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Shao G, Himmelfarb J, Hinds BJ. Strategies for optimizing urea removal to enable portable kidney dialysis: A reappraisal. Artif Organs 2022; 46:997-1011. [PMID: 35383963 DOI: 10.1111/aor.14185] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 12/23/2021] [Accepted: 01/10/2022] [Indexed: 12/01/2022]
Abstract
BACKGROUND Portable hemodialysis has the potential to improve health outcomes and quality of life for patients with kidney failure at reduced costs. Urea removal, required for dialysate regeneration, is a central function of any existing/potential portable dialysis device. Urea in the spent dialysate coexists with non-urea uremic toxins, nutrients, and electrolytes, all of which will interfere with the urea removal efficiency, regardless of whether the underlying urea removal mechanism is based on urease conversion, direct urea adsorption, or oxidation. The aim of the current review is to identify the amount of the most prevalent chemicals being removed during a single dialysis session and evaluate the potential benefits of an urea-selective membrane for portable dialysis. METHODS We have performed a literature search using Web of Science and PubMed databases to find available articles reporting (or be able to calculate from blood plasma concentration) > 5 mg of individually quantified solutes removed during thrice-weekly hemodialysis sessions. If multiple reports of the same solute were available, the reported values were averaged, and the geometric mean of standard deviations was taken. Further critical literature analysis of reported dialysate regeneration methods was performed using Web of Science and PubMed databases. RESULTS On average, 46.0 g uremic retention solutes are removed in a single conventional dialysis session, out of which urea is only 23.6 g. For both urease- and sorbent-based urea removal mechanisms, amino acids, with 7.7 g removal per session, could potentially interfere with urea removal efficiency. Additionally for the oxidation-based urea removal system, plentiful nutrients such as glucose (24.0 g) will interfere with urea removal by competition. Using a nanofiltration membrane between dialysate and oxidation unit with a molecular weight cutoff (MWCO) of ~200 Da, 67.6 g of non-electrolyte species will be removed in a single dialysis session, out of which 44.0 g are non-urea molecules. If the membrane MWCO is further decreased to 120 Da, the mass of non-electrolyte non-urea species will drop to 9.3 g. Reverse osmosis membranes have been shown to be both effective at blocking the transport of non-urea species (creatinine for example with ~90% rejection ratio), and permissive for urea transport (~20% rejection ratio), making them a promising urea selective membrane to increase the efficiency of the oxidative urea removal system. CONCLUSIONS Compiled are quantified solute removal amounts greater than 5 mg per session during conventional hemodialysis treatments, to act as a guide for portable dialysis system design. Analysis shows that multiple chemical species in the dialysate interfere with all proposed portable urea removal systems. This suggests the need for an additional protective dialysate loop coupled to urea removal system and an urea-selective membrane.
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Affiliation(s)
- Guozheng Shao
- Department of Materials Science & Engineering, University of Washington, Seattle, Washington, USA.,Center for Dialysis Innovation, University of Washington, Seattle, Washington, USA
| | - Jonathan Himmelfarb
- Center for Dialysis Innovation, University of Washington, Seattle, Washington, USA.,Division of Nephrology, Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Bruce J Hinds
- Department of Materials Science & Engineering, University of Washington, Seattle, Washington, USA.,Center for Dialysis Innovation, University of Washington, Seattle, Washington, USA
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Gomez M, Maduell F. A unidimensional diffusion model applied to uremic toxin kinetics in haemodiafiltration treatments. MATHEMATICAL MEDICINE AND BIOLOGY-A JOURNAL OF THE IMA 2019; 36:223-240. [PMID: 29912346 DOI: 10.1093/imammb/dqy008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 05/21/2018] [Indexed: 11/14/2022]
Abstract
Kinetic modelling in haemodialysis is usually based upon the resolution of volume-defined compartment models. The interaction among these compartments is described by purely diffusive processes. In this paper we present an alternative kinetic model for uremic toxins in post-dilutional haemodiafiltration treatments by means of a unidimensional diffusion equation. A wide range of solutes such as urea, creatinine, $\beta _{2}$-microglobulin, myoglobin and prolactin were studied by imposing appropriate boundary and initial conditions in a virtual [0,1] domain. The diffusivity along the domain and the extraction rate at the dialyser are the kinetic parameters which were fitted by least-squares for every studied solute. The accuracy of the presented volumeless model as well as the behavior of the proposed kinetic parameters could be an alternative to the compartment description for a variety of molecular weight uremic toxins undergoing different treatment configurations.
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Affiliation(s)
- Miquel Gomez
- Laboratori Experimental de Nefrologia i Trasplantament (LENIT), Fundació Clínic per a la Recerca Biomèdica (FCRB), Hospital Clínic de Barcelona, Spain
| | - Francisco Maduell
- Department of Nephrology and Renal Transplantation, Institut Clínic de Nefrologia i Urologia (ICNU), Hospital Clínic de Barcelona, Villaroel, Barcelona, Spain
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Kirkman DL, Scott M, Kidd J, Macdonald JH. The effects of intradialytic exercise on hemodialysis adequacy: A systematic review. Semin Dial 2019; 32:368-378. [PMID: 30968465 DOI: 10.1111/sdi.12785] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Dialysis adequacy is an independent predictor of high mortality rates in hemodialysis patients. Intradialytic exercise is a potential strategy to increase uremic solute removal by increasing blood flow to low perfusion tissue beds. The purpose of this review is to establish the efficacy of intradialytic exercise for hemodialysis adequacy. Additionally, this review aims to provide practical information to aid health care professionals implement intradialytic exercise for dialysis adequacy. Database and hand searches identified 15 published interventional studies that implemented intradialytic exercise for dialysis adequacy as a primary outcome measure in adult maintenance hemodialysis patients. Data pertaining to dialytic solute clearance of urea, creatinine, beta2 microglobulin, phosphate, and potassium were extracted. Mean differences, normalized to percentages, and effect sizes were calculated and reported. The current data pertaining to the use of intradialytic exercise for improving dialysis adequacy in terms of Kt/Vurea or small molecule uremic toxin clearance are equivocal. Limited data showed that intradialytic exercise has no effect middle molecule toxin (beta2 - microglobulin) clearance. Intradialytic exercise favored increased phosphate removal showing medium to large effects for reduced serum concentrations, reduced rebound and increased clearance. In summary, supervised light to moderate intradialytic aerobic cycling appears to be beneficial for increasing phosphate removal and may be an adjunct therapy for patients failing to meet clinical phosphate targets. Further work is required to establish the effect of intradialytic exercise on Kt/Vurea and other middle molecule and protein bound solutes. Research aimed at establishing the most effective exercise prescription for improved solute clearance is warranted.
