Renal Function Replacement by Hemodialysis: Forty-Year Anniversary and a Glimpse into the Future at Hand (original) (raw)
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In vitro performance of hemodialysis membranes after repeated processing
American Journal of Kidney Diseases, 2003
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 chlorinebased 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. Am J Kidney Dis 42:561-566.
Challenges and Advances in Hemodialysis Membranes
Advances in Membrane Technologies, 2020
Hemodialysis (HD) is a filtration vital process through which the bloods' toxins and contaminations are removed. However, several immune system activations occur during dialysis, which can result in morbidity and mortality. The efficiency of the currently available blood purification process is hindered, on one hand, by the deficient toxins and middle molecule removal, and on the other hand, with the loss of valuable blood components (such as plasma and its constituents). This chapter offers an overview of the challenges and advances in HD membranes. It includes an introduction of the end stage renal disease, concepts of dialysis, its historical background, and the path through which the configurations and materials evolved. The interactions between membrane polymeric materials with human blood is also discussed. The aspect of material modification is one of the critical areas in HD technology as it targets to solve the most immediate and prevalent HD issue of membrane bioincompatibility. High flux dialysis (HFD) and hemofiltration (HF) are introduced and discussed. This class of membranes was introduced to solve middle molecule (such as β2-microglobulin) related challenges. This chapter highlights the question of why the issue of incompatible materials still exists along with current membrane modifications.
Membrane innovation: closer to native kidneys
Nephrology Dialysis Transplantation, 2018
Modern methods in analytical biochemistry have established that uraemia is associated with the retention of proteins, both in their native state and post-translationally modified, over a wide range of molecular weights up to 60 kDa. Evidence is accumulating that these higher molecular weight retention solutes are important uraemic toxins, and therapies such as online haemodiafiltration (HDF), which enhance their removal, are associated with improved outcomes. However, HDF has limitations regarding cost, clinical implementation and the need for an external source of sterile substitution solution to maintain fluid balance. New membranes that have a solute removal profile more closely approaching that of the glomerular filtration barrier when used for conventional haemodialysis, while at the same time not allowing the passage of clinically significant amounts of beneficial proteins, are needed to address these limitations. Tighter control of the molecular characteristics of the polymers used for membrane fabrication, along with the introduction of additives and improvements in the manufacturing process, has led to membranes with a tighter pore size distribution that allows the use of an increased absolute pore size without leaking substantial amounts of albumin. At the same time, the wall thickness and internal diameter of membrane fibres have been decreased, enhancing convective transport within the dialyser without the need for an external source of substitution solution. These new expanded range membranes provide a solute removal profile more like that of the native kidney than currently available membranes when used in conventional haemodialysis.
Improved outcome for haemodialysis patients treated with high-flux membranes
Nephrology Dialysis Transplantation, 2000
Improved survival for haemodialysis patients with dialyser ultrafiltration coefficients exceeding has been reported for synthetic, high-flux biocompat-15-20 ml/mmHg/h. The improved outcomes for ible membranes. The reported data fail to answer the patients dialysed on these membranes could reflect question whether improved survival is related to an improved biocompatibility [7] or increased clearance effect of enhanced biocompatibility or to increased of uraemic toxins of larger molecular size not cleared clearance of larger molecular species of putative by low-flux dialysers [8-10]. A recent report from the uraemic toxins. A retrospective analysis of 715 patients Italian Dialysis Study Group [11] failed to resolve this treated by continuous haemodialysis for up to 5 years issue despite a study design intended to separate the was undertaken. Low-flux polysulfone dialysis was effects of the biocompatibility and the convective effects used exclusively for 252 patients and 463 patients were of different treatment strategies. exposed for at least 3 months to high-flux polysulfone The currently accepted 'gold standard' for patient dialysis. Patients treated with high-flux dialysis had a survival on haemodialysis treatment was achieved by lower mortality (21 vs 36 per 1000 years) and signific-Charra and co-workers in Tassin, France [12,13] utilizantly lower standardized mortality ratio. For noning long-slow dialysis on cuprophane membranes. diabetic