Bidirectional Solute Transport in Peritoneal Dialysis

1994 ◽  
Vol 14 (4) ◽  
pp. 327-337 ◽  
Author(s):  
Jacek Waniewski ◽  
Olof Heimbürger ◽  
Min Sun Park ◽  
Andrzej Werynski ◽  
Bengt Lindholm
Keyword(s):  
Peritoneal Dialysis ◽  
Mass Transport ◽  
Solute Transport ◽  
Experimental Studies ◽  
Convective Transport ◽  
Sieving Coefficient ◽  
Middle Molecules ◽  
Bidirectional Transport ◽  
Transport Of Macromolecules ◽  
Reabsorption Rate

Objective Three transport components are involved in solute transport in peritoneal dialysis: diffusion, convective transport, and peritoneal reabsorption of dialysate (fluid and solutes). The relative impact of these components on measurable transport characteristics (dialysateto-plasma concentration ratio, diffusive mass transport coefficient, unidirectional clearances) may depend on the direction of solute transport, that is, from blood to dialysate or vice versa. The application of the bidirectional characteristics for the assessment of fluid and solute transport in peritoneal dialysis is reviewed and evaluated. Data Sources Theoretical analysis as well as computer simulations were applied to discuss available data from our own studies on peritoneal transport as well as from published clinical, experimental, and theoretical studies in the same field. Study Selection Thirty-three relevant clinical and experimental studies as well as theoretical analyses derived from the literature were reviewed. Data Extraction Data were extracted to highlight current controversies in the literature concerning the assessment of peritoneal reabsorption rate based on transport of macromolecules, middle molecules, and small solutes. Results Peritoneal reabsorption is the main component of the transport of macromolecules infused into the peritoneal cavity, and these solutes are currently being used for the assessment of the rate of reabsorption. In contrast, diffusive transport and peritoneal reabsorption cannot be experimentally discriminated for small solutes which exhibit negligible sieving through the membrane in convective transport (i.e., solutes with sieving coefficient equal to 1). For middle molecules each transport component may be of importance and may have an independent impact on bidirectional transport characteristics. Conclusions Middle molecules, with sieving coefficients substantially less than 1, may be applied for estimation of peritoneal reabsorption rate using bidirectional transport characteristics, as apparent diffusive mass transport coefficients or unidirectional clearances. However, an independent measurement of sieving coefficient is necessary for this method.

scholarly journals Physiological Interpretation of Solute Transport Parameters for Peritoneal Dialysis

2001 ◽  
Vol 3 (3) ◽  
pp. 177-190 ◽  
Author(s):  
Jacek Waniewski
Keyword(s):  
Peritoneal Dialysis ◽  
Solute Transport ◽  
Transport Coefficients ◽  
Convective Transport ◽  
Capillary Wall ◽  
Combined Processes ◽  
Transport Parameters ◽  
Lymphatic Absorption ◽  
Penetration Depths ◽  
Good Agreement

A mathematical model for solute distribution within the tissue due to combined processes of diffusion and convective transport through the tissue, through the capillary wall, and by lymphatic absorption, during the exchange of the solute between an organ and external medium is applied for the description of the transport of small, middle and macro — molecules. The analytical solutions of the transport equations for the steady state are described. A parameter that characterizes the concentration profiles, the penetration depth, for combined diffusive and convective transport through the tissue is described as a function of the penetration depths for pure diffusive and pure convective transport components. The equation for the solute transport across the tissue surface is similar to a phenomenological formula widely used for the description of clinical and experimental peritoneal dwell studies. The phenomenological transport parameters may therefore be interpreted using the local transport coefficients for the tissue, the capillary wall, and lymphatic absorption. Theoretical estimations of those parameters are in good agreement with clinical data about solute transport in patients on continuous ambulatory peritoneal dialysis.

