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      A New Semiempirical Mathematical Model for Prediction of Internal Filtration in Hollow Fiber Hemodialyzers

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          Abstract

          The potential of convective solute transport for blood purification has been widely explored. New techniques (such as hemodiafiltration), based on a combination of diffusion and convection techniques, have been developed. Owing to the internal filtration/backfiltration (IF/BF) phenomenon, high-flux dialysis also relies on a convective component, which, however, is hard to quantify and thus optimize. In this work, we developed a mathematical model designed to supply the clinician with a quantification of the IF/BF fluxes taking place during high-flux dialysis. IF fluxes are predicted based on the machine settings and blood hematocrit/protein concentration. The hydraulic characteristics of commercial dialyzers were derived from bloodless bench tests. Moreover, an in vitro blood test was conducted on a 1.8 m<sup>2</sup> polysulfone dialyzer using an established scintigraphic analysis, for verification of model prediction accuracy. Results of simulations show that the IF/BF rate is sensitive to the blood flow rate and (to a lesser extent) to the dialysate flow rate. Increasing net ultrafiltration rates resulted in parallel increases of direct filtration and simultaneous decreases of BF. IF/BF is rather influenced by blood composition, due to the complex dependence of oncotic pressure and blood viscosity upon hematocrit and plasma protein concentration. Simulation results showed an excellent agreement with the experimental results obtained with scintigraphy, with only a 3% prediction error. With respect to some previous works, this model is simpler in its theoretical approach. It allows implementation into a user-friendly software tool and might be used to predict the convective component in high-flux dialysis and possibly to optimize it.

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          Most cited references 17

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          Effect of increased convective clearance by on-line hemodiafiltration on all cause and cardiovascular mortality in chronic hemodialysis patients – the Dutch CONvective TRAnsport STudy (CONTRAST): rationale and design of a randomised controlled trial [ISRCTN38365125]

          Background The high incidence of cardiovascular disease in patients with end stage renal disease (ESRD) is related to the accumulation of uremic toxins in the middle and large-middle molecular weight range. As online hemodiafiltration (HDF) removes these molecules more effectively than standard hemodialysis (HD), it has been suggested that online HDF improves survival and cardiovascular outcome. Thus far, no conclusive data of HDF on target organ damage and cardiovascular morbidity and mortality are available. Therefore, the CONvective TRAnsport STudy (CONTRAST) has been initiated. Methods CONTRAST is a Dutch multi-center randomised controlled trial. In this trial, approximately 800 chronic hemodialysis patients will be randomised between online HDF and low-flux HD, and followed for three years. The primary endpoint is all cause mortality. The main secondary outcome variables are fatal and non-fatal cardiovascular events. Conclusion The study is designed to provide conclusive evidence whether online HDF leads to a lower mortality and less cardiovascular events as compared to standard HD.
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            Overview of clinical studies in hemodiafiltration: What do we need now ?

            Despite several technical advances in dialysis treatment modalities and a better patient care management including correction of anemia, suppression of secondary hyperparathyroidism, lipid and oxidative stress profiles improvement, the morbidity and the mortality of dialysis patients still remain still elevated. Recent prospective interventional trials in hemodialysis (HEMO study and 4D study) were not very conclusive in showing any significant improvement in dialysis patient outcomes. High-efficiency convective therapies, such as online hemodiafiltration (HDF), are claimed to be superior to conventional diffusive hemodialysis (HD) in improving the dialysis efficacy and in reducing intradialytic morbidity and all-cause and cardiovascular mortality in dialysis patients. The aim of this report was, first, to review the evidence-based facts tending to prove the superiority of HDF vs. HD in terms of efficacy and tolerance, and, second, to analyze the needs to prove the clinical superiority of HDF in terms of reducing morbidity and all-cause mortality of dialysis patients. A systematic review of studies comparing HDF and HD has been performed in the microbiological safety of online production, the solute removal capacity of small and medium-size uremic toxins, and its implication in the reduction of the bioactive dialysis system vs. patient interaction. Major planned randomized international studies comparing HDF and HD in terms of morbidity and mortality have been reviewed. To conclude, it is thought that these long-term prospective randomized trials will clarify on a scientific evidence-based level the putative beneficial role of high-efficiency HDF modalities on dialysis patient outcomes.
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              Enhancement of convective transport by internal filtration in a modified experimental hemodialyzer

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                Author and article information

                Journal
                BPU
                Blood Purif
                10.1159/issn.0253-5068
                Blood Purification
                S. Karger AG
                0253-5068
                1421-9735
                2006
                December 2006
                21 December 2006
                : 24
                : 5-6
                : 555-568
                Affiliations
                aDipartimento di Bioingegneria, Politecnico di Milano and bResearch Division, Estor SpA, Milan, and Departments of cNuclear Medicine and dNephrology, St. Bortolo Hospital, Vicenza, Italy
                Article
                97079 Blood Purif 2006;24:555–568
                10.1159/000097079
                17124424
                © 2006 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 8, Tables: 1, References: 28, Pages: 14
                Product
                Self URI (application/pdf): https://www.karger.com/Article/Pdf/97079
                Categories
                Original Paper

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