The primary aim of this study is to compare the instantaneous and total consumption of sevoflurane using 2 different concentrations and different minute / fresh gas flow to fill the system in the initial phase of anesthesia. Its secondary purpose is to compare the depth of anesthesia and hemodynamic parameters between the two groups.~A total of 70 patients between the ages of 18-65 will be included in the study.in 2.5 % sevoflurane grup After reaching 1 MAC level with 4 lt / min fresh gas flow and 2.5% sevoflurane concentration in the initial stage in 35 patients, anesthesia maintenance will be continued with 0.5 lt / min fresh gas flow and 2 -4% sevoflurane concentration with the target of 1 MAC. in sevoflurane 8 % group for 35 patients, after reaching 1 (MAC) level with 1 lt / min fresh gas flow and 8% sevoflurane concentration in the initial phase, maintenance of anesthesia will be continued with 0.5 lt / min fresh gas flow and 2 -4% sevoflurane concentration with the target of 1 MAC. . The depth of anesthesia for both groups will be measured by the Bispectral Index (BIS). BIS values between 40 and 60 are appropriate values for general anesthesia, for this value 1 MAC sevoflurane inhalation anesthesia and remifentanil infusion (0.1-0.3mcg / kg / min) will be used.
After reaching 1 MAC level with 4 lt / min fresh gas flow and 2.5% sevoflurane concentration in the initial stage in 35 patients, anesthesia maintenance will be continued with 0.5 lt / min fresh gas flow and 2 -4% sevoflurane concentration with the target of 1 MAC. For 35 patients, after reaching 1 (MAC) level with 1 lt / min fresh gas flow and 8% sevoflurane concentration in the initial phase, maintenance of anesthesia will be continued with 0.5 lt / min fresh gas flow and 2 -4% sevoflurane concentration, targeting 1 MAC.