Central venous-to-arterial CO2 difference as a biomarker of outcome in children who underwent surgery for congenital heart disease

Abstract

Background: In congenital heart surgery, low cardiac output syndrome (LCOS) is a major cause of morbidity in the immediate post-operative period. A decrease in cardiac output leads to an increase in tissue oxygen consumption. Several biomarkers such as venous oxygen saturation (SvO2 ), arteriovenous oxygen difference (DavO2 ), and lactate can assess tissue perfusion in the presence of LCOS. Recently, central venous to arterial CO2 difference (∆CO2 ) has been proposed as a biomarker of tissue ischemia that could be used as a predictor of death in neonatal patients. This study aimed to analyze the relationship between ∆CO2 and immediate post-operative outcomes in pediatric patients undergoing congenital heart surgery and its correlation with DavO2, SvO2, and lactate. Methods: We conducted a longitudinal study of patients aged 0-18 years who underwent congenital heart surgery with or without cardiopulmonary bypass at the Instituto Nacional de Pediatría, from March 2019 to March 2021. Results: Eighty-two patients were included; the median age was 17 months. About 59% had a ∆CO2 ≥ 6 mmHg. Patients with ∆CO2 ≥ 6 mmHg had a vasoactive-inotropic score > 5 (p < 0.001), DavO2 > 5 mL/dL (p = 0.048), and lactate > 2 mmol/L (p = 0.027), as well as a longer hospital stay (p = 0.043). Patients with ∆CO2 > 6 mmHg and vasoacti-ve-inotropic score ≥ 10 were 12.6 times more likely to die. Conclusion: ∆CO2 is a good marker of tissue hypoperfusion and outcome in the post-operative period of congenital heart surgery.