Using the ΔvapCO2 / Cav02 Ratio as a Prognostic Marker and Predictor of Complications After Cardiac Surgery

Cardiac surgery is widely used to solve valvular or coronary problems and often requires the use of cardiopulmonary bypass or extracorporeal circulation (EC).

The EC itself produces a series of changes in the macro- and microcirculation hemodynamic and physiological consequences in the hours following surgery that can be difficult to analyze.

During postoperatively management, different monitoring methods are used to optimize different hemodynamic and analytical variables.

Sometimes, monitored variables are corrected but the patient still develops complications such as kidney failure, prolonged mechanical ventilation or even death. In fact, it is not well known either if it is sufficient to correct the variables called "macrodynamics " such as mean arterial pressure (MAP) , stroke volume (SV), pulmonary artery occlusion pressure (PCWP) and cardiac index (CI) or if it is necessary to correct other "micro-dynamics" variables like lactate, to achieve a certain central venous oxygen saturation (ScvO2) or arteriovenous CO2 difference(ΔvapCO2).

In tissue hypoxia, damping of excess protons by bicarbonate increase CO2 production; therefore the relationship between CO2 production and oxygen consumption (VCO2/VO2 ratio or respiratory quotient) increases. This ratio can be simplified relating ΔvapCO2 and O2 content arteriovenous difference (ΔvapCO2 / Cav02 ratio). In shock, anaerobic metabolism is one of the primary energy source. In this situation, ΔvapCO2 / Cav02 is > 1.