Phosphate Removal With Several Thrice-Weekly Dialysis Methods in Overweight Hemodialysis Patients

Background: Currently available phosphate binders are associated with either hypercalcemia or high costs, which limit their use in hemodialysis patients. Whether modifying dialysis prescription to intensify small-solute clearance also leads to better phosphate clearance is unknown. Study Design: Randomized crossover trial. Participants: Large patients (>80 kg; N = 18) who could not achieve adequate Kt/V during a standard 4-hour thrice-weekly prescription of maintenance hemodialysis. Intervention: 2 high-flux dialyzers in parallel for 4 hours in comparison to 3 other dialysis modalities (4 hours of standard hemodialysis, 4.5 hours of hemodialysis, and 4 hours of hemodialysis with increased dialysate flow). Outcomes: (1) Predialysis serum phosphate level, (2) postdialysis phosphate level, (3) phosphate clearance, and (4) phosphate removal, all assessed during the last midweek session for each of the 4 different modalities. Results: Mean baseline predialysis serum phosphate level was 5.95 +/- 1.95 mg/dL. Using 2 dialyzers in parallel was associated with a significant decrease in predialysis serum phosphate level compared with standard hemodialysis (1.33 mg/dL lower; P = 0.01). Mean serum postdialysis serum phosphate levels during the last treatment of the double-dialyzer period were also lower by 0.43 and 0.74 mg/dL than during the last treatment of the standard-hemodialysis (P = 0.05) and increased-dialysate-flow (P < 0.001) periods, respectively. The double-dialyzer strategy also was associated with greater phosphate clearance (113.4 mL/min; 95% confidence interval [CI], 101.4 to 125.3) than the other 3 strategies (83.9 mL/min; 95% Cl, 71.6 to 96.2; 86.6 mL/min; 95% Cl, 73.8 to 99.3; and 83.0 mL/min; 95% Cl, 71.1 to 94.9), but not greater phosphate removal. Limitations: Small sample size, short study duration, and results of phosphate removal analysis inconclusive. Conclusion: Use of 2 dialyzers in parallel for 6 weeks in overweight hemodialysis patients led to substantially lower predialysis phosphate levels. Future studies should explore the potential contribution of increased dialyzer surface area to better control of serum phosphate levels in maintenance hemodialysis patients. Am J Kidney Dis 54:1108-1115. (C) 2009 by the National Kidney Foundation, Inc.