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

Small and Middle Molecular Weight Solute Clearance in Nocturnal Intermittent Peritoneal Dialysis

Objectives

To determine the dialysate-to-plasma (D/P) concentration ratios and peritoneal dialytic clearance (ClD) of substances with a wide range of molecular weights in subjects receiving a simulated nocturnal intermittent peritoneal dialysis (NIPD) session.

Design

Open-label single-dose study.

Subjects

Six end-stage renal disease patients undergoing peritoneal dialysis (PD).

Setting

Clinical research center of a university-affiliated hospital.

Interventions

Subjects received intravenous gentamicin and vancomycin on the first day of the study. Subjects received no PD until their return on the following day, when subjects underwent a simulated NIPD session utilizing four 2- to 2.5-L peritoneal dialysate dwells of 2 hours. Blood and dialysate samples were collected immediately before the session and after each dialysate dwell for determination of urea, creatinine, gentamicin, vancomycin, and β2-microglobulin (β2M) concentrations. Each solute's D/P concentration ratio and peritoneal ClD were calculated.

Measurements and Main Results

The (mean ±SD) 2-hour D/P concentration ratios were 0.78 ± 0.05 (urea), 0.49 ± 0.11 (creatinine), 0.38 ± 0.08 (gentamicin), 0.11 ± 0.06 (vancomycin), and 0.07 ± 0.03 (β2M). Peritoneal ClD values (mL/min of dialysis) were 19.0 ± 2.8 (urea), 12.1 ± 3.5 (creatinine), 8.4 ± 2.8 (gentamicin), 2.7 ± 1.5 (vancomycin), and 1.7 ± 0.8 (β2M). The D/P concentration ratios and peritoneal ClD values for urea, creatinine, and gentamicin were significantly different from vancomycin and β2M (repeated measures ANOVA, p < 0.05). β2-Micro-globulin peritoneal ClD was strongly related to gentamicin peritoneal ClD ( r = 0.96, p < 0.05).

Conclusion

Small molecular weight solutes have significantly greater D/P and peritoneal ClD than middle molecular weight solutes in NIPD. In NIPD, daily peritoneal ClD of β2M is lower than that reported in continuous ambulatory PD. NIPD also results in lower drug ClD than that reported in continuous ambulatory PD studies.

Ultrafiltration Rate as a Dose Surrogate in Pre-Dilution Hemofiltration

For critically ill patients treated with continuous hemofiltration (HF), doses recently shown to improve survival can usually be achieved only in the pre-dilution mode. However, use of the pre-dilution mode results in reduced treatment efficiency, relative to post-dilution at the same ultrafiltration rate (Qf) and blood flow rate (Qb). The objective of this study is to determine the effect of Qf on removal parameters for solutes over a wide molecular weight spectrum in pre-dilution HF. Experiments were performed in an isovolemic, plasma-based pre-dilution system with Qb=200 ml/min. Removal parameters were measured for a 1.2 m2 polysulfone hemofilter (HF1200, Minntech) at Qf values of 20, 40, and 60 ml/min, corresponding to 17, 34 and 51 ml/h/kg for a 70 kg patient (N=3 hemofilters for each Qf). Clearance of urea and creatinine (small solute surrogates) was derived from plasma and ultrafiltrate concentrations at 30, 60, 120, 180, and 240 min while clearance of vancomycin and inulin (middle molecule surrogates) was estimated from changes in plasma concentrations over time. In addition, the sieving coefficient (SC) of vancomycin and inulin was measured at the same time points and at baseline (T=0 min). Our findings indicate pre-dilution had a predictable effect on clearance for each solute, as clearance increased linearly with Qf. Sieving coefficient values were not significantly influenced by either Qf or time and the equivalence of SC values in the middle molecule range suggest attenuation of secondary membrane effects. These data indicate filter performance can largely be preserved despite high Qf values by use of pre-dilution. Moreover, Qf appears to be a reasonable dose surrogate in pre-dilution HF.

