Residual Ethylene Oxide in Hollow-Fiber Dialyzers

The deaeration and extraction kinetics of ethylene oxide (ETO) in hollow-fiber dialyzers were examined. The investigations showed that both deaeration and extraction can be described by two additive first-order kinetic expressions. The ETO content of membranes decreased rapidly at first, followed by a second slower decrease. Even after prolonged storage time, residual ETO was still detectable in the milligram range. These residuals cannot be eliminated by the usual rinsing of the dialyzer prior to use.     

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.     

Mediation of Hypersensitivity Reactions During Hemodialysis by IgE Antibodies Against Ethylene Oxide

Sera from 329 hemodialysis patients, 46 of whom had experienced a hypersensitivity-type reaction during hemodialysis, were screened by an enzyme-allergosorbent test (EAST) for IgE antibodies specific for ethylene oxide (ETO). In seven of nine patients who had experienced a severe hypersensitivity reaction (type II or type III), high titers of IgE antibodies against ETO (greater than 3.0 PRU/mL) were found. However, plasma levels of IgE specific for ETO were in the normal range (less than 0.35 PRU/mL) in most (30/37) patients who had experienced a mild (type I) reaction. Selected sera from patients who had experienced severe reactions were further examined for IgE directed against isopropyl myristate (IPM), 2-chloroethanol, and extracts from unsterilized dialyzers. Importantly elevated serum levels of specific IgE against these substances could not be documented. Extracts of an ETO-sterilized, hollow-fiber dialyzer were positive, whereas extracts of an ETO-sterilized dialyzer containing a flat membrane were negative in the EAST. This difference can be explained by the different amounts of ETO present in the dialyzers. We conclude that ETO causes most severe hypersensitivity reactions by an IgE-mediated mechanism. On the other hand, the pathogenesis of mild (type I) reactions is less clearly associated with ETO allergy. Our results also suggest that other potentially allergenic substances in dialyzers (e.g., IPM, 2-chloroethanol) rarely induce specific IgE antibodies in dialysis patients.     

Ethylene Oxide (ETO) as a Major Cause of Anaphylactoid Reactions in Dialysis (A review)

Ethylene oxide (ETO), an alkylating compound of high chemical reactivity, is widely used for gas sterilization, but recently serious ETO side reactions have been recognized. With chronic ETO exposure, increased spontaneous abortion, sister chromatid exchange, and leukemia are observed. After medical use of ETO outside nephrology, contact dermatitis, cardiopulmonary shock (during cardiopulmonary surgery), allergic local reactions to ETO sterilized lenses, and anaphylactoid reactions to ETO sterilized catheters have been described. In numerous dialysis patients widespread hypersensitivity to ETO has been documented by skin prick test and ETO radioallergosorbent test (RAST). Furthermore an anaphylactoid "first-use reaction" was described in dialyzed patients, most of whom were using hollow-fiber dialyzers. After long discussions whether complement activation versus hypersensitivity is the cause of such acute anaphylactoid reactions, more recent studies using either ETO RAST or basophil degranulation tests implicate ETO hypersensitivity as their major cause. The high prevalence of sensitization to ETO and the frequency, unpredictability, and potential danger of anaphylactoid reactions to ETO lead to the conclusion that ETO sterilization of dialyzers should be discontinued, since alternative modalities of sterilization are currently available.     

Sorbent Membranes Used in a Conventional Dialyzer Format

The possibility of installing sorbent membranes into proven dialyzer configurations could result in certain advantages over dialyzers with conventional membranes. A sorbent membrane dialyzer might prove superior in that it allows a higher clearance in the middle molecule molecular weight range, thereby shortening dialysis time and possibly allowing a reduction in the amount of dialysate fluid required. Finally, this device could be used without dialysate if the technician's goal is to eliminate a single substance readily adsorbed by charcoal. For example, this would apply to the treatment of certain intoxications. In vitro data were established for six substances in the molecular weight range of 60 to 5200 daltons and compared to corresponding results for conventional Cuprophan dialyzers. Clinical evaluation of sorbent membrane dialyzers for patients with uremia and intoxication, both with and without use of dialysate, has proven effective with no adverse reactions.     

