In this trial, the investigators aim to evaluate the cerebral perfusion of patients with transcranial doppler ultrasound (TCD) and near-infrared spectroscopy (NIRS) during lumbar disc surgery.
The investigators will divide participants into three groups according to their blood pressure history after preoperative evaluation of the participants.
The investigators will enroll normotensive participants in group 1(control group). Participants with diagnosis of high blood pressure will be enrolled to group 2. In the third group, participants who don't have any diagnosis of high blood pressure, but actual blood pressure is higher than the physiological levels at the preoperative evaluation will be enrolled to group 3.
First measurements of TCD and NIRS, will be performed at preoperative period. Second measurements will be obtained after anesthesia induction. Third measurement will be performed after prone position. Forth measurement will be taken after 1 hour of surgical incision. The last measurement will be performed at the postoperative period.
During all these measurements, blood gas samples, invasive arterial blood pressures, pulse variation index (PVI), electrocardiography (ECG), peripheral oxygen saturation (SpO2), peak pressure of airway and end-tidal carbon dioxide (EtCO2) levels will also be recorded.
All participants will be evaluated for their cognitive functions with mini-mental and confusion assessment method (cam) tests at the preoperative and postoperative periods.