Status of Hemodialysis of Drugs in 2002

Hemodialysis is a life-sustaining chronic therapy for individuals with end stage renal disease (ESRD). It is also frequently used for days to weeks for patients with acute renal failure who are awaiting the recovery of their kidneys from the acute toxic or traumatic event. Both populations of patients often require complex pharmacotherapeutic regimens, and it is not uncommon for them to be receiving 10 or more concomitant medications. Optimization of care for these patients is dependent on the selection of the most appropriate drug as well as dosage regimen design, which accounts for the influence of hemodialysis therapy on drug disposition. During the last 10 to 15 years there have been several significant changes in the prescribed dose of dialysis and the composition and size of dialyzers available for use. Furthermore, reuse of dialyzers, which was rare in the early 1980s, is now common; it is employed with over 70% of patients with ESRD. The new synthetic dialyzers, which are now used for over 60% of ESRD patients in the United States, are uniformly associated with dramatic improvements in drug removal; dialysis clearance increases of 3 to 10 fold were common for the few drugs evaluated. The influence of these changes in hemodialysis therapy on drug disposition are discussed in a quantitative fashion, and a conceptual framework for drug therapy regimen decision making is presented. For the majority of the drugs reviewed, however, there were no data in the literature regarding dialyzability with currently available dialyzers. The generation of dialyzability data for old and new pharmacotherapeutic agents with state of the art dialysis procedures is clearly needed.

Dialyzer reuse and mortality risk in patients with end-stage renal disease: a systematic review

BACKGROUND AND AIM

Robust evidence about dialyzer reuse effects on mortality is not available. Our aim was to summarize the evidence for the effectiveness of dialyzer reuse compared to single use in patients with end-stage renal disease.

METHODS

We searched MEDLINE, Embase, CINAHL, SciELO, LILACS, USRDS ADR, universities' theses databases and annals of congress from major nephrology societies. Reviewers performed the study selection and data extraction independently. We used the GRADE approach to assess the quality of the evidence. Mortality was the primary outcome.

RESULTS

A total of 1,190 studies were retrieved, and 14 were included in the review (n = 956,807 patients). The disinfectants used on dialyzer reprocessing were hypochlorite, formaldehyde, glutaraldehyde, and peracetic acid. The evidence available from the studies was of very low quality. Most studies found no differences between groups. In studies with statistically significant differences, these differences were not observed in all groups and they varied by the type of disinfectant, time of observation and treatment unit.

CONCLUSIONS

No significant differences were identified for the superiority or inferiority of dialyzer reuse versus single use when assessing the mortality of patients with end-stage renal disease. Studies of higher quality, including randomized clinical trials, are required to provide conclusive evidence regarding the effectiveness and safety of dialyzer reuse.

Antibiotic pharmacokinetic and pharmacodynamic considerations in patients with kidney disease

Although pharmacokinetic changes occurring in kidney disease are well described, pharmacodynamics in kidney disease is rarely considered. Knowledge of pharmacodynamic principles can allow a clinician to maximize an antibiotic's effectiveness while minimizing adverse effects and antibacterial resistance. An antibiotic's pharmacokinetic and pharmacodynamic profiles should drive dose adjustment decisions in patients with kidney disease. For example, although the half-lives of beta-lactams and aminoglycosides are both prolonged in these patients, beta-lactams exhibit time-dependent antibacterial activity; consequently, maintenance doses should be smaller but given at the same interval. In contrast, aminoglycosides are concentration-dependent antibiotics; hence prolongation of the dosing interval while using larger doses may be advantageous. The timing of drug administration in relation to hemodialysis may be used to achieve specific pharmacodynamic goals. Aminoglycosides given before hemodialysis generate high peaks, whereas subsequent dialytic drug removal minimizes the area under the serum concentration-time curve, potentially decreasing the risk of developing toxicity. Furthermore, new dialysis prescribing patterns (eg, automated peritoneal dialysis, nocturnal dialysis) affect pharmacokinetic and pharmacodynamic parameters in ways not appreciated by clinicians. Studies quantifying the often considerable drug removal with these therapies, as well as efforts to identify pharmacodynamic targets in patients with kidney disease are essential. This paper reviews pharmacodynamic as well as pharmacokinetic issues that should be considered when prescribing antibiotics to treat infections in this population.

