Increased systemic cardiac output improves arterial oxygen saturation in bidirectional cavopulmonary shunt

The low arterial oxygen saturation (SaO2) after bidirectional cavopulmonary shunt (BCPS) predicts poor prognosis. The venous oxygen saturation of inferior vena cava (SivcO2), as well as the pulmonary blood flow/systemic blood flow ratio (Q p/Q s) affects the SaO2. The purpose of this study is to determine whether SivcO2 or Q p/Q s should be increased to achieve better outcomes after BCPS. Forty-eight patients undergoing BCPS were included. Data of patients' age and body weight, SivcO2, Q p/Q s, pulmonary artery (PA) pressure and resistance, PA area index, morphology of ventricle, atrioventricular valve regurgitation, and history of PA plasty were collected. Stepwise multiple logistic regression analyses were used to investigate which of the factors most affected the SaO2 after BCPS. There was a significant correlation between SivcO2 and SaO2 (r = 0.771, P < 0.00001). There was no strong correlation between Q p/Q s and SaO2 (r = 0.358, P < 0.05). Stepwise multiple logistic regression analyses revealed that both SivcO2 (r = 0.49, 95 % confidence interval (CI) 0.37-0.62, P < 0.0001) and Q p/Q s (r = 11.1, 95 % CI 3.3-18.9, P = 0.007) most affected SaO2 after BCPS. Since the SivcO2 has a stronger correlation than Q p/Q s with SaO2, despite the fact that both raising Q p/Q s and raising cardiac output can increase SaO2, raising cardiac output should be considered prior to Q p/Q s to raise the SaO2 after BCPS.