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Affiliation(s)
- Danielle L Kirkman
- Department of Kinesiology and Health Sciences, Virginia Commonwealth University, Richmond, Virginia
| | - Matthew Scott
- Department of Kinesiology and Health Sciences, Virginia Commonwealth University, Richmond, Virginia
| | - Jason Kidd
- Department of Internal Medicine, Division of Nephrology, Virginia Commonwealth University, Richmond, Virginia
| | - Jamie H Macdonald
- School of Sport Health and Exercise Sciences, Bangor University, Wales, UK
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Leypoldt JK, Storr M, Agar BU, Boschetti-de-Fierro A, Bernardo AA, Kirsch AH, Rosenkranz AR, Krieter DH, Krause B. Intradialytic kinetics of middle molecules during hemodialysis and hemodiafiltration. Nephrol Dial Transplant 2018; 34:870-877. [DOI: 10.1093/ndt/gfy304] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2018] [Indexed: 11/14/2022] Open
Affiliation(s)
| | | | - Baris U Agar
- Baxter Healthcare Corporation, Deerfield, IL, USA
| | | | | | - Alexander H Kirsch
- Clinical Division of Nephrology, Medical University of Graz, Graz, Austria
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Variable-Volume Kinetic Model to Estimate Absolute Blood Volume in Patients on Dialysis Using Dialysate Dilution. ASAIO J 2018; 64:77-85. [PMID: 28742531 DOI: 10.1097/mat.0000000000000608] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Long- and short-term adverse outcomes in hemodialysis (HD) have been associated with intradialytic hypotension, a common HD complication and significant cause of morbidity. It has been suggested that knowledge of absolute blood volume (ABV) could be used to significantly improve treatment outcomes. Different dilution-based protocols have been proposed for estimating ABV, all relying on the classic mono-exponential back-extrapolation algorithm (BEXP). In this paper, we introduce a dialysate dilution protocol and an estimation algorithm based on a variable-volume, two-compartment, intravascular blood water content kinetic model (VVKM). We compare ABV estimates derived using the two algorithms in a dialysate dilution study including three arterio-venous (AV) and three central-venous (CV) access patients, and multiple bolus injection tests (3-5) within each of several (2-6) HD treatments. The distribution of differences between ABV estimated from the two methods showed negligible systematic difference between the mean values of ABVs estimated from the BEXP and VVKM algorithms, however, the VVKM estimates were 53% and 42% more precise for the CV and AV patients, respectively. Good agreement was observed between measured and VVKM-estimated blood water concentration with the root-mean-square error (RMSE) less than 0.02 kg/kg (2%) and 0.03 kg/kg (3%) for AV and CV patients, respectively. The dilution protocol and the new VVKM-based estimation algorithm offer a noninvasive, inexpensive, safe, and practical approach for ABV estimation in routine HD settings.
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Bianchi C, Lanzarone E, Casagrande G, Costantino ML. A Bayesian approach for the identification of patient-specific parameters in a dialysis kinetic model. Stat Methods Med Res 2018; 28:2069-2095. [PMID: 29325494 DOI: 10.1177/0962280217745572] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Hemodialysis is the most common therapy to treat renal insufficiency. However, notwithstanding the recent improvements, hemodialysis is still associated with a non-negligible rate of comorbidities, which could be reduced by customizing the treatment. Many differential compartment models have been developed to describe the mass balance of blood electrolytes and catabolites during hemodialysis, with the goal of improving and controlling hemodialysis sessions. However, these models often refer to an average uremic patient, while on the contrary the clinical need for customization requires patient-specific models. In this work, we assume that the customization can be obtained by means of patient-specific model parameters. We propose and validate a Bayesian approach to estimate the patient-specific parameters of a multi-compartment model, and to predict the single patient's response to the treatment, in order to prevent intra-dialysis complications. The likelihood function is obtained by means of a discretized version of the multi-compartment model, where the discretization is in terms of a Runge-Kutta method to guarantee convergence, and the posterior densities of model parameters are obtained through Markov Chain Monte Carlo simulation. Results show fair estimations and the applicability in the clinical practice.
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Affiliation(s)
- Camilla Bianchi
- 1 Department of Chemistry, Materials and Chemical Engineering, Politecnico di Milano, Milan, Italy
| | - Ettore Lanzarone
- 2 Istituto di Matematica Applicata e Tecnologie Informatiche (IMATI), Consiglio Nazionale delle Ricerche (CNR), Milan, Italy
| | - Giustina Casagrande
- 1 Department of Chemistry, Materials and Chemical Engineering, Politecnico di Milano, Milan, Italy
| | - Maria Laura Costantino
- 1 Department of Chemistry, Materials and Chemical Engineering, Politecnico di Milano, Milan, Italy
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7
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Sirich TL. Obstacles to reducing plasma levels of uremic solutes by hemodialysis. Semin Dial 2017; 30:403-408. [DOI: 10.1111/sdi.12609] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tammy L. Sirich
- The Department of Medicine; VA Palo Alto Health Care System and Stanford University; Palo Alto CA USA
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Carlson N, Mortensen OH, Axelsen M, Pedersen RS, Heaf JG. Clearance of Sclerostin, Osteocalcin, Fibroblast Growth Factor 23, and Osteoprotegerin by Dialysis. Blood Purif 2017; 44:122-128. [PMID: 28554171 DOI: 10.1159/000465513] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 02/24/2017] [Indexed: 11/19/2022]
Abstract
INTRODUCTION Fibroblast growth factor (FGF23), sclerostin, osteocalcin, and osteoprotegerin are important factors that control mineral bone metabolism. End-stage renal disease is associated with the pronounced dysregulation of mineral bone metabolism; however, the impact and clearance of mineral bone metabolism factors during dialysis remain largely undescribed. METHODS In a cross-sectional study, 10 chronic hemodialysis patients were treated with hemodialysis for 8 h using a high-flux filter and a dialysate bath of 50% calculated total body water continuously recycled at a rate of 500 mL/min. Plasma and dialysate concentrations of FGF23, sclerostin, osteoprotegerin, and osteocalcin were measured at 1, 2, 4, 6, and 8 h permitting the estimation of dialysis clearance. RESULTS Clearance of FGF23 was 7.7 mL/min, of sclerostin was 7.6 mL/min, of osteoprotegerin was 1.2 mL/min, and of osteocalcin was 19.7 mL/min. Clearance of FGF23 was correlated to sclerostin and osteoprotegerin clearance and also to the ultrafiltration rate. Although, osteocalcin blood concentrations decreased during dialysis, they rebounded within 6 h. Overall, no significant changes in blood concentrations of the measure mineral bone metabolism factors were observed. CONCLUSIONS The intradialytic clearance of osteocalcin, FGF23, sclerostin, and osteoprotegerin occurs; however, only clearance of FGF23 is directly correlated with the ultrafiltration rate. The effects of dialytic clearance on mineral bone metabolism are, however, uncertain and intradialytic plasma concentrations of the studied substrates remained largely unchanged.