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.

Phosphate clearance for bleach reprocessed polysulfone hemodialyzers: effects of electrostatic interactions

Hyperphosphatemia is a major problem for hemodialysis patients due to inadequate phosphate clearance during dialysis. The objective of this study was to understand the effects of bleach reprocessing on phosphate clearance. Data were obtained using Fresenius polysulfone dialyzers exposed to bleach in an in vitro dialysis. The phosphate clearance decreased slightly after a single reprocessing cycle, with more than a 10% reduction observed after 15 cycles. Streaming potential measurements showed that bleach reprocessing caused an increase in the negative charge on the polysulfone membrane, suggesting that the change in phosphate clearance was due to an increase in electrostatic repulsion. The changes in clearance and surface charge were consistent with theoretical calculations of the effects of electrostatic interactions on solute diffusion. These results provide the first evidence that bleach reprocessing can reduce phosphate clearance due to electrostatic interactions between the phosphate anion and negatively charged dialysis membranes.

Improving hollow fiber dialyzer efficiency with a recirculating dialysate system. I: Theory and applicability

The mathematical theory that underlies a novel non-regenerated recirculating dialysate system (RDS) for improving diffusive clearance in hemodialyzers is presented. The theory states the conditions that hemodialyzers must meet to be suitable in RDS optimization. We have verified the applicability of the RDS for several Cuprophan and polysulfone (PS) commercial dialyzers, showing that PS (synthetic) membranes achieve the highest increments of diffusive clearance. A numerical simulation analysis over more general conditions defined by the dimensionless groups of the system demonstrated that the highest diffusive clearance improvements are achieved in dialyzers operating with a low value of the diffusive mass-transfer area/blood flow rate ratio. This study has provided the base for the assessment of the performance of the RDS as compared to several high-efficiency systems, presented in Part II of this work [M. Prado, L. M. Roa, A. Palma, and J. A. Milan, Ann. Biomed. Eng. (2004) submitted].

Dialyser reuse-associated mortality and hospitalization risk in incident Medicare haemodialysis patients, 1998-1999

BACKGROUND

The reuse of haemodialysers has been practiced in the United States for >20 years. We investigated mortality and hospitalization risk according to various reuse practices, testing the hypothesis that outcomes are improved in patients treated with dialysers cleaned with bleach and sterilized with formaldehyde.

METHODS

We studied 1998 and 1999 incident Medicare haemodialysis patients, with follow-up through December 31, 2000 (49 273 patients). Clinical conditions and dialysis therapy were characterized from Medicare claims data. Included were patients who could be linked to a dialysis provider. Demographic characteristics were obtained from the Centers for Medicare and Medicaid Services (CMS) Medical Evidence Report. Mortality information was obtained from the CMS ESRD Death Notification; hospitalization information, from Medicare in-patient claims files. Data on reuse practices were obtained from the annual survey of haemodialysis units conducted by the Centers for Disease Control and Prevention.

RESULTS

Cox regression analyses found no significant differences in mortality or first-hospitalization risk for patients in dialysis units not using bleach as a cleaning agent. Outcomes for patients treated in units using glutaraldehyde did not vary according to use of bleach. In the analysis of first-hospitalization risk, there was no difference according to various germicide/bleach combinations. Overall, there was no significant difference in relative risk of death or in hospitalization risk among the reuse groups (including the no-reuse group).

CONCLUSIONS

For the 1998-1999 period, reuse practices were not associated with a survival advantage or disadvantage. Our findings may reflect the National Kidney Foundation's 1997 introduction of clinical practice guidelines, the intent of which was to bring about increased consistency of care within the dialysis community in the United States.

