In coronary artery bypass graft employing the surgical technique of intermittent aortic cross-clamping appeared the controversy of the need of lung ventilation on prevention of the hypoxemia. The purpose of this work was to verify the importance of lung ventilation on oxygen transport and acidbase balance in blood that will reperfuse the myocardium following aortic desclamping. Ten patients undergoing coronary artery bypass graft under moderate hypothermia were divided in two groups: I - Lung ventilation was carried out after aortic desclamping. II - Lung ventilation wasn't done following aortic desclamping. Blood samples were collected from the left right atrium, aorta, radial and pulmonary artery and the both sides of bypass circuit (venous and arterial). Oxygem saturation, oxygen tension, carbon dioxide tension, and blood pH were evaluated in the both groups. The results showed no statistical difference between groups concerning oxygen saturation. The pH decreases significantly in patients of Group II, due to a sharp elevation of PCO2. Although no significative hypoxemia could be observed, the respiratory acidosis that appeared in Group II suggests the importance of ventilation of the lungs as soon as possible after aortic desclamping. It is important to remember that myocardial contractility may be depressed by hydrogen ions (H+) in excess.
myocardial revascularization; lung ventilation; aortic desclamping