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Affiliation(s)
- Nicholas Carlson
- Department of Nephrology, Herlev Hospital, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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9
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Schneditz D, Niemczyk S, Sauseng N, Bachler I, Zierler E, Lackner HK, Hafner-Giessauf H. Osmotic and Hemodynamic Effects of Hypertonic Glucose During Hemodialysis. ASAIO J 2017; 63:824-831. [PMID: 28338477 DOI: 10.1097/mat.0000000000000574] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
It was the purpose to quantify the hemodynamic effects of a bolus of hypertonic glucose injected into the extracorporeal system in a group of stable and nondiabetic patients during hemodialysis (HD). Glucose and electrolytes were measured in frequent intervals. Arterial blood pressures and heart rates were continuously recorded by noninvasive vascular unloading technique. Beat-to-beat stroke volume, cardiac output, and total peripheral resistance were determined by Modelflow method. Relative blood volumes were continuously measured by ultrasonic and optical means. Eight patients were studied in two treatments. Although arterial pressures and heart rates remained stable, stroke volume and cardiac output transiently increased above (19.2 ± 12.3%) and total peripheral resistance dropped below baseline (18.2 ± 8.6%) by a comparable magnitude. Relative blood volume transiently increased above baseline at 100% (104.9 ± 1.0%). Glucose concentrations were significantly related to relative blood volumes (r = 0.86, p < 0.001). In spite of a substantial increase in blood volume, a bolus of hypertonic glucose does not increase arterial pressures in nondiabetic patients because of concomitant vasodilatation. The relative increase in blood volume quantified by noninvasive HD technology follows the course of glucose and could be used as a surrogate to characterize patients with regard to their glucose metabolism during HD.
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Affiliation(s)
- Daniel Schneditz
- From the *Institute of Physiology, Medical University of Graz, Graz, Austria; †Department of Internal Diseases, Military Institute of Medicine, Warsaw, Poland; and ‡Division of Nephrology, Department of Internal Medicine, Medical University of Graz, Graz, Austria
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10
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Seminars in Dialysis: The 100 Most Highly Cited Papers. Semin Dial 2016; 29:518-520. [PMID: 27774673 DOI: 10.1111/sdi.12536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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11
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Kromke M, Palomino-Schätzlein M, Mayer H, Pfeffer S, Pineda-Lucena A, Luy B, Hausberg M, Muhle-Goll C. Profiling human blood serum metabolites by nuclear magnetic resonance spectroscopy: a comprehensive tool for the evaluation of hemodialysis efficiency. Transl Res 2016; 171:71-82.e1-9. [PMID: 26924041 DOI: 10.1016/j.trsl.2016.02.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 01/28/2016] [Accepted: 02/02/2016] [Indexed: 10/22/2022]
Abstract
Hemodialysis remains the standard therapy to treat patients affected with end-stage renal disease by removing metabolites accumulated in blood plasma. The efficiency of hemodialysis is mainly monitored by urea clearance, which is routinely checked in clinical laboratory practice. However, there is mounting evidence that the clearance behavior of selected single metabolites is not sufficient to predict long-term outcome of treatment. To address this problem, we evaluated the potential of nuclear magnetic resonance spectroscopy for monitoring hemodialysis efficiency by comprehensive profiling of blood serum metabolites. We carried out a pilot study with a cohort of end-stage chronic kidney disease patients (n = 29), analyzing their serum prior and immediately after hemodialysis. To account for supposed variability in the accumulation of metabolites and efficiency of hemodialysis, patients' blood sera were repeatedly collected over a period of several months. Our results revealed that the metabolic profile in terms of concentrations varied considerably between patients but was comparably constant on the patient's level over the period of 4 months. Interestingly, also the individual clearance of the metabolites was characteristic for each patient. Thus, it is conceivable that the observed patient-dependent clearance patterns reflect to some extent the patients' long-term perspectives. We conclude that nuclear magnetic resonance spectroscopy is an optimal tool to complement traditional clinical methods based on a single variable, providing comprehensive and much more global information, which is crucial for patient evaluation and the development of improved treatments of kidney failure.
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Affiliation(s)
- Marika Kromke
- Karlsruhe Institute of Technology, Institute of Organic Chemistry, Karlsruhe, Germany
| | - Martina Palomino-Schätzlein
- Karlsruhe Institute of Technology, Institute of Organic Chemistry, Karlsruhe, Germany; Centro de Investigación Príncipe Felipe, Valencia, Spain
| | - Horst Mayer
- Städtisches Klinikum Karlsruhe, Karlsruhe, Germany
| | | | - Antonio Pineda-Lucena
- Centro de Investigación Príncipe Felipe, Valencia, Spain; Instituto de Investigación Sanitaria La Fe, Valencia, Spain
| | - Burkhard Luy
- Karlsruhe Institute of Technology, Institute of Organic Chemistry, Karlsruhe, Germany; Karlsruhe Institute of Technology, Institute for Biological Interfaces 4, Karlsruhe, Germany
| | | | - Claudia Muhle-Goll
- Karlsruhe Institute of Technology, Institute of Organic Chemistry, Karlsruhe, Germany; Karlsruhe Institute of Technology, Institute for Biological Interfaces 4, Karlsruhe, Germany.
