Effect of carotid artery corrected flow time guided fluid therapy to prevent post-induction hypotension in elective abdominal surgery: a randomized controlled clinical trial

Background Post-induction hypotension (PIH) is associated with adverse postoperative outcomes in patients undergoing abdominal surgery, and preoperative fluid optimization can reduce its incidence. This study evaluated the short-term effectiveness of preoperative fluid therapy guided by carotid corrected flow time (FTc) thresholds. Methods Adult patients undergoing abdominal surgery were randomly divided into two groups. During preparation, one group received a continuous infusion of Ringer's acetate solution (10 mL/kg/h). In the other group (intervention group), patients with FTc below 334.15ms were given repeated infusions of Ringer's acetate solution at approximately 3 ml/kg of fluid before induction of anesthesia and ultrasound assessment until FTc was above 334.15ms. The primary outcome was the incidence of PIH. Results Finally, 146 patients were analyzed, and the overall incidence of PIH was 35.61%. The incidence of PIH in the intervention group was lower than in the control group (17 vs 35; 23.6% vs 47.3%; p  = 0.003). The relative risk reduction (RRR) for PIH was reduced by approximately 50%, and the absolute risk reduction (ARR) was decreased by 23.7% for the two groups. Crystal fluid supplementation before operation in the intervention group was higher than that in the control group (350 mL vs 260 mL, p  < 0.01). Meanwhile, for patients treated with additional fluid, FTc values were moderately negatively associated with the amount of fluid replenishment before anesthesia (r = -0.406, p  < 0.001). Conclusion Preoperative fluid therapy with an FTc cutoff value of 334.15 ms as the threshold could effectively reduce the incidence of PIH and did not have adverse effects on short-term outcomes such as postoperative exhaust defecation.