To test the hypothesis that neutrophils play a role in lung injury during cardiopulmonary bypass, granulocyte elastase and myeloperoxidase release from pulmonary circulation were measured, as well as the respiratory index, before and after cardiopulmonary bypass. The production of granulocyte elastase and myeloperoxidase in the pulmonary circulation, and the respiratory index also elevated significantly after cardiopulmonary bypass. Furthermore, the level of granulocyte elastase and myeloperoxidase released from pulmonary circulation correlated with the changes of the respiratory index and preoperative pulmonary artery pressure. These data indicate that neutrophils play a major role in pulmonary dysfunction occurring after cardiopulmonary bypass, which is accentuated in patients with pulmonary hypertension.

To test the hypothesis that neutrophils play a role in ischemia/reperfusion injury during heart surgery, granulocyte elastase and myeloperoxidase release from coronary circulation were measured before and after aortic cross-clamping. The production of granulocyte elastase and myeloperoxidase across the coronary circulation elevated significantly after release of aortic cross-clamp. Furthermore, the level of granulocyte elastase and myeloperoxidase released from coronary circulation demonstrated positive correlation with the duration of the aortic cross-clamp. These data indicate that neutrophils play a major role in ischemia/reperfusion injury occurring during heart surgery.