The effect of dialyzer reprocessing on performance and beta 2-microglobulin removal using polysulfone membranes

Dialyzer Reuse-Part II: Advantages and Disadvantages

Although single dialyzer use and reuse by chemical reprocessing are both associated with some complications, there is no definitive advantage to either in this respect. Some complications occur mainly at the first use of a dialyzer: a new cellophane or cuprophane membrane may activate the complement system, or a noxious agent may be introduced to the dialyzer during production or generated during storage. These agents may not be completely removed during the routine rinsing procedure. The reuse of dialyzers is associated with environmental contamination, allergic reactions, residual chemical infusion (rebound release), inadequate concentration of disinfectants, and pyrogen reactions. Bleach used during reprocessing causes a progressive increase in dialyzer permeability to larger molecules, including albumin. Reprocessing methods without the use of bleach are associated with progressive decreases in membrane permeability, particularly to larger molecules. Most comparative studies have not shown differences in mortality between centers reusing and those not reusing dialyzers, however, the largest cluster of dialysis-related deaths occurred with single-use dialyzers due to the presence of perfluorohydrocarbon introduced during the manufacturing process and not completely removed during preparation of the dialyzers before the dialysis procedure. The cost savings associated with reuse is substantial, especially with more expensive, high-flux synthetic membrane dialyzers. With reuse, some dialysis centers can afford to utilize more efficient dialyzers that are more expensive; consequently they provide a higher dose of dialysis and reduce mortality. Some studies have shown minimally higher morbidity with chemical reuse, depending on the method. Waste disposal is definitely decreased with the reuse of dialyzers, thus environmental impacts are lessened, particularly if reprocessing is done by heat disinfection. It is safe to predict that dialyzer reuse in dialysis centers will continue because it also saves money for the providers. Saving both time for the patient and money for the provider were the main motivations to design a new machine for daily home hemodialysis. The machine, developed in the 1990s, cleans and heat disinfects the dialyzer and lines in situ so they do not need to be changed for a month. In contrast, reuse of dialyzers in home hemodialysis patients treated with other hemodialysis machines is becoming less popular and is almost extinct.

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.

Extended Reuse of Polysulfone Hemodialysis Membranes Using Citric Acid and Heat

The concomitant use of citric acid and prolonged exposure to heat (CAH) is an increasingly common alternative to purely chemical means of reusing dialyzers. However, there are no data on the effects of reprocessing dialyzers with CAH beyond 15 uses. Increasing the number of reuses with CAH cannot be systematically undertaken unless its safety is documented. We hypothesized that discarding polysulfone dialyzers after the 25th rather than the 15th use would result in increased clearance of beta2-microglobulin (beta2MG) without clinically significant changes in small solute clearance or albumin loss. We studied 15 Fresenius F80B polysulfone dialyzers in five chronic hemodialysis patients. Dialyzers were reprocessed using 1.5% citric acid solution heated to 95 degrees C. Representative fractional collection and 10 minute timed collections of dialysate were performed at baseline and during uses 5, 10, 15, 20, and 25 for each dialyzer. Dialysate-side urea, creatinine, and beta2MG clearances were calculated, and total albumin was measured in dialysate. We used a mixed model to adjust for repeated measures (both within a given dialyzer and for the multiple dialyzers per patient). Of the 15 dialyzers studied, 3 (20%) failed before the 25th use. There was no significant change in urea or creatinine clearance with additional reuse (overall p values 0.20 and 0.60, respectively). A sustained increase in beta2MG clearance was observed after the fifth treatment compared with the first use (p < 0.001). Fractional collection showed that dialysate albumin loss increased significantly with additional reuses (p < 0.001) but did not increase significantly above baseline until treatment 25. Reprocessing of polysulfone dialyzers with CAH 25 times significantly increased albumin loss and beta2MG clearance but did not appear to affect urea or creatinine clearance. Increasing the maximum number of uses to 20 may permit cost savings compared with current practice without additional risk.

Effect of hemodialysis membranes on beta 2-microglobulin amyloidosis

Early after the identification of beta(2)-microglobulin amyloidosis (A beta(2)M) as the cause of carpal tunnel syndrome, it was thought that hemodialysis was a major cause in the development of the disease. It was subsequently shown that hemodialysis was not necessary for the development of dialysis-related amyloidosis; however, it was believed that the different dialysis membranes did modulate the progression of the disease. Current data demonstrate that hemodialysis fails to prevent or reverse the disease, but there is substantial evidence that high-flux, high-efficiency dialyzers slow its progression. Many factors related to hemodialysis have been evaluated in relation to A beta(2)M, including the effect of the bioincompatibility of the membrane, the capacity of the different membranes to remove beta(2)M, and the effect of reuse on beta(2)M levels. Moreover, there have been intensive efforts to evaluate, explore, and improve the different mechanisms in beta(2)M removal, with adsorption as a promising prospect. With the available evidence, it seems that the removal of beta(2)M by the membrane plays the most important role in modulating the disease outcome and rate of progression, although a large, long-term, multicentered and randomized study is still lacking to prove this relationship. However, it is possible that with the continuing advances in optimizing the beta(2)M removal efficiency of the different membranes, the frequency and severity of the disease can be substantially decreased.

