The Effect of Preoperative Aspirin and/or Heparin Therapy on Coagulation and Postoperative Blood Loss after Coronary Artery Bypass Surgery.

Objective: To assess the effects of preoperative aspirin and/or intravenous heparin therapy on perioperative coagulation tests and postoperative blood loss for 24-hour after coronary artery bypass surgery.

Methods: Multiple conventional coagulation tests, activated clotting time, thrombelastograph, skin bleeding time and platelet aggregation were performed before induction of anaesthesia, following protamine administration and after skin closure in 45 patients.

Results: There was no significant difference in either coagulation tests or postoperative blood loss (median of 860 mL with a range of 275 to 2800 mL, versus 833 ml with a range of 500-1380 mL) between the aspirin and no-aspirin patients. Preoperative heparin therapy affected most coagulation tests (e.g. international normalised ratio, activated partial thromboplastin time, thrombin clotting time, prothrombin time, activated clotting time and coagulation time of thrombelastography) before anaesthesia. The effects disappeared following protamine administration and after skin closure. Post operative blood loss was not significantly increased for the heparin group compared with the no-heparin group (median of 850 mL with a range of 700-1400 mL, versus 856 mL with a range of 275-2800 mL, respectively). Similar results were seen in patients receiving preoperative co-administration of aspirin and heparin compared with patients receiving aspirin alone. There was no suppression of platelet activity in patients receiving preoperative heparin or co-administration of aspirin and heparin. However, such suppression was found in patients receiving aspirin only.

Conclusion: This study suggests that preoperative aspirin ingestion and intravenous heparin therapy should be administered as indicated and that concerns about the risk of postoperative bleeding should not lead to modification or cessation of such therapy.