Association between the blood urea nitrogen to albumin ratio and all-cause mortality in critically ill patients with liver cirrhosis

The prognosis for critically ill patients with liver cirrhosis in the intensive care unit (ICU) remains uncertain. This study aimed to investigate the association between the Blood Urea Nitrogen to Albumin Ratio (BAR) at ICU admission and mortality in patients with liver cirrhosis. A retrospective cohort study was conducted using data from the MIMIC-IV database. The primary and secondary outcomes were 28-day and 180-day all-cause mortality after ICU admission, respectively. Patients were stratified into high- and low-BAR groups based on an optimal cutoff value determined by ROC analysis. To evaluate the association between BAR and all-cause mortality, we employed multivariate Cox regression models with comprehensive covariate adjustments. The survival experience stratified by BAR was visualized using Kaplan-Meier curves. Furthermore, we utilized restricted cubic splines to examine the potential non-linear relationship between BAR and the risk of mortality, complemented by interaction and subgroup analyses to assess the consistency of this association. A total of 3,268 adult patients with liver cirrhosis were included. The optimal BAR cutoff was 9.25. Compared to the low-BAR group, patients in the high-BAR group (≥ 9.25) had significantly higher 28-day (46.5% vs. 17.5%) and 180-day (54.0% vs. 24.9%) mortality rates. After multivariable adjustment, a high BAR remained independently associated with increased risks of 28-day (HR: 1.65, 95% CI: 1.42–1.92) and 180-day mortality (HR: 1.41, 95% CI: 1.21–1.64). BAR demonstrated good predictive ability for both 28-day mortality (AUC: 0.752) and 180-day mortality (AUC: 0.744), which was comparable to APS III and significantly better than SOFA, OASIS, GCS, and Charlson scores. Restricted cubic spline analyses revealed the mortality risk increased only modestly at BAR levels below approximately 9.25, but rose steeply and nonlinearly once BAR exceeded this threshold, indicating a potential threshold effect. The BAR is an independent predictor of short-and long-term mortality in critically ill cirrhotic patients. Its calculation at ICU admission may serve as a potential tool for early risk stratification, potentially facilitating timely clinical interventions.