SPECIFIC COMPLEMENT INHIBITION WITH HEPARIN-COATED EXTRACORPOREAL CIRCUITS

Background. Although it is well established that heparin-coated extrac orporeal circuits reduce complement activation during cardiac operatio ns, little in vivo information is available on the reduction in altern ative and classic pathway activation. Methods. In a prospective, rando mized study involving patients undergoing coronary artery bypass graft ing with standard full heparinization, we compared heparin-coated circ uits (Duraflo II) (10 patients) with uncoated circuits (10 patients) a nd assessed the extent of initiation of complement activation by detec ting iC3 (C3b-like C3) concentrations, classic pathway activation by C 4b/c (C4b, iC4b, C4c) concentrations, terminal pathway activation by s oluble C5b-9 concentrations, and C3 activation by C3a (C3a desArg) and C3b/c (C3b, iC3b, C3c) concentrations. Results. Heparin-coated extrac orporeal circuits significantly reduced circulating complement activat ion product C3b/c and soluble C5b-9 concentrations at the end of cardi opulmonary bypass and after protamine sulfate administration compared with the uncoated circuits, but not iC3, C4b/c, or C3a concentrations. Conclusions. Heparin-coated extracorporeal circuits reduce complement activation through the alternative complement pathway, probably at th e C3 convertase level, and, consequently, the terminal pathway. C3b/c seems to be a more sensitive marker than C3a to assess complement acti vation during cardiac operations.