Prognostic value of blood urea nitrogen trajectories for massive gastrointestinal bleeding and mortality in sepsis: a multicenter retrospective cohort study

Background: Massive gastrointestinal bleeding (MGB) is a life-threatening critical complication among patients with sepsis. Although static blood urea nitrogen (BUN) has been widely recognized as a conventional prognostic biomarker for critical illness, the clinical value of dynamic BUN longitudinal trajectories in predicting subsequent MGB and long-term mortality remains insufficiently clarified. This study aimed to identify early BUN trajectory phenotypes and further evaluate their independent prognostic performance in septic patients. Methods: This multicenter retrospective landmark cohort study ultimately enrolled 3016 adult sepsis patients with a strict day-5 observational boundary. Group-based trajectory modeling was used to classify early BUN changing patterns within the first 5 days after admission. Cox regression and Fine-Gray competing-risk models were applied to explore the relationships between different BUN trajectories and postlandmark MGB as well as 28-day in-hospital mortality. Results: Three stable BUN trajectory subgroups were determined, including low-stable, moderate-stable, and high-stable types. After the 5-day landmark, 48 cases of MGB and 467 in-hospital deaths were recorded. After full confounding adjustment, the high-stable BUN trajectory was associated with higher risks of MGB and mortality, with stable statistical results in competing-risk analysis. Conclusion: Early dynamic BUN trajectories can effectively distinguish heterogeneous risk stratification in sepsis. A persistently high BUN trajectory is an independent adverse prognostic factor for MGB and mortality, which can serve as a simple and practical monitoring indicator and deserves prospective validation in future studies.