 The investigators have recently seen, that a significant drop in platelet numbers following cardiac surgery is associated with increased mortality and risk of acute kidney injury. The investigators hypothesize that such thrombocytopenia is a result of excessive perioperative platelet activation and resultant release of inflammatory and tissue injurious signals by activated platelets. Platelet activation will be characterized during and after cardiac surgery and examine its correlation with inflammatory responses and perioperative end-organ injury. 