Effects of ultrafiltration on solute clearances in parallel plate dialyzers.

Clearances of small and large solutes were measured at increasing transmembrane pressure in 3 types of parallel plate dialyzers. Both laboratory and clinical studies were performed. As in previously reported studies in coils, diffusive transport appears to decrease as transmembrane pressure increases. This may reflect blood channel widening, bath channeling, and/or membrane masking by mesh support. For small solutes, decreases in diffusive transport were enough to offset gains by solvent drag and total clearances decreased. In some studies, decreases in small solute clearances with increasing ultrafiltration were large enough to compromise dialysis efficiency.