Low - flow Anesthesia in Overweight Patients: Comparison between Desflurane and Sevoflurane

Abstract

Background: This study aimed to study the kinetic behaviors of desflurane compared with sevoflurane during high - flow wash - in, 1L - flow maintenance and early recovery profile in overweight adult patients. Methods: Forty unpremedicated adult patients (Aged 18 - 65, BMI 25 - 35) were enrolled to receive either desflurane or sevoflurane anesthesia. After induction of anesthesia, desflurane 4% or sevoflurane 1.5% in a fresh gas flow of 6 L/min (N₂O:O₂ = 3:3) was administered via an absorber circuit. After 10 minutes, the inflow was decreased to 1 L/min (N₂O:O₂ = 0.5:0.5) and desflurane or sevoflurane was then switched to 5% or 2% respectively, and maintained throughout the surgery. At the end of the procedure, the vaporizer was turned off and the inflow was back to 6 L/min of O₂. Delivered concentration (FD), inspired concentration (FI) and end - tidal concentration (FA) of the anesthetics were measured and recorded from start until extubation. The times from discontinuation of the anesthetics to eye opening on command and extubation were also recorded. Results: During high - flow wash - in, the FA/FI were comparable between the two groups with the ratios of 0.89 + 0.05 vs 0.88 + 0.02 at minute 10. While in low - flow maintenance, the FI of both groups gradually increased with corresponding increases of FA. During the 1st hour of low flow, the FA/FI were not significantly different with the ratios of 0.91 + 0.03 vs 0.89 + 0.02 at minute 60. When back to high flow of O2 at the end of surgery, desflurane was washed out faster than sevoflurane. There were significant differences between groups with respects to the time to eye opening on command (5.20  1.72 vs 6.73  2.10 min, p = 0.008) and time to extubation (6.62  0.40 vs 8.63  0.45 min, p = 0.002). Conclusions: In overweight adult patients, desflurane and sevoflurane provide comparably fast wash-in during the 1^st hour of l L/min maintenance flow. However, desflurane has faster wash-out and provides faster early recovery.