Foreign particles contaminating hemodialyzers and methods of removing them by rinsing

Foreign particles contaminating hemodialyzers constitute a risk of microembolism and allergic reactions in hemodialysis patients. We investigated the size distribution of particles, and the effects of striking headers of dialyzers and flow rates of rinsing saline on the elimination of foreign particles from dialyzers. Saline used for rinsing was filtered through a Millipore filter, and the particles thus removed were observed microscopically. We also checked changes in particle counts in a closed circuit consisting of a dialyzer and blood lines during 5 h of continuous circulation with a blood pump. The number of contaminating particles increased exponentially as their size decreased. For the sake of reproducibility we counted particles having diameters larger than 3.0 micron to monitor the rinsing efficiency. During rinsing, particles in the dialyzer were effectively eliminated by striking the headers of the dialyzer. We found that striking should be started immediately after the blood line is filled with saline, and that variation in saline flow rates in the range of 350-700 ml/min of saline does not affect the rinsing efficiency. By filtration of saline used for rinsing, particles, mostly ranging from 5 to 200 micron in length, of many shapes and colors were found. Among them were fibers having a length of as much as a few millimeters. Once dialyzers were rinsed effectively, there was almost no change in particle counts in a closed circuit consisting of a dialyzer and blood lines. To rinse dialyzers effectively, at least 1,000 ml of saline are necessary, and striking the headers of dialyzers throughout the rinsing procedure is important.     

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.     

Plate, Coil, and Hollow-Fiber Cuprammonium Cellulose Dialyzers: Discrepancy Between Incidence of Anaphylactic Reactions and Degree of Complement Activation

During the past 10 years, the incidence of severe anaphylactic reactions during dialysis [type A first-use syndrome (FUS)] at our center has been much lower when using cuprammonium cellulose plate (CC-P) dialyzers (0/37, 750 dialyses) or coil (CC-C) dialyzers (0/32, 500) than when using cuprammonium cellulose hollow-fiber (CC-F) dialyzers (8/21,022 dialyses, p less than 0.005 by Chi-square). To determine if the difference in type A FUS incidence between the three dialyzer types could be explained by differences in complement activation, we compared plasma concentrations of C3a des-arginine (des arg) in patients undergoing dialysis with these three varieties of dialyzers. Plasma C3a des arg values increased markedly in the dialyzer outflow blood with the three dialyzer configurations. The levels were similar with the dialyzer types when results were corrected for membrane surface area. Also, the degree of leukopenia was not markedly different with the three dialyzer types. Our findings suggest that complement activation per unit surface area is similar during dialysis with plate, coil, and hollow-fiber cuprammonium cellulose dialyzers. The lack of correlation between the degree of complement activation and the incidence of type A FUS suggests that membrane-induced complement activation is not of primary importance to type A dialyzer hypersensitivity reactions.     

Ethylene Oxide Sensitivity in Hemodialysis Patients

Sera from 138 patients who had experienced hypersensitivity-type reactions while on hemodialysis (reactors) were examined retrospectively by the radioallergosorbent test (RAST) for specific IgE antibody to ethylene oxide (ETO). Seventy-eight hemodialysis patients without a history of reaction were also evaluated as controls. Elevated serum RAST values (greater than 2.0) were more common in reactors (63%) than in controls (11%, p less than 0.001). In a second study, RAST assays were performed using human serum albumin conjugated to ETO (HSA-ETO) as antigen and also using a concentrate of fluid used to rinse ETO-sterilized dialyzers ("dialyzer extract") as antigen. The RAST ratios obtained with HSA-ETO were similar to those obtained using the dialyzer extract (rank order correlation coefficient = 0.829, p less than 0.001). In a third study, RAST inhibition was demonstrated both by HSA-ETO and dialyzer extract. Our results, extending previously published reports, suggest that hypersensitivity to ETO might play an important role in hemodialysis-associated hypersensitivity-type reactions.     

