Effect of reuse on dialyzer efficacy

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.

UNRESOLVED ISSUES IN DIALYSIS: Dialyzer Best Practice: Single Use or Reuse?

Outcome studies have shown either no additional risk or a small additional risk for hospitalization and mortality associated with reprocessing dialyzers. Although the risks from reprocessing dialyzers have yet to be fully elucidated, reuse can be done safely if it is performed in full compliance with the standards of Association for the Advancement of Medical Instrumentation (AAMI). Like most industrial processes, however, complete control of the reuse process in a clinical environment and full compliance with regulations at all times is difficult. Potential errors and breakdowns in the reuse process are continuing concerns. The quality controls for reprocessing of dialyzers are not equal to the rigor of the manufacturing process under the purview of the U.S. Food and Drug Administration (FDA). Therefore, if one were to determine "best practice," single use is preferable to reuse of dialyzers based on medical criteria and risk assessment. The long-term and cumulative effects of exposure to reuse reagents are unknown and there is no compelling medical indication for reprocessing of dialyzers. The major impediment when deciding to convert from reuse to single use of dialyzers is economic. The experience in Fresenius Medical Care-North America (FMCNA) facilities demonstrates that converting from a practice of reuse to single use is achievable. However, the overall economic impact of conversion to single use is provider specific. The dominance of reuse has been negated of late by a major shift in practice toward single use. Physicians and patients should be well informed in making decisions regarding the practice of single use versus reuse of dialyzers.

Effect of Peracetic Acid Reprocessing on the Transport Characteristics of Polysulfone Hemodialyzers

Peracetic acid is used extensively for reprocessing hemodialyzers, despite several indications that reprocessing alters the dialyzer transport characteristics. The objective of this study was to obtain quantitative data for the effects of peracetic acid reprocessing on the clearance and sieving coefficients of urea, vitamin B12, and polydisperse dextrans using Fresenius F80A polysulfone dialyzers. Reprocessing restored the urea and vitamin B12 clearance to close to their original values. However, the reprocessed dialyzers had substantially lower clearance of the larger molecular weight dextrans, which was attributed to reductions in the effective pore size caused by residual plasma proteins within the membrane. Storage in peracetic acid provided some additional removal of residual proteins, although the clearance and sieving coefficients of the larger dextrans remained well below their original values. Peracetic acid caused no degradation of the membrane polymer, in sharp contrast to results obtained with bleach reprocessing.

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.

In vivo measurement of hemodialyzer fiber bundle volume: theory and validation

BACKGROUND

Fiber bundle volume (FBV), the space within the blood compartment of hollow fiber dialyzers, may decrease during treatment due to clotting. The clots may be flushed out of the dialyzer prior to measurements of FBV by dialyzer reprocessing equipment and a significant drop in FBV during the session may go unrecognized.

METHODS

FBV was measured (1) from the transit time of a saline bolus passing through the dialyzer as recorded by ultrasound dilution sensors placed on the arterial and venous blood lines; (2) from the change in blood concentration induced by a step change in the rate of ultrafiltration as recorded by the venous sensor.

RESULTS

In vitro FBV ranged from 47 to 121 ml. Paired absolute differences between the ultrasound and volumetric measurements (flushing saline out of the dialyzer into a graduated cylinder) were 0.16 +/- 4.23% (N = 42) and 2.10 +/- 7.26% (N = 13) for the bolus and ultrafiltration methods, respectively. In vivo reproducibility of the bolus and ultrafiltration methods were 2.65 +/- 2.11% (N = 122) and 3.79 +/- 3.93% (N = 32), respectively. During 31 treatments the FBV by dilution showed an average decrease of 4.17 +/- 8.60%, and in 6 cases FBV fell more than 10%, while measurements of the same FBV by reuse equipment showed an increase of 0.99 +/- 5.82%, P < 0.01.

CONCLUSIONS

FBV measured by the dilution methods was accurate and reproducible. Preliminary results suggest that in vivo FBV may differ significantly from results reported by reprocessing machines.

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.

The effect of dialyzer reuse on dialysis delivery

It is well documented that the reprocessing of dialyzers may reduce their solute clearance capabilities. However, the effect of dialyzer reuse has never been assessed in an uncontrolled clinical practice setting. We addressed this issue in a prospective 436-patient, 34-center study. All patients underwent formal urea kinetic modeling monthly, usually for 3 sequential months. Dialyzers were reprocessed and reused in the usual manner for each unit. As a result, urea kinetic modeling was performed in individual patients using dialyzers with differing numbers of prior uses. For each patient, Kt/V urea for the treatment using the dialyzer with the most reuses (mean, 13.8) was compared with that with the treatment using the dialyzer with the fewest reuses (mean, 3.8). The mean Kt/V delivered for high reuse treatments was significantly lower than that for low reuse treatments (1.05 v 1.10, P = 0.002). Prescribed Kt/V in high and low reuse treatments was identical. Individual centers appeared to differ substantially (P = 0.06) in the effect of reuse on delivered Kt/V. Of the 23 centers using formalin-based reprocessing, an average difference of > or = 0.12 (mean, 0.17) in Kt/V between high and low reuse treatments was seen in 10 centers. Dialyzer reprocessing significantly impairs dialysis delivery, an effect that may be related to the methods and procedures in individual dialysis centers.

