Bulk mass transport limitations during high-flux hemodialysis.

Solute clearance during high-flux hemodialysis is determined by the combined effects of solute convection and diffusion in the membrane, blood, and dialysate. Previous studies have focused almost entirely on the membrane transport phenomena, largely ignoring the potential contribution from bulk mass transport across the fluid boundary layers in the blood and dialysate. This study presents a theoretical analysis of the coupled transport equations in the membrane, blood, and dialysate including the contributions from both convective and diffusive transport in each of these regions. The resulting theoretical expression for the solute flux demonstrates that bulk mass transfer limitations can have an important effect on solute transport and, in turn, solute clearance during high-flux hemodialysis.