Renal resistive index and serum creatinine changes in icu patients receiving vasopressor therapy: a prospective cohort study

Acute kidney injury (AKI) is a common complication in critically ill patients receiving vasopressor therapy. Serum creatinine, the standard biomarker for AKI, rises relatively late and is influenced by several non-renal factors. The renal resistive index (RRI), measured by Doppler ultrasonography, may provide an earlier assessment of intrarenal hemodynamic changes. This study evaluated the association between serial RRI measurements and renal function in vasopressor-treated intensive care unit (ICU) patients. In this prospective single-center cohort study, 120 adult ICU patients requiring norepinephrine infusion were enrolled. RRI, serum creatinine, urine output, mean arterial pressure, and norepinephrine dose were recorded daily for seven days or until ICU discharge or death. Longitudinal changes were analyzed using linear mixed-effects models. Multivariable regression and receiver operating characteristic (ROC) analyses were used to assess the association and discriminatory performance of baseline RRI for AKI occurrence during the seven-day observation period. AKI developed in 38 patients (31.7%). Patients with AKI had significantly higher baseline RRI than those without AKI (0.79 ± 0.07 vs. 0.68 ± 0.06, P < 0.001). RRI remained persistently elevated in the AKI group, whereas it gradually declined in patients without AKI (all P < 0.05). Baseline RRI was independently associated with higher Day-7 serum creatinine (β = 0.28, P = 0.014) and AKI development (OR = 2.15, 95% CI 1.12–4.14, P = 0.021). Baseline RRI showed moderate discrimination for AKI (AUC = 0.71, 95% CI 0.62–0.80). Patients with elevated baseline RRI had longer ICU and hospital stays. Elevated baseline and persistently increased RRI were independently associated with subsequent AKI and worsening renal function in vasopressor-treated ICU patients. Serial bedside RRI assessment may complement conventional biomarkers for early identification of patients at increased risk of AKI.