Phosphorus Clearance Using Two Hemodialyzers Placed in Parallel

Control of hyperphosphatemia is a major goal in patients with end-stage renal disease. However, removal of retained inorganic phosphorus during hemodialysis remains a major problem. We compared clearances and total phosphate removal in large patients treated with two F-80 dialyzers (Fresenius Medical Care of North America, Lexington, MA, U.S.A.) placed in parallel, and small patients dialyzed with a single F-80 dialyzer (SD). Clearances were obtained using total dialysate collections. Eight dialysate collections (5 patients) using double parallel dialyzers (DD group) were compared with 5 dialysate collections (4 patients) using single dialyzers (SD group). Blood and dialysate flow rates and time of dialysis treatment were identical between the groups. The DD group's Kt/V _urea was 1.46 ± 0.13; SD group's Kt/V _urea was 1.35 ± 0.09 (p = 0.2). Absolute phosphorus removal was 1594 ± 300 mg for the DD group, compared to 1108 ± 285 mg in the SD group (p = 0.03). Urea clearance in the DD group was 285 ± 25 mL/minute and 251 ± 27 mL/ min in the SD group (p = 0.082). Phosphorus clearance was 178 ± 32 mL/min in the DD group and 149 ± 38 mL/min in the SD group (p = 0.039). There was no correlation between phosphorus clearance and dialyzer reuse. The bulk of phosphorus removal was achieved during the first 2 hours of hemodialysis. This finding is consistent with the hypothesis that there are at least two pools of body phosphorus. Using hemodialyzers placed in parallel led to higher phosphate clearance and total phosphorus removal. This higher phosphate removal may be related in part to increasing the concentration gradient for transfer out of a second compartment.