Tranxemic Acid

The goal of this clinical trial is to the dose effect of tranexamic acid and the level of ACT on bleeding in adult cardiac surgery. The main questions it aims to answer are: 1. Does higher dose of tranexamic acid reduce the amount of bleeding and blood transfusion? 2. Does lower ACT level during cardiac surgery reduce the amount of bleeding and blood transfusion? Participants will divided into four groups which have different tranexamic acid dose and ACT level during cardiac surgery to see if there is any different in the amount of bleeding and blood transfusion.