patients the 5-year probability of survival Cost and other imperatives make it unlikely that most was significantly greater for high-flux patients haemodialysis providers could revert to the Tassin (Kaplan-Meier: 92% vs 69%; P=0.036). High-flux model. Although the data from Tassin suggest that dialysis significantly reduced the adverse effect of age much of the benefit of long-slow dialysis relates to on survival. In a Cox proportional hazard model improved control of hypertension an additional factor membrane flux (high vs low) was one of the covariates is likely to be the high solute clearances achieved by with strong predictor value for reduction of death risk long-slow dialysis. Although we can assume that the in non-diabetic patients. Although other variables may Tassin patients had no significant clearance of middle explain the better survival of patients exposed to highand larger molecules, the prolonged dialysis time (24 h flux dialysis the data reported here suggest that higher per week) would be expected to achieve higher mass membrane flux, implying higher clearance of larger transfer for larger small solutes (e.g. 300-1000 Da) molecular species and independent of biocompatibility, than an equivalent Kt/V urea provided by short dialysis is associated with improved survival for haemodialysis sessions. patients. To achieve higher clearance for larger molecular species in a shorter time requires the application of dialyser membranes with higher sieving coefficients for branes less has been focused on the effect of the Correspondence and offprint requests to: M. Nandakumar, National enhanced convective solute transport of these mem-Kidney Foundation, Singapore, 81 Kim Keat Road, Singapore branes. In an attempt to resolve this issue we report 328 836. here a large series of 715 patients dialysed continuously
The Rise of Expanded Hemodialysis
Blood purification, 2017
The low water permeability feature of original cellulosic membranes was considered an advantage in the absence of dialysis equipment that are capable of controlling water removal. The advent of ultrafiltration control systems led to the development and use of high-flux (HF) membranes that allowed improved middle molecule removal including β-2 microglobulin. Further advances in technology allowed better control over the structure and permeability of membranes. Different polymers and improved spinning modalities led to significant advances in solute removal and hemocompatibility. Inner surface modification produced a reduction in membrane thrombogenicity and protein-membrane interaction with a less tendency to fouling and permeability decay. Further evolution in technology led to the development of a new class of membranes referred to as protein-leaking membranes or super-flux or high cutoff (HCO). These membranes are more permeable than conventional HF membranes and allow some passag...
Materials Chemistry and Physics, 2020
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Biocompatible membranes in acute renal failure
1996
Does the choice of dialyser membrane affect outcome in the treatment of acute renal failure (ARF)? Work by many research groups has failed to conclusively prove the benefit of biocompatible membranes on the activation of selected cellular responses. This well designed but under-powered crossover study candidly admits to showing no measureable outcome benefit in the use of biocompatible membranes and concludes that evidence to back the use of such membranes is still under investigation. The large number of exclusions, on clinical grounds, raises doubts about the validity of any conclusions drawn from the study. Also, the use of intermittant haemodialysis (IHD) as the mode of treatment, limits the relevance of the paper to the intensive therapy unit setting. However, the choice of dialyser membrane is of potential concern in all modes of renal replacemnet therapy, both continuous venovenous haemofiltration (CVVH) and IHD, and any demonstrable impact on survival would be very valuable in what is a high mortality group.
Online Hemodiafiltration: A Multipurpose Therapy for Improving Quality of Renal Replacement Therapy
Contributions to Nephrology, 2008
By combining diffusive and enhanced convective clearances, hemodiafiltration (HDF) offers the most efficient and biocompatible renal replacement therapy modality at the present time. HDF increases solute mass transfer and enlarges the molecular weight spectrum of uremic toxins, and reduces the microinflammation profile of dialysis patients. Online (ol) production of substitution fluid by 'cold sterilization' of dialysis fluid gives access to virtually an unlimited amount of sterile and non-pyrogenic solution. ol-HDF provides a multipurpose platform that permits to develop and customize HDF options (HDF, post-, pre-, mixed-, mid-dilution) to patients' needs. With these unique features, ol-HDF should be considered as a dialysis platform permitting to develop new options such as feedback-controlled volemia, automation of priming and restitution and daily treatment schedule. At the present time, ol-HDF offers major options to enhance dialysis efficacy and to improve global care of patients.