Dialysate to blood transport of macromolecules during peritoneal dialysis

1989 ◽  
Vol 257 (6) ◽  
pp. H1851-H1859
Author(s):  
J. K. Leypoldt ◽  
A. S. Chiu ◽  
R. P. Frigon ◽  
L. W. Henderson
Keyword(s):  
Peritoneal Dialysis ◽  
Peritoneal Cavity ◽  
Convective Transport ◽  
Peritoneal Membrane ◽  
Macromolecular Transport ◽  
Diffusive Permeability ◽  
New Zealand White Rabbits ◽  
Blood Transport ◽  
Area Product ◽  
Transport Of Macromolecules

Asymmetrical transport of macromolecules between plasma and the peritoneal cavity results primarily from unidirectional lymphatic removal from the peritoneal cavity. Recent work suggests, however, that macromolecular transport across the peritoneal-plasma barrier via the capillary wall (i.e., the peritoneal membrane) may also be asymmetrical. We determined the diffusive and convective transport properties for creatinine, p-aminohippurate, and neutral dextran (13-40 A) across the peritoneal membrane in the dialysate to blood direction during peritoneal dialysis using isotonic and hypotonic solutions in awake New Zealand White rabbits. Values of the diffusive permeability-area product that were calculated during the isotonic exchange were similar to, yet somewhat smaller than, those previously determined in the blood to dialysate direction for all test solutes. Solute reflection coefficients that were calculated during the hypotonic exchange were variable, yet the resulting mean solute reflection coefficient values for all the test solutes were similar to those previously determined in the blood to dialysate direction. We conclude that asymmetrical peritoneal transport of macromolecules with radii less than 40 A is not due to asymmetrical transport across the peritoneal membrane.

Mass Transport Modelling in Porous Media Using Delay Differential Equations

2006 ◽  
Vol 258-260 ◽  
pp. 586-591
Author(s):  
António Martins ◽  
Paulo Laranjeira ◽  
Madalena Dias ◽  
José Lopes
Keyword(s):  
Porous Media ◽  
Differential Equations ◽  
Mass Transport ◽  
Delay Differential Equations ◽  
Dispersion Model ◽  
Flow Characteristics ◽  
Convective Transport ◽  
Transport Modelling ◽  
Flow Field Characteristics ◽  
Delay Differential

In this work the application of delay differential equations to the modelling of mass transport in porous media, where the convective transport of mass, is presented and discussed. The differences and advantages when compared with the Dispersion Model are highlighted. Using simplified models of the local structure of a porous media, in particular a network model made up by combining two different types of network elements, channels and chambers, the mass transport under transient conditions is described and related to the local geometrical characteristics. The delay differential equations system that describe the flow, arise from the combination of the mass balance equations for both the network elements, and after taking into account their flow characteristics. The solution is obtained using a time marching method, and the results show that the model is capable of describing the qualitative behaviour observed experimentally, allowing the analysis of the influence of the local geometrical and flow field characteristics on the mass transport.

scholarly journals Low-Polydispersity Glucose Polymers as Osmotic Agents for Peritoneal Dialysis

2015 ◽  
Vol 35 (4) ◽  
pp. 428-435
Author(s):  
John K. Leypoldt ◽  
Catherine M. Hoff ◽  
Alp Akonur ◽  
Clifford J. Holmes
Keyword(s):  
Peritoneal Dialysis ◽  
Standard Deviation ◽  
Average Molecular Weight ◽  
Fluid Collection ◽  
Experimental Studies ◽  
Total Carbohydrate ◽  
Glucose Polymer ◽  
New Zealand White Rabbits ◽  
Osmotic Agent ◽  
Osmotic Agents

