Increasing dialysate flow rate increases dialyzer urea clearance and dialysis efficiency: an in vivo study

Clearance of urea depends on the dialysis solution flow rate as well. A faster dialysis solution flow rate increases the efficiency of diffusion of urea from blood to dialysate. An in vivo study was used in order to examine the effect of increasing dialysate flow rate (Q D ) on dialyzer urea clearance and dialysis efficiency expressed as Kt/V and URR. Group assignment was at the patient level rather than the facility level. The study subjects consisted of 138 hemodialysis patients on 3-times-per-week dialysis regimens. One way ANOVA test, Student's t test and Logistic regression analysis were used to analyze the data. Statistically significant increase in Kt/V and URR was noted as the dialysate flow increased from 500 to 800 mL/min when a moderate efficiency dialyzer with large surface area (1.6 m 2 ) and high flux high efficiency dialyzers were used (P < 0.05). For moderate efficiency dialyzers with large surface area, Kt/V increased by 5.86% (P= 0.022628) and URR increased by 4.31% (P= 0.02263). Low efficiency and small surface area (1.2 m 2 and 1.3 m 2 ) dialyzer did not show an improvement in Kt/V or URR with increase in dialysate flow rate. Increasing Q D from 500 to 800 mL/min is associated with a statistically significant increase in Kt/V, URR and dialyzer clearance in moderate efficiency low flux and high efficiency high flux dialyzers. Hemodialysis with Q D of 800 mL/min should be considered in selected patients not achieving adequacy despite extended treatment times and optimized blood flow rates.