Dialyzer reuse: what we know and what we don't know

Despite extensive clinical experience, the effects of different reuse procedures have not been fully evaluated. The available data suggest that the effect of reuse on dialyzer performance depends upon the type of chemicals employed, the membrane type, and the size of the solute whose removal is being assessed. The effect of reuse on urea clearance is essentially defined by the residual cell volume with a total cell volume of > 80% associated with a dialyzer clearance that is within 10% of its original value. The effect of reuse on large solute clearance can be dramatic, with the procedure resulting in substantial changes in the beta2-microglobulin clearance of different dialyzers. Of note is the limited data available regarding the effect of reuse procedures on dialyzers processed more than 20 times.

Effects of dialyzer reuse on the permeability of low-flux membranes

Little attention has been given to the effects of reuse on the permeability of low-flux membranes, especially regarding middle molecules. We studied two different types of low-flux membranes at reuses 0, 6, and 12 in five patients undergoing hemodialysis with the following combinations of membrane and sterilant: cellulose diacetate membrane and formaldehyde, polysulfone membrane and formaldehyde, cellulose diacetate membrane and peracetic acid, and polysulfone and peracetic acid. The permeability of the membranes was assessed through the hydraulic ultrafiltration coefficient (K(UF)), sieving coefficient for beta(2)-microglobulin (B2M), and vitamin B(12) and albumin concentrations in ultrafiltrate. After 12 reuses, total cell volume (TCV) tended to be reduced in both cellulose diacetate and polysulfone dialyzers irrespective of the sterilant used, but significance was only found for the first set of dialyzers. Cellulose diacetate dialyzers reprocessed with either formaldehyde or peracetic acid showed an important reduction in K(UF) (31% [P < 0.05] and 23% [P < 0.05], respectively). A significant elevation in K(UF) was found in polysulfone membranes reprocessed with peracetic acid (41%; P < 0.05), but no alterations in K(UF) were found in polysulfone membranes reprocessed with formaldehyde. Cellulose diacetate membranes were intrinsically more permeable to B2M than polysulfone membranes (sieving coefficient, 6. 85 +/- 2.53 versus 0.04 +/- 0.02 x 10(-2); P < 0.001), which was not modified by any of the sterilants. Vitamin B(12) levels in ultrafiltrate decreased to an undetectable level in four of five samples collected after 12 reuses in polysulfone membranes reprocessed with peracetic acid (90 +/- 71 to 3 +/- 8 pg/mL; P < 0. 05 versus reuse 0). Albumin leakage occurred in two of five samples after the 12th reuse, but only in polysulfone membranes reprocessed with peracetic acid. Our findings suggest that reuse of low-flux polysulfone dialyzers reprocessed with peracetic acid is associated with structural damage of the membrane and a reduced permeability to middle molecules.

Dialyzer-dependent changes in solute and water permeability with bleach reprocessing

The effects of bleach reprocessing on the performance of high-flux dialyzers have not been comprehensively characterized. We compared the effects of automated bleach/formaldehyde reprocessing on solute and hydraulic permeability for cellulose triacetate (CT190) and polysulfone (F80B) dialyzers using an in vitro model. Dialyzers were studied after initial blood exposure (R0) and after 1 (R1), 5 (R5), 10 (R10), and 15 (R15) reuse cycles. Ultrafiltration coefficient (K(uf)), serial clearances, and/or sieving coefficients (SCs) of urea, creatinine, vancomycin, inulin, myoglobin, and albumin were determined. Urea, creatinine, and vancomycin clearances and SCs did not significantly differ from R0 to R15 with either dialyzer. Inulin clearances and SC also did not significantly change from R0 to R15 for the CT190. However, these same values for the F80B significantly increased (P < 0.05). The inulin clearance and SC values for the CT190 dialyzer were significantly higher than those for the F80B at all stages except R15. Myoglobin clearances significantly increased over 15 reuses for both dialyzers (P < 0.01). However, CT190 myoglobin clearances were significantly higher at all stages (R0 = 37.7 +/- 9.7; R15 = 52.5 +/- 8.8 mL/min) than the F80B (R0 = negligible; R15 = 41.3 +/- 16.5 mL/min; P < 0.01). Albumin pre- and postdialysis SCs significantly increased for both dialyzers (P < 0.01). K(uf) for R0 and R15 were 52.3 +/- 3.3 and 52.6 +/- 7.6 mL/h/mm Hg for CT190 (P = not significant) and 48.8 +/- 4.4 and 87.3 +/- 7.0 mL/h/mm Hg for F80B (P < 0.0001). We conclude that bleach reprocessing significantly increases larger solute and hydraulic permeability of high-flux cellulosic and polysulfone dialyzers. This effect is more pronounced for the polysulfone membrane. Until 10 reuses or greater, the removal of solutes greater than 1,500 d is significantly compromised with the polysulfone dialyzer used in this study.

