Conventional stepwise vs. vital capacity rapid inhalation induction at two concentrations of sevoflurane.

Background And Objective: A multicentre study was conducted to compare three methods of inhalation induction with sevoflurane in adult premedicated patients.

Methods: One-hundred-and-twenty-five adult patients of ASA I-II were scheduled for short elective surgical procedures (< 90 min) under general anaesthesia with spontaneous ventilation of the lungs via a laryngeal mask airway. Patients were randomly assigned to one of three groups: conventional stepwise inhalation induction group (Group C) or vital capacity rapid inhalation induction groups at 4.5% (Group VC4.5) or at 8% sevoflurane (Group VC8). Before anaesthetic induction, fentanyl 1 micro kg(-1) was given and the face mask applied with the anaesthetic breathing system primed with sevoflurane 4.5% or 8% in the respective vital capacity groups. Loss of eyelash reflex, time to cessation of finger tapping, laryngeal mask insertion, side-effects and adequacy of induction were recorded.

Results: The time to loss of eyelash reflex was significantly shorter in both vital capacity groups vs. the control group: VC8: 68 +/- 7 s; and VC4.5: 94 +/- 6.5 s vs. C: 118 +/- 6.4s (P < 0.0001). Significant differences were found in all pairwise comparisons for time to cessation of tapping: Group VC8 (62 +/- 7 s), Group VC4.5 (85 +/- 6 s) and Group C (116 +/- 6 s; P < 0.0001). The time to laryngeal mask insertion was significantly shorter in the Group VC8 (176 +/- 13 s) compared with the other two groups, Group VC4.5 (219 +/- 13 s) and Group C (216 +/- 9 s). There were no significant differences in the incidence of side-effects between the three groups.

Conclusions: Inhalation induction of anaesthesia with sevoflurane with the three techniques tested is safe, reliable and well accepted by the patients. The vital capacity rapid inhalation group primed with sevoflurane 8% was the fastest method with no relevant side-effects.