♦BackgroundPeritoneal dialysis (PD) solutions containing icodextrin as the osmotic agent have advantages during long dwells. The glucose polymers that constitute icodextrin are a heterogeneous mix of molecules with a polydispersity [ratio of weight-average to number-average molecular weight (Mw/Mn)] of approximately 2.6. The present study evaluates whether modifications in the polydispersity and concentration of glucose polymers can improve ultrafiltration (UF) without an associated increase in carbohydrate absorption (CA).♦MethodsComputer simulations using a three-pore model of peritoneal transport during a long dwell in PD patients predict that, in general, compared with 7.5% icodextrin, glucose polymers with a Mw greater than or equal to 7.5 kDa, a polydispersity less than 2.6, and concentrations greater than 7% could achieve higher UF without higher CA. Based on the simulations, we hypothesized that, compared with 7.5% icodextrin, glucose polymers with a Mw of 18 – 19 kDa and a polydispersity of 2.0 at 11% concentration could achieve higher UF without a higher CA. We tested this hypothesis in experimental studies using 8-hour dwells in New Zealand White rabbits. In those studies, UF was measured by complete fluid collection, and CA was measured by subtracting the total carbohydrate in the collected fluid from the carbohydrate initially infused.♦ResultsThe UF was higher with 11% 19 kDa glucose polymer than with 7.5% icodextrin (mean ± standard deviation: 89 ± 31 mL vs 49 ± 15 mL; p = 0.004) without higher CA (5.2 ± 0.9 g vs 5.0 ± 0.9 g, p = 0.7). Similar results were seen with the 11% 18 kDa glucose polymer, which, compared with 7.5% icodextrin, resulted in higher UF (mean ± standard deviation: 96 ± 18 mL vs 66 ± 17 mL; p < 0.001) without higher CA (4.8 ± 0.7 g vs 5.2 ± 0.6 g, p = 0.2).♦ConclusionsThe findings demonstrate that, compared with 7.5% icodextrin solution, long-dwell PD solutions containing 11% glucose polymers with a Mw of 18–19 kDa and a polydispersity of 2.0 can provide higher UF without higher CA.

scholarly journals An intravascular bioartificial pancreas device (iBAP) with silicon nanopore membranes (SNM) for islet encapsulation under convective mass transport

Lab on a Chip ◽  
2017 ◽  
Vol 17 (10) ◽  
pp. 1778-1792 ◽  
Author(s):  
Shang Song ◽  
Charles Blaha ◽  
Willieford Moses ◽  
Jaehyun Park ◽  
Nathan Wright ◽  
...  
Keyword(s):  
Mass Transport ◽  
Cell Density ◽  
Porcine Model ◽  
Convective Transport ◽  
Bioartificial Pancreas ◽  
Islet Encapsulation ◽  
Nanopore Membranes

The SNM-based iBAP demonstrates viability and functionality at clinically relevant cell density and hemocompatibility under convective transport in a porcine model.

scholarly journals IR-Photometry Method for Measuring Glucose Concentration in Peritoneal Dialysis Fluid

2021 ◽  
Vol 24 (4) ◽  
pp. 68-78
Author(s):  
N. M. Zhilo ◽  
M. O. Mikhailov ◽  
E. L. Litinskaia ◽  
K. V. Pozhar
Keyword(s):  
Peritoneal Dialysis ◽  
Optical System ◽  
Glucose Concentration ◽  
Experimental Studies ◽  
The Body ◽  
Artificial Kidney ◽  
Dialysis Fluid ◽  
Glucose Content ◽  
Peritoneal Dialysis Fluid ◽  
Dialysate Solution

