This observational study aims to learn whether changes in the internal jugular vein during anesthesia induction can help predict low blood pressure and kidney injury after surgery. The main questions it aims to answer are:

1. Can the internal jugular vein collapsibility index before anesthesia predict low blood pressure during induction?
2. Can the change in internal jugular vein collapsibility from before to just after anesthesia predict low blood pressure during surgery and acute kidney injury after surgery?

Participants will have routine ultrasound scans of the neck before anesthesia and again shortly after they fall asleep for surgery. Researchers will also record blood pressure during surgery and measure kidney function after surgery using routine blood tests. and again shortly after they fall asleep for surgery. Researchers will also record blood pressure during surgery and measure kidney function after surgery using routine blood tests.

This is a single-centre prospective observational study of adults undergoing major abdominal or visceral surgery under general anesthesia. The study is designed to see whether bedside ultrasound measurements of the internal jugular vein can help identify participants who are at risk of low blood pressure during anesthesia induction and acute kidney injury after surgery.

Participants will have one ultrasound scan while awake before anesthesia and a second scan shortly after loss of consciousness following propofol induction. The researchers will calculate the internal jugular vein collapsibility index from both scans and determine the change between them. They will then compare these measurements with blood pressure changes during the induction period and with postoperative kidney function, which will be assessed using routine creatinine tests.

The study includes adults aged 18 years and older who are having elective or urgent non-emergency major abdominal or visceral surgery. Participants must receive propofol for anesthesia induction and must have blood pressure monitoring during surgery. People with emergency surgery, dependence on dialysis, major anatomic abnormalities that prevent ultrasound scanning of the neck, or other conditions that would invalidate the ultrasound measurement will not be included.

The study does not change routine anesthesia care. The ultrasound scans and blood tests are added only for research purposes, and the results are intended to help predict risk rather than guide treatment during the study itself.

Inclusion Criteria:

• Elective or Urgent (Non-emergent) major abdominal/ visceral surgery under general anesthesia
• General anesthesia with propofol induction (TCI/ manual)
• Expected surgical duration > 60 minutes
• Continous BP monitoring (Invasive arterial line or non-invasive cuff at 2 minute recording intervals)
• Serum creatinine and eGFR (CKD-EPI) available within 30 days prior to surgery
• Written informed consent obtained before surgery
• Patient accessible by phone 30 days postoperatively

Exclusion Criteria:

• Emergency surgery (immediate life-saving, consent unobtainable)
• End-stage renal disease (eGFR < 15 mL/min/1.73 m²) or dialysis-dependent
• Concomitant cardiac surgery or carotid endarterectomy
• Liver transplantation
• Known Internal Jugular Vein/ Inferior Vena Cava thrombosis or Superior Vena Cava syndrome
• Any anatomical neck abnormalities precluding Internal jugular vein ultrasound
• Induction with ketamine or etomidate as sole Induction agent
• Neuraxial anesthesia (spinal or epidural) before propofol induction
• Active decompensated heart failure (NYHA IV or acute pulmonary edema at time of Surgery)
• Same-admission reoperation within 30-day study window
• Withdrawal of consent at any point

The study population consists of adults aged 18 years and older undergoing major abdominal or visceral surgery under general anesthesia with propofol induction at the Department of Anestesiology and Intensive Care Department in the Emergency County Hospital in Târgu Mureș. Patients will be enrolled prospectively in the preoperative period if they meet eligibility criteria, have routine perioperative blood pressure monitoring, and are able to undergo internal jugular vein ultrasound before and immediately after induction. The cohort will be followed through postoperative days 1 to 3 for creatinine-based assessment of acute kidney injury.