On-line clearance: a useful tool for monitoring the effectiveness of the reuse procedure

Reprocessing of a dialyzer for repeated use in the same patient is widely practiced. The dialyzer fiber bundle volume (FBV) is monitored as an indicator of the dialyzer's suitability for continued use, with standards for reprocessed dialyzers requiring a FBV of greater than 80% of a new dialyzer to be maintained. We have used on-line measurement of clearance of sodium (OLC module, Fresenius Medical Care, Walnut Creek, CA) to assess small molecule clearance changes during and between treatments for a group of 29 chronic hemodialysis patients who reused high flux polysulfone dialyzers (F80, Fresenius Medical Care, Lexington, MA) reprocessed using citric acid and heat (95 degrees C). Data pertaining to the initial, 5th, 10th, and 15th uses were analyzed and showed that, within a single dialysis session, there was a trend for the clearance to reduce throughout the treatment (p < 0.001). Overall, there was also a trend for clearances to decline with increasing number of reuses (p < 0.008). Changes in FBV occurred, but such changes remained within the guidelines suggested by standards. It is concluded that on-line clearance measurements provide a simple noninvasive method to monitor dialyzer performance over each use and between uses.

In vitro performance of hemodialysis membranes after repeated processing

BACKGROUND

Dialyzers reprocessed with chlorine-based solutions have been associated with increases in ultrafiltration coefficient and middle-molecule removal. Increased pore size has been hypothesized as the mechanism for the latter phenomenon. Dialyzers exposed to Amukin-D (Amuchina Int Inc, Gaithersburg, MD), a chlorine-based reprocessing agent, were evaluated for changes in molecular weight (MW) cutoff and ultrafiltration properties.

METHODS

In vitro MW cutoff studies were performed on Fresenius F-80A (Fresenius, Lexington, MA) and Gambro Polyflux 17 (Gambro, Lakewood, CO) hemodialyzers that were reprocessed 20 times using Amukin-D. Permeability (Uf-A), defined as the area from the ultrafiltered compartment (Uf) compared with the area from the equivalent arterial compartment (A), for dextran across the hemodialyzer membrane was determined after the initial use and after reuses 1, 5, 10, 15, and 20 by using size-exclusion chromatography.

RESULTS

Uf-A for dextran increased approximately 10-fold between hemodialyzer reuses 1 and 5. Thereafter, additional reprocessing did not increase the Uf-A ratio further. MW cutoff increased during these 5 washes and did not change thereafter.

CONCLUSION

Reprocessing with Amukin-D increased the MW cutoff and permeability of both hemodialyzers between reuses 1 and 5, resulting in a greater ultrafiltration rate and greater middle-molecule removal. After reuse 5, there were no further increases in MW cutoff with additional reprocessing in either hemodialyzer. This suggests that reprocessing and storage of each hemodialyzer with Amukin-D affects the permeability of dextran in a nonlinear fashion and to a finite level, such that subsequent reprocessing has no further effect on the MW cutoff of the membrane.

Rapid microtiter plate assay for determination of inulin in human plasma and dialysate

A rapid, sensitive, and reproducible microtiter plate assay for the determination of inulin in human plasma, dialysate, and phosphate-buffered saline (PBS) was developed. Plasma or PBS samples (100 microl aliquots) were prepared by the addition of indole-3-acetic acid (150 microl) and HCl (3 ml) and then briefly vortex-mixed. Samples were then incubated in a 60 degrees C water bath for 20 min, cooled in a room temperature water bath for 40 min, then diluted with deionized, distilled water (DDW; 3 ml) and again vortex-mixed. Finally, an aliquot (200 microl) of each sample was transferred to a 96-well microtiter plate and read spectrophotometrically at 490 nm. Dialysate samples were processed in a similar manner, but required an initial enzymatic step in order to remove dextrose and minimize assay interference. Samples (100 microl aliquots) were prepared by the addition of glucose oxidase/catalase solution (100 microl), briefly vortex mixed, and then incubated in a 37 degrees C water bath for 60 min, samples were then reacted with indole-3-acetic acid as before. Calibration curves were linear over the concentration range of 0.5-4 mg/ml or 0.025-0.4 mg/ml for plasma or PBS and dialysate, respectively; correlation coefficients (r(2)) were >0.99. The intra- and inter-day coefficients of variation in plasma, PBS, and dialysate were <15%. This method is well suited for the rapid analysis of large numbers of samples and is currently being used for in vitro investigations of solute removal by hemodialysis.

