Postoperative acute kidney injury (AKI) after cardiac surgery is a major complication that worsens patient outcomes and increases healthcare costs. This study aimed to investigate the association between intrarenal venous flow (IRVF) and the risk of postoperative AKI, duration of mechanical ventilation, and intensive care unit (ICU) length of stay. This prospective observational cohort study enrolled patients undergoing cardiopulmonary bypass (CPB) cardiac surgery at a provincial tertiary hospital in Zhejiang Province from 1 April 2022 to 31 March 2023. Clinical, laboratory and ultrasonographic data were collected. The primary outcome was AKI within 7 days after surgery; secondary outcomes were duration of mechanical ventilation and ICU length of stay. Covariates were selected using LASSO and Boruta algorithms. Multivariable logistic regression assessed the association between IRVF grade and AKI. Receiver operating characteristic (ROC) and calibration curves evaluated predictive performance, and sensitivity analyses tested the robustness of findings. Violin plots and bar charts compared ventilation duration and ICU stay across IRVF grades. Among the 240 patients included, 59 (24.6%) developed AKI after surgery. In multivariable analysis, IRVF grade was associated with postoperative AKI. After full adjustment, patients with IRVF grade 3 had 6.35 times higher odds of AKI than those with grade 1 (OR 6.35, 95% CI 2.37–17.02; P < 0.001). Sensitivity analyses confirmed the robustness of this association. The IRVF-based model showed modest discrimination (AUC 0.688, 95% CI 0.614–0.761) and acceptable calibration. AKI predominantly occurred in patients with IRVF grades 2 and 3. Patients with IRVF grade 3 had a significantly longer mean duration of mechanical ventilation. Mean ICU length of stay was longer for grades 2 and 3, although only the difference between grades 1 and 2 reached statistical significance. IRVF is associated with AKI following CPB cardiac surgery and correlates with prolonged mechanical ventilation and extended ICU length of stay. Bedside assessment of IRVF has the potential to serve as a useful tool for early risk stratification of postoperative AKI.
Zhao et al. (Tue,) studied this question.