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Kron S, Schneditz D, Leimbach T, Aign S, Kron J. Vascular refilling is independent of volume overload in hemodialysis with moderate ultrafiltration requirements. Hemodial Int 2016; 20:484-91. [DOI: 10.1111/hdi.12417] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Susanne Kron
- Department of Nephrology; Charité Universitätsmedizin Berlin; Berlin Germany
| | - Daniel Schneditz
- Institute of Physiology, Medical University of Graz; Graz Austria
| | - Til Leimbach
- KfH Kidney Center Berlin-Köpenick; Berlin Germany
| | - Sabine Aign
- KfH Kidney Center Berlin-Köpenick; Berlin Germany
| | - Joachim Kron
- KfH Kidney Center Berlin-Köpenick; Berlin Germany
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Protein-Bound Uremic Toxin Profiling as a Tool to Optimize Hemodialysis. PLoS One 2016; 11:e0147159. [PMID: 26799394 PMCID: PMC4723122 DOI: 10.1371/journal.pone.0147159] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 12/29/2015] [Indexed: 12/20/2022] Open
Abstract
Aim We studied various hemodialysis strategies for the removal of protein-bound solutes, which are associated with cardiovascular damage. Methods This study included 10 patients on standard (3x4h/week) high-flux hemodialysis. Blood was collected at the dialyzer inlet and outlet at several time points during a midweek session. Total and free concentration of several protein-bound solutes was determined as well as urea concentration. Per solute, a two-compartment kinetic model was fitted to the measured concentrations, estimating plasmatic volume (V1), total distribution volume (Vtot) and intercompartment clearance (K21). This calibrated model was then used to calculate which hemodialysis strategy offers optimal removal. Our own in vivo data, with the strategy variables entered into the mathematical simulations, was then validated against independent data from two other clinical studies. Results Dialyzer clearance K, V1 and Vtot correlated inversely with percentage of protein binding. All Ks were different from each other. Of all protein-bound solutes, K21was 2.7–5.3 times lower than that of urea. Longer and/or more frequent dialysis that processed the same amount of blood per week as standard 3x4h dialysis at 300mL/min blood flow showed no difference in removal of strongly bound solutes. However, longer and/or more frequent dialysis strategies that processed more blood per week than standard dialysis were markedly more adequate. These conclusions were successfully validated. Conclusion When blood and dialysate flow per unit of time and type of hemodialyzer are kept the same, increasing the amount of processed blood per week by increasing frequency and/or duration of the sessions distinctly increases removal.
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Ismael S, Savalle M, Trivin C, Gillaizeau F, D'Auzac C, Faisy C. The consequences of sudden fluid shifts on body composition in critically ill patients. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2014; 18:R49. [PMID: 24666889 PMCID: PMC4057272 DOI: 10.1186/cc13794] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 03/13/2014] [Indexed: 12/31/2022]
Abstract
INTRODUCTION Estimation of body composition as fat-free mass (FFM) is subjected to many variations caused by injury and stress conditions in the intensive care unit (ICU). Body cell mass (BCM), the metabolically active part of FFM, is reported to be more specifically correlated to changes in nutritional status. Bedside estimation of BCM could help to provide more valuable markers of nutritional status and may promote understanding of metabolic consequences of energy deficit in the ICU patients. We aimed to quantify BCM, water compartments and FFM by methods usable at the bedside for evaluating the impact of sudden and massive fluid shifts on body composition in ICU patients. METHODS We conducted a prospective experimental study over an 6 month-period in a 18-bed ICU. Body composition of 31 consecutive hemodynamically stable patients requiring acute renal replacement therapy for fluid overload (ultrafiltration ≥5% body weight) was investigated before and after the hemodialysis session. Intra-(ICW) and extracellular (ECW) water volumes were calculated from the raw values of the low- and high-frequency resistances measured by multi-frequency bioelectrical impedance. BCM was assessed by a calculated method recently developed for ICU patients. FFM was derived from BCM and ECW. RESULTS Intradialytic weight loss was 3.8 ± 0.8 kg. Percentage changes of ECW (-7.99 ± 4.60%) and of ICW (-7.63 ± 5.11%) were similar, resulting ECW/ICW ratio constant (1.26 ± 0.20). The fall of FFM (-2.24 ± 1.56 kg, -4.43 ± 2.65%) was less pronounced than the decrease of ECW (P < 0.001) or ICW (P < 0.001). Intradialytic variation of BCM was clinically negligible (-0.38 ± 0.93 kg, -1.56 ± 3.94%) and was significantly less than FFM (P < 0.001). CONCLUSIONS BCM estimation is less driven by sudden massive fluid shifts than FMM. Assessment of BCM should be preferred to FFM when severe hydration disturbances are present in ICU patients.
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Kirkman DL, Roberts LD, Kelm M, Wagner J, Jibani MM, Macdonald JH. Interaction between intradialytic exercise and hemodialysis adequacy. Am J Nephrol 2013; 38:475-82. [PMID: 24296748 DOI: 10.1159/000356340] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 10/10/2013] [Indexed: 11/19/2022]
Abstract
BACKGROUND/AIMS According to mathematical modeling, intradialytic exercise of sufficient intensity and duration implemented in the second half of dialysis should be as efficacious as increasing dialysis time for dialysis adequacy. This assumption has not been tested in vivo. METHODS In this controlled trial, 11 hemodialysis (HD) patients (mean (SD) age 56 (13) years) were recruited. Each patient completed three trial arms in a randomized order: routine care (CONT), increased HD time of 30 min (TIME), and intradialytic exercise (EXER), 60 min of cycling at 90% of the lactate threshold in the last 90 min of HD. The primary outcome was eKt/Vurea. Secondary outcomes included reduction and rebound ratios of urea, creatinine, phosphate and β2-microglobulin. Outcomes were calculated from blood sampling collected pre-, post- and 30 min post-HD and confirmed with dialysate sampling. RESULTS Exercise was not as efficacious as increased HD time for eKt/Vurea (EXER vs. CONT, mean change (95% CI): 0.03 (-0.05 to 0.12); TIME vs. CONT: 0.15 (0.05-0.26)). Exercise was less efficacious at improving reduction ratios of urea and creatinine. However, exercise was more efficacious than increased dialysis time for phosphate reduction ratio (EXER vs. CONT: 8.6% (0.5-16.7); TIME vs. CONT: 5.0% (-1.0 to 11.1)). CONCLUSION This study utilized a rigorously controlled in vivo design to test mathematical models and assumptions regarding dialysis adequacy. Intradialytic exercise towards the end of HD cannot replace the prescription of increased HD time for dialysis adequacy, but may be an adjunctive therapy for serum phosphate control.
