Prognostic Value of the Perioperative Neutrophil–Lymphocyte Ratio for Adverse Outcomes in Pediatric Congenital Heart Surgery: A Retrospective Cohort Study

Background: The neutrophil–lymphocyte ratio (NLR) is a simple, cost-effective marker of systemic inflammation. This study aims to evaluate the association between perioperative NLR and postoperative outcomes in pediatric patients undergoing congenital heart surgery with cardiopulmonary bypass (CPB). Methods: We retrospectively reviewed 70 patients under 18 years of age who underwent surgery between 2018 and 2023. NLR was measured preoperatively and on postoperative days (POD) 0, 1, 2, 3, and 6. Receiver operating characteristic analysis identified optimal cutoffs, and associations with postoperative outcomes were assessed. Results: The preoperative NLR cutoff of 1.14 (AUC = 0.75) was associated with prolonged mechanical ventilation (>72 h) (p = 0.02), extended intensive care unit (ICU) stay (p = 0.004), and longer hospital stay (p = 0.006). NLR values on POD3 (AUC = 0.74) and POD6 (AUC = 0.78) also demonstrated strong predictive ability for these outcomes. Conclusions: Elevated perioperative NLR—particularly preoperative values ≥1.14—is associated with prolonged mechanical ventilation, longer ICU admission, and extended hospitalization in pediatric congenital heart surgery. NLR may serve as a practical biomarker for early risk stratification and postoperative management.