Cardiopulmonary bypass (CPB) is a process that uses a pump that temporarily takes over the function of the heart and lungs during cardiac surgery to maintain blood circulation and oxygenation. Using CPB during cardiac surgery can result in complications with blood clotting. Blood clotting is achieved when molecules in the blood, called platelets, are able to form together with the help of other clotting factors to form a clot. A drug called desmopressin (DDAVP) is used to help blood clot properly by increasing the amount of clotting factors in the blood. Several studies have shown that desmopressin has the ability to reduce the amount of blood transfusions needed for cardiac surgery patients in the postoperative period. At LHSC desmopressin is frequently requested by Cardiac Surgeons and Anesthesiologists to stop bleeding and promote blood clotting where required. A test called TEG6s platelet mapping is a blood test used to help manage the use of blood products by being able to provide information on platelet function and blood clotting activity. At the moment, there is a lack of information regarding the use of TEG6s platelet mapping to analyze the effect of desmopressin on blood clotting in cardiac surgery patients after CPB. The purpose of this study is to investigate the dose-related effects of desmopressin on platelet function in patients undergoing cardiac surgery with CPB. By using TEG6s platelet mapping, this study aims to observe dynamic changes in platelet function following desmopressin administration at various time points in the perioperative and postoperative periods.