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Affiliation(s)
- Danielle L Kirkman
- College of Health and Behavioural Sciences, Bangor University, Bangor, UK
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17
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Azar AT. Adaptive network based on fuzzy inference system for equilibrated urea concentration prediction. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2013; 111:578-591. [PMID: 23806679 DOI: 10.1016/j.cmpb.2013.05.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Revised: 04/05/2013] [Accepted: 05/23/2013] [Indexed: 06/02/2023]
Abstract
Post-dialysis urea rebound (PDUR) has been attributed mostly to redistribution of urea from different compartments, which is determined by variations in regional blood flows and transcellular urea mass transfer coefficients. PDUR occurs after 30-90min of short or standard hemodialysis (HD) sessions and after 60min in long 8-h HD sessions, which is inconvenient. This paper presents adaptive network based on fuzzy inference system (ANFIS) for predicting intradialytic (Cint) and post-dialysis urea concentrations (Cpost) in order to predict the equilibrated (Ceq) urea concentrations without any blood sampling from dialysis patients. The accuracy of the developed system was prospectively compared with other traditional methods for predicting equilibrated urea (Ceq), post dialysis urea rebound (PDUR) and equilibrated dialysis dose (eKt/V). This comparison is done based on root mean squares error (RMSE), normalized mean square error (NRMSE), and mean absolute percentage error (MAPE). The ANFIS predictor for Ceq achieved mean RMSE values of 0.3654 and 0.4920 for training and testing, respectively. The statistical analysis demonstrated that there is no statistically significant difference found between the predicted and the measured values. The percentage of MAE and RMSE for testing phase is 0.63% and 0.96%, respectively.
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Affiliation(s)
- Ahmad Taher Azar
- Faculty of computers and Information, Benha university, Benha, Egypt.
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Toward the optimal dose metric in continuous renal replacement therapy. Int J Artif Organs 2013; 35:413-24. [PMID: 22466995 DOI: 10.5301/ijao.5000041] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/15/2011] [Indexed: 11/20/2022]
Abstract
PURPOSE There is no consensus on the optimal method to measure delivered dialysis dose in patients with acute kidney injury (AKI). The use of direct dialysate-side quantification of dose in preference to the use of formal blood-based urea kinetic modeling and simplified blood urea nitrogen (BUN) methods has been recommended for dose assessment in critically-ill patients with AKI. We evaluate six different blood-side and dialysate-side methods for dose quantification. METHODS We examined data from 52 critically-ill patients with AKI requiring dialysis. All patients were treated with pre-dilution CVVHDF and regional citrate anticoagulation. Delivered dose was calculated using blood-side and dialysis-side kinetics. Filter function was assessed during the entire course of therapy by calculating BUN to dialysis fluid urea nitrogen (FUN) ratios q/12 hours. RESULTS Median daily treatment time was 1,413 min (1,260-1,440). The median observed effluent volume per treatment was 2,355 mL/h (2,060-2,863) (p<0.001). Urea mass removal rate was 13.0 ± 7.6 mg/min. Both EKR (r²=0.250; p<0.001) and KD (r²=0.409; p<0.001) showed a good correlation with actual solute removal. EKR and KD presented a decline in their values that was related to the decrease in filter function assessed by the FUN/BUN ratio. CONCLUSIONS Effluent rate (mL/kg/h) can only empirically provide an estimated of dose in CRRT. For clinical practice, we recommend that the delivered dose should be measured and expressed as KD. EKR also constitutes a good method for dose comparisons over time and across modalities.
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Fridolin I, Karai D, Kostin S, Ubar R. Accurate Dialysis Dose Evaluation and Extrapolation Algorithms During Online Optical Dialysis Monitoring. IEEE Trans Biomed Eng 2013; 60:1371-7. [DOI: 10.1109/tbme.2012.2234458] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Azar AT, Yashiro M, Schneditz D, Roa LM. Double Pool Urea Kinetic Modeling. MODELLING AND CONTROL OF DIALYSIS SYSTEMS 2013. [DOI: 10.1007/978-3-642-27458-9_13] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Pellizzaro CO, Thomé FS, Veronese FV. Effect of Peripheral and Respiratory Muscle Training on the Functional Capacity of Hemodialysis Patients. Ren Fail 2012. [DOI: 10.3109/0886022x.2012.745727] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Eloot S, Van Biesen W, Vanholder R. A Sad but Forgotten Truth: The Story of Slow-Moving Solutes in Fast Hemodialysis. Semin Dial 2012; 25:505-9. [DOI: 10.1111/j.1525-139x.2012.01107.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Electrocardiographic P-wave characteristics in patients with end-stage renal disease: P-index and interatrial block. Int Urol Nephrol 2012; 45:511-7. [DOI: 10.1007/s11255-012-0187-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 04/20/2012] [Indexed: 11/25/2022]
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Abstract
Adequate dialysis is difficult to define because we have not identified the toxic solutes that contribute most to uremic illness. Dialysis prescriptions therefore cannot be adjusted to control the levels of these solutes. The current solution to this problem is to define an adequate dose of dialysis on the basis of fraction of urea removed from the body. This has provided a practical guide to treatment as the dialysis population has grown over the past 25 years. Indeed, a lower limit to Kt/V(urea) (or the related urea reduction ratio) is now established as a quality indicator by the Centers for Medicare and Medicaid for chronic hemodialysis patients in the United States. For the present, this urea-based standard provides a useful tool to avoid grossly inadequate dialysis. Dialysis dosing, however, based on measurement of a single, relatively nontoxic solute can provide only a very limited guide toward improved treatment. Prescriptions which have similar effects on the index solute can have widely different effects on other solutes. The dose concept discourages attempts to increase the removal of such solutes independent of the index solute. The dose concept further assumes that important solutes are produced at a constant rate relative to body size, and discourages attempts to augment dialysis treatment by reducing solute production. Identification of toxic solutes would provide a more rational basis for the prescription of dialysis and ultimately for improved treatment of patients with renal failure.
