Backdiffusion rather than backfiltration enhances endotoxin transport through highly permeable dialysis membranes

Endotoxin transfer from dialysate to blood by backfiltration has been reported to occur when highly permeable dialysis membranes available for efficient removal of beta-2-microglobulin are used clinically. Little is known concerning endotoxin transfer from dialysate to blood by diffusion. The present paper describes technical determination of diffusive and convective clearances for endotoxins based on conventional mass and momentum transfer models. Fractional diffusive transport of endotoxins with molecular weights of 1,000 and 10,000 daltons approximated unity. This indicates that clean-up of contaminated dialysate is necessary for safe hemodialysis treatment with highly permeable dialysis membranes. Diffusive in-flow of endotoxin with a molecular weight of 1,000 was calculated to be 278 and 88 pg/min for PAN-12CX2 and MC0.8H at an endotoxin concentration of inflowing dialysate of 2 pg/ml. These results demonstrate that dialysate should be carefully cleaned to prevent diffusive inflow of endotoxins from dialysate to blood.