Blood contact with artificial surfaces during BVAD support

Persistently elevated levels of cytokines (IL-6, IL-8) during the course of mechanical circulatory support correlate well with fatal outcome. To determine the influence of blood/artificial surface interaction on the chronic inflammatory process, we studied the biocompatibility of silicone and polyurethane membranes in vitro. Cultures of isolated mononuclear cells or whole blood were incubated for 24 hours in tubes coated with silicone or polyurethane, both used in the construction of ventricular assist systems. Concentrations of several inflammatory mediators were measured in the supernatant. Our results can be summarized as follows: a) Monocytes were stimulated to release inflammatory cytokines like IL-8 and MIP-1a, particularly when silicone was involved; b) Both silicone and polyurethane stimulated thrombocytes thus resulting in the release of P-Selectin and PDGF-AB, although polyurethane was a stronger stimulus, c) Moderate complement activation was triggered by contact with either of the artificial surfaces. However, the prevention of most of these effects by coating the artificial surface with protein and the lack of correlation between in vitro data and serum levels of IL-6 and IL-8 during the course of circulatory support suggest that the persistence of inflammatory cytokines during BVAD support is not caused by blood/surface interaction.