Research report: 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 general anesthesia for elective abdominal surgery frequently experience a drop in blood pressure shortly after induction, a complication known as post-induction hypotension (PIH). A prospective, randomized controlled trial published in BMC Anesthesiology tested whether tailoring preoperative fluid loading to an ultrasound measurement of the subclavian vein could reduce this risk. The researchers reported that a subclavian vein collapsibility index (SCV-CI)-guided prehydration strategy was associated with a lower incidence of PIH than a routine fixed-dose infusion.

Because hypovolemia is considered a key contributor to PIH, the study team hypothesized that using this bedside ultrasound measure to decide how much fluid to give before induction might prevent the blood pressure fall.

In the trial, 178 adult patients scheduled for elective abdominal surgery were randomized in a 1:1 ratio. The intervention group (Group S, n = 89) underwent subclavian vein ultrasound assessment before induction, while the control group (Group C, n = 89) did not. Patients in the intervention group were further subdivided according to their measured SCV-CI, with a cutoff of 45.4%.

Patients whose SCV-CI was 45.4% or higher, indicating greater collapsibility, received repeated 100 mL boluses of compound sodium acetate Ringer’s solution, with the vein reassessed after each bolus until the index fell below the threshold. Patients in the intervention group whose index was already below 45.4%, and all patients in the control group, received a routine fixed-dose infusion of the same solution at 10 mL/kg/h for 20 minutes before induction. The primary outcome was the comparison of PIH incidence between the overall intervention group and the control group.

The primary analysis included 172 of the 178 randomized participants with available outcome data: 87 in the control group and 85 in the intervention group. Post-induction hypotension occurred in 28 of 85 patients (32.9%) in the intervention group compared with 45 of 87 patients (51.7%) in the control group. This corresponded to a relative risk of 0.64 (95% confidence interval, 0.44 to 0.92) and a risk difference of -18.8 percentage points (95% CI, -33.3% to -4.3%), with P = 0.013.

The authors also reported a post-hoc multivariable model that included the total administered fluid volume and other covariates. In that model, allocation to the guided strategy remained associated with lower odds of PIH (odds ratio, 0.394; 95% CI, 0.180 to 0.862; P = 0.020). Notably, the intervention group received a larger volume of prehydration before induction than the control group, with a median of 300 mL (interquartile range 200 to 400 mL) versus 190 mL (interquartile range 170 to 220 mL), P < 0.001. This difference in fluid volume is an important consideration when interpreting the benefit, since the guided approach inherently delivered more fluid to patients judged hypovolemic by the ultrasound measure.

Within the intervention group, the researchers conducted an exploratory analysis comparing the two subgroups defined by the collapsibility cutoff. The observed PIH incidence was 35.8% (19 of 53) among patients who required boluses to reach the target and 28.1% (9 of 32) among those already below the threshold, a difference that was not statistically significant (P = 0.463). This exploratory comparison suggests that the overall benefit observed in the trial cannot be clearly attributed to reaching a specific collapsibility target alone.

The trial was registered with the Chinese Clinical Trial Registry (ChiCTR2600116511) on 12 January 2026. As a single study in adult elective abdominal surgery patients, its findings apply to that population and protocol, and the reported association between the guided strategy and lower PIH incidence would benefit from confirmation in other surgical settings. The authors concluded that an SCV-CI-guided prehydration strategy was associated with a lower incidence of post-induction hypotension in patients undergoing elective abdominal surgery, adding a bedside ultrasound option to the tools anesthesiologists may use to individualize fluid management before induction.

Subject of Research: Subclavian vein collapsibility index-guided prehydration to prevent post-induction hypotension in elective abdominal surgery

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

Article References: Ning, Y., Liu, M., Liu, Z., Zhao, H., Zhang, Y., Gao, D., Hui, K., & Zhang, L. (2026). Effect of subclavian vein collapsibility index-guided prehydration on preventing post-induction hypotension in patients undergoing elective abdominal surgery: a prospective, randomized controlled trial. BMC Anesthesiology. https://doi.org/10.1186/s12871-026-04352-3

Image Credits: AI Generated

DOI: 10.1186/s12871-026-04352-3

Keywords: anesthesia, hypotension, subclavian vein, ultrasound, prehydration, randomized controlled trial, abdominal surgery, fluid management, volume status, point-of-care ultrasound, Effect, subclavian