Effect of RenNew-D as a sterilant on the performance of reused dialyzers

RenNew-D (Alcide), a novel demand-release sporocidal agent, was employed instead of formaldehyde in the reprocessing for reuse of cuprophan hollow fiber dialyzers (Gambro) and the performance of these dialyzers was evaluated over 40 consecutive dialyses in six patients on maintenance hemodialysis. When RenNew-D was part of automated reprocessing performed with 4.3% bleach as specified by the manufacturer (Lixivitron), dialyzer survival was prolonged (16.7 +/- 7.2 uses) and hemodialysis neutropenia was unchanged with reuse. When RenNew-D was part of manual reprocessing conducted in the absence of bleach, marked improvement in dialyzer biocompatibility was observed but with a decreased survival (4.8 +/- 3.0). The majority of dialyzer failures were due to a fall in fiber bundle volume below a 85% set limit. Small solute clearances were maintained with both types of reprocessing. Dialyses were well tolerated throughout. Our data suggest that RenNew-D is a safe and efficacious product which can serve as a valuable alternative to formaldehyde for the purpose of dialyzer reuse.     

Relationship between dialyzer reuse and the presence of anti-N-like antibodies in chronic hemodialysis patients.

One hundred eleven chronic hemodialysis patients from five dialysis units were tested for the presence of antibodies reactive with red blood cell N substance; 77 patients were available for follow-up study after 18 to 24 months. Initially, 18 patients (16%) had serum anti-N-like antibodies. Thirteen of these patients were in a home dialysis program and were reusing hollow fiber dialyzers. The other five had practiced hollow fiber dialyzer reuse in the past. None of 37 patients using coil dialyzers had anti-N-like antibody. On follow-up testing, anti-N-like antibody persisted in all patients restudied except for one who had a successful renal transplant. Anti-N-like antibodies developed in four additional patients: three were reusing hollow fiber dialyzers at the time, but one had not reused dialyzers for 24 months. Statistical analyses indicated that dialyzer reuse, hollow fiber dialyzers, and home dialysis were significantly related to the presence of anti-N-like antibodies. We interpret the clinical and statistical data to indicate that dialyzer reuse is the major clinical factor in the development of anti-N-like antibody. The likely mechanism involves the prolonged exposure of red cells trapped in the dialyzer to formaldehyde used in preparing dialyzers for reuse. No adverse clinical effects of anti-N-like antibodies were evident in our patients, but hemolysis and acute transplant failure have been reported by others.     

Impact of bleach cleaning on the performance of dialyzers with polysulfone membranes processed for reuse using peracetic Acid

Dialyzer performance may change with reuse depending on whether or not the dialyzer is cleaned with bleach. Bleach is usually used in conjunction with formaldehyde as the germicide. Because few data are available for dialyzers cleaned with bleach and disinfected with peracetic acid, we examined dialyzer performance in a cross-over study of dialyzers containing polysulfone membranes reprocessed using bleach and peracetic acid or peracetic acid alone. Each dialyzer was used for a total of 16 treatments, or until it failed standard criteria for continued use. Urea, beta2-microglobulin, and albumin removal were determined during the first, second, seventh, and 16th use of each dialyzer. Urea removal did not differ between the two reprocessing methods and did not change with reuse. Overall, beta2-microglobulin removal remained unchanged in dialyzers reprocessed with peracetic acid alone, but tended to increase after the seventh use in dialyzers reprocessed with bleach and peracetic acid. Approximately 60% of beta2-microglobulin removal resulted from trapping of beta2-microglobulin at the dialyzer membrane. Albumin loss into the dialysate was clinically insignificant throughout the study with both reprocessing methods. These data show that the clearance of both small and large molecules by dialyzers containing polysulfone membranes is well maintained by reprocessing with peracetic acid and that additional cleaning with bleach has limited impact on performance.     

