Somatic movement and oesophageal motility during isoflurane anaesthesia

The quantal responses for somatic movement, and spontaneous and provoked lower oesophageal contractions (motility) were noted at the time of incision in 72 patients aged 40-65 yr, receiving varying concentrations of isoflurane. Probit analysis of the alveolar concentration of isoflurane required to prevent somatic movement revealed an MAC or EC50 (95% confidence limits) of 1.00 (0.82-1.17)% and EC95 of 2.16 (1.69-3.89)%. The EC50 of isoflurane to suppress spontaneous lower oesophageal contractions was 1.27 (1.12-1.43)%, and the EC95 2.13 (1.78-3.22)%. The EC50 for provoked lower oesophageal contractions was 1.31 (0.93-3.48)% and the EC95 was 6.18% (unable to compute confidence limits).