Prognostic value of blood urea nitrogen to albumin ratio in critically ill cirrhotic patients with ascites

Cirrhosis complicated by ascites is associated with high mortality in ICU settings, yet reliable prognostic biomarkers remain limited. While the blood urea nitrogen-to-albumin ratio (BAR) has been identified as a prognostic marker in various critical illnesses, its role in cirrhotic patients with ascites remains underexplored. This study aimed to investigate the association between BAR and all-cause mortality (ACM) in cirrhotic patients with ascites admitted to the ICU. This retrospective cohort study analyzed data from 1516 cirrhotic patients with ascites, sourced from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database (Version 3.1). The blood urea nitrogen-to-albumin ratio (BAR) was calculated using blood urea nitrogen (BUN) and serum albumin (ALB) levels, both measured within 24 h of ICU admission. Patients were stratified into tertiles based on the distribution of BAR. The primary outcome was 30-day mortality, and the secondary outcome was 90-day mortality. Kaplan-Meier survival analysis and Cox proportional hazards regression models were used to evaluate the association between BAR and mortality, adjusting for demographics, comorbidities, laboratory parameters, vital signs, and disease severity scores. Restricted cubic spline (RCS) analysis was employed to examine potential non-linear relationships. The predictive performance of BAR was compared to established clinical scoring systems, including the Child-Turcotte-Pugh (CTP) score, the Model for End-Stage Liver Disease (MELD), the Sequential Organ Failure Assessment (SOFA) score, and the Simplified Acute Physiology Score II (SAPS-II). Among the 1516 cirrhotic patients with ascites (median age: 59 years; 63.72% male), the 30-day and 90-day mortality rates were 32% and 39%, respectively. BAR levels were significantly higher in non-survivors compared to survivors [13.01 (IQR 13.74) vs. 9.61 (IQR 9.88), p < 0.001]. Kaplan-Meier analysis demonstrated progressively worse survival across BAR quartiles (log-rank p < 0.001 for both 30-day and 90-day outcomes). In fully adjusted Cox regression models, higher BAR (as a continuous variable) was independently associated with increased 30-day (HR 1.03, 95% CI 1.02-1.03, p < 0.001) and 90-day mortality (HR 1.02, 95% CI 1.02-1.03, p < 0.001). RCS analysis revealed a U-shaped association, with threshold values identified at BAR = 6.06 for 30-day mortality and BAR = 5.81 for 90-day mortality. The C-index for BAR in predicting 30-day mortality was 0.595, which was comparable to the CTP (0.585) and SIRS (0.583) scores, but lower than SOFA (0.662), SAPS-II (0.681), and MELD (0.669). Importantly, the inclusion of BAR into existing scoring systems consistently enhanced predictive accuracy. Subgroup analyses demonstrated that these associations remained robust across different age, gender, and comorbidity groups (all p-values for interaction > 0.05). An elevated BAR at ICU admission is independently and consistently associated with higher short-term and intermediate-term mortality in cirrhotic patients with ascites. BAR serves as a simple, cost-effective, and easily accessible prognostic tool that improves risk stratification when combined with established clinical scores. Early assessment of BAR may enable timely clinical interventions, potentially enhancing outcomes in critically ill cirrhotic patients with ascites.