Abstract

Objective: The objective of this study was to evaluate the association between the minimal count of lymphocyte (Ly_Min) after cardiac surgery with cardiopulmonary bypass and the occurrence of infections within the first 30 postoperative days (POD). Methods: From a local European Congenital Heart Surgeons Association (ECHSA) database, all cardiac surgeries with cardiopulmonary bypass in children under 18 years old between January 2014 and December 2021 were eligible. Infections occurring within 30 POD were prospectively recorded according to ECHSA definitions, and classified into sepsis, pneumonia, wound infection, mediastinitis or endocarditis. For each surgery, Ly_Min was collected during the first 2 POD and the optimal threshold for predicting infection was chosen using receiver operating characteristic curve analysis. Univariate and multivariate logistic regression analyses were performed to identify variables associated with the risk of infection. Results: Of 1428 surgeries conducted over the 8-year period, 111 (8%) were complicated by at least 1 infection, including pneumonia (n = 45), wound infection (n = 41), sepsis (n = 24), mediastinitis (n = 20) and endocarditis (n = 3). Mean Ly_Min in the first 2 POD was lower in the infected group compared with the noninfected group (1.32 ± 0.81 vs. 1.81 ± 1.05 × 10 9 /L, P < 0.001). After adjusting for confounders, Ly_Min <1.105 × 10 9 /L within the first 1 POD was independently associated with an increased risk of postoperative infections (adjusted odds ratio = 1.75, 95% confidence interval: 1.10–2.79, P = 0.019). Conclusions: In this large single-center cohort of pediatric cardiac surgeries, Ly_Min during the first 2 POD was associated with the development of infections within 30 days after cardiopulmonary bypass.