Abstract: Objective To explore the predictive value of venous-arterial-carbon dioxide partial pressure difference and arteriovenous oxygen content difference (Pv-aCO2 /Ca-vO2) to hypoxia during cardiopulmonary bypass (CPB) in infants with cyanotic congenital heart disease (CCHD). Methods Thirty children (0-1 year-old) with CCHD underwent cardiac surgery were enrolled. Arterial blood carbon dioxide partial pressure［pa(CO2)］, central venous blood carbon dioxide partial pressure［pv(CO2)］, arterial oxygen partial pressure［pa(O2)］, central venous oxygen partial pressure［pv(O2)］, arterial oxygen saturation (SaO2), central venous oxygen saturation (SvO2), arterial hemoglobin concentration (CaHb), central venous hemoglobin concentration (CvHb), arterial blood lactate (Lac), mean arterial pressure (MAP) and nasopharyngeal temperature were recorded, and arterial blood gas and venous blood gas were also checked at five different points of time: after tracheal intubation (T1), 5 min after ascending aortic clamping (T2), 5 minutes after the ascending aorta was opened (T3), off CPB (T4), end of ultrafiltration (T5). Pv-aCO2/Ca-vO2 was calculated according to formula. Changes of Pv-aCO2/Ca-vO2, Lac, MAP and nasopharyngeal temperature were comparison at each time points. Data of blood creatinine for seven consecutive days after surgery were recorded. The correlation between Pv-aCO2 / Ca-vO2 and Lac at each time point was analyzed. The receiver operating characteristic (ROC) curve was used to analyze the predicted value of Pv-aCO2/Ca-vO2 to hypoxia at different time points. According to the Kidney Disease: Improving Global Outcomes (KDIGO), infants with acute kidney injury (AKI) were diagnosed. The incidence of AKI was compared at each time point between infants with high Pv-aCO2 /Ca-vO2 and infants with high Lac. Results Pv-aCO2/Ca-vO2 and Lac were significantly increased in T1 compared with that of T2, T3 and T4 (P＜ 0.01). There was no significant difference in Pv-aCO2/Ca-vO2 between T5 and T1 (P＞0.05). Lac was significantly higher at T5 than that of T1 (P＜0.05). Pv-aCO2 /Ca-vO2 and Lac were significantly lower at T5 compared with those of T4 (P＜0.01 and 0.05). Compared with T1, MAP and nasopharyngeal temperature were significantly lower at T2 (P＜0.05). There was no statistical difference at other time points (P＞0.05). Values of Pv-aCO2/Ca-vO2 were positively correlated with Lac at T2 and T3 (r=0.87, P＜0.01; r=0.68, P＜0.01). The area under the curve (AUC) for predicting hypoxia of Pv-aCO2/Ca-vO2 at T2 was 0.926 (95% CI: 0.670-0.997, P＜0.0001), the cut-off value of Pv-aCO2 / Ca-vO2 was 0.35, the diagnostic sensitivity for hypoxia was 100% and the specificity was 77.78%. There was no statistical significance for predicted hypoxia with AUC of Pv-aCO2 / Ca-vO2 at T3 (P＞0.05). Compared with the incidence of postoperative AKI in infants with Lac＞3 mmol/L at T2, the incidence of postoperative AKI was significantly higher in infants with Pv-aCO2/Ca-vO2＞0.35 at T2 (P＜ 0.05). Conclusion During CPB in infants with CCHD, when Pv-aCO2 / Ca-vO2 is higher than 0.35 at 5 min after aortic clipping, it can identify hypoxia and predict postoperative AKI better than Lac.

Key words: infant, newborn, diseases, heart defects, congenital, cardiopulmonary bypass, diagnosis, differential, hypoxia, cyanotic congenital heart disease, Pv-aCO2/Ca-vO2