Blood urea nitrogen-to-albumin ratio independently predicts 30-day mortality in acute respiratory failure patients: a retrospective cohort study.

Background: It is crucial to identify patients at high risk for acute respiratory failure (ARF) to provide appropriate and optimal clinical treatment. While previous studies have explored the use of prognostic biomarkers based on a combination of blood urea nitrogen (BUN) and albumin levels, no reports to date have evaluated its utility across a wide range of ARF etiologies in a large and diverse critical care population. Therefore, we aimed to ascertain the association between the BUN-to-albumin ratio (BAR) and mortality in these patients.

Methods: Data recorded in the first 24 h following intensive care unit (ICU) admission, including demographics, vital signs, laboratory test results, comorbidities, and score systems were retrieved from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. A general additive model was used to determine whether there was a non-linear relationship between BAR and 30-day mortality. A multivariate Cox analysis was performed to measure the association between them.

Results: The study enrolled 9,734 patients with ARF. In comparison to survivors, non-survivors exhibited higher BAR [10.79 (6.25-18.81) 7.35 (4.48-13.62), P<0.001]. The correlation between baseline BAR and 30-day all-cause mortality in patients with ARF was non-linear, with a significant inflection point (11.76 mg/g). The Kaplan-Meier curve demonstrated that ARF patients had higher 30-day all-cause mortality rates when they had higher BAR levels (>11.76 mg/g) with hazard ratio (HR) 1.54 [95% confidence interval (CI): 1.39-1.70].

Conclusions: A high BAR was linked to a higher risk of mortality in ARF patients. BAR is a straightforward and possibly useful prognostic biomarker for ARF.