Internal Jugular Vein Ultrasound and Acute Kidney Injury After Abdominal Surgery

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.