Correlation of Venous to Arterial Carbon Dioxide Partial Pressure Difference with other Cardiac Output Indices in Patients Undergoing Intracardiac Repair for Tetralogy of Fallot

Background: Clearance of tissue carbon dioxide by circulation is measured by venous to arterial carbon dioxide partial pressure difference (AVCO2 ) and is correlated with cardiac output (CO) in critically ill adult patients. This study aimed to correlate AVCO2 with other CO indices like arteriovenous oxygen saturation difference (AVO2 ), central venous oxygen saturation (ScVO2 ), and serum lactate in pediatric patients undergoing intracardiac repair (ICR) for tetralogy of Fallot (TOF). Methods: We conducted a prospective observational study in 50 patients, of age 5months to 5 years, undergoing ICR for TOF and analyzed AVO2 , AVCO2 , ScVO2 , and lactate from arterial and venous blood gas pairs obtained at different time intervals from admission to pediatric intensive care unit(PICU)(T0 ), at 6 h (T1 ), 12 h (T2 ), 24 h (T3 ), and 48 h (T4 ) postoperatively. Bivariate correlations were analyzed using Pearson for parametric variables. Results: Admission AVCO2 was not correlated with AVO2 (R2 = 0.166, P = 0.246), ScVO2 (R2 = ?2.2, P = 0.124), and lactate (R2 = ?0.07, P = 0.624). At T1 , AVCO2 was correlated with AVO2 (R2 = 0.283, P = 0.0464) but not with ScVO2 (R2 = ? 0.25, P = 0.079) and lactate (R2 = ?0.07, P = 0.623). At T2 , T3 and T4 , AVCO2 was correlated with AVO2 (R2 = 0.338,0.440 & 0.318, P = 0.0162, 0.0013, and 0.024), ScVO2 (R2 = ? 0.344, ? 0.488, and ?0.366; P = 0.0143, <0.0001, and 0.017), and lactate (R2 = 0.305, 0.467 and 0.607; P = 0.0314, 0.00062 and <0.0001). AVCO2 was negatively correlated with ScVO2 . No correlation observed between admission AVCO2 and mechanical ventilation duration. Two nonsurvivors had higher value of admission AVCO2 compared to survivors. Conclusion: AVCO2 is correlated with other CO surrogates like AVO2 , ScVO2 , and lactate in pediatric patients undergoing ICR for TOF.