Beta 2-microglobulin kinetics in maintenance hemodialysis: a comparison of conventional and high-flux dialyzers and the effects of dialyzer reuse

beta 2-Microglobulin (beta 2M) forms synovial and bony amyloid deposits in long-term hemodialysis patients. To define the kinetics of beta 2M during hemodialysis and the effects of dialyzer reprocessing, we measured serum beta 2M, plasma C3a, and neutrophil counts immediately predialysis; 15, 90, and 180 minutes after beginning dialysis; and 15 minutes postdialysis in ten chronic hemodialysis patients. The studies were performed during first and third uses of cuprammonium rayon and polysulfone dialyzers processed by rinsing with water, then bleach, in an automated system (Seratronics DRS 4) and then packed in 1.5% formaldehyde. Mean serum beta 2M (corrected for ultrafiltration) decreased by 16.6% +/- 18.1% with new cuprammonium dialyzers and 57.1% +/- 12.8% with new polysulfone dialyzers. Dialyzer reprocessing had no significant effect on this decline. Predialysis serum beta 2M decreased by 30.4% +/- 15.5% 1 month after switching from cuprammonium to polysulfone dialyzers; these levels remained stable after 3 months of dialysis with polysulfone. Complement activation and neutropenia during dialysis were significantly more marked with cuprammonium, but were not affected by reprocessing of either dialyzer. In vitro adsorption of 124I-beta 2M to polysulfone fibers was greater than to cuprammonium; adsorption was not influenced by dialyzer reprocessing.     

The effects of reprocessing cuprophane and polysulfone dialyzers on beta 2-microglobulin removal from hemodialysis patients

To further define the relationship between dialyzer reuse and the removal of beta 2-microglobulin (beta 2M) during dialysis, 26 patients who received hemodialysis were studied. Thirteen patients were dialyzed with conventional cuprophane dialyzers, and thirteen patients were dialyzed with high-flux polysulfone dialyzers. Patients in each group were dialyzed with only new dialyzers during the primary-use phase of the study, and reprocessed dialyzers during the reuse phase. Dialyzers were used six times during the reuse phase. Serum beta 2M levels were measured both predialysis and postdialysis, and adjusted for fluid loss. Dialysis with conventional cuprophane new dialyzers during the primary-use phase of the study resulted in a 3.3% increase in serum beta 2M levels, and a 2.4% increase in serum beta 2M levels during the reuse phase. The difference in the change of the concentration of beta 2M between primary-use and reuse phases was not statistically significant. Dialysis with high-flux polysulfone new dialyzers during the primary-use phase was associated with a decrease of 59.5% in the mean postdialysis concentration of serum beta 2M compared with the predialysis level. A corresponding decrease of 62.6% in serum beta 2M levels was observed after dialysis with high-flux polysulfone reprocessed dialyzers during the reuse phase. These data show no evidence of an adverse effect on the clearance of beta 2M during dialysis from the reuse of dialyzers up to six times. The results confirm previous studies that have reported that high-flux dialysis with polysulfone dialyzers removes substantial amounts of beta 2M, and dialysis with conventional cuprophane dialyzers does not.     

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.     

Association of dialyzer reuse and hospitalization rates among hemodialysis patients in the US

OBJECTIVES: To determine if reuse of hemodialyzers is associated with higher rates of hospitalization and their resulting costs among end-stage renal disease (ESRD) patients. METHODS: Noncurrent cohort study of hospitalization rates among 27,264 ESRD patients beginning hemodialysis in the United States in 1986 and 1987. RESULTS: Dialysis in free-standing facilities reprocessing dialyzers was associated with a greater rate of hospitalization than in facilities not reprocessing (relative rate (RR) = 1.08, 95% confidence interval (CI), 1.02-1.14). This higher rate of hospitalization was observed with dialyzer reuse using peracetic/acetic acids (RR = 1.11, CI 1. 04-1.18) and formaldehyde (RR = 1.07, CI 1.00-1.14), but not glutaraldehyde (p = 0.97). There was no difference among hospitalization rates in hospital-based facilities reprocessing dialyzers with any sterilant and those not reprocessing. Hospitalization for causes other than vascular access morbidity in free-standing facilities reusing dialyzers with formaldehyde was not different from hospitalization in facilities not reusing. However, reuse with peracetic/acetic acids was associated with higher rates of hospitalization than formaldehyde (RR = 1.08, CI 1.03-1.15). CONCLUSIONS: Dialysis in free-standing facilities reprocessing dialyzers with peracetic/acetic acids or formaldehyde was associated with greater hospitalization than dialysis without dialyzer reprocessing. This greater hospitalization accounts for a large increment in inpatient stays in the USA. These findings raise important concerns about potentially avoidable morbidity among hemodialysis patients. Copyright Copyright 1999 S. Karger AG, Basel     

