Objective To observe the changes of the oxygen delivery （DO2） and the oxygen consumption （VO2） during off-pump coronary surgery （OPCABG）. Methods Thirty patients undergoing elective OPCABG were enrolled in this study. Hemodynamic measurements and arterial blood gases were recorded after sternotomy （BASE）, exposure and stabilization of the left anterior descending coronary artery （LAD）, the right coronary artery （RCA） and the left circumflex coronary artery （LCX）, and before closing thoracic （END）. Results There were no significant changes in mean arterial pressure throughout the operation, and the minimum was 71.0 mmHg±9.4 mmHg. Compared with the base, during the period of LAD, cardiac index （CI） decreased from 2.63 L·min -1 ·m -2 ±0.33 L·min -1 ·m -2 to 2.36 L·min -1 ·m -2 ±0.37 L·min -1 ·m -2 （P<0.01）; During periods of RCA and LCX, CI decreased 22% （P<0.01） and 24% (P<0.01. After the heart was restored to its anatomical position, CI was 2.31 L· min -1 ·m -2 ±0.27 L· min -1 ·m -2 （P<0.01）. With the couse of the operation , DO2 decreased from 452 ml·min -1 ·m -2 ±78 ml·min -1 ·m -2 （BASE） to 357 ml·min -1 ·m -2 ±69 ml·min -1 ·m -2 （P<0.01） （END）. The minimal value（341 ml·min -1 ·m -2 ±64 ml·min -1 ·m -2 ） appeared after LCX. There was no significant change in VO2. Conclusion DO2 decreases to the minimum when exposure and stabilization of LAD in these patients. Appropriate sterns position, capacity, heart rate, and positive inotropic drugs are necessary.
