAP amplitude and the responses evoked by RS8 were observed. Only after the inhalation of sevoflurane 2MAC, mean single CAP amplitude was depressed significantly to 82.6 % of control. Under halothane and isoflurane anesthesia, the depression of single CAP amplitude was not observed at any concentration. Additionally, the most prominent fading responses were observed in sevoflurane-inhaled cats when the results obtained by 100Hz-RS8 were compared under 2MAC of three different anesthetic agents. Our results suggest that sevoflurane has the most potent neuromuscular inhibitory effect through both post- and presynaptic inhibitory mechanisms.