This study compares the effect of three different dose levels of tranexamic acid（TXA）in reducing blood loss and transfusion requirements in cardiac valve surgery.

The effect of TXA to reduce perioperative blood loss and blood transfusion has been well established in many trials, but the optimal dosage of TXA in cardiac surgery has always been a problem of debate. This is a single-center randomized controlled trial to study different dose regimens of TXA in cardiac surgery. We use three different dose levels of TXA in cardiac valve surgery with CPB, and see if there are any differences in perioperative blood loss and transfusion requirements. Serious adverse events and seizure attacks are also recorded until three months after surgery.

Inclusion Criteria:

• patients aged between 18 to 60 years old scheduled for cardiac valve surgery (replacement or plasty) requiring CPB

Exclusion Criteria:

• known allergy to TXA, combined CABG operation or other cardiac procedures other than valve surgery, previous cardiac surgery, EF<45% or cardiothoracic ratio>0.65, serious coagulation disorder, serious hepatic insufficiency, receiving antiplatelet therapy at any time within 7 days of surgery, receiving low molecular weight heparin at any time within 24 hours of surgery, and pregnancy.