Neutrophil lysosomal enzyme release and complement activation during cardiopulmonary bypass

Complement activation and neutrophil degranulation were concomitantly studied during uncomplicated cardiopulmonary bypass (CPB). Plasma concentrations of complement factor C4, complement split product C3d, the neutrophil lysosomal enzyme elastase complexed with alpha 1-proteinase inhibitor (PI) and fibronectin were measured in 12 patients, C3d and elastase/PI increased significantly during CPB (volume-corrected results). The C3d rise was almost linear, whereas elastase/PI showed exponential increase. Mean elastase/PI and mean C3d concentrations at different times during CPB covaried closely. The study showed that during CPB neutrophil lysosomal enzyme release is intimately related to complement activation, although activation of the two systems may be caused by a common third activator within the extracorporeal circuit.