The hypothesis of this study is that the antifibrinolytic drugs aprotinin and tranexamic acid equally influence bleeding tendency and transfusion requirement in patients undergoing first time cardiac procedures with a low risk of increased postoperative bleeding.Only patients undergoing first time CABG or first time aortic valve replacement are included in this study.

Excessive bleeding during and after cardiac surgery is a serious complication. It exposes patients to the risk of allogeneic blood transfusion or other blood products and the risk of mediastinal re-exploration.Antifibrinolytic drugs like aprotinin and tranexamic acid are proven to reduce bleeding tendency and transfusion requirement in cardiac surgery. The efficacy of these drugs is proven, especially for the unspecific proteinase inhibitor aprotinin, however, there are concerns about the safety and the high costs of this drug. There are only limited head-to-head comparisons of these two drugs.

In this double-blind, prospective, controlled study the efficacy of aprotinin and tranexamic acid is compared. Primary outcome is the 24 hours postoperative drainage blood loss and the percentage of patients requiring allogeneic blood transfusion during the hospital stay. Subgroups of patients undergoing CABG surgery or aortic valve replacement are predefined for combined and separate data analysis.The power of the study is calculated for this subgroup-analysis.

Secondary outcome measurements are molecular marker of activation of hemostasis up to the 5th postoperative day.

Inclusion Criteria:

• informed consent
• Patients undergoing primary CABG or Aortic valve replacement surgery

Exclusion Criteria:

• Previous sternotomy
• OPCAB surgery
• urgent/emergency operation
• Coumadin treatment
• previous aprotinin exposure
• preoperative renal impairment (Creatinine > 2 mg/dL)
• patients refusing blood transfusions
• no informed consent