Hyperlactatemia (HL) during cardiopulmonary bypass (CPB) is relatively frequent in infants and associates with increased morbidity and mortality. Studies on adults have shown that carbon dioxide production index (VCO₂i) during CPB is linked to the occurrence of HL, with ‘critical thresholds’ for VCO₂i reported to be 60 mL/min/m². However, considering infants have a higher metabolic rate and lower tolerance to hypoxia, the critical threshold of VCO₂i in infants cannot be replied to the existing adults’ standards. The objective of this study is to investigate the association of VCO₂i during CPB and HL, and explore the critical VCO₂i threshold during CPB in infants.

VCO₂i predicts hyperlactatemia during cardiopulmonary bypass in pediatric cardiac surgery (pGDP-VCO₂i) is a nested case-control study. A cohort of consecutive pediatric patients of less than 3 years of age, undergoing congenital cardiac surgeries between May 2021 and December 2023 in West China Hospital will be enrolled. The VCO₂i levels of each patient will be recorded every 5 min during CPB. The primary outcome is the rate of HL. The infants will be divided into two groups based on the presence or not of HL. Pre- and intraoperative factors will be tested for independent association with HL. Then, we will make an analysis, and the critical value of VCO₂i will be obtained. The postoperative outcome of patients with or without HL will be compared.

This will be the first trial to investigate the association of VCO₂i during CPB and HL, and explore the critical VCO₂i threshold during CPB in pediatrics. The results of this study are expected to lay a foundation for clinical application of goal-directed perfusion (GDP) management strategy, and optimize the perfusion strategy and improve the prognosis of pediatric patients undergoing cardiac surgery.