Modified VExUS score for cardiac surgery-associated kidney injury and adverse outcomes: a prospective cohort study

This study aimed to evaluate the utility of a Modified Venous Excess UltraSound (M-VExUS) score, incorporating dynamic inferior vena cava (IVC) indices, to evaluate severe postoperative venous congestion linked with increased Cardiac Surgery-Associated Acute Kidney Injury (CSA-AKI) and other adverse outcomes after cardiac surgery. This is a prospective cohort study of 199 patients admitted to the ICU after elective coronary artery bypass grafting and/or aortic valve replacement. The M-VExUS score replaces the static IVC diameter with dynamic indices: the collapsibility index (spontaneously breathing) or the distensibility index (mechanical ventilation). The association between M-VExUS grade 3 (severe congestion) and AKI was evaluated using multivariable logistic regression. Severe venous congestion (18.1%) was associated with CSA-AKI according to the univariate analysis (OR 2.6, 95% CI 1.07–6.07; p = 0.03). Notably, persistent M-VExUS grade 3 substantially increased this risk (OR 6.76, 95% CI 2-22.91; p = 0.007) and shifted AKI toward more advanced KDIGO stages ( p = 0.005). Highlighting the need for dynamic indices, 25% of patients presented a static dilated IVC (≥ 20 mm) without Doppler-defined congestion. Severe congestion also identified a distinct high-risk phenotype characterized by hemodynamic vulnerability, increased vasoactive-inotropic support, prolonged mechanical ventilation and significantly higher rates of major complications (myocardial infarction, AV block), resulting in longer intensive care unit (ICU) and hospital stays. In multivariable analysis, preoperative creatinine (aOR 4.75, 95% CI 1.74–12.94; p = 0.002) and cardiopulmonary bypass time (aOR 1.02, 95% CI 1.003–1.033; p = 0.018) remained independently associated with CSA-AKI during ICU stay, while M-VExUS grade 3 did not reach independent statistical significance. An exploratory model evaluating the subgroup with persistent M-VExUS grade 3, adjusted for the same clinical covariates, did not show a statistically significant independent association (aOR 3.67, 95% CI 0.41–32.81; p = 0.245). M-VExUS identifies a high-risk phenotype characterized by systemic hemodynamic vulnerability with a higher incidence of postoperative complications. While not independently associated with CSA-AKI after adjusting for baseline risk, M-VExUS provides real-time physiological insights into a patient’s volume tolerance. Consequently, serial bedside assessment with M-VExUS may act as a valuable adjunct to standard monitoring, providing complementary physiological information to proactively identify exhausted venous reserve during the early postoperative phase. Whether M-VExUS-guided fluid or diuretic management can safely improve clinical outcomes remains a hypothesis that warrants prospective interventional evaluation. Not applicable.