Effect of Clopidogrel (Plavix) on Postoperative Bleeding in Patients Undergoing Coronary Artery Bypass Surgery.

* Running title: Effect of Clopidogrel on Postoperative Bleeding in Patients undergoing Coronary Artery Bypass Surgery * Title: Clopidogrel and bleeding in patients undergoing coronary artery bypass grafting. Is surgical delay necessary in patients using clopidogrel? And if so, which is the safety time interval when clopidogrel should be stopped before surgery in order to avoid bleeding and other related complications. * Background: By blockade of the platelet ADP receptor, clopidogrel inhibits the binding of fibrinogen to the platelet GPIIb/IIIa receptor complex, thereby preventing platelet aggregation from ADP stimulation. Some authors suggest that the platelet function is completely recovered in 7 days after stopping clopidogrel in healthy subjects. Other researches suggest full recovery of platelet function in 3 to 5 days. * Study objectives: To investigate if the interruption of the clopidogrel is necessary before CABG in order to prevent bleeding and other complications. To trace the increased risk patients for postoperative bleeding and to individualize the therapy according to TEG measurements. * Design: A prospective, randomized mono- center study * Patients: Patients who are receiving elective or urgent CABG surgery and are pre-treated at least 5 days before surgery with clopidogrel * Primary endpoint: To determine if there are significant differences in blood loss, transfusions and rethoracotomies in the three selected groups of patients treated with clopidogrel To asses the predictive value of the TEG clot strength in postoperative bleeding in patients using Clopidogrel. * Secondary endpoints: Death, myocardial infarction, stroke, respiratory failure, renal failure requiring dialysis, mediastinitis,readmission rates within 30 days from discharge, and ICU and hospital lengths of stay * Risks: Using standard dose of aprotinin, we consider no increased risk in blood loss and other related complications for this three groups of patients. * Possible benefit