Effect of cardiopulmonary bypass on pulmonary gas exchange: A prospective randomized study

Background. Conventional coronary artery bypass surgery is associated with postoperative pulmonary dysfunction. Inflammation due to cardiopulmonary by pass has been regarded as one of the main causes. In this study, we investi gated the effect of coronary revascularization with or without cardiopulmon ary bypass on pulmonary function. Methods. Fifty-two patients (40 male, mean age 60.1 years) were prospective ly randomized to undergo coronary revascularization via median sternotomy, with or without normothermic cardiopulmonary bypass. Alveolar-arterial oxyg en gradients were measured before and after induction of anesthesia, postop eratively in the intensive care unit during mechanical ventilation and 6 ho urs after tracheal extubation. The techniques of anesthesia and mechanical ventilation were standardized throughout Results. Patient characteristics w ere similar in the two groups. The alveolar-arterial oxygen gradients incre ased progressively throughout the perioperative period, with no significant differences in the two groups at any time during the study. Conclusions. Myocardial revascularization with or without cardiopulmonary b ypass caused a similar degree of pulmonary dysfunction, as assessed by alve olar-arterial oxygen gradient. Our study suggests that the deterioration in pulmonary gas exchange associated with cardiac surgery is due to factors o ther than the use of cardiopulmonary bypass. (C) 2000 by The Society of Tho racic Surgeons.