Cytokine filtration and adsorption during pre- and postdilution hemofiltration in four different membranes.

In the present in vitro study we investigated filtration and adsorption of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and interleukin-8 (IL-8) during predilution and postdilution hemofiltration with polysulfone, polyacrylonitrile, polyamide and cellulose triacetate membranes. The median sieving coefficient (SC) for all membranes was 0.0 for TNF-alpha, below 0.15 for IL-6 and below 0.15 for IL-8 during postdilution hemofiltration. Differences in SC between filtration modes were less than 0.05. Maximal differences in SC between membranes were 0.11 for IL-6, 0.0 for TNF-alpha, and 0.11 for IL-8. The progressive decrease in cytokine concentrations was identical between the two filtration modes and most pronounced with the polyacrylonitrile membrane (reduction 77% for IL-6, 39% for TNF-alpha and 95% for IL-8 after 4 h of hemofiltration). The relative contribution of adsorption to the reduction in cytokines was 100% for TNF-alpha for all membranes, between 53 (cellulose triacetate) and 83% (polyacrylonitrile) for IL-6, and for IL-8 between 0 (polysulfone) and 100% (polyacrylonitrile). In conclusion, the reduction in TNF-alpha, IL-6 and IL-8 was most impressive with the polyacrylonitrile membrane after 4 h of hemofiltration and was largely due to adsorption. Adsorption of TNF-alpha, IL-6 and IL-8 was also seen with the other membranes. None of the membranes filtered TNF-alpha. Sieving of IL-6 and IL-8 was low for all membranes with only marginal differences between membranes or between filtration modes.