Dilemma of Membrane Biocompatibility and Reuse

Abstract: Numerous articles have been published on the multiple use of dialyzers and on the effect of different reprocessing chemicals and techniques on the dialyzer biocompatibility and performance. The results often appear contradictory, especially those comparing standard biocompatibility parameters. Despite this confusion, a discerning review of the published works allows certain limited conclusions to be drawn. Reprocessing of used hemodialyzers changes the biocompatibility profile of a dialyzer as defined by the parameters complement activation. leukopenia, and cytokine release. The effect of reprocessing depends on the chemicals and reprocessing technique applied and also on the type of membrane polymer being subjected to the reprocessing procedure. Reports of pyrogenic reactions indicate that the flux of the membrane also influences how suitable it is for safe reuse. An increased risk of allergic and pyrogenic reactions appears to be associated with dialyzer reuse. Furthermore, there has been a lack of investigations into the immunologic effect of the layer of adsorbed and chemically altered proteins that remains on the inner surface of reprocessed dialyzers. We conclude that the clinical benefit of dialyzer reuse cannot be generally accepted from a biocompatibility point of view.     

Dialyzer performance over prolonged reuse

Studies were performed in patients on maintenance hemodialysis to evaluate the role of prolonged dialyzer reuse in the management of end-stage renal disease. For this purpose the patients were dialyzed without interruption with the same hollow fiber dialyzers (GambroR 120M) reprocessed with the Lixivitron IIR equipment. The data obtained from in vivo clearances in sixteen patients demonstrate that membrane permeability to small solutes (urea, creatinine, phosphate) is maintained up to thirty dialyzer uses. In vitro studies confirmed this observation and established that clearances of larger solutes (vitamin B12) are also maintained over similar extensive dialyzer reuse. Hematological and blood gas studies were performed serially during dialysis in five additional patients. Although circulating leucocyte and neutrophil counts, hemoglobin concentration as well as arterial pH and partial pressures of oxygen and carbon dioxide changed appropriately during dialysis, there was no observable difference from the first to the twentieth use of the same dialyzer. Thus, these results clearly demonstrate that prolonged dialyzer reuse in end-stage renal disease patients constitutes a stable form of renal replacement therapy provided adequate dialyzer reprocessing is applied.     

Dialyzer reuse-Part I: Historical perspective

The first apparatus for hemodialysis in animals, made painstakingly by Abel et al. in their laboratory at the beginning of 20th century, was cleaned with acid-pepsin to digest blood, disinfected with thymol, and reused for up to 30 experiments for as long as 8 months. The obvious incentive was saving time. In the early years of hemodialysis in patients, dialyzers and lines were assembled and sterilized immediately before dialysis. Various methods of dry and moist heat sterilization and miscellaneous chemical agents were employed for disinfection. Significant time was required to assemble the dialyzers, so there was an incentive to reuse previously assembled dialyzers to save time, especially for home hemodialysis. Bleach to clean and formaldehyde to disinfect the membranes and lines was used for this purpose. Preassembled dialyzers, commercially introduced in the 1950s, were the most expensive components of hemodialysis systems, therefore reprocessing of these dialyzers was the most effective way to save money. Refrigeration of coil dialyzers with blood, introduced in the mid-1960s, was associated with frequent febrile reactions and was soon abandoned. Preassembled coil and plate dialyzers permitted almost complete return of blood after dialysis and led to the introduction of chemical disinfection for dialyzer reprocessing. A variety of disinfectants have been used. Formaldehyde was the most common disinfectant until the end of the 1970s. Sodium hypochlorite was used to clean the majority of dialyzers and to sterilize dialyzers with polyacrylonitrile membranes. In the early 1980s, peracetic acid and glutaraldehyde started to compete with formaldehyde. By the 1990s, formaldehyde had become less popular than peracetic acid. In the mid-1990s, disinfection and membrane cleaning with acetic acid and heat was introduced. Manual reprocessing was replaced by early reuse machines in the mid-1970s and a more sophisticated second generation of automated hemodialyzer reprocessing machines followed in the late 1970s. Recently disinfection of dialyzers with moist heat has resumed. Saving both time for the patient and money for the provider were the main motivations for designing a new machine for daily home hemodialysis. The machine, developed in the 1990s, cleans and moist-heat disinfects the dialyzer and lines in situ so they do not need to be changed for a month. In contrast, the reuse of dialyzers in home hemodialysis patients treated with other hemodialysis machines has become less popular and is almost extinct.     

