Blood urea nitrogen-to-albumin ratio and risk of congestive heart failure in critically ill acute respiratory failure patients: evidence from MIMIC-IV

By combining information on renal function with nutritional status and systemic inflammatory burden, the blood urea nitrogen (BUN)-to-albumin ratio (BAR) is emerging as a useful marker of prognosis across diverse critically ill populations. However, data are limited on the association between BAR and the risk of incident congestive heart failure (CHF) in critically ill patients with acute respiratory failure (ARF), and on whether BAR predicts in-hospital mortality (IHM) among ARF patients complicated by CHF. We conducted a retrospective cohort study using the Medical Information Mart for Intensive Care IV (MIMIC-IV) as our data source. Adults presenting with acute respiratory failure (ARF) were eligible at their first ICU admission. BAR measured on ICU admission defined three tertile groups (Q1–Q3). Incident CHF served as the primary endpoint; IHM following CHF development in ARF patients served as the secondary endpoint. We assessed clinical outcomes in relation to BAR using Kaplan–Meier curves alongside Cox proportional hazards models. To examine potential dose–response relationships, we fitted restricted cubic spline (RCS) models. Robustness was examined through multivariable adjustment and multiple sensitivity analyses. 11,156 critically ill ARF patients were included in the final analysis. In multivariable-adjusted Cox regression models, compared with patients in the lowest BAR tertile (Q1), those in the middle and highest tertiles had significantly higher risks of CHF (Q2: HR = 1.31, 95% CI: 1.19–1.44; Q3: HR = 1.48, 95% CI: 1.33–1.64; both P < 0.001). Among ARF patients with concomitant CHF, higher BAR levels were independently associated with increased IHM (Q2: HR = 1.15, 95% CI: 1.04–1.29, P = 0.010; Q3: HR = 1.28, 95% CI: 1.13–1.44, P < 0.001). RCS analyses revealed a significant nonlinear dose–response relationship between BAR and the risk of incident CHF (P for nonlinear < 0.001), whereas a positive association was observed between BAR and IHM among CHF patients in the fully adjusted model. Sensitivity analyses yielded results generally consistent with the primary findings. Elevated BAR was associated with a higher risk of CHF in critically ill patients with ARF and with higher IHM among ARF patients complicated by CHF. As a simple, inexpensive, and readily available laboratory parameter, BAR may serve as a potential marker associated with cardiovascular risk and prognosis in critically ill patients with ARF.