Novel and Current Techniques to Produce Endotoxin-Free Dialysate in Dialysis Centers

Dialysis water and dialysate are prepared starting from municipal tap water, which is not of sufficient quality for hemodialysis and has to be treated to remove chemical and microbiological contaminants. Logistic requirements of treating many patients simultaneously, use of concentrated bicarbonate, use of centralized water treatment systems, and biofilm growth in distribution pipes and storage tanks often cause contamination dialysis water and dialysate with bacteria and endotoxins. In high-flux dialysis with bicarbonate, endotoxins may transfer from dialysate into blood exposing patients to serious acute and chronic complications. In this article, design and operation of systems used in dialysis centers to treat water from the tap to the hemodialyzer is presented and discussed with respect to microbiological contamination. A critical role is played by ultrafiltration (UF) across hydrophobic synthetic membranes, which effectively removes endotoxins from the dialysate by combined filtration and adsorption right before it enters the hemodialyzer. Its use is limited and costly because repeated sterilization worsens membrane separation properties. Hence, preparation and use of ceramic membranes are discussed that might reduce the costs to treat the dialysate. In fact, ceramic membranes are more resistant to harsh operating conditions than polymeric membranes and may represent an alternative for endotoxin removal.