Induction characteristics with 3% and 8% sevoflurane in adults: an evaluation of the second stage of anaesthesia and its haemodynamic consequences

Abstract

The second stage of anaesthesia was examined during 3 and 8% sevoflurane induction to see if any shortening of its duration was at the expense of cardiovascular stability. Fourteen volunteers underwent consecutive, randomly ordered inductions. Pupil size, skin sympathetic activity, plasma catecholamines, blood pressure and heart rate were measured. Eight per cent sevoflurane produced significantly shorter times to loss of consciousness (mean 68 s (SD 18) vs. mean 150 s (SD38)) and durations of second stage (mean 58 s (SD 38) vs. mean 91 s (SD 46)). Blood pressure, heart rate and sympathetic nerve responses were the same in both groups. Compared with baseline, skin sympathetic activity was greatest during pre-oxygenation (not significant) and unaltered during second stage. Both groups showed significantly increased plasma norepinephrine and heart rate and decreased blood pressure from baseline. Eight per cent sevoflurane induction produced a shorter second stage than 3% with equal cardiovascular stability and the same sympathetic response.