Effects of small concentrations of isoflurane on some psychometric measurements

Abstract

We have investigated the effects of 9.5% and 14.1% MAC concentrations of isoflurane on some psycho metric measurements. Both concentrations de pressed peak saccadic velocity (P<0.01), choice reaction time (P<0.05) and visual analogue scores for sedation (P<0.05), but not the critical flicker fusion threshold. The incidence of errors in saccade tasks increased in a dose-related fashion, which made analysis of peak saccadic velocity less ac curate at more than 10% MAC. The percentage error itseff was an indicator of the depth of sedation. All the objective measures correlated highly with the estimated brain tension of isoflurane (r2=0.86-0.96), but not the visual analogue score for sedation (r2=0.51). This suggests that a com bination of peak saccadic velocity, percentage error and choice reaction time is a potentially useful batch of tests to measure recovery from anaesthesia. (Br. J. Anaesth. 1993; 71: 839-844) © 1993 British Journal of Anaesthesia.