The Prognostic Value of Venous Base Excess in Emergency Department Patients with and without Renal Dysfunction

Objective　Base excess (BE), a marker of the metabolic component of acid-base balance, reflects systemic tissue perfusion and metabolic disturbances. Although its prognostic utility has been established in critical care, evidence in unselected emergency department (ED) populations is limited. Venous BE correlates well with arterial BE and it can be measured rapidly without invasive sampling. Because BE may be influenced by the renal function, its prognostic value in patients with and without renal dysfunction remains unclear. This study aimed to evaluate the association between venous BE at ED presentation and in-hospital mortality in patients with and without renal dysfunction.Methods　We retrospectively analyzed all adult patients who visited our ED between April 2018 and March 2023 and underwent venous BE measurement upon arrival. Patients were categorized into five BE groups: ≤-9, -9 to -3, -3 to +3, +3 to +9, and ＞+9 mmol/L. The primary outcome was in-hospital mortality. Kaplan-Meier and Cox proportional hazards analyses were performed. Patients were stratified according to the presence or absence of renal dysfunction, defined as an estimated glomerular filtration rate (eGFR) of ＜60 mL/min/1.73 m². Subgroup Cox models were adjusted for age and sex, and interaction terms between BE categories and renal dysfunction were included to assess effect modification.Results　A total of 2,629 patients were included (median age, 77 years; 51% male). The overall in-hospital mortality rate was 10% and differed significantly across the BE groups. In patients with renal dysfunction, the hazard ratios for BE ≤-9 and BE ＞+9 were 11.57 and 7.41, respectively, whereas in those without renal dysfunction, the corresponding values were 16.24 and 4.25. No statistically significant interaction was detected between the BE categories and renal dysfunction.Conclusion　Venous BE measured at ED presentation independently predicts in-hospital mortality in an unselected adult population. Venous BE was associated with in-hospital mortality in both patients with and without renal dysfunction. Venous BE is a simple, rapid, and noninvasive biomarker suitable for early risk stratification in emergency settings.