Impact of eosinophil levels on postoperative clinical outcomes in patients undergoing extracorporeal circulation: a retrospective cohort study

Extracorporeal circulation (ECC) is an essential operation in many cardiac surgeries, but contact between blood and connecting tubes can activate inflammatory factors and adversely affect complement. Previous studies have often focused on macrophages and neutrophils, while eosinophils have emerged as a new research hotspot due to their potential association with improved outcomes in recovery. The current research investigated the association between eosinophils and clinical prognosis in ECC patients. Data from the MIMIC-IV database were evaluated in this retrospective study, including 1,719 patients who underwent ECC. Eosinophil counts were categorized into tertiles, and their associations with 90-day mortality and the duration of mechanical ventilation were estimated with multivariable Cox regression models and linear regression, respectively. To assess survival results amongst eosinophil tertiles, the Kaplan-Meier survival analysis was employed. A lower 90-day death rate (HR for the highest tertile vs. lowest: 0.3, 95% CI: 0.1–0.5, P < 0.001) and fewer hours spent on mechanical ventilation (Tertile 3: -29.1 h, P < 0.001) were both substantially correlated with higher eosinophil levels. These findings remained consistent across multivariate models, indicating an independent association with improved outcomes of eosinophils. Maintaining eosinophil levels above 0.009 was notably linked to better survival outcomes after ECC. Elevated eosinophil levels, particularly above 0.009, are associated with improved survival and reduced mechanical ventilation duration in ECC patients. Eosinophil levels may serve as a potential prognostic biomarker, though future studies are needed to determine their clinical utility in guiding postoperative management.