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Affiliation(s)
- Timothy W. Meyer
- Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, California
| | - Tammy L. Sirich
- Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, California
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Lacson E, Brunelli SM. Hemodialysis Treatment Time: A Fresh Perspective. Clin J Am Soc Nephrol 2011; 6:2522-30. [DOI: 10.2215/cjn.00970211] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Hayes W, Hothi DK. Intradialytic hypotension. Pediatr Nephrol 2011; 26:867-79. [PMID: 20967553 DOI: 10.1007/s00467-010-1661-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Revised: 09/09/2010] [Accepted: 09/10/2010] [Indexed: 11/27/2022]
Abstract
Intradialytic hypotension (IDH) is common in children during conventional, 4 hour haemodialysis (HD) sessions. The declining blood pressure (BP) was originally believed to be caused by ultrafiltration (UF) and priming of the HD circuit, however emerging data now supports a multifactorial aetiology. Therefore strategies to improve haemodynamic stability need to be diverse and address specific patient requirements or risks. In the treatment of IDH immediate action is required to stop or reduce the severity of symptoms that may precede or follow. Typically UF is slowed or stopped, a fluid bolus is given and in resistant cases the HD session is prematurely discontinued. Patients complete their treatment under-dialysed and volume expanded. Chronically, repeated episodes of IDH cause devastating, multi-system morbidity with an increased risk of mortality. This had provided the impetus for more haemodynamically friendly dialysis prescriptions that attenuate the risk of IDH. During pediatric HD several preventative strategies have been tested but with variable success. Of these, dialysate sodium profiling, UF guided by relative blood volume (RBV) algorithms, cooling and intradialytic mannitol appear to be the most effective. However in refractory cases one may be left with no option but to switch dialysis modality to haemodiafiltration (HDF) or more frequent or prolonged HD regimens.
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Affiliation(s)
- Wesley Hayes
- Nephrology Department, Nottingham Children's Hospital, Nottingham, UK
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Abstract
PURPOSE OF REVIEW The length of time (Td) required for adequate maintenance hemodialysis therapy is perceived as a substantial patient burden. Technological advancements have allowed shortening Td over the past three decades. However, failure to detect improved outcomes with higher dialysis dose has prompted renewed interest in the potential impact of longer Td. RECENT FINDINGS Ongoing trials are focused on increasing the frequency of treatments, although the feasibility of having most patients agreeing to more than five treatments per week remain doubtful. Furthermore, survival was better in short daily hemodialysis with Td of 180 vs. 90 min. Within thrice weekly dialysis, several recent epidemiological studies have shown improved survival associated with Td more than 4 h. Improved outcomes for long in-center nocturnal hemodialysis (6-8 h, 3×/week), similar to what has been performed in Tassin for the last 30 years, have also been reported. SUMMARY Compelling rationale and recent outcome data support use of longer Td. Improved management of salt and water may be the cause for the dissociation of dialysis time and small molecule clearance. In most industrialized countries, hemodialysis care systems in place have the capacity to accommodate it. Until such time that results from prospective randomized trials are available, we believe that physicians should prescribe and exert all efforts to convince thrice weekly hemodialysis patients to accept 4 h as minimum Td.
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Urea kinetics and intermittent dialysis prescription in small animals. Vet Clin North Am Small Anim Pract 2011; 41:193-225. [PMID: 21251518 DOI: 10.1016/j.cvsm.2010.12.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Hemodialysis improves survival for animals with acute kidney injury beyond what would be expected with conventional management of the same animals. Clinical evidence and experience in human patients suggest a role for earlier intervention with renal replacement to avoid the morbidity of uremia and to promote better metabolic stability and recovery. For a large population of animal patients, it is the advanced standard for the management of acute and chronic uremia, life-threatening poisoning, and fluid overload for which there is no alternative therapy.
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Ponda MP, Quan Z, Melamed ML, Raff A, Meyer TW, Hostetter TH. Methylamine clearance by haemodialysis is low. Nephrol Dial Transplant 2009; 25:1608-13. [PMID: 20019016 DOI: 10.1093/ndt/gfp629] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Dialysis adequacy is currently judged by measures of urea clearance. However, urea is relatively non-toxic and has properties distinct from large classes of other retained solutes. In particular, intracellularly sequestered solutes are likely to behave differently than urea. METHODS We studied an example of this class, the aliphatic amine monomethylamine (MMA), in stable haemodialysis outpatients (n = 10) using an HPLC-based assay. RESULTS Mean MMA levels pre-dialysis in end-stage renal disease subjects were 76 +/- 15 microg/L compared to 32 +/- 4 microg/L in normal subjects (n = 10) (P < 0.001). Mean urea reduction was 62% while the reduction ratio for MMA was 43% (P < 0.01). MMA levels rebounded in the 1 hour post-dialytic period to 85% of baseline, whereas urea levels rebounded only to 47% of baseline. MMA had a much larger calculated volume of distribution compared to urea, consistent with intracellular sequestration. Measures of intra-red blood cell (RBC) MMA concentrations confirmed greater levels in RBCs than in plasma with a ratio of 4.9:1. Because of the intracellular sequestration of MMA, we calculated its clearance using that amount removed from whole blood. Clearances for urea averaged 222 +/- 41 ml/min and for MMA 121 +/- 14 ml/min, while plasma clearance for creatinine was 162 +/- 20 ml/min (P < 0.01, for all differences). Using in vitro dialysis, in the absence of RBCs, solute clearance rates were similar: 333 +/- 6, 313 +/- 8 and 326 +/- 4 ml/min for urea, creatinine and MMA, respectively. These findings suggest that the lower MMA clearance relative to creatinine in vivo is a result of MMA movement into RBCs within the dialyser blood path diminishing its removal by dialysis. CONCLUSION In conclusion, we find that, in conventional haemodialysis, MMA is not cleared as efficiently as urea or creatinine and raise the possibility that RBCs may limit its dialysis not merely by failing to discharge it, but by further sequestering it as blood passes through the dialyser.