Effects of hemodialyzer reuse on clearances of urea and beta2-microglobulin. The Hemodialysis (HEMO) Study Group

Although dialyzer reuse in chronic hemodialysis patients is commonly practiced in the United States, performance of reused dialyzers has not been extensively and critically evaluated. The present study analyzes data extracted from a multicenter clinical trial (the HEMO Study) and examines the effect of reuse on urea and beta2-microglobulin (beta2M) clearance by low-flux and high-flux dialyzers reprocessed with various germicides. The dialyzers evaluated contained either modified cellulosic or polysulfone membranes, whereas the germicides examined included peroxyacetic acid/acetic acid/hydrogen peroxide combination (Renalin), bleach in conjunction with formaldehyde, glutaraldehyde or Renalin, and heated citric acid. Clearance of beta2M decreased, remained unchanged, or increased substantially with reuse, depending on both the membrane material and the reprocessing technique. In contrast, urea clearance decreased only slightly (approximately 1 to 2% per 10 reuses), albeit statistically significantly with reuse, regardless of the porosity of the membrane and reprocessing method. Inasmuch as patient survival in the chronic hemodialysis population is influenced by clearances of small solutes and middle molecules, precise knowledge of the membrane material and reprocessing technique is important for the prescription of hemodialysis in centers practicing reuse.

National Kidney Foundation report on dialyzer reuse. Task Force on Reuse of Dialyzers, Council on Dialysis, National Kidney Foundation

The Council on Dialysis of the National Kidney Foundation convened an expert panel to evaluate the current practice and literature related to the reuse of hemodialyzers. The panel reviewed and evaluated literature related to reuse since the last report of the National Kidney Foundation recommendations on reuse was published in 1988. The group sought to develop a consensus concerning the effect of reuse of hemodialyzers on mortality; the efficiency of delivered hemodialysis when reused hemodialyzers are used in the clinical setting; the clinical effects of reused dialyzers as compared with dialyzers not reused on intradialytic symptoms; infections in patients using reused dialyzers; and the effect of reused dialyzers on complement activation, cytokine production, and beta2-microglobulin metabolism and clearance. In addition, the panel reviewed the literature on the potential toxicity of germicides used in the processing of dialyzers for reuse as well as recent changes in federally mandated regulations concerning labeling of dialyzers for reuse, the monitoring of the reuse process, and the effectiveness of reused dialyzers to achieve a prescribed delivered clearance as estimated by urea kinetic modeling or by percent urea reduction. The National Kidney Foundation takes no position for or against dialyzer reuse. The principal reason for the practice of reuse is economical. In view of the uncertainties related to the safety and biological impact of reuse procedures, the task force recommends that a full discussion of the issue of reuse and its potential beneficial and detrimental effects be undertaken with each patient. There is no conclusive evidence to substantiate the notion that either morbidity or mortality associated with single use or reuse is different. Microbial contamination of the water used for dialyzer reprocessing increases patient morbidity. The chemical quality of water used for dialyzer reprocessing should, at least, fall within the same standards as those recommended for product water intended for hemodialysis. Dialyzers should not be reprocessed from patients who have tested positive for hepatitis B surface antigen. The effects of reprocessing high-flux dialyzers on beta2-microglobulin clearance are dependent on the reprocessing technique, the number of reuses, and the nature of the dialyzer membrane used. There are insufficient data on the effects of reuse on beta2-microglobulin behavior to make uniform recommendations. Untoward effects of reused dialyzers may still occur in spite of rigorous adherence to the AAMI guidelines. For example, use of the total cell volume method for assessing changes in small molecule clearances will not show the loss of performance attributable to dialysate shunting. For this reason, the measurement of Kt/V for urea as recommended by the AAMI or the determination of the urea reduction ratio (URR) is strongly recommended at least monthly to gauge the adequacy of the dialysis procedure. Given the significant fall in dialyzer efficiency for urea removal that can occur after repeated uses of a dialyzer, dialysis prescriptions in units practicing reuse should be designed to deliver a Kt/V or URR value that exceeds the dose used for patients treated with single-use dialyzers to make allowance for any possible reuse-induced reduction in dialyzer efficiency. Technicians and other personnel responsible for the reprocessing of dialyzers should receive proper training. These health care providers should be certified in reprocessing by an examining body so that professional competency can be assured.

