Objective: Bleeding complications have been a major concern in certain thoracic surgery operations, especially decortication and pulmonary resection for inflammatory pulmonary infection. Prevention of plasminogen activation and fibrinolysis by aprotinin administration has been shown to reduce perioperative bleeding during operations associated with high blood consumption. Methods: Use of blood products (packed red cells, whole blood), chest tube drainage, analgesic requirement, chest tube duration for the patients undergoing major thoracic operations were recorded. In a double blind randomized fashion, patients were assigned to two groups receiving aprotinin (n = 51), at a loading dose of 10(6) kallikrein inhibitory units (KIU) followed by an infusion of the same dose during chest closure or receiving placebo (n = 52). On a daily basis, red-cell percentages of total fluid from drainage bottles were recorded and using the blood hematocrit level of the patient of the day before, the corrected value for the patient's blood volume equivalent of daily drainage was calculated. Results: There was a significant reduction in perioperative use of donor blood (0.98 +/- 0.92 vs. 0.45 +/- 0.32 unite P = 0.0026), and total chest tube drainage (corrected value for the corresponding blood volume) (28.2 +/- 36.9 vs. 76.9 +/- 53.3 ml, P = 0.0004) (mean standard deviation) in the aprotinin group. However, aprotinin did not reduce postoperative transfusion or decrease in hematocrit level due to thoracic operations. In high transfusion-risk thoracic surgery patients (patients who underwent decortication, pulmonary resection for inflammatory lung disease and chest wall resection), the perioperative transfusion was only 0.50 +/- 1.08 units in aprotinin group, compared with 1.94 +/- 0.52 units in control group (P = 0.003). Postoperative transfusion was also reduced in aprotinin administrated group (0.53 +/- 0.56 vs. 1.38 +/- 0.97 units, P = 0.02). The mean total blood loss was decreased to nearly one third of the blood loss of the control group (41 +/- 28 ml vs. 121 +/- 68 ml P = 0.001). Conclusion: Aprotinin significantly reduced perioperative transfusion requirement and postoperative bleeding during major thoracic operations. Aprotinin decreased perioperative transfusion needs. Moreover, patients who were at risk of greater blood loss during and after certain thoracic operations had a greater potential to benefit from prophylactic perioperative aprotinin treatment. (C) 2001 Elsevier Science B.V, All rights reserved.