SEPARATED FLOWS IN ARTIFICIAL ORGANS - A CAUSE OF EARLY THROMBOGENESIS

Separated flow is unavoidable in artificial blood-wetted devices. Surf aces bound by separated flows cause abnormal protein adsorption, then platelet adhesion and activation, and eventually thrombogenesis and em bolization. A prolonged abnormal adsorption pattern is expected, espec ially in separated flows, as blood first displaces a wetting liquid du ring start-up of a device. The authors obtained patterns of immunoglob ulin C (IgC), fibrinogen, and high molecular weight kininogen (HMK) ad sorption in and near a separated flow. The flow was induced in flowing saline, replaced at time zero by plasma. The separated flow was induc ed behind a 4 mm bar introduced into a steady shear flow (Re = 26.4) i n an apparatus designed so that the surface behind the bar was a stand ard glass microscope slide. The staining technique revealed the distri bution of each protein of interest over the surface of the slide, and was applied to slides residing in the flow for 1, 5, 10, 30, and 60 mi n after the introduction of plasma (final dilution, 3.5% and 8.5%). Re sults show the expected, rapid disappearance of fibrinogen from surfac es near (but not in) the separated region, and prolonged appearance an d even more prolonged disappearance of fibrinogen from the surface bou nding the separated region. Slides removed from the apparatus, when ex posed to a platelet suspension, showed that platelets adhered where fi brinogen was present on the surface.