Summary

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 μg 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 ± 6.4 s (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.

Summary

Background and objective: Both the bispectral and the patient state indices are derived from the electroencephalogram and have been proposed as a measure of the same clinical target, the hypnotic component of anaesthesia. The present study evaluated whether there is concordance between the bispectral and the patient state indices with regard to end-points measured simultaneously in patients undergoing surgery under general anaesthesia.

Methods: Fifty-seven patients scheduled for elective abdominal, orthopaedic (Groups 1 and 2) or cardiac surgery (Group 3) under general anaesthesia were enrolled in the study. Anaesthesia was performed using remifentanil/sevoflurane (Group 1, 19 patients), remifentanil/propofol (Group 2, 19 patients) or sufentanil/propofol/isoflurane (Group 3, 19 patients). The bispectral and the patient state indices were simultaneously recorded. Pearson’s correlation between these two indices was calculated for the complete data and each group. The percentage of bispectral index values in the recommended range for general anaesthesia (45–60) that were confirmed by levels of patient state index (25–50) was calculated and vice versa.

Results: Overall correlation between the bispectral and the patient state indices was 0.667, 0.671 in Group 1, 0.650 in Group 2 and 0.675 in Group 3 (P < 0.01). For values of the bispectral index between 45 and 60, only 40% of corresponding patient state index values were between 25 and 50. For patient state index values of 25–50, only 50% of the corresponding bispectral index values were in the range of 45–60.

Conclusions: Concordance between the bispectral and patient state indices is relatively weak, whereas both are thought to reflect the same clinical target, the hypnotic component of anaesthesia. As a consequence, further studies are required to compare reliability of both indices as indicators of different levels of hypnosis.

We report two cases of left vocal fold palsy following use of the laryngeal mask airway. In both cases anaesthesia was uneventful with a duration of about 60 minutes. It is proposed that high intra-cuff pressures induced during anaesthesia resulted in distension of the hypopharynx and subsequent neuropraxia of the motor branches of the recurrent laryngeal nerve and the external branch of the superior laryngeal nerve.