We frequently encounter cognitive impairments in patients over 65 undergoing Lower extremity surgery, depending on comorbidities and the choice of anesthesia method. The current development of neuraxial anesthesia techniques and close monitoring devices helps us prevent and detect cognitive impairment early in these patients. In this study, we aimed to investigate the effects of different anesthesia techniques (general anesthesia/spinal anesthesia) applied in orthopedic cases on patient fluid status (pleth variablity index) and regional cerebral oxygenation (NIRS), and their relationship with cognitive dysfunction.