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 (AVCO(2)) and is correlated with cardiac output (CO) in critically ill adult patients. This study aimed to correlate AVCO(2) with other CO indices like arteriovenous oxygen saturation difference (AVO(2)), central venous oxygen saturation (ScVO(2)), 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 5 months to 5 years, undergoing ICR for TOF and analyzed AVO(2), AVCO(2), ScVO(2), and lactate from arterial and venous blood gas pairs obtained at different time intervals from admission to pediatric intensive care unit (PICU) (T(0)), at 6 h (T(1)), 12 h (T(2)), 24 h (T(3)), and 48 h (T(4)) postoperatively. Bivariate correlations were analyzed using Pearson for parametric variables. RESULTS: Admission AVCO(2) was not correlated with AVO(2) (R(2) = 0.166, P = 0.246), ScVO(2) (R(2) = -2.2, P = 0.124), and lactate (R(2) = -0.07, P = 0.624). At T(1), AVCO(2) was correlated with AVO(2) (R(2) = 0.283, P = 0.0464) but not with ScVO(2) (R(2) = - 0.25, P = 0.079) and lactate (R(2) = -0.07, P = 0.623). At T(2), T(3) and T(4), AVCO(2) was correlated with AVO(2) (R(2) = 0.338,0.440 & 0.318, P = 0.0162, 0.0013, and 0.024), ScVO(2) (R(2) = - 0.344, - 0.488, and -0.366; P = 0.0143, <0.0001, and 0.017), and lactate (R(2) = 0.305, 0.467 and 0.607; P = 0.0314, 0.00062 and <0.0001). AVCO(2) was negatively correlated with ScVO(2). No correlation observed between admission AVCO(2) and mechanical ventilation duration. Two nonsurvivors had higher value of admission AVCO(2) compared to survivors. CONCLUSION: AVCO(2) is correlated with other CO surrogates like AVO(2), ScVO(2), and lactate in pediatric patients undergoing ICR for TOF.