In Elderly Patients, Does Goal-directed Fluid Management Using the Carotid Corrected Flow Time (CC-FT) Index, Compared to Routine Fluid Management, Affect the Occurrence of Post-induction Hypotension?

This study aims to find out whether using a simple ultrasound measurement of blood flow in the neck artery can help doctors decide how much fluid to give older patients before general anesthesia, and thereby reduce the drop in blood pressure that commonly occurs after anesthesia induction. Older adults are more likely to experience low blood pressure during anesthesia, and such drops have been linked to kidney injury, heart injury, and even death after surgery. Giving too little fluid can worsen organ blood supply, while giving too much can cause fluid overload, lung swelling, and heart strain. Currently, doctors often rely on static measures such as central venous pressure, or on invasive dynamic measures such as pulse pressure variation, but these have limited accuracy or require expensive equipment and invasive procedures. Carotid corrected flow time (FTc), measured non-invasively with ultrasound, reflects left ventricular preload and has shown promise for predicting fluid responsiveness, including in spontaneously breathing patients. However, evidence in older adults undergoing abdominal surgery remains limited to observational studies, and higher-level evidence from randomized trials is needed. We therefore plan a single-center, prospective, randomized, parallel-controlled trial in 70 patients aged 65 years or older scheduled for elective abdominal surgery under general anesthesia. Participants will be randomly assigned 1:1 to an FTc-guided prehydration group or a conventional fluid group. In the intervention group, if FTc falls below 340.7 ms, 250 mL of lactated Ringer's solution will be infused over 15 minutes, and FTc will be re-measured until it reaches at least 340.7 ms, in addition to a background infusion of 6 mL/kg/h started 30 minutes before induction. The control group will receive the same background infusion without FTc-guided adjustment. The primary outcome is the incidence of post-induction hypotension, defined as mean arterial pressure below 65 mmHg or a decrease of more than 20% from baseline within 15 minutes after induction. Secondary outcomes include the area under the curve of mean arterial pressure change from baseline during induction, intraoperative use of vasoactive agents, actual pre-induction fluid volume, postoperative pulmonary complications (pulmonary edema), acute kidney injury, myocardial injury, adverse events in the post-anesthesia care unit, time to first flatus and defecation, and all-cause mortality within 30 days after surgery.

Primary Hypothesis

Compared with conventional fluid management, carotid FTc-guided prehydration before anesthesia induction will reduce the incidence of post-induction hypotension in older patients undergoing elective abdominal surgery under general anesthesia.