Red Cell Distribution Width as a Predictive Biomarker for Early Lung Injury in Pediatric Patients Following Cardiopulmonary Bypass

<b>Background:</b> Red cell distribution width (RDW) has emerged as a prognostic biomarker in various clinical contexts. This retrospective study evaluated the predictive utility of RDW for cardiopulmonary bypass-associated acute lung injury (CPB-ALI) in pediatric patients undergoing cardiac surgery. <b>Methods:</b> A total of 166 children were enrolled and classified into CPB-ALI and non-ALI groups. Preoperative and postoperative RDW values were analyzed. <b>Results:</b> Postoperative RDW was significantly higher in the CPB-ALI group (15.40% vs. 13.78%, <i>p</i> < 0.001). Multivariate logistic regression identified postoperative RDW as an independent predictor of CPB-ALI (OR: 1.35, 95% CI: 1.10-1.64, <i>p</i> = 0.003). Receiver operating characteristic analyses yielded an AUC of 0.732, and restricted cubic spline analyses revealed a nonlinear association between RDW and CPB-ALI risks (<i>p</i> < 0.001). Higher postoperative RDW levels were positively correlated with prolonged mechanical ventilation duration, ICU stay, and total hospital stay (<i>p</i> < 0.001 for all). <b>Conclusions:</b> These findings suggest that postoperative RDW is a cost-effective and accessible biomarker for the early identification of CPB-ALI and may inform individualized perioperative management in pediatric cardiac surgery.