Clinical investigation of the role of membrane structure on blood contact and solute transport characteristics of a cellulose membrane

Regenerated cellulose membranes contain cellulose chains with crystalline and amorphous regions in the direction of extrusion. A study was undertaken to investigate if reduced contact surface arising from alteration of pore size alters biocompatibility (complement activation (C3a and C5a) and neutropenia) and solute transport. The average pore size for the membrane studied (RC HP400A) was 7.23 compared to 2.76 nm for the standard membrane (Cuprophan®). C3a levels rose to 6861±1595 compared to 2723±1228 ng/ml for Cuprophan® at 15 min after initial blood contact (P<0.0001). C5a levels also rose to 30.1±11.9 compared to 21.3±6.6 ng/ml for Cuprophan® (P=0.18). Both fractions gradually returned to baseline levels thereafter. Circulating white cell count fell rapidly over the same time period to 39±17% of the baseline value by 15 min and was similar to Cuprophan® (27.5±11.2%) (P=0.25). A small (<10%) change in platelet numbers was noted for both membranes. Removal of urea (60 Da) was independent of pore size; however, the RC HP400A removed β2 microglobulin (11 818 Da). These findings indicate that pore distribution fails to influence material-induced complement activation but influences large solute transport.