Determination of albumin and myoglobin in dialysate and ultrafiltrate samples by high-performance size-exclusion chromatography

A high-performance size-exclusion chromatographic method was developed, validated and implemented for simultaneous and quantitative determination of albumin and myoglobin along with inulin, vancomycin and creatinine in dialysate and ultrafiltrate samples from in vitro hemodialysis experiments. The experimental parameters including mobile phase pH, ionic strength, detection wavelength, flow-rate, injection volume were first optimized for the determination of albumin, myoglobin, inulin, vancomycin and creatinine. The peak height ratio and detection limits of the proteins were then comparatively studied at 210, 254 and 280 nm by UV and diode array detection. The method was further validated by evaluating the linearity, precision and accuracy of the proteins. The assay was finally implemented to the simultaneous and quantitative determination of the proteins in dialysate and ultrafiltrate samples.

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.

Effect of membrane composition and structure on solute removal and biocompatibility in hemodialysis

Effect of membrane composition and structure on solute removal and biocompatibility in hemodialysis. Significant changes in extracorporeal membranes have occurred over the past five decades in which hemodialysis (HD) has been available as a therapy for both acute renal failure (ARF) and end-stage renal disease (ESRD). For cellulosic membranes, these changes have included a reduction in thickness, hydroxyl group substitution, and an increase in pore size. These modifications have resulted in enhanced efficiency of small solute removal, a broader spectrum of overall solute removal, and an attenuation of complement activation in comparison to the thick, unsubstituted cellulosic membranes of low permeability used in the early days of HD therapy. Synthetic membranes, originally developed specifically for use in high-flux HD and hemofiltration, have also evolved during this same time period. In fact, the initially clear distinction between low-flux regenerated cellulosic and high-flux synthetic membranes has become blurred, as membrane formulators have developed products designed to appeal to enthusiasts for both membrane formats. The purpose of this review is to characterize both the solute removal and biocompatibility characteristics of dialysis membranes according to their composition (that is, polymeric makeup) and structure. In this regard, the manner in which membrane biocompatibility interacts with flux is highlighted.

The effects of peracetic acid-hydrogen peroxide reprocessing on dialyzer solute and water permeability

We characterized the effects of peracetic acid-hydrogen peroxide (PAHP) reprocessing on hemodialyzer permeability to water and solutes of various molecular weights and compared these effects within and between dialyzers. An aqueous-based solution containing urea, creatinine, vancomycin, inulin, myoglobin, and albumin was dialyzed for 60 minutes with a hemodialyzer after undergoing 0, 1 , 5, 10, and 15 reuse cycles. Solute clearance, sieving coefficient (SC), and ultrafiltration coefficient were determined. We found that PAHP reprocessing significantly decreased water and solute removal (urea, creatinine, vancomycin, inulin) by cellulose triacetate dialyzers (CT190) over 15 reuses (p<0.05) but did not affect the permeability of polysulfone dialyzers (F80A). Inulin removal was significantly lower for F80A than for CT190 (p<0.0001 and p<0.001 for clearance and SC values, respectively). Myoglobin and albumin removal by CT190 significantly decreased over 15 reuses (p<0.05), but no protein was detected in dialysate or ultrafiltrate at any reuse number for F80A. Reprocessing with PAHP alters dialyzer permeability; the effect is more pronounced for the CT190 dialyzer, but removal of solutes with molecular weight above 1500 Da is significantly lower with F80A dialyzers than with CT190. These changes in dialyzer permeability should be considered when determining optimal reuse procedures.