Characterization and Identification of Substances Isolated from Dialyzer Extracts

The organic phase of dialyzer dried extracts obtained from Cuprophan hollow fiber and polyacrylonitrile AN 69 parallel-plate dialyzers, all sterilized by ethylene oxide, were submitted to light and polarized light microscopy, infrared (IR) spectrophotometry, and gas chromatography coupled with mass spectrometry. Colorless polygonal (approximately 5 X 20 micron) and needle-like (approximately 3 X 50 micron) crystals were found in great quantity on microscopy examination. IR spectrophotometry of the crystals embedded in potassium bromide disc showed specific spectra in the 1400-800 cm-1 wave number range and typical peaks on wave number assigned for hydroxy or amine (3420 cm-1), aromatic hydrogen (3060 cm-1), methyl, methylenic, or methenyl (2960-2860 cm-1), and carbonyl (1715 cm-1) groups can be demonstrated. Seven peaks were detected on gas chromatography of the organic solution containing crystals. Fatty acids and undefined compounds could originate from the dialyzer. Phtalates may leach from blood tubing, used in the rinsing procedure, and BHT is a stabilizer of ethyl ether used as solvent. These compounds could also originate from the dialyzer since phtalates are widely used as a plasticizer and BHT an antioxidant for various polymers.     

Dialyzer Reuse Following Manual Reprocessing with a New Sterilant, RenNew-D

Dialysis patients are at risk for toxicity from formaldehyde used in the reprocessing of dialyzers for reuse; therefore, replacing formaldehyde as a dialyzer sterilant would be advantageous. The potential for RenNew-D as a sterilizing agent was investigated in seven stable in-center hemodialysis patients over 20 consecutive dialyses with cuprammonium cellulose hollow-fiber dialyzers. Treatment with RenNew-D showed no toxicity to patients or dialyzers except for two blood leaks occurring in one patient. The mean number of dialyzer uses was 4.9. In all the dialyzers that passed functional testing small solute clearances were maintained with reuse. The ability of RenNew-D to improve the biocompatibility of reused dialyzers was documented with mean neutrophil counts falling to only 78% of initial values during first reuse of dialyzers processed with RenNew-D compared with a decrease in neutrophil count to 2% of initial values during first use of the same dialyzers. Our results suggest that RenNew-D may be a useful alternative to formaldehyde for the purpose of dialyzer reuse. A reuse procedure that includes processing with RenNew-D is associated with improved biocompatibility, possibly because of maintenance of the blood-derived membrane coating established during prior dialysis.     

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.     

β-2-Microglobulin and Main Granulocyte Components in Hemodialysis Patients

Plasma levels of granulocyte elastase in complex with alpha 1-proteinase inhibitor (E-alpha 1-PI) increased during hemodialysis from 110 +/- 10 to 506 +/- 66 micrograms/L using dialyzers made of polyamide, from 95 +/- 2.2 to 211 +/- 54 micrograms/ml with hemophane and from 114 +/- 10 to 203 +/- 25 using dialyzers made of polysulfone. Plasma lactoferrin values were also significantly higher during hemodialysis with polyamide (772 +/- 110 micrograms/L) compared with hemophane (268 +/- 2.2) and the polysulfone (278 +/- 31 micrograms/L) dialyzer. After dialysis each dialyzer was rinsed. We found the lowest concentration of lactoferrin (902 +/- 254 micrograms/L) and E-alpha 1-PI (739 +/- 162 micrograms/L) after rinsing polysulfone dialyzers, whereas the highest concentrations were observed after rinsing the polyamide dialyzer (lactoferrin: 2,426 +/- 314; E-alpha 1-PI: 1,134 +/- 144 micrograms/L). Hemodialysis with polysulfone dialyzers caused significantly lower plasma levels of beta-2-microglobulin compared with polyamide or hemophane membranes despite significantly lower levels in the rinsing solutions. Our data indicate that low plasma levels of main granulocyte component observed with polysulfone and hemophane dialyzers are not the result of higher membrane adsorption of E-alpha 1-PI and lactoferrin. These main granulocyte components are not related to beta-2-microglobulin levels of both plasma and rinsing solutions.     

