Figure 31

Centers using high-flux dialyzers have increased threefold from 1986 to 1996 because of their ability to remove middle molecules. (From Tokars and coworkers [1]; with permission.)

DEFINITIONS OF FLUX, PERMEABILITY, AND EFFICIENCY

Flux

Measure of ultrafiltration capacity

Low and high flux are based on the ultrafiltration coefficient (Kuf) Low flux: Kuf <10 mL/h/mm Hg High flux: Kuf >20 mL/h/mm Hg Permeability

Measure of the clearance of the middle molecular weight molecule (eg, ß2-microglobulin) General correlation between flux and permeability Low permeability: ß2-microglobulin clearance <10 mL/min High permeability: ß2-microglobulin clearance >20 mL/min Efficiency Measure of urea clearance

Low and high efficiency are based on the urea KoA value Low efficiency: KoA <500 mL/min High efficiency: KoA >600 mL/min

Ko—mass transfer coefficient; A—surface area.

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