Effect of subclavian vein collapsibility index-guided prehydration on preventing post-induction hypotension in patients undergoing elective abdominal surgery: a prospective, randomized controlled trial

Patients undergoing elective abdominal surgery often develop post-induction hypotension (PIH) due to hypovolemia. The subclavian vein collapsibility index (SCV-CI) can reflect the patient’s volume status. In this randomized controlled trial, 178 adult patients were randomized in a 1:1 ratio to the intervention group (Group S; n = 89) or the control group (Group C; n = 89). Before induction, Group S received subclavian vein (SCV) ultrasound assessment. According to the SCV-CI, Group S was further subdivided into Group A (SCV-CI ≥ 45.4%) and Group B (SCV-CI<45.4%). Patients in Group A received repeated 100 mL boluses of compound sodium acetate Ringer’s solution, with reassessment after each bolus until SCV-CI fell below 45.4%. Patients in Group B and Group C received a routine fixed-dose infusion (10 mL/kg/h) of compound sodium acetate Ringer’s solution for 20 min before induction. The primary outcome was the comparison of the incidence of PIH between Group C and Group S. The primary analysis included 172 of the 178 randomized participants with available outcome data (Group C, n = 87; Group S, n = 85). The incidence of PIH was lower in Group S than in Group C (28/85 [32.9%] vs. 45/87 [51.7%]; relative risk, 0.64, 95% confidence interval [95% CI], 0.44 to 0.92; risk difference, -18.8%, 95% CI, -33.3% to -4.3%; P = 0.013). In a post-hoc multivariable model including total administered fluid volume and other covariates, allocation to Group S remained associated with lower odds of PIH (odds ratio, 0.394, 95% CI, 0.180 to 0.862; P = 0.020). Notably, Group S received a larger volume of prehydration before induction compared with Group C (300 [200 to 400] mL vs. 190 [170 to 220] mL, P < 0.001). In an exploratory analysis within Group S, the observed PIH incidence was 35.8% (19/53) in Group A and 28.1% (9/32) in Group B ( P = 0.463). An SCV-CI-guided prehydration strategy was associated with a lower incidence of PIH in patients undergoing elective abdominal surgery. Chinese Clinical Trial Registry, ChiCTR2600116511. Registered on 12 January 2026.