Acute Anaphylactoid Reactions During Hemodialysis in France

A retrospective survey of anaphylactoid reactions during dialysis in France was conducted. In 52 of 112 hemodialysis units surveyed 111 patients who had suffered one or more anaphylactoid reactions during dialysis were identified. According to the Hamilton/Adkinson classification, in 31 patients reactions were minor, in 54 patients moderate, and in 26 patients severe. Four patients died of their reactions. A preponderance of reactions (75 and 11%) occurred with cuprammonium cellulose hollow-fiber and plate dialyzers, respectively. Severe dialyzer reactions were found to occur more frequently after the long (weekend) interdialytic interval. In an in vitro study, six brands of cuprammonium cellulose hollow-fiber dialyzers were rinsed with water and the eluates analyzed by size exclusion chromatography for contaminant particles. Substantial variation in the amount of extractable material was found between dialyzers of different brands, despite the fact that all dialyzers used membranes from the same manufacturer. Previous data by others has suggested that this extractable material is a derivative of cellulose. Results of our epidemiologic survey in France are similar to those previously reported in the United States and suggest an increased incidence of dialyzer reactions with ethylene oxide-sterilized cuprammonium cellulose dialyzers. The presence of cellulose-derived particles in the rinsing fluid of such dialyzers and the possible increased incidence of reactions after the long (weekend) interdialytic interval suggest that allergy to cellulose-derived particles eluted from cellulosic dialyzers may contribute to dialyzer hypersensitivity reactions.     

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.     

Role of Dialyzer Contaminants in the Allergic Epiphenomena of Hemodialysis

Abstract: Cuprophan hollow-fiber dialyzers contain contaminants including 1,2,3-propanetriol, carbohydrates, Limulus amebocyte lysate-reactive material, and particulates. In a clinical study, the role of these substances in the allergic-type response seen in some hemodialysis patients was examined. Patients were dialyzed three times per week for 6-week intervals with each of four dialyzer preparations designed to vary the burden of contaminants presented to the patient. Predialysis eosinophil counts and serum immunoglobulin (Ig) E levels were obtained weekly. White cell and platelet counts and plasma C3a and C5a levels were measured during dialysis for each dialyzer preparation. Dialyzer preparation had no effect on predialysis eosinophil counts or IgE levels. All patients demonstrated transient leukopenia and complement activation during dialysis, the magnitudes of which were unaffected by the type of dialyzer preparation. At the levels found in the dialyzers studied, it was questioned whether water-soluble extractables or particulates play any role in the allergic epiphenomena of hemodialysis.     

Formaldehyde kinetics and bacteriology in dialyzers

The kinetics of formaldehyde washout in new and reused dialyzers with 2% (w/v) and 4% formaldehyde solution was studied. Using a standard method of rinsing, the concentration of formaldehyde decreases exponentially, but the rate of decrease and the steady-state level depends on the type of dialyzer. The residual quantity of formaldehyde using a 4% solution is more than twice that seen with a 2% solution in similar dialyzers. Bacteriological tests on water-adapted, formaldehyde-resistant organisms indicate that a significant proportion of these organisms can survive a 4-hr incubation with 4% formaldehyde at 20 degrees C. However, increasing the temperature of incubation to 40 degrees C or the addition of ethanol up to 8% (v/v) improved the bacteriological efficacy of formaldehyde. Under these conditions, a 1% formaldehyde solution allows eradication of all organisms tested. Similar results were observed in multiple-use dialyzers inoculated with the same organisms. There was no effect of incubation at 40 degrees C on the in vitro clearance determinations of new and reused dialyzers.     

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.     

Immunologic Studies of Hollow-Fiber Dialyzer Extracts

Abstract: Testing failed to detect free isocyanates in dialyzer rinses or significant levels of immunoglobulin E antibodies to isocyanate-protein conjugates in the serum of individuals reacting during hemodialysis with dialyzers containing Cuprophan membranes. Extended immunization of rabbits with Limulus lysate-reactive material from dialyzer rinses demonstrated antigenic activity of the rinse that appears to originate from cotton linters used in hollow-fiber membranes. The possibility that an immunologic response to these antigens may be a mechanism in adverse reactions to hemodialysis is discussed.