Effect of heparin modeling on delivered hemodialysis therapy

Heparin anticoagulation is standard practice in hemodialysis. To assess the effect of adequate heparinization on dialysis delivery, 28 chronic dialysis patients (mean age, 55 +/- 17 years; 18 men, 10 women) were selected for heparin modeling (HM). Polysulfone dialyzers were used. The dialysis prescription was kept unchanged, and an automated nonbleach reuse procedure was used. Measurements of time average concentration of urea (TACurea), KT/V delivered, normalized protein catabolic rate (nPCR), hematocrit, and dialyzer total blood compartment volumes [TBCVs] (fiber bundle volume [FBV] + header volume) were evaluated before and after heparin dosages were changed as indicated by HM. Heparin dosage increased from 2,400 +/- 841 IU to 4,398 +/- 3,112 IU (P < 0.002). While there was no significant change in nPCR (pre 0.84 +/- 0.34 v post 0.83 +/- 0.30), the effective clearance as measured by urea clearance improved from 212.8 +/- 37 to 240.1 +/- 49 mL/min (P < 0.05), KT/V remained unchanged, and TACurea decreased from 48.8 +/- 22.3 to 35.8 +/- 21.5 mg/dL (P < 0.05). Dialyzer TBCVs were unchanged (from 116 +/- 17 to 114 +/- 17 mL, NS). We conclude that the use of an appropriate dose of heparin during hemodialysis will improve polysulfone dialyzer clearance, increase the delivered KT/Vurea, and reduce TACurea. Heparin dosing should be given close attention because it does affect the dialysis dose delivered.

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

Increased biocompatibility and lower cost are the two major arguments favoring routine dialyzer reprocessing. The impact of longer-term reprocessing is critical to the practical use of polysulfone membranes (PMs), because of the possibility of decreasing efficiency and performance, especially in the removal of beta 2-microglobulin (beta 2M), a protein that has been implicated in the development of dialysis-associated amyloidosis (DDA). In this study, we examine urea clearance (Kd), urea mass transfer coefficient (h0), ultrafiltration coefficient (K(uf)), and percent removal of beta 2M up to 24 uses. The study involved 11 patients on hemodialysis for 5.27 +/- 4.6 years, with a mean age of 62.5 +/- 9.7 years and average run-time treatment of 2.78 +/- 0.3 hours. PMs were tested after being reprocessed manually using bleach and formaldehyde. The efficacy of the dialyzer was examined on uses 1, 5, 10, 15, 20, and 24, and the percent removal of beta 2M was determined except in the twentieth use and corrected for ultrafiltration. The Kd obtained through 24 uses showed no significant change, although h0 was significantly increased in the fifteenth use, and K(uf) was significantly increased in the 10th and 20th use (P < 0.05). The percent removal of beta 2M increased significantly from 44.1 +/- 2.8 (mean +/- SEM) in the first use to 59.4 +/- 2.19 (P < 0.05) in the 10th use, and 62.1 +/- 4.07 and 63.1 +/- 4.27 in the 15th and 24th uses, respectively (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of reprocessing high-flux polysulfone dialyzers with peroxyacetic acid on beta 2-microglobulin removal in hemodiafiltration

The reuse of dialyzers is widely practiced, especially in the United States. Despite this, the effects of reuse on the efficacy of removal of solutes and more recently proteins such as beta 2-microglobulin (beta 2M) are the subject of much debate. There is considerable evidence to suggest that reuse after cleansing and sterilizing with formalin, with or without bleach, maintains dialyzer performance. In this study, we have examined peroxyacetic acid use as the cleansing and sterilizing agent using Renatron machines. We analyzed reuse in 24 patients using polysulfone membranes in a hemodiafiltration (HDF) unit over a 2-year period. The mean maximum number of uses achieved was 20.1 +/- 0.5. Several factors considered clinically to influence the number of reuses achievable (hemoglobin, white blood cell, and platelet levels, erythrocyte sedimentation rate [ESR], and fibrinogen and total protein levels) were found not to influence the maximum number of uses obtainable. We then assessed prospectively the performance of 26 polysulfone dialyzers after peroxyacetic acid reprocessing up to 20 times, particularly with regard to their ability to remove beta 2M. We report that this combination of polysulfone membranes reprocessed with peroxyacetic acid used for HDF up to 20 times exhibits a maintained high level removal of compounds beyond a molecular weight (MW) of 12,000. Any secondary membrane formation that occurs appears not to influence the subsequent removal of beta 2M. Thus, we would recommend the use of peroxyacetic acid for reprocessing dialyzers in a safe and efficacious manner.