Effect of Dialyzer Reprocessing Methods on Complement Activation and Hemodialyzer-Related Symptoms

The effects of different dialyzer processing methods and of reuse on complement activation and dialyzer-related symptoms were studied in 96 maintenance hemodialysis patients. New dialyzers were either unprocessed (Group 1) or machine-washed with bleach and stored in formaldehyde (Group 2). Reused dialyzers were manually cleansed using the combination of bleach and formaldehyde (Group 3), or machine-washed in formaldehyde (Group 4) or peracetic acid (Group 5). Prewashed new dialyzers (Group 2) were associated with greater complement activation during dialysis when compared with unprocessed, new dialyzers (Group 1) (p less than 0.05). Reused, unbleached but formaldehyde-treated or peracetic acid-treated dialyzers (Groups 4 and 5) were associated with reduced complement activation (p less than 0.05). Complement activation was not reduced when bleach was used for reprocessing (Group 3). The percentage of patients without symptoms during dialysis was significantly greater with reused dialyzers than with new dialyzers (Groups 3 through 5 versus Groups 1 and 2; 39 versus 25%; p = 0.035). The severity of total symptoms correlated significantly (p = 0.0004) with complement activation. Our results suggest that total symptoms during dialysis are correlated with the degree of complement activation. However, trends in the data pertaining to chest pain suggest that factors other than complement activation may be important in the pathogenesis of some dialyzer-related symptoms.     

Severe dialyzer dysfunction undetectable by standard reprocessing validation tests

It is generally accepted that careful monitoring of total cell volume and ultrafiltration rates will ensure adequate function of reprocessed dialyzers. During routine urea kinetic measurements we noted that the percent of patients with clearances less than 200 ml/min increased from 5% to 48% despite adherence to these validation tests. As these patients did not have evidence of recirculation in the vascular access, possible causes of dialyzer dysfunction were investigated. Injection of methylene blue into the dialysate port revealed non-uniform flow of dialysate in dialyzers from patients with markedly reduced clearances. In vitro studies of dialyzers subjected to sequential daily reprocessing, without patient exposure, demonstrated that in vitro clearances declined in one lot but not another. The initial clearances of 218 +/- 4 ml/min fell progressively to 112 +/- 18 (P less than 0.001) after 15 reuses. No effects of reprocessing were found in a different lot (230 +/- 2 vs. 226 +/- 4 ml/min). Soaking the dialyzers from the affected lot in either the disinfectant or dialysate solution caused a decline in the clearances which was less than that of serial reuse. Although the magnitude of the problem of dialyzer malfunction with reuse is unknown, careful attention to dialyzer function is warranted in patients treated with reprocessed dialyzers.     

Effect of Reuse on Dialyzer Efficacy

The effect of reuse on dialyzer efficacy was examined by measuring blood compartment volume and dialyzer mass transfer coefficient (maximum dialyzer clearance) as a function of dialyzer use number. The 102 polysulfone dialyzers tested (F60 and HF80, Fresenius) were reprocessed on Renatron machines using peroxyacetic acid as the dual cleansing and sterilizing agent. Each dialyzer was used an average of 14.4 +/- 5.7SD times and was tested once (twice for 13/102 dialyzers) during a routine dialysis session at an arbitrary use number (7.6 +/- 5.3; range 1 to 24). The parameters tested were found to decrease only marginally with reuse, corresponding to a blood compartment volume loss of approximately 1% (R = 0.04) over a 5-week/15-use period and a decrease in dialyzer mass transfer coefficient of approximately 3% (R = 0.07 and 0.06) over the same period for urea and creatinine, respectively. It was concluded that the loss in dialyzer efficacy is negligible over the average use period of almost 5 weeks per dialyzer.     

