Effect of halothane, isoflurane and desflurane on lower oesophageal sphincter tone.

We have studied the effects of volatile anaesthetics on lower oesophageal sphincter (LOS) tone in three groups of eight pigs allocated randomly to receive end-tidal concentrations of 0.5, 1.0 and 1.5 MAC of desflurane, isoflurane or halothane for 15 min. LOS and oesophageal barrier pressures (BrP = LOSP - gastric pressure) were measured using a manometric method. The decrease in BrP paralleled the decrease in LOS pressure and was significant at 0.5 MAC for isoflurane and at 1.0 MAC for halothane. At 1.5 MAC, BrP values were approximately 62% of baseline values for halothane, 37% for isoflurane and 83% for desflurane. Inter-group comparisons showed that BrP did not differ at baseline and at 0.5 MAC. At 1.0 MAC the effect of isoflurane on BrP was significantly different from desflurane (P < 0.001) and halothane (P < 0.02) whereas the effect of desflurane on BrP was not significantly different from halothane. At 1.5 MAC the effect of isoflurane on BrP was significantly different from desflurane (P < 0.01) and halothane (P < 0.05) whereas the effect of desflurane on BrP was not significantly different from halothane. We conclude that desflurane maintained BrP and this may be clinically important in patients at high risk of regurgitation.