Complement activation during cardiopulmonary bypass by heparin-protamine interaction.

Circulating concentrations of split products of the third complement factor (C3c and C3d) were measured in five patients before, during and after cardiopulmonary bypass. In all patients, C3d concentrations increased significantly in samples obtained after the administration of protamine sulphate. Similarly, circulating C3c was seen only in those samples obtained immediately after protamine administration. In vitro experiments demonstrated that activation of the complement system was attributable to the heparin-protamine complex, and was dose-dependent. The activation of complement was not associated with any clinically detectable adverse effects.