Blood urea nitrogen and in-hospital mortality in critically ill patients with MI or cardiogenic shock: Analysis of the MIMIC-IV database.

Background: Blood urea nitrogen (BUN) reflects renal function and metabolic catabolism and thus can be a potential biomarker in severe illness. The purpose of this investigation was to assess whether independent associations exist between admission BUN concentrations and hospital mortality in critically ill adults with acute myocardial infarction (MI) or cardiogenic shock (CS). Associations were assessed using tertiles of mean BUN during the hospital admission and mean BUN within 24 h of ICU entry. Methods: Using MIMIC-IV (v3.1), we conducted a retrospective cohort study of first ICU admissions (2008-2019) in adults identified by ICD-9/10 codes for acute myocardial infarction and/or cardiogenic shock. The primary exposure was mean BUN during hospitalization, categorized into tertiles; first-24-h BUN was analyzed as a sensitivity exposure. Analyses used complete cases. Results: We included 6719 patients. In-hospital mortality climbed from 5.2% to 25.8% across average BUN tertiles. In multivariable logistic regression, higher mean BUN was associated with increased odds of in-hospital mortality across tertiles and per standard-deviation increase. Findings were directionally consistent when first-24-h BUN was used as the exposure. Model diagnostics supported acceptable collinearity and fit. Conclusions: Among critically ill adults with acute myocardial infarction and/or cardiogenic shock, higher BUN, particularly mean BUN during hospitalization, was independently associated with in-hospital mortality. Early BUN (first 24 h) showed a similar signal, supporting BUN as a simple adjunct for bedside risk assessment.