Weight-stratified analysis of the heterogeneous effects of miniaturized cardiopulmonary bypass on perioperative outcomes in children with congenital heart disease: A retrospective cohort study

Introduction Miniaturized cardiopulmonary bypass (CPB) circuits may reduce intraoperative transfusion in pediatric cardiac surgery, but their effects across body weight categories remain unclear. This study compared transfusion and outcomes between conventional and miniaturized CPB circuits, emphasizing weight-stratified analyses. Methods This retrospective study included 3,196 pediatric cardiac surgery patients (2015–2024) receiving conventional ( n = 548) or miniaturized ( n = 2,648) circuits. Primary outcomes were transfusion avoidance during CPB, in the ICU, and combined. Secondary outcomes included ICU length of stay, mechanical ventilation, ultrafast-track extubation, 24-h chest tube drainage (normalized to mL/kg), and hematocrit dynamics. Multivariable logistic regression and subgroup analyses were performed. Results Miniaturized circuits improved CPB transfusion avoidance overall (47.9% vs. 29.0%; P < 0.001), especially in children weighing 3–9 kg (all P < 0.01). ICU transfusion avoidance was lower with miniaturized circuits overall (82.1% vs. 94.5%; P < 0.001), except in the 1–2 kg subgroup. Combined avoidance was higher with miniaturized circuits across 3–9 and 12–13 kg (all P < 0.05). ICU length of stay was shorter with miniaturized circuits in most weight subgroups, whereas it was prolonged in the 2–3 kg subgroup (150 vs. 75 h; P < 0.001). Overall mean 24-h chest tube drainage was significantly lower in the miniaturized group (9.05 ± 9.10 vs. 10.82 ± 7.76 mL/kg; P < 0.001); however, stratified analysis showed a significant increase only in the 4–5 kg subgroup (14.52 ± 7.88 vs. 11.96 ± 6.69 mL/kg; P = 0.046), with no differences in other weight strata. Multivariable analysis indicated that miniaturized circuits were an independent predictor of increased ICU transfusion risk (OR 2.59; P < 0.001), whereas higher body weight was associated with reduced risk (OR 0.76 per kg; P < 0.001). Conclusions Miniaturized CPB circuits reduce intraoperative transfusion, particularly in children weighing 3–9 kg, but are associated with higher postoperative ICU transfusion and variable effects on chest tube drainage that are weight-dependent. The net benefit appears weight-dependent. These findings underscore the need for weight-stratified circuit selection, although further prospective studies are warranted.