The hemolytic product free-hemoglobin (fHb) reduces nitric oxide (NO) bioavailability. The present study aims to establish whether transfusions of stored allogenic blood or intraoperative autologous salvaged blood result in increased circulating fHb levels and NO consumption with effects on arterial NO-dependent blood flow measured in isolated left mammary artery rings and by peripheral artery tonometry in patients undergoing CABG surgery.