Effect of Low Flow Anesthetics on Neurocognitive Decline in the Elderly

Inclusion Criteria: * Age\>65 * Consenting to participate * Scheduled for surgery longer than 2 hours under GA * Able to read and write Exclusion Criteria: * Age\<65 * Refusing to participate * Existing visual impairment preventing the patient from reading or writing * Unable to read and write * Existing major neurocognitive disorder * Use of TIVA or regional techniques * Allergies to the volatile agents * Uncontrolled DM, acute alcohol intoxication * Conditions increasing tissue oxygen consumption (sepsis, thyrotoxicosis, etc.) * Anticipation/existence of major hemorrhage * Haemodynamic instability \> 10 min or more than 5 times intraoperatively