SINGLE VITAL CAPACITY INHALATIONAL ANESTHETIC INDUCTION IN ADULTS ISOFLURANE VS SEVOFLURANE

Purpose: To evaluate whether isoflurane is as suitable as sevoflurane for the single vital capacity breath (VCB) method of inhalational indu ction in patients premedicated with midazolam. Methods: A randomised, controlled, double-blind study involving 67 ASA I-II patients aged bet ween 18-50 yr undergoing elective surgery under general anaesthesia. A il participants received premedication with 0.03 mg.kg(-1) midazolam i v. Using a primed circle absorber circuit, inhalational induction of a naesthesia was performed with the single VCB method using either isofl urane 3.5% or sevoflurane 7.5% in nitrous oxide 67% in oxygen, represe nting approximately equivalent MAC-multiples of 3.6 MAC. Isoflurane wa s compared with sevoflurane in terms of rapidity, efficacy, safety and acceptability of induction. Results: With the single VCB method, sevo flurane produced a faster (45 +/- 21 vs 71 +/- 22 sec, P < 0.01), more successful (100% vs 75.8%, P < 0.01) induction of anaesthesia, with f ewer induction-related complications (11.8% vs 84.8%, P < 0.01) than d id isoflurane. There was also greater patient acceptability of inducti on with sevoflurane (76.4% vs 42.4%, P < 0.05). Conclusion: In adults given midazolam premedication, isoflurane is not as suitable as sevofl urane for single VCB inhalational anaesthetic induction technique as i t is associated with slower, more complicated induction and less patie nt acceptability.