Figure 327

Effect of the dialysate flow rate (Qd) on the urea clearance rate by a high-efficiency dialyzer with a urea KoA value of 800 mL/min. At low blood flow rates (<200 mL/min), no difference exists in urea clearance rates between the two different Qd conditions, because equilibrium in urea concentrations between blood and dialysate is readily achieved. When the blood flow rate is high (>300 mL/min), the higher Qd maintains a higher concentration gradient for diffusion of urea, and therefore, the urea clearance rate is higher. Recent studies have shown that the KoA value of dia-lyzers also increases with higher dialysate flow rates [4], presumably because of more uniform distribution of dialysate flow. Therefore, the actual urea clearance rate may increase further (red line). Ko—mass transfer coefficient; A—surface area.

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