Differences in Bio-incompatibility among Four Biocompatible Dialyzer Membranes Using in Maintenance Hemodialysis Patients

Abstract

Background: Following the introduction of modified cellulosic and then synthetic membrane dialyzers, it was realized that the dialyzer bio-incompatibility depends on the membrane composition. We designed a prospective, randomized, cohort study of 6 months to determine several parameters of biocompatibility in maintenance hemodialysis (MHD) patients treated with four different membrane dialyzers. Methods: There were 60 MHD patients enrolled in the study. In baseline, synthetic low-flux dialyzer, polysulfone (PS) membrane was used in all patients for at least 3 months. Then the patients were randomly divided into three groups according to different dialyzer membranes. Synthetic high-flux dialyzer group, ployethersulfone membrane, cellulose triacetate (CTA) high-flux membrane, and synthetic low-flux dialyzer, polymethylmethacrylate (PMMA) membrane were used in 6 months. A new dialyzer was used for each study treatment, and there was no dialyzer reuse. The biocompatibility markers and solutes removal markers were detected repeatedly at different time points. Results: The blood levels of highly sensitive C reactive protein, interleukin (IL)-1β, and interleukin (IL)-13 showed no difference among different groups at al time points. However, the blood complement levels and white blood cell counts were significantly different among three groups. When the dialyzers changed from PS to PMMA membrane, C3a levels and white blood cell counts changed significantly (p < 0.05). Moreover, the changes of C5a levels were significantly different between group CTA and group PMMA in month 3 (p < 0.05). Conclusion: There were much more differences on bio-incompatibility among different dialyzer membranes.     

Residual Formaldehyde in Dialyzers: Quantity, Location, and the Effect of Different Methods of Rinsing

When formalin-sterilized dialyzers were rinsed by our standard technique (similar to that used in many other dialysis centres) undesirable concentrations of formaldehyde were found in the dialyzers at the start of dialysis. When the technique was modified by passing part of the saline through the blood compartment immediately before connection and discarding the saline left in the dialyzer at the time of connection, the concentration of formaldehyde infused into the patient fell below 2 μg/ml. However, the dialyzers still contained up to 13 mg of formaldehyde which leached slowly from the dialyzer during simulated dialysis. Some residual formaldehyde was found in several components of the dialyzer but the great majority was contained in the cellulose membrane.     

Urea kinetics with dialyzer reuse--a prospective study

We performed a prospective study to examine the impact of dialyzer reuse on KT/V under rigidly standardized conditions on 3 membrane types. Heparin dosage was standardized with ACT during an eight week run-in period and remained unchanged through the study. Post dialysis BUN and weight were obtained at five minutes after exactly 80 +/- 0.5 l of blood were processed through the dialyzer. Dialyzers were reused after automated glutaraldehyde processing and after ensuring >80% open fiber bundles. Each membrane type was utilized 3 times on a set of 3 patients; each individual dialyzer was reused 8 times. KT/V was done on the 1st, 2nd, 4th and 8th uses of each dialyzer (36 measurements) starting mid week; BUN measurements were grouped. The KT/V (mean +/- SD) for the 1st, 2nd, 4th, and 8th uses of the cellulose acetate dialyzer were 1.3 +/- 0.2, 1.3 +/- 0.3, 1.3 +/- 0.2, 1.3 +/- 0.2 respectively; the corresponding values of the cuprophane dialyzer were 1.4 +/- 0.3, 1.4 +/- 0.3, 1.3 +/- 0.4, 1.3 +/- 0.3 respectively; and those of the polysulfone dialyzer 1.7 +/- 0.3, 1.6 +/- 0.2, 1.6 +/- 0.2 respectively. By a 3 way ANOVA there were no significant differences between the 1st and subsequent uses of any of the dialyzers tested. Conclusions: Reuse of dialyzers up to 8 times does not result in a loss of urea clearance. We believe this model is useful for further studies on reuse and quality assurance. Copyright Copyright 1999 S. Karger AG, Basel     

Anaphylactoid reactions associated with reuse of hollow-fiber hemodialyzers and ACE inhibitors.

From July 18 through November 27, 1989, 12 anaphylactoid reactions (ARs) occurred in 10 patients at a hemodialysis center in Virginia. One patient required hospitalization; no patients died. ARs occurred within minutes of initiating dialysis and were characterized by peripheral numbness and tingling, laryngeal edema or angioedema, facial or generalized sensation of warmth, and/or nausea or vomiting. All 12 ARs occurred with dialyzers that had been reprocessed with an automated reprocessing system. A cohort study, including all patients undergoing dialysis sessions on the six days when an AR occurred, showed that the patients who experienced ARs were significantly more likely than patients who did not to be treated with angiotensin-converting enzyme (ACE) inhibitors (7/10 vs. 3/33; relative risk = 7.9; 95% confidence interval = 2.5 to 25.2) and to have been exposed to reused dialyzers rather than to new dialyzers (12/70 sessions vs. 0/31; P = 0.016). In those sessions using a reused dialyzer, the mean number of dialyzer uses in case-sessions was significantly higher than for noncase-sessions (10.3 vs. 6.2; P = 0.016). After reuse of dialyzers was discontinued at the center, no further ARs occurred, despite the continued administration of ACE inhibitors. This is the first report of an outbreak of ARs associated exclusively with reused dialyzers. We hypothesize that interactions between a dialyzer that has been repeatedly reprocessed and reused, blood, and additional factors, such as ACE inhibitors, increased the risk of developing ARs.     

