Oxygen delivery and consumption in the perioperative period of coronary artery bypass grafting without blood transfusion

Abstract

The perioperative changes in relationship between oxygen delivery$\dot D_{O_2 }$ and oxygen consumption$\dot V_{O_2 }$ were examined in forty patients who underwent coronary artery bypass grafting (CABG) without blood transfusion. Hemodilution was performed to maintain hematocrit of 19.2±1.8% during cardiopulmonary bypass (CPB). Hemodynamic and metabolic parameters were measured in four stages; before CPB (stage I), after CPB (stage II), after ICU arrival (stage III), and the following day (stage IV). In each stage, there was a strong positive correlation between$\dot V_{O_2 }$ and$\dot D_{O_2 }$. In stage I, a decrease in$\dot D_{O_2 }$ was met with low$\dot V_{O_2 }$, and there was no imbalance between them (r=0.67,P<0.01).$\dot V_{O_2 }$ increased significantly in stage II, and this increased$\dot V_{O_2 }$ was compensated by an increase in$\dot D_{O_2 }$ sufficiently to meet tissue oxygen demand (r=0.59,P<0.01). In stage III and IV, the increases in tissue oxygen requirements were met by increases in oxygen extraction ratio (r=0.81,P<0.01, r=0.60,P<0.01, respectively) reflected in lowered mixed venous oxygen tension and saturation. From these results, it is assumed that the adequate relationship between$\dot V_{O_2 }$ and$\dot D_{O_2 }$ can be maintained in the perioperative period of CABG without blood transfusion.