Cardiopulmonary bypass (CPB) is a unique clinical scenario that results in widespread activation of the hemostatic system. Conventional CPB interferes with normal hemostasis by diluting hemostatic cells and proteins, through reinfusion of shed blood, and through activation on the bypass circuit surface of multiple systems including platelets, the kallikrein-kinin system, and fibrinolysis . Besides, deleterious effects of cardiopulmonary bypass (CPB) are partly sequelae of blood-foreign surface reactions. The arterial filter is the part of the CPB circuit where blood cells are exposed to high mechanical stress and where cellular aggregates may fasten in large quantitiesiec.

This is a clinical and observational study. It is being performed in the surgical center and intensive care unit of the Heart Institute (InCor) from Faculty of Medicine, University of São Paulo (FMUSP), on patients undergoing cardiac surgery, who satisfy inclusion and exclusion criteria. In the preanesthetic visit, patient assessment of the criteria described in study methodology is verfied. During the surgery, a blood sample is taken to analyze hemostatic function in the begin of cardiopulmonary bypass, before arterial filter (pre-filter) and in the end of cardiopulmonary bypass, after arterial filter (post-filter). Other routine laboratory exams is being colected until first postoperative day, on the eletronic medical records. At the end of surgery, the arterial filter is withdrawn from cardiopulmonary bypass circuit to be prepared and analysed by SEM. Ten arterial filter samples from pre-determined sites and sizes are sent to the clinical laboratory for evaluation of platelet and leukocyte gene expression in arterial filter. Patients will be followed until hospital discharge or 28 days after surgery, regarding allogeneic transfusion needs, reoperation and thromboembolic events.

Inclusion Criteria:

• Cardiac surgeries with extracorporeal circulation in patients older than 18 years
• Written and signed informed consent
• Preanesthetic assessment and preoperatory exams in accordance with study methodology

Exclusion Criteria:

• Active infection;
• Previously coagulopathy;
• Antiplatelet therapy use until 10 days before surgery (except acetylsalicylic acid and enoxaparin that may be used in prophylactic doses until 24h before surgery);

Patients undergoing cardiac surgery with cardiopulmonary bypass (CPB)