Introduction. The transition of glucose into the blood during automated peritoneal dialysis with regeneration of the dialysis fluid leads to a decreased removal of excess fluid from the body and corresponding violations of the water-salt balance.Aim. To consider a system for automatically maintaining the concentration of glucose in the dialysate solution, which provides effective ultrafiltration, as well as to propose a non-contact photometric feedback sensor.Materials and methods. The sensor is an optical system of an IR laser diode with a power of 30 mW and a wavelength of 1600 nm, a photodiode and a quartz tube, through which the test solution circulates. The sensor measures the attenuation of the radiation passing through the solution in a pulsed mode and calculates the glucose concentration. The selected combination of digital filters provides compensation for the noise of the optical system. Experimental studies of the efficiency of the sensor were carried out on peritoneal dialysis solutions with various concentrations of urea, creatinine, uric acid and glucose. At the beginning of the experiments, the sensor was calibrated in a pure solution.Results. It was shown that the developed sensor makes it possible to measure the concentration of glucose in a solution for peritoneal dialysis in the range of 42…220 mmol / l with a relative error of about 15%. The time of one measurement is about 1 minute, which makes it possible to obtain up-to-date information on the current concentration of the solution.Conclusion. This combination of characteristics will allow the sensor to be used in artificial kidney wearable devices for assessing the glucose content in the solution, calculating the time to change the solution and as a feedback sensor in a system for maintaining the concentration of the osmotic agent.

Haemodialysis

2020 ◽  
pp. 4861-4874
Author(s):  
Robert Mactier
Keyword(s):  
Antihypertensive Drugs ◽  
Dry Weight ◽  
Hollow Fibre ◽  
Convective Transport ◽  
Intradialytic Hypotension ◽  
Countercurrent Flow ◽  
Dialysis Dose ◽  
Maintenance Haemodialysis ◽  
Middle Molecules ◽  
Small Solute

Maintenance haemodialysis (HD) is a highly successful treatment for patients with established renal failure and is the default therapy when other renal replacement therapy options are not available. HD uses the countercurrent flow of blood and dialysate through a hollow fibre dialyser to maximize the concentration gradient for diffusive transport of solutes. A hydrostatic gradient across the dialyser membrane induces ultrafiltration (UF) of water and convective transport of solutes by solvent drag. High-flux membranes are standard in most HD centres and are needed to achieve significant removal of middle molecules, of which β‎2-microglobulin (the cause of dialysis-related amyloid) is the prime example. The technique of haemodiafiltration contributes additional convective removal of fluid and better clearance of middle molecules. The need to secure and maintain reliable vascular access is fundamental to achieving adequate dialysis and maintaining health. An arteriovenous fistula is the preferred option, with fewer complications and longer survival than other access options. For historical and pragmatic reasons, HD is normally provided three times per week. Working definitions of adequacy are based on small-solute—typically urea—removal. The optimal dialysis dose has not been well defined, but minimum targets of delivered dose measured by urea reduction ratio and normalized urea clearance (Kt/V) have been established. The main acute complication of HD is intradialytic hypotension, resulting from an imbalance between the UF rate and the rate of vascular refill. Underlying cardiovascular disease, antihypertensive drugs, autonomic dysfunction, shortened dialysis times, large interdialytic fluid gains, and inaccurate dry-weight assessment all predispose. In the longer term, dialysis-related amyloidosis is a disabling, progressive condition caused by the polymerization of β‎2-microglobulin within tendons, synovium, and other tissues.

Monitoring of Long-Term Peritoneal Membrane Function

2001 ◽  
Vol 21 (2) ◽  
pp. 225-232 ◽  
Author(s):  
Simon J. Davies
Keyword(s):  
Peritoneal Dialysis ◽  
Solute Transport ◽  
Water Transport ◽  
Drop Out ◽  
Published Data ◽  
Peritoneal Membrane ◽  
Membrane Function ◽  
Technique Survival ◽  
Ultrafiltration Failure

