Association of fluid balance trajectories and cumulative fluid balance with in-hospital mortality in patients with acute pancreatitis.

BACKGROUND

Fluid resuscitation represents a cornerstone of early management in acute pancreatitis (AP). Accumulating evidence suggests that positive fluid balance (FB) is independently associated with adverse outcomes, including pulmonary edema and abdominal compartment syndrome. This study aimed to identify distinct FB trajectories during the initial 72 h in ICU-admitted patients and comprehensively evaluate their associations with in-hospital mortality, incorporating both dynamic trajectory patterns and static cumulative measures.

METHODS

We analyzed data from 1,026 adult AP patients admitted to the ICU using the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. An external validation cohort of 271 patients from the eICU Collaborative Research Database (eICU-CRD) was used for replication. Latent class mixed models (LCMM) were employed to identify distinct FB trajectories. The primary outcome was in-hospital mortality; secondary outcome was ICU length of stay (LOS). Restricted cubic splines (RCS) were used to assess nonlinear associations between cumulative FB (CumFB) and outcomes.

RESULTS

Three distinct FB trajectories were delineated: Low FB (80.02%, consistently low net balance), High-Fall FB (11.99%, initially high volume followed by rapid de-escalation), and Rise-Fall FB (7.99%, progressive early accumulation peaking before declining). The Rise-Fall trajectory was independently associated with higher in-hospital mortality and prolonged ICU LOS. RCS revealed a U-shaped association between CumFB and mortality, with risks rising at CumFB >25 mL/kg-a threshold similarly associated with extended ICU LOS. These findings were corroborated in the eICU-CRD cohort.

CONCLUSION

The Rise-Fall FB trajectory is independently associated with poor outcomes, manifesting as both increased mortality and prolonged ICU LOS, while CumFB exhibits a nonlinear association with outcomes.