The importance of pulmonary artery circulation during cardiopulmonary bypass

This study sought to determine changes in transpulmonary difference in blood cells and alveolar-arterial oxygen (A-aO2) gradient when pulmonary artery circulation was obstructed in patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB). Eighteen patients were divided into group A (control group; X-clamp placed on aorta, n = 9) and group B (pulmonary ischaemia group; X-clamp placed on aorta and pulmonary artery, n = 9). Haematological parameters were compared before CPB and up to 90 min after declamping. A-aO2 gradient differences were compared before and 2 h and 6 h after declamping. A transpulmonary increase in leucocyte levels normalized after 60 min in group A but remained higher in group B. A transpulmonary increase in neutrophils normalized after 60 min in group A and 90 min in group B. Increased lymphocyte levels normalized after 30 min in group A and 90 min in group B. A-aO2 gradient was determined as: group A (294.8 +/- 74.3) and group B (321.2 +/- 73.3) before X-clamping; group A (132.7 +/- 22.7) and group B (236.6 +/- 41.5) 2 h after declamping; and group A (72.2 +/- 22.7) and group B (189.4 +/- 88.9) 6 h after declamping. When pulmonary artery circulation was obstructed during the X-clamping period, leucocyte, neutrophil and lymphocyte sequestration within both lungs increased, and an increased A-aO2 gradient was observed because of tissue damage. To prevent post-operative complications, precautions to maintain normal pulmonary artery circulation are recommended.