Association between blood urea nitrogen-to-creatinine ratio and 28-day mortality in acute kidney injury patients undergoing continuous renal replacement therapy

This study aims to investigate the association between the blood urea nitrogen-to-creatinine (BUN/Cr) ratio and 28-day mortality in critically ill patients with acute kidney injury (AKI) who received continuous renal replacement therapy (CRRT). We conducted a retrospective cohort study using data from the DATADRYAD database ( www.datadryad.org ). The study population was divided into four groups based on the quartiles of BUN/Cr levels measured prior to the initiation of CRRT. Multivariate Cox proportional hazards models and Kaplan-Meier analysis were used to assess this relationship, while restricted cubic spline (RCS) analysis was utilized to explore potential non-linear associations. Additionally, subgroup analysis was conducted to assess consistency across groups. A total of 1,137 critically ill patients with AKI who received CRRT were included. The highest BUN/Cr quartile demonstrated a significantly increased mortality risk (HR: 1.66, 95% CI: 1.34-2.06, p < 0.001) compared to the lowest quartile. Multivariate Cox regression analysis revealed that, even after adjusting for potential confounders, an elevated BUN/Cr ratio remained a significant and independent predictor of increased 28-day mortality. RCS analysis revealed a J-shaped relationship (p for nonlinearity < 0.001) between the BUN/Cr ratio and 28-day mortality, with a sharp increase in the risk of death above the threshold of 15.0. Subgroup analysis confirmed consistency across most subgroups, except for patients with hypertension (p for interaction = 0.035), where the association was stronger in individuals with hypertension. Higher BUN/Cr ratios are independently associated with increased 28-day mortality in AKI patients who received CRRT, exhibiting a non-linear relationship. The BUN/Cr ratio may serve as a cost-effective and accessible prognostic marker for this population, helping to identify high-risk patients for targeted interventions.