Effect of bleach reprocessing upon the clearance characteristics and surface charge of polysulfone hemodialyzers.

The effects of reprocessing upon hemodialysis have been debated since the introduction of this practice. The objective of this study was to develop a quantitative understanding of the effects of bleach reprocessing upon Fresenius polysulfone dialyzers. Data were obtained for the clearance of urea, vitamin B12, and polydisperse dextrans before and after reprocessing, both with and without exposure to plasma in a simulated dialysis session. Bleach reprocessing of the native dialyzer caused a significant increase in solute clearance because of the removal of polyvinylpyrrolidone from the membrane copolymer. This was confirmed by zeta potential measurements that showed a substantial increase in the negative charge on the membrane surface. Exposure to plasma proteins during hemodialysis effectively protected the dialyzer from chemical degradation by the bleach, with only small changes in solute clearance after the optimal reprocessing cycle. However, inadequate exposure to bleach was unable to restore the original solute clearance while over cleaning with bleach caused an increase in clearance. Considerable care must be taken in the proper design of reprocessing cycles for hemodialysis membranes.