Maintaining blood compartment volume in dialyzers reprocessed with peracetic acid maintains Kt/V but not beta2-microglobulin removal

A dialyzer is reused if its blood compartment volume is 80% of its initial value, a condition believed to ensure that the urea clearance remains at 90% of its initial value. This criterion was developed for dialyzers containing low permeability cellulose membranes reprocessed with formaldehyde. We tested the hypothesis that the criterion is also valid for more permeable membranes when dialyzers are reprocessed with peracetic acid/hydrogen peroxide. Kt/V for urea and reduction in beta2-microglobulin concentration were measured for up to 15 uses in dialyzers containing polysulfone or cellulose membranes. Kt/V for urea did not change for either dialyzer provided blood compartment volumes remained 80% of their initial value. The reduction in plasma beta2-microglobulin concentration from predialysis to postdialysis was 30% for the first use of the dialyzer containing polysulfone membranes, but decreased significantly (P = 0.042) following reuse to 12% for the tenth use. For the dialyzers containing cellulose membranes, the reduction in plasma beta2-microglobulin concentration was 18% for the first use and decreased to 12% by the twelfth use; however, this change was not significant. We conclude that removal of urea is maintained during reuse with peracetic acid/hydrogen peroxide provided the blood compartment volume remains 80% of its initial value. However, removal of beta2-microglobulin may not be maintained, even though blood compartment volumes remain at 80% of their initial value.

Dialysate protein losses with bleach processed polysulphone dialyzers

We measured dialysate protein losses from polysulphone dialyzers undergoing repetitive processing with bleach and formaldehyde. The entire dialysate was collected during the first, fifth and tenth use of F-80 dialyzers. Dialysate protein concentration was 1.5 +/- 0.4 mg/dl N = 11 +/- SEM) during the first use, 2.1 +/- 0.3 mg/dl during the fifth use and 3.6 +/- 0.5 mg/dl (N = 10) during the tenth use. In a follow-up study, dialyzers were evaluated for up to 25 uses. After 12 to 15 uses dialysate protein was 7.9 +/- 0.8 mg/dl (N = 13), after 16 to 20 uses; 12.0 +/- 1.2 mg/dl (N = 13) and after 23 to 25 uses; 19.9 +/- 2.1 mg/dl (N = 5). Mean dialysate volume was 83.9 +/- 1.1 liters (N = 63) yielding total protein losses of up to 20.7 grams per treatment. Dialysate albumin losses, which were unmeasurable during the first use of the dialyzers, revealed a similar increase with reuse resulting in a mean value of 14.4 +/- 3.2 mg/dl after 23 to 25 reuses (N = 5). Dialysate beta-2 microglobulin (beta 2m) levels were 1.05 +/- 0.13 mg/l for dialyzers bleached < 10 times (N = 32) versus 1.54 +/- 0.15 mg/liter for dialyzers bleached > 10 times (N = 31, P < 0.02 vs. < 10 reuses). A random sampling of dialyzers processed without bleach for 8, 14, 15, 24 and 25 reuses revealed minimal protein losses, ranging from 1.4 to 2.7 mg/dl with no relation to reuse number and no measureable albumin.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino acid and albumin losses during hemodialysis

Protein and calorie malnutrition are prevalent in chronic hemodialysis (HD) patients and has been linked to increased mortality and morbidity in this patient population. Concern has been raised that the open pore structure of high flux membranes may induce the loss of more amino acids (AA) compared to low flux membranes. To address this issue, we prospectively analyzed pre- and post-HD plasma AA profiles with three different membranes in nine patients. Simultaneously, we measured dialysate AA losses during HD. The membranes studied were: cellulosic (cuprophane-CU), low flux polymethylmethacrylate (LF-PMMA), and high flux polysulfone (HF-PS) during their first use. Our results show that pre-HD plasma AA profiles were abnormal compared to controls and decreased significantly during HD with all dialyzers. The use of HF-PS membranes resulted in significantly more AA losses into the dialysate when compared to LF-PMMA membranes (mean +/- SD; 8.0 +/- 2.8 g/dialysis for HF-PS, 6.1 +/- 1.5 g/dialysis for LF-PMMA, p < 0.05, and 7.2 +/- 2.6 g/dialysis for CU membranes, P = NS). When adjusted for surface area and blood flow, AA losses were not different between any of the dialyzers. We also measured dialysate AA losses during the sixth reuse of the HF-PS membrane. Losses of total AA increased by 50% during the sixth reuse of HF-PS membrane compared to its first use. In addition, albumin was detected in the dialysate during the sixth reuse of HF-PS membrane. We therefore measured albumin losses in all patients dialyzed with HF-PS membranes as a function of reuse.(ABSTRACT TRUNCATED AT 250 WORDS)