Relationship Between Blood Urea Nitrogen to Albumin Ratio and Risks of Mortality and Delirium in Pancreatitis Patients: A Retrospective Analysis of the MIMIC-IV Database.

BACKGROUND AND OBJECTIVE: This study is aimed at evaluating the predictive value of the blood urea nitrogen-to-albumin ratio (BAR) for both mortality and delirium risk in patients with pancreatitis. Pancreatitis carries a substantial mortality risk and significant long-term sequelae, with delirium being a severe neurological complication, underscoring the clinical need for effective prognostic markers.

METHODS: A retrospective cohort study was performed using the MIMIC-IV v3.0 database. A total of 1748 ICU patients meeting diagnostic criteria for pancreatitis (ICD-9/10 codes: 577.0, 577.1, K85) with documented baseline blood urea nitrogen (BUN) and albumin levels were included. BAR was calculated (BUN[mg/dL]/Albumin[g/dL]) and patients were stratified into quartiles (Q1: BAR < 3.0; Q2: BAR 3.0-5.0; Q3: BAR 5.0-9.2; Q4: BAR ≥ 9.2). The primary endpoints were all-cause mortality and delirium occurrence (identified using ICD-9 codes 293.0, 293.1, and ICD-10 codes F05, F05.9). Multivariable Cox proportional hazards regression (mortality) and logistic regression (delirium) were employed, adjusting for demographics, illness severity scores (GCS, SAPS II, OASIS, and Charlson Comorbidity Index), and comorbidities. Restricted cubic splines (RCS) were used to explore nonlinear associations.

RESULTS: Higher BAR levels significantly correlated with greater disease severity: compared with Q1, Q4 exhibited a higher Charlson Comorbidity Index and mortality rate. BAR was an independent predictor of delirium; each 1-unit increase in BAR was associated with a 2.7% increased risk of delirium (adjusted OR = 1.027, 95% CI: 1.009-1.044), and patients in Q4 had a significantly higher risk compared with those in Q1 (adjusted OR = 1.882, 95% CI: 1.157-3.108). After multivariable adjustment, BAR was not significantly independently associated with mortality (Q4 adjusted HR = 1.022, p = 0.8). RCS analysis revealed BAR > 9.0 as a high-risk threshold, characterized by delirium OR > 1.78 and mortality HR > 1.97. The BAR quartile model yielded AUCs of 0.635 and 0.599 for predicting mortality and delirium, respectively, indicating modest predictive ability.

CONCLUSION: BAR independently predicts delirium risk and reflects disease severity in pancreatitis patients, but does not demonstrate significant independent predictive value for mortality after accounting for confounders. The identified threshold (BAR > 9.0) supports the utility of BAR as a supplementary biomarker for delirium risk stratification in this population.