This study aims to investigate whether the Internal Jugular Vein Collapsibility Index (IJV-CI), measured via ultrasonography, can predict hypotension (low blood pressure) that occurs after the induction of general anesthesia. Researchers will measure the diameter of the internal jugular vein in patients before surgery and compare these measurements with the blood pressure changes during the first minutes of anesthesia. The goal is to determine if IJV-CI can be used as a reliable, non-invasive tool to identify patients at higher risk of developing anesthesia-induced hypotension.

Patients aged 18-65 scheduled for elective laparoscopic cholecystectomy under general anesthesia will be included in the study. Exclusion criteria are as follows: Obesity (BMI > 35 kg/m²), presence of Atrial Fibrillation or serious cardiac arrhythmia, history of neck surgery or any pathology preventing internal jugular vein measurement, advanced heart failure (Ejection Fraction < 40%), severe valvular disease, peripheral vascular disease, emergency surgery, and refusal to participate in the study.

Upon arrival in the operating room, patients will be placed in a supine position. The Internal Jugular Vein (IJV) diameter will be monitored using a linear ultrasound probe during spontaneous breathing before anesthesia induction. The maximum and minimum diameters of the IJV during the respiratory cycle will be measured. The Internal Jugular Vein Collapsibility Index (IJV-CI) will be calculated using the following formula: [(IJV maximum diameter - IJV minimum diameter) / IJV maximum diameter] x 100.

Standard anesthesia induction will be performed. Non-invasive blood pressure and heart rate will be monitored and recorded at baseline (0 min), and at 1, 2, 3, 5, 7, 9, and 10 minutes following induction. Post-induction hypotension is defined as a decrease in mean arterial pressure (MAP) of more than 20% from the baseline value. The relationship between the pre-induction IJV-CI values and the development of hypotension during these specific time intervals will be statistically analyzed.

Inclusion Criteria:

• Patients aged 18-65 years.
• Patients with ASA (American Society of Anesthesiologists) physical status I, II, or III.
• Patients scheduled to receive general anesthesia.
• Patients scheduled for elective laparoscopic cholecystectomy.

Exclusion Criteria:

• Patients with obesity (Body Mass Index > 35 kg/m²).
• Patients with Atrial Fibrillation or other serious cardiac arrhythmias.
• Patients with a history of neck surgery or any pathology preventing Internal Jugular Vein (IJV) measurement.
• Patients with advanced heart failure (Ejection Fraction < 40%).
• Patients with severe valvular heart disease.
• Patients with peripheral vascular disease.
• Patients undergoing emergency surgery.
• Patients who are unwilling to participate in the study.

The study population consists of adult patients aged 18-65 who are scheduled to undergo elective laparoscopic cholecystectomy under general anesthesia. Participants will be selected from patients who meet the ASA I-III physical status criteria. The study focuses on evaluating pre-induction internal jugular vein characteristics using routine clinical monitoring data in a perioperative setting.

Individual participant data will not be shared to protect patient confidentiality and privacy in accordance with local ethical committee guidelines and institutional data protection policies.