NORIHISA KITAMOTO

BACKGROUND: Retrograde autologous priming and venous antegrade priming replace the cardiopulmonary bypass circuit crystalloid with patient blood to mitigate hemodilution. However, their effectiveness in pediatric patients, particularly when analyzed as continuous variables, remains unclear. AIMS: We aimed to evaluate the effects of autologous priming techniques on blood conservation and patient safety during pediatric cardiac surgery. METHODS: This retrospective cohort study included 191 patients (age 0-14 years; weight > 6 kg) who underwent repair of ventricular and/or atrial septal defects. The primary endpoint was the correlation between the priming volume reduction rate (proportion of priming solution replaced) and the hematocrit retention ratio (hematocrit immediately after cardiopulmonary bypass initiation divided by pre-bypass hematocrit). Secondary outcomes, including transfusion rates, regional cerebral oxygen saturation, and lactate levels, were compared between a retrograde autologous priming group (n = 144) and a control group (n = 47). All patients underwent venous antegrade priming. RESULTS: The priming volume reduction rate correlated positively with the hematocrit retention ratio (Spearman's ρ = 0.545, p < 0.001). Multiple regression confirmed this independent association: a 0.1 increase in the priming volume reduction rate corresponded to a 0.5% absolute increase in hematocrit at bypass initiation. The retrograde autologous priming group had a significantly higher transfusion-free surgery rate (93.1% vs. 76.6%; relative risk ratio 1.22; p = 0.005). Regarding safety and the postoperative course, no significant intergroup differences were found in trends in regional cerebral oxygen saturation (Time × retrograde autologous priming interaction) or in lactate levels. Similarly, intensive care unit and hospital lengths of stay did not differ significantly between groups. Safety analyses suggested no evidence of cerebral perfusion suppression during retrograde autologous priming. CONCLUSION: These findings suggest that even partial retrograde autologous priming is effective to mitigate hemodilution and is independently associated with improved hematocrit retention and a significant reduction in transfusion risk after initiation of cardiopulmonary bypass in pediatric patients. TRIAL REGISTRATION: This study was registered with the UMIN Clinical Trials Registry, Japan, prior to commencement (Trial ID: R000067879).