Background. We propose a 1-1-12 wash-in scheme for desflurane-nitrous oxide (N2O) low-flow anesthesia. The objective of our\nstudy was to determine the time to achieve alveolar concentration of desflurane (FAD) at 1, 2, 3, 4, 5, and 6%. Methods.We enrolled\n106 patients scheduled for elective surgery under general anesthesia. After induction and intubation, wash-in was started with a\nfresh gas flow (FGF) of N2O:O2 1 : 1 L min?1 and vaporizer concentration of desflurane (FD) of 12%. Ventilation was controlled to\nmaintain PACO2 at 30ââ?¬â??35mmHg. Results. The FAD rose rapidly from 0 to 4% in 2 min in a linear manner in 0.5 min increments.\nAn FAD of 6% was achieved in 4 min in a linear fashion from FAD of 4% but in 1 min increments. An FAD of 1 to 6% occurred at\n0.6, 1, 1.5, 2, 3, and 4 min. Heart rate during wash-in showed a statistically, albeit not clinically, significant pattern of increase. By\ncontrast, blood pressure slightly decreased during this period. Conclusions.We developed a 1-1-12 wash-in scheme using a FGF of\nN2O:O2 1 : 1 L min?1 and FD of 12% for desflurane-nitrous oxide low-flow anesthesia. A respective FAD of 1, 2, 3, 4, 5, and 6?n\nbe expected at 0.6, 1, 1.5, 2, 3, and 4 min.
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