Removal of high-molecular-weight solutes during high-efficiency and high-flux haemodialysis.

BACKGROUND Although urea clearance is often increased during high-efficiency and high-flux haemodialysis to compensate for short treatment times, the impact of these treatment modalities on the removal of larger uraemic toxins has not been thoroughly investigated. METHODS We compared solute removal rates for five haemodialysis treatment strategies in vitro using neutral dextrans (molecular radii between 15 and 50 A) as marker macromolecules. Removal rates were assessed by the decrease in dextran concentration within the reservoir of a model circuit using outdated human plasma as the test solution. Results for high-efficiency haemodialysis (CA110 dialyser at a blood flow rate of 400 ml/min and TAF175 dialyser at a blood flow rate of 300 ml/min) and high-flux haemodialysis (CT190G dialyser at a blood flow rate of 300 ml/min and F60 dialyser at a blood flow rate of 300 ml/min) were compared with those for conventional haemodialysis (CA110 dialyser at a blood flow rate of 200 ml/min). RESULTS Dextran clearances were dependent on the dialyser employed, and they decreased with molecular size and time for each treatment strategy. Removal rates were greatest using the CT190G and F60 dialysers, intermediate for the TAF175 dialyser, and lowest for the CA110 dialyser at either blood flow rate. CONCLUSION The results of this study demonstrate that increasing blood flow rates alone to increase urea clearance may not provide adequate removal of high-molecular-weight solutes. The use of high-flux or large surface area, high-efficiency dialysers are more effective in maintaining the removal of high-molecular-weight solutes when treatment time is shortened.