Cytokine Removal in Extracorporeal Blood Purification: An in vitro Study

Cytokines are among the main target substances that have to be removed effectively in order to improve the patient's health status in the treatment of sepsis, septic shock, and liver diseases. Although there are various medical devices commercially available, the success of their clinical use is limited. The aim of this in vitro study was to compare 3 different medical devices with respect to their clearance for the cytokines interleukin-6 (IL-6), IL-8, IL-1β, and tumor necrosis factor alpha. The medical devices that were tested are the whole blood adsorbent CytoSorb, the high cutoff filter EMiC2, and the hemofilter HemofeelCH 1.8.

The study was carried out on the multiFiltrate machine with 1 L human plasma for 8 h. Samples for cytokine quantification were taken at defined time points from the plasma pool. Each experiment was conducted in triplicates, and clearance was calculated for all tested cytokines.

All 3 medical devices showed good cytokine removal. The highest clearance for all cytokines was achieved by hemoperfusion with Cytosorb. IL-8 and IL-6 clearance were higher with Hemofeel (continuous venovenous hemodiafiltration) than with EMiC2 (continuous venovenous hemodialysis) because the polymethyl methacrylate (PMMA)-based membrane Hemofeel is able to remove these 2 cytokines by adsorption. Protein and albumin loss was highest withCytosorb and lowest with EMiC2.

The mechanisms of cytokine removal by blood purification include convection, diffusion, and adsorption. PMMA-based filters are able to combine all 3 mechanisms for certain cytokines. Cytosorb showed the best adsorption kinetics, while dialysis with polystyrene-based membranes offers the best biocompatibility because they do not show any unspecific adsorption of other plasma components.