Association between blood urea nitrogen to serum albumin ratio and in-hospital mortality of patients with chronic obstructive pulmonary disease in the intensive care unit: a retrospective cohort study

Abstract Background Blood urea nitrogen to serum albumin ratio (BAR) was found to be a valuable tool for predicting mortality in different diseases. However, few studies have explored the association between BAR and in-hospital mortality in critically ill patients with chronic obstructive pulmonary disease (COPD). The current research intended to explore the relationship between BAR and in-hospital mortality rates of patients with COPD in the intensive care units. Methods We conducted a retrospective cohort study that included 729 critically ill patients with COPD. Clinical data were collected from the Medical Information Mart for Intensive Care IV (MIMIC IV) database. Correlation between BAR and in-hospital mortality was assessed by the multivariable logistic regression analysis. The subgroup analysis was stratified according to relevant covariates. Mortality among BAR-based groups was evaluated using the Kaplan–Meier curve, and intergroup differences in survival were assessed through the log-rank test. Additionally, a receiver operating characteristic (ROC) curve was constructed, and the corresponding area under the curve (AUC) was calculated to predict in-hospital mortality. Results Our investigation included 729 patients, of whom 18.5% (135 patients) died in the hospital. BAR was presented as a continuous variable in the multivariable logistic regression model. In-hospital mortality increased by 3% when BAR increased each unit (odds ratio [OR] = 1.03, 95% confidence interval [95% CI] = 1.00–1.06). When BAR was presented as a categorical variable, patients were at a higher risk of in-hospital mortality in the highest BAR group (OR [95% CI] = 3.66 [1.67–8.03]) than those in the lower BAR groups. Additionally, subgroup analysis results were consistent among all groups. The Kaplan–Meier curve revealed statistically significant differences in hospital survival among BAR-based groups (log rank p < 0.01). The AUC of in-hospital mortality for sequential organ failure assessment (SOFA) + BAR was superior to SOFA (SOFA + BAR: AUC = 0.657; SOFA: AUC = 0.607). Conclusion High BAR had a positive correlation with high risks of in-hospital mortality in critically ill patients with COPD. This finding needs to be confirmed by further investigations.