The primary aim of this study is to determine the effectiveness of BIS-guided propofol administration to avoid hypotension in propofol induction in geriatric patients. Mean arterial pressure (MAP) below 60 mmHg is defined as hypotension. The secondary aims include finding the differences between the entry MAP and the MAP at each measurement, determining the difference between the entry MAP and the lowest MAP, determining the ratio of hypotensive and normotensive MAP measurements, determining the number of patients with severe hypotension (MAP\<50 mmHg), determining the number of patients receiving vasopressor therapy and drug dosage, determining the number of patients who underwent Trendelenburg, and those who developed tachycardia (HR\>100/min), determining the number of patients who developed hypertension (MAP\>140), and finding the correlation between BIS values and MAP. T.R. In the Ministry of Health Ankara City Hospital Urology Operating Room, general anesthesia will be applied, and ventilation will be provided with LMA as two different approaches for patients over 65 years of age; By evaluating OAA/S-based propofol induction and BIS-guided propofol inductions, the investigators aim to investigate whether the use of BIS reduces the risk of developing hypotension by reducing the propofol dose in anesthesia induction. T.R. After receiving ethics committee approval at the Ministry of Health Ankara City Hospital Urology Operating Room, 122 patients over the age of 65 who will receive general anesthesia and ventilation with a laryngeal mask (LMA) under elective conditions will be included in the study.

The study will be designed as a prospective randomized controlled trial. A total of 122 patients undergoing elective surgery in the urology operating room will be divided into two groups, Group O and Group B, using computer-assisted randomization. Group O will undergo an anesthesia induction guided by OAA/S, while Group B will undergo a general anesthesia induction guided by BIS.

After being admitted to the operating room, Group O will have recorded heart rate (HR) in beats per minute, systolic arterial blood pressure (SAB) in mmHg, diastolic arterial blood pressure (DAB) in mmHg, mean arterial blood pressure (OAB) in mmHg, peripheral oxygen saturation (SpO2), and BIS values. Four milliliters per kilogram of appropriate balanced crystalloid solution will be administered 2 minutes after the start, and HR, SAB, DAB, OAB, SpO2, and BIS values will be reevaluated. These values will be recorded every 2 minutes for 14 minutes. Premedication will not be administered, and anesthesia induction will begin with 1 mcg/kg fentanyl. Many commonly used anesthesia induction agents, including propofol, can cause significant and even life-threatening drops in blood pressure, respiratory depression, and other adverse events. The dose ranges of propofol decrease with age, leading to the FDA's recommendation to reduce the induction dose from 2-2.5 mg/kg in geriatric patients to 1-1.5 mg/kg. In the clinic, a standard initial dose of 1.5 mg/kg of propofol and an infusion rate of 100 mg/min are applied in geriatric patients. The initial dose for both groups will be 1.5 mg/kg, and the infusion rate will be 100 mg/min. An additional 20 mg of propofol will be administered every 30 seconds until the Observer's Assessment of Alertness/Sedation (OAA/S) score is 1. In case of hypotension, the management of hypotension (vasopressor treatment, Trendelenburg position, fluid loading) is left to the discretion of the responsible anesthesiologist. Anesthesia maintenance will be provided with volatile anesthetics. At the end of the procedure, hemodynamic parameters (SAB, DAB, OAB, HR, SpO2), BIS values, Observer's Assessment of Alertness/Sedation Scale (OASS), time to reach OAA/S 1, anesthesia induction drug and doses, hypotension treatment, and airway equipment placement time will be recorded.

Upon admission to the operating room, Group B will have recorded heart rate (HR) in beats per minute, systolic arterial blood pressure (SAB) in mmHg, diastolic arterial blood pressure (DAB) in mmHg, mean arterial blood pressure (OAB) in mmHg, peripheral oxygen saturation (SpO2), and BIS values. Four milliliters per kilogram of appropriate balanced crystalloid solution will be administered 2 minutes after the start, and HR, SAB, DAB, OAB, SpO2, and BIS values will be reevaluated. These values will be recorded every 2 minutes for 14 minutes. Premedication will not be administered, and anesthesia induction will begin with 1 mcg/kg fentanyl. The time delay between propofol injection and the decrease in BIS index depends on the drug transition time (from the injection site to the effect site) and the index calculation time. Time delays between 14 and 155 seconds have been reported for the BIS index. In the study, the BIS index will be evaluated every 30 seconds. The initial dose and infusion rate will be applied as in Group O, with the target index in the BIS group being 40-60. An additional dose of 20 mg will be planned every 30 seconds until the target index is reached. In case of hypotension, the management of hypotension (vasopressor treatment, Trendelenburg position, fluid loading) is left to the discretion of the responsible anesthesiologist. At the end of the procedure, hemodynamic parameters (SAB, DAB, OAB, HR, SpO2), BIS values, time to reach BIS \<60, Observer's Assessment of Alertness/Sedation Scale (OASS), anesthesia induction drug and doses, hypotension treatment, and airway equipment placement time will be recorded.

The sample size calculation was performed using MedCalc 15.8 (MedCalc Software bvba, Ostend, Belgium). It was determined that a minimum of 122 patients (61 + 61) is sufficient for P1 = 0.6, P2 = 0.3, α = 0.05, and a power of 90% (1-β).