[Central venous blood oxygen saturation and venous to arterial PCO2 difference after combined heart valve surgery]

The aim of our study was to investigate the relationship between central venous oxygen saturation (ScvO2) and venous-to-arterial difference in PCO2 (Pv-aCO2) and their role in the assessment of balance between oxygen delivery and consumption after combined valve surgery. The prospective observation study included 38 adult patients with acquired valvular hear diseases, requiring surgical correction of two or more valves using cardiopulmonary bypass. All patients were divided into 2 groups according to the central value of central venous oxygen saturation (ScvO2): low ScvO2 (ScvO2 < 70%) and high ScvO2 (ScvO2 > 70%). In both groups blood gases, Pv-aCO2, lactate concentration, hemodynamic parameters, cardiac index, oxygen delivery and oxygen consumption were assessed. During the postoperative period there was a decrease of ScvO2 < 70% in 26% of patients which was accompanied by increased Pv-aCO2 > 5 mmHg and by risen oxygen consumption. We observed a moderate correlation between ScvO2 and Pv-aCO2 during the early postoperative period: at the end of surgery, 6 and 12 hours after it (rho = -0.53; -0.62 and -0.43 respectively, n = 38, p < 0.01). The changes in ScvO2 and Pv-aCO2 regressed after 24 hours in ICU. Thus, decreased ScvO2 and increased Pv-aCO2 after combined valve surgery are related and reflect the rise in oxygen consumption.