Objective Peritoneal membrane function influences dialysis prescription and clinical outcome and may change with time on treatment. Increasingly sophisticated tools, ranging from the peritoneal equilibration test (PET) to the standard permeability analysis (SPA) and personal dialysis capacity (PDC) test, are available to the clinician and clinical researcher. These tests allow assessment of a number of aspects of membrane function, including solute transport rates, ultrafiltration capacity, effective reabsorption, transcellular water transport, and permeability to macromolecules. In considering which tests are of greatest value in monitoring long-term membrane function, two criteria were set: those that result in clinically relevant interpatient differences in achieved ultrafiltration or solute clearances, and those that change with time in treatment. Study Selection Clinical validation studies of the PET, SPA, and PDC tests. Studies reporting membrane function using these methods in either long-term (5 years) peritoneal dialysis patients or longitudinal observations (> 2 years). Data Extraction Directly from published data. Additional, previously unpublished analysis of data from the Stoke PD Study. Results Solute transport is the most important parameter. In addition to predicting patient and technique survival at baseline, there is strong evidence that it can increase with time on treatment. Whereas patients with initially high solute transport drop out early from treatment, those with low transport remain longer on treatment, although, over 5 years, a proportion develop increasing transport rates. Ultrafiltration capacity, while being a composite measure of membrane function, is a useful guide for the clinician. Using the PET (2.27% glucose), a net ultrafiltration capacity of < 200 mL is associated with a 50% chance of achieving less than 1 L daily ultrafiltration at the expense of 1.8 hypertonic (3.86%) exchanges in anuric patients. Using a SPA (3.86% glucose), a net ultrafiltration capacity of < 400 mL indicates ultrafiltration failure. While there is circumstantial evidence that, with time on peritoneal dialysis, loss of transcellular water transport might contribute to ultrafiltration failure, none of the current tests is able to demonstrate this unequivocally. Of the other membrane parameters, evidence that interpatient differences are clinically relevant (permeability to macro-molecules), or that they change significantly with time on treatment (effective reabsorption), is lacking. Conclusion A strong case can be made for the regular assessment by clinicians of solute transport and ultrafiltration capacity, a task made simple to achieve using any of the three tools available.

Influence of Dialysis Membranes on the Convective Transport of Middle Molecules

1986 ◽  
Vol 9 (6) ◽  
pp. 421-426 ◽  
Author(s):  
A.L. M. de Francisco ◽  
J. Gordillo ◽  
J.G. Cotorruelo ◽  
L. Ruiz ◽  
M. Gonzalez ◽  
...  
Keyword(s):  
High Performance ◽  
Convective Transport ◽  
Maintenance Hemodialysis ◽  
Gel Chromatography ◽  
High Flux ◽  
Solute Transfer ◽  
Effective Form ◽  
Middle Molecules ◽  
Dialysis Membranes ◽  
Chromatographic Profiles

Ultrafiltrates from 10 patients in chronic maintenance hemodialysis (7 males and 3 females) were obtained simultaneously using three different membranes: cuprophan, polyacrilonitrile and polysulfone. Middle molecules (MM) chromatographic profiles and total MM amount were determined by gel chromatography and high performance liquid chromatography. The convective transport of MM was similar and not membrane related. Hemofiltration, a predominantly convective solute transfer procedure using high flux membranes such as polyacrilonitrile and polysulfone, in which large amounts of fluids have to be ultrafiltered, is an effective form of MM removal.

Animal Models in Peritoneal Dialysis Research: A Need for Consensus

2005 ◽  
Vol 25 (1) ◽  
pp. 16-24 ◽  
Author(s):  
Siska Mortier ◽  
Norbert H. Lameire ◽  
An S. De Vriese
Keyword(s):  
Animal Model ◽  
Peritoneal Dialysis ◽  
Animal Models ◽  
Solute Transport ◽  
Experimental Models ◽  
Research Groups ◽  
Experimental Animals ◽  
Collective Effort ◽  
Study Duration

The development of an adequate animal model for peritoneal research remains an object of concern. In vivo peritoneal dialysis (PD) research is hampered by the large variety of available models that make interpretation of results and comparison of studies very difficult. Species and strain of experimental animals, method of peritoneal access, study duration, measures of solute transport and ultrafiltration, and sampling for histology differ substantially among the various research groups. A collective effort to discuss the shortcomings and merits of the different experimental models may lead to a consensus on a standardized animal model of PD.

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