Impact of carbon dioxide tension during cardiopulmonary bypass on tissue perfusion in neonates undergoing cardiac surgery using autologous umbilical cord blood

Abstract

Objective: Previously, we reported that the oxyhemoglobin dissociation curve is shifted leftward in patients who receive autologous umbilical cord blood (UCB) during neonatal open heart surgery. In this study, we assessed whether allowing the pCO2 to rise during hypothermic cardiopulmonary perfusion would shift the curve back to the right and improve tissue oxygenation. Methods: The study population included prenatally diagnosed patients with transposition of the great arteries. The study cohort was divided into two groups and consisted of early patients originally managed with lower pCO2 levels (Group I, n=42, 2009-12) and later patients subsequently managed with higher pCO2 levels (Group II, n=38, 2012-14). Results: Patients received similar volumes of collected autologous UCB (Group I, 80 ml; Group II, 75ml, p=0.207) with a similar mean level of HbF during CPB (Group I, 90±8%; Group II, 87±9%, p=0.310). Higher levels of pCO2 during CPB (Group I, 31 mmHg; Group II, 37 mmHg, p=0.011) resulted in a rightward shift of the oxyhemoglobin dissociation curve (increased p50O2) (Group I, 19.5±3.4 mmHg; Group II, 22.5±2.2 mmHg, p=0.011). The use of a higher pCO2 strategy was associated with decreased serum lactate during CPB (Group I, 4.7±2 mmol/l; Group II, 2.8±1.4 mmol/l, p=0.001), decreased duration of mechanical ventilation (Group I, 46h; Group II, 22h, p<0.001) and decreased of length of intensive care unit (ICU) stay (Group I, 7.6±2.6, Group II, 5.6±2.2, p=0.003) Conclusions: A higher pCO2 during CPB in neonates who underwent open heart surgery using UCB resulted in a rightward shift of the oxyhemoglobin dissociation curve and was associated with improved serum lactate levels.