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.

Cardiopulmonary bypass (CPB) during cardiac surgery is frequently complicated by disturbances in coagulation parameters and platelet function. Desmopressin (DDAVP) has been utilized to enhance platelet adhesion and aggregation by increasing plasma levels of von Willebrand factor (vWF) and factor VIII that plays a crucial role in blood clotting. Several studies demonstrated a positive effect of DDAVP in hemostasis (particularly in patients with qualitative platelet dysfunction), reduced blood transfusion and bleeding in the post operative period.

Viscoelastic testing, specifically TEG (Thromboelastography) platelet mapping and TEG6s and have been shown to be helpful in managing the use of blood products, fresh frozen plasma (FFP), platelets and fibrinogen, in coagulopathic patient post cardiopulmonary bypass. Desmopressin is given at a dose 0.3 micrograms/kg intravenously over 15 to 30 minutes as a standard dose in cardiac surgery, up to 20 mcg which is the United States Food and Drug Administration (US FDA) recommended dose for Hemophilia treatment and the most commonly cited dose used in cardiac surgery after cardiopulmonary bypass. The TEG6s platelet mapping shows baseline platelet function and receptor-specific platelet function and inhibition. This assessment is based on four different assays including Koalin, Activator F, ADP (Adenosine Diphosphate), AA (Arachidonic Acid). At the current time there is limited literature looking at the qualitative effect of desmopressin on platelet function using TEG6s platelet mapping analysis. The purpose of this study is to investigate the dose-related effects of desmopressin on platelet function in patients undergoing cardiac surgery. By using TEG6s platelet mapping we aim to observe dynamic changes in platelet function following desmopressin administration at various time points in perioperative and postoperative periods.

Informed, written consent will be obtained prior to the start of surgery.

Participants that are enrolled in this study will have their surgery proceed according to plan and will be placed under general anesthesia using standard of care practices. Cardiopulmonary bypass will be implemented in accordance with standard of care practices. Desmopressin will be given to participants at a dose of 0.3mcg/kg, up to 20 mcg after protamine reversal at the end of cardiopulmonary bypass.

Platelet function will be assessed by TEG platelet mapping at the following points:

1. T1 TEG6s: after arterial line insertion before skin incision.
2. T2 TEG6s: after protamine (baseline function after CPB)
3. T3 TEG6s: 30 minutes after desmopressin
4. T4 TEG6s: 6 hours after (intensive care unit) ICU admission
5. T5 TEG6s: 24hours after ICU admission

This will involve drawing 4 ml of blood from patients at each of the above time points (5 blood draws total), in a dark green-top (Sodium Heparin) Vacutainer® tube by the Cardiac Anesthesiologist who will be also running the test on the TEG Machine. The study team will also collect information such as participant age, biological sex, height, weight, medications, medical history, surgical details, results of preoperative and postoperative blood work, and details of their postoperative recovery.

Inclusion Criteria:

1. Age 18 years and above
2. Undergoing elective cardiac surgery with cardiopulmonary bypass
3. Able to provide informed consent

Exclusion Criteria:

1. Hyponatremia
2. Allergy to desmopressin or its components
3. History of coronary artery disease with thrombosis
4. Recent history of thromboembolic events (Stroke/TIA/DVTs)
5. Severe Renal Impairment Creatinine Clearance<30 ml/min
6. Inability to communicate in the English language

This is a prospective, observational, single centre study being conducted at London Health Sciences Centre (LHSC) with adults undergoing elective cardiac surgery with cardiopulmonary bypass to investigate the dose-related effects of desmopressin on platelet function in patients undergoing cardiac surgery.