"Effects of Fluid Status and Regional Cerebral Oxygenation on Postoperative Cognitive Dysfunction in Patients Undergoing Lower Extremity Surgery Under General and Spinal Anesthesia."

Inclusion Criteria: * Patients over the age of 65 * Patients with an American Society of Anesthesiologists (ASA) score of II-III * Patients with a Mini Mental State Examination (MMSE) score of ≥24 on the first day before surgery Exclusion Criteria: * Patients with coagulation disorders * Patients with a history of anticoagulant medication use * Patients with advanced organ failure * Patients with Alzheimer's disease or advanced dementia * Patients with allergies to the medications used in the study * Mental Retardation * Patients with a wound infection at the site of spinal anesthesia * Patients with a history of cerebrovascular hemorrhage * Patients who did not consent;