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

The second stage of anaesthesia was examined during 3 and 8% sevoflurane in duction to see if any shortening of its duration was at the expense of card iovascular stability. Fourteen volunteers underwent consecutive, randomly o rdered inductions. Pupil size, skin sympathetic activity, plasma catecholam ines, blood pressure and heart rate were measured. Eight per cent sevoflura ne 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 (S D 38) vs. mean 91 s (SD 46)). Blood pressure, heart rate and sympathetic ne rve responses were the same in both groups. Compared with baseline, skin sy mpathetic activity was greatest during pre-oxygenation (not significant) an d unaltered during second stage. Both groups showed significantly increased plasma norepinephrine and heart rate and decreased blood pressure from bas eline. Eight per cent sevoflurane induction produced a shorter second stage than 3% with equal cardiovascular stability and the same sympathetic respo nse.