SYNTHETICALLY MODIFIED CELLULOSE - AN ALTERNATIVE TO SYNTHETIC MEMBRANES FOR USE IN HEMODIALYSIS

Renal replacement therapy relies predominantly on the use of cellulose -based membranes. Such membranes have a biocompatibility profile which is inferior to membranes manufactured from synthetic polymers. Synthe tically modified cellulose (SMC) is a new, low-flux haemodialysis memb rane in which hydroxyl groups have been replaced with benzyl groups. T he biocompatibility profile characterized by changes in white cell and platelet counts and the activation of complement components (C3a, C5a and C5b-9) have been studied in vivo and compared with those of cellu lose acetate, unmodified cellulose (Cuprophan(C)) and low-flux polysul phone (Fresenius Polysulfone(TM)) in the same group of patients. For S MC, the white cell count at 15 min declined to 65.6% of pretreatment l evel, compared with 63.8% for the cellulose acetate, 79.6% for low-flu x polysulphone and 28.1% for Cuprophan(C),thereafter returning to pret reatment levels. Both modified cellulose membranes were superior to un modified cellulose (P = 0.001); the differences between the modified c ellulose membranes were not significant statistically. The changes ind uced by all three cellulose-based membranes exceeded those for low-flu x polysulphone (P = 0.001). Associated with the neutropenia was a redu ction in platelet count, but this was independent of membrane type. Th e mean time-averaged concentrations of C3a(des Arg) over 150 min were 1168 ng ml(-1) (SMC), 1030 ng ml(-1) (cellulose acetate), 1297 ng ml(- 1) (Cuprophan) and 790 ng ml(-1) (low-flux polysulphone). Equivalent v alues for C5a(des Arg) were 6.12 (SMC), 2.98 (cellulose acetate), 11.0 3 (Cuprophan) and 1.33 ng ml(-1) (low-flux polysulphone). C5b-9 values were 385 (SMC), 386 (cellulose acetate), 177 (Cuprophan) and 185 ng m l(-1) (low-flux polysulphone). For each of the complement components t he differences between the membranes were significant [P = 0.0009 (C3a (des Arg)), P = 0.0001 (c5a(des Arg) and C5b-9)]. The levels of C5b-9 generated during dialysis also showed a significant positive correlati on compared to C5a for all membranes considered as a single group (Pea rson's correlation coefficient = 0.870, P = 0.0001). It is concluded t hat the modification of the cellobiosic unit is a promising approach t o improve the biocompatibility profile of cellulose-based membranes. T he two different methods of modification lead to similar improvements in biocompatibility compared with unmodified cellulose, but as yet do not match that of low-flux polysulphone. (C) 1997 Elsevier Science Lim ited. All rights reserved.