Jpn J Artif Organs 29 (5), 623-629 It has been reported that complement components and cytokines can be activated during cardiopulmonary bypass (CPB). In this study, complement and cytokine activation was evaluated in two groups assigned by timing of protamine administration after CPB. Thirty patients who underwent coronary artery bypass grafting were randomly assigned to two groups (group A or B). Patients in group A were administered protamine five minutes after CPB termination; those in group B were administered protamine thirty-five minutes after CPB termination. All patients were perfused with heparin-coated circuits and received 300 IU/kg heparin and 3 mg/kg protamine. C3a, C4a, IL-6, IL-8, and TNF-a levels were measured. C3a and C4a levels increased significantly after protamine administration in both groups. Cytokine levels were not affected by protamine administration in either group. IL-6 level increased significantly after aortic declamping. This study yield the following three findings: (1) complement was activated via the classical pathway after protamine administration, (2) IL-6 was released significantly after aortic declamping, and (3) IL-8 and TNF-a levels were affected by neither aortic declamping nor protamine administration.

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