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Affiliation(s)
- Manish P Ponda
- Division of Nephrology, Department of Medicine, Albert Einstein College of Medicine, Room 615, Ullmann Building, 1300 Morris Park Ave, Bronx, NY 10461, USA
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Schneditz D, Platzer D, Daugirdas JT. A diffusion-adjusted regional blood flow model to predict solute kinetics during haemodialysis. Nephrol Dial Transplant 2009; 24:2218-24. [DOI: 10.1093/ndt/gfp023] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Schneditz D. The Convertibility of Online Clearance Measurements. Am J Kidney Dis 2008; 52:7-9. [DOI: 10.1053/j.ajkd.2008.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2008] [Accepted: 05/16/2008] [Indexed: 11/11/2022]
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Debowska M, Waniewski J, Lindholm B. Bimodal dialysis: theoretical and computational investigations of adequacy indices for combined use of peritoneal dialysis and hemodialysis. ASAIO J 2007; 53:566-75. [PMID: 17885329 DOI: 10.1097/mat.0b013e31810c06d2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
A theoretically correct method for evaluating the adequacy of bimodal dialysis (BMD), a combination of peritoneal dialysis (PD) and hemodialysis (HD) in the same patient, is lacking. We therefore performed computer simulations using a variable-volume, two-compartment urea kinetic model for 1-week treatments with 1) HD with three sessions, HD3, 2) continuous ambulatory PD, CAPD, 3) 6 days of CAPD and 1 day with HD session, and 4) 5 days of CAPD and 2 days with HD. Four dialysis adequacy indices (KT/V, stdKT/V, fractional solute removal, FSR, and equivalent clearance, EKR) were analyzed using four different reference methods for normalization of urea amount and concentration: 1) peak value, 2) peak average value, 3) time average value, and 4) treatment time average value. The analyses show that a proposed simplified rule of adding one third of weekly FSR for HD3 for each dialysis session and one seventh of weekly FSR for CAPD for each PD day for prediction of weekly FSR for BMD provides a fair prediction, although some corrections may be necessary, depending on the chosen reference method. In particular, KT/V may be added using this rule. We conclude that theoretically correct adequacy indices for BMD may be defined and calculated by using numerical simulations.
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Affiliation(s)
- Malgorzata Debowska
- Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland
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Affiliation(s)
- Timothy W Meyer
- Stanford University School of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, USA
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Eloot S, Torremans A, De Smet R, Marescau B, De Deyn PP, Verdonck P, Vanholder R. Complex Compartmental Behavior of Small Water-Soluble Uremic Retention Solutes: Evaluation by Direct Measurements in Plasma and Erythrocytes. Am J Kidney Dis 2007; 50:279-88. [PMID: 17660029 DOI: 10.1053/j.ajkd.2007.05.009] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Accepted: 05/18/2007] [Indexed: 11/11/2022]
Abstract
BACKGROUND Although scanty data suggest that large solutes show kinetic behavior different from urea, there are virtually no data comparing the kinetics of urea with those of other small water-soluble uremic compounds, which are believed to behave similarly. STUDY DESIGN Cross-sectional study of kinetics of urea and guanidino compounds in plasma and erythrocyte compartments during a single hemodialysis session. SETTING & PARTICIPANTS Six stable hemodialysis patients on standard low-flux dialysis therapy. PREDICTORS Reduction ratios (RRs) of urea calculated from plasma and erythrocyte concentrations. OUTCOMES RRs for guanidino compounds calculated from measurements of both plasma and erythrocyte concentrations. MEASUREMENTS Blood samples were collected from the dialyzer inlet and outlet at 0, 5, 15, 30, and 120 minutes and at the end of the session. Plasma and erythrocyte concentrations of urea and guanidino compounds (creatinine [CTN], guanidinosuccinic acid [GSA], guanidinoacetic acid [GAA], guanidine [G], and methylguanidine [MG]) were determined. RESULTS Postdialysis plasma RR was higher for GSA (82% +/- 3%) compared with urea (77% +/- 2%; P < 0.01), whereas CTN (69% +/- 4%), GAA (49% +/- 14%), G (55% +/- 7%), and MG (55% +/- 7%) showed smaller RRs (P < 0.01). In erythrocytes, GSA (45% +/- 1%), G (10% +/- 13%), and MG (27% +/- 10%) showed markedly smaller RRs than urea (59% +/- 6%; P < 0.05). Finally, significant differences were found between plasma and erythrocyte RRs for urea, GSA, G, and MG (P < 0.01). LIMITATIONS Discrepancies were found between the biochemical and mathematical approaches. Hence, the erythrocyte compartment does not necessarily conform to the kinetic nonperfused compartment. CONCLUSIONS Our data indicate by means of direct estimations that the compartmental behaviors of guanidino compounds and urea are substantially different. Hence, we should consider that not all changes in concentrations in uremia and dialysis are representatively reflected by urea kinetics, even when considering other small water-soluble substances, such as the guanidino compounds.
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Affiliation(s)
- Sunny Eloot
- Institute for Biomedical Technology, Ghent University, Ghent, Belgium.
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Debowska M, Waniewski J, Lindholm B. An integrative description of dialysis adequacy indices for different treatment modalities and schedules of dialysis. Artif Organs 2007; 31:61-9. [PMID: 17209962 DOI: 10.1111/j.1525-1594.2007.00341.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dialysis adequacy indices that are applied for the evaluation of the efficiency of urea removal include fractional water volume cleared from urea during dialysis (KT T/V), fractional solute removal (FSR), and equivalent urea clearance (EKR). Using a constant-volume, one-compartment urea kinetic model for an anuric patient, the FSR and EKR are shown to depend on only three nondimensional parameters: (i) KT/V, where K is the dialyzer clearance for hemodialysis (HD) or peritoneal mass transport coefficient for peritoneal dialysis (PD), T is the time period of dialysis, and V is urea distribution volume; (ii) T/Tc, where Tc is the length of treatment cycle; and (iii) VD/V, where VD is the volume of dialysis fluid applied. In particular, analytical formulas for FSR and EKR, valid for HD as well as for PD, were derived as functions of these three parameters. Numerical simulations, performed using a two-compartment urea kinetic model, showed that the analytical formulas are valid also for the two-compartment model, except for short, highly effective HD, where the overestimation of FSR and EKR using the analytical formulas is however, not higher than 20 and 16%, respectively. KT T/V is equal to KT/V for HD and FSR for PD. Thus, our formulas provide an integrative description of the relationships between dialysis efficiency indices and operational dialysis parameters that is valid for all modalities and schedules of dialysis. They may be applied not only for standard HD and continuous ambulatory PD, but also for HD with circulating dialysis fluid or intermittent forms of PD.
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Affiliation(s)
- Malgorzata Debowska
- Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland.