Reprocessing of capillary dialyzers

Changes in biocompatibility parameters of the cuprophan membrane, used repeatedly after reprocessing, were assessed. It is demonstrated that when the dialyzer is applied for the second of third time, cuprophan membrane loses its ability to induce acute dialysis leucopenia, typical for first application. Repeatedly used dialyzers also failed to cause bone-marrow irritation, which at first use induced a release of juvenile neutrophils into the circulation. Prior to first application, 6 dialyzers were subjected to 3 reprocessing procedures each. In all three, the cellulose membrane did not lose its ability to cause acute leucopenia. Therefore, the chemical reagents used in reprocessing (hydrogen peroxide, sodium hypochlorite and formaldehyde) are not the cause of membrane's loss of ability to induce leucopenia. Used for 3 times running, capillary dialyzers do not essentially lose their effective capillary volume. To determine whether the dialyzer is suitable for repeated use, both visual and objective check-up of the device is necessary. Some aspects of reprocessing technology are discussed.     

Dialyzer Reuse: Interaction Between Dialyzer Membrane, Disinfectant (Formalin), and Blood During Dialyzer Reprocessing

Abstract: The growing practice of dialyzer reuse in recent years is mainly based on medical and economic considerations. However, adverse reactions such as immunohemolytic anemia due to anti-N_from antibody associated with dialyzer reuse have been reported. In this study, scanning electron microscopy and cytologic staining were used to evaluate the interaction between blood components and the reprocessed synthetic dialyzer membrane (polysulfone) after disinfectant (formaldehyde) treatment. The results showed that various blood components such as fibrin and blood cells still adhered to the dialyzer membrane after reprocessing. The study also demonstrated that the adhered denatured blood components could be detached by sonication andlor simulated hemodialysis and then gain access into the circulation. The re-entry of the denatured blood components to the patients exposed to reused dialyzers may result in an enhanced imrnunological response which may contribute to antibody formation (such as anti-N_from antibody) with a reused hemodialyzer.     

High-flux dialysis lowers plasma leptin concentration in chronic dialysis patients

Leptin is a protein produced by fat cells and involved in body weight regulation. Plasma leptin is significantly higher in some hemodialysis (HD) patients than in normal controls. We examined the influence of dialyzer membrane biocompatibility and flux on elevated plasma leptin concentrations in hemodialysis patients. Employing a crossover design, leptin and tumor necrosis factor-alpha (TNF-alpha) levels were serially determined in eight chronic dialysis patients. Patients were dialyzed sequentially on low-flux cellulosic (TAF) dialyzers, low-flux (F8) polysulfone, high-flux (F80B) polysulfone, then low-flux polysulfone and cellulosic dialyzers again. Mean leptin concentrations were similar when low-flux polysulfone or cellulosic dialyzers were employed (141.9+/-24.2 microg/L versus 137.8+/-18.4 microg/L, respectively (P=NS). In contrast, leptin fell significantly on the high-flux polysulfone dialyzer (99.4+/-16.2 microg/L) compared with cellulosic (P < 0.005), and low-flux polysulfone dialyzers (P < 0.02). Leptin clearance by the high-flux polysulfone dialyzer was significantly higher than the low-flux dialyzers (50.4+/-21.5 v -9.6+/-10.3 mL/min; P=0.043), but did not account fully for the 30% decline in plasma leptin during the high-flux arm of the study. Concentrations of TNF-alpha were lower when high-flux polysulfone dialyzers were employed, but there was no correlation of individual TNF-alpha levels with leptin concentrations. High-flux dialysis lowers plasma leptin concentrations an average of 30%, but biocompatibility does not influence leptin levels. The decrease in plasma leptin on high-flux dialysis cannot be explained solely by enhanced clearance.