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Pahlka RB, Sonnad JR. The effects of dialysis on 131I kinetics and dosimetry in thyroid cancer patients--a pharmacokinetic model. HEALTH PHYSICS 2006; 91:227-37. [PMID: 16891898 DOI: 10.1097/01.hp.0000214660.13440.64] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Currently, an accepted post-surgical treatment of patients with thyroid carcinoma is administration of an ablative dose of I. This treatment is well established based on extensive experience and modeling. However, for patients with renal disease, reduced iodine removal rates result in controversial thyroid doses and potentially excessive red bone marrow doses. There are differences of opinion regarding I dose recommendations ranging from a reduction in dose to an increase in dose compared with conventional amounts. Determination of suitable doses must take into account varying dialysis protocols and absorbed dose considerations to the thyroid and sensitive tissues such as red bone marrow. The specific aim of this study was to develop a simple yet comprehensive compartmental model for I kinetics in patients with thyroid carcinoma and end stage renal disease, which accounts for dialysis and provides absorbed dose estimates for the thyroid as well as the red bone marrow. STELLA, a compartmental modeling software program, was used to develop a kinetic model that includes the blood pool, thyroid, gastrointestinal tract, kidneys, bladder, and a conventional dialysis machine. Benchmarking was performed to demonstrate the validity of the model with data obtained from ICRP 30 and MIRD Dose Estimate Report No. 5. Iodine kinetics were simulated for normal patients, thyroid cancer patients, and patients with thyroid cancer and renal failure undergoing two standard types of dialysis, hemodialysis and continuous ambulatory peritoneal dialysis (CAPD). Results in this work show that thyroid doses to patients with thyroid cancer and renal failure on hemodialysis or CAPD are slightly higher than doses to patients with thyroid cancer and normal renal function. These results further indicate that red bone marrow doses to patients with thyroid cancer and renal failure on dialysis can be significantly higher than red bone marrow doses to patients with thyroid cancer and normal renal function, and thus these patients could benefit from a reduction in administered activity. Thyroid doses and red bone marrow doses to patients on standard hemodialysis depend on both dialysis frequency and the time interval between administration and first dialysis. The results in this study provide guidelines on how much activity a patient on dialysis should receive based on thyroid and red bone marrow absorbed dose (Gy MBq) considerations. This study should help to clarify some of the contradictory recommendations regarding I dose for thyroid carcinoma patients with renal failure.
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Affiliation(s)
- Raymond B Pahlka
- INP-606 Everett Tower, University of Oklahoma Health Sciences Center, Oklahoma, OK 73190, USA
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Waniewski J, Debowska M, Lindholm B. Theoretical and Numerical Analysis of Different Adequacy Indices for Hemodialysis and Peritoneal Dialysis. Blood Purif 2006; 24:355-66. [PMID: 16685118 DOI: 10.1159/000093199] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2005] [Accepted: 03/17/2006] [Indexed: 11/19/2022]
Abstract
BACKGROUND Apart from KT/V, equivalent urea clearance (EKR) and fractional solute removal (FSR) can also be used to assess the dialysis adequacy. Our objective was to analyze the relationships between these indices for different dialysis modalities and schedules, using urea kinetic modeling. METHODS EKR and FSR were calculated for HD (three or six times per week), automatic nightly PD (ANPD) and CAPD using the following reference values of urea concentration and mass in the body: peak, peak average, time average and treatment time average. RESULTS The standard KT/V approach is related to the treatment time average, whereas the standard EKR is related to the time average reference values. In spite of KT/V = 3.5 (K meaning dialyzer clearance or peritoneal diffusive mass transport coefficient), EKR and FSR were lower for ANPD and CAPD than for HD. The ratio of EKR to FSR was essentially the same for the different treatment modalities (range 3.48-4.07 ml/min). This could be explained by the theoretical analysis which predicts the value of EKR/FSR = V/Tc, independent of the treatment modality and schedules (V is a solute distribution volume, Tc is the time of the full dialysis cycle). CONCLUSION Whereas the index KT/V in its standard form cannot be used to compare different dialysis regimens, EKR and FSR provide very similar evaluation of different dialysis modalities and schedules, and may be considered as equivalent measures for comparative studies of dialysis adequacy.
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Affiliation(s)
- Jacek Waniewski
- Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland
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Jung A, Krisper P, Haditsch B, Stauber RE, Trauner M, Holzer H, Schneditz D. Bilirubin Kinetic Modeling for Quantification of Extracorporeal Liver Support. Blood Purif 2006; 24:413-22. [PMID: 16847391 DOI: 10.1159/000094575] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Indexed: 11/19/2022]
Abstract
BACKGROUND/AIM To provide a measure of treatment dose for extracorporeal liver support (ELS). METHODS The kinetics of conjugated bilirubin were described by a two-compartment model (Vc, Vp) with central elimination (K) and constant generation rate (G). The transfer of solute between compartments was modeled by intercompartmental clearance (Kpc). The central compartment (Vc) was assumed as a constant fraction of total volume (Vc = 0.3*Vt). RESULTS Eight patients were studied during 35 treatments lasting 6 h each. The average K, Vt, Kpc, G, and mass of conjugated bilirubin removed were 18.6 +/- 3.9 ml/min, 9.1 +/- 3.8 liters, 103 +/- 108 ml/min, 0.33 +/- 0.15 mg/min, and 641 +/- 275 mg, respectively. The reduction ratio (48 +/- 10%) measured as the change in post- to pre-treatment concentrations underestimated the modeled fraction of bilirubin mass removed (54 +/- 13%) essentially because of significant conjugated bilirubin appearance during treatments. CONCLUSIONS Kinetic analysis provides an improved measure of treatment dose as generation, distribution, and elimination of conjugated bilirubin are jointly considered.
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Affiliation(s)
- Aleksandra Jung
- Institut of Physiology, Center for Physiological Medicine, Medical University of Graz, Graz, Austria
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Abstract
Recent outcome trials in chronic dialysis patients raise concerns about the relationship between delivered urea Kt/V and survival. Nevertheless, measurement of delivered small solute clearance remains the most common approach to quantify therapy. The purpose of this review is to provide an overview of the numerous factors influencing small solute clearance during hemodialysis. Although the focus of the review is on the manner in which dialyzer characteristics influence small solute clearances, factors related to other aspects of the extracorporeal circuit and to the patient will also be discussed.
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Affiliation(s)
- Zhongping Huang
- Center for Biomedical Engineering, University of Kentucky, Louisville, Kentucky, USA
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Uhlin F, Fridolin I, Magnusson M, Lindberg LG. Dialysis dose (Kt/V) and clearance variation sensitivity using measurement of ultraviolet-absorbance (on-line), blood urea, dialysate urea and ionic dialysance. Nephrol Dial Transplant 2006; 21:2225-31. [PMID: 16611681 DOI: 10.1093/ndt/gfl147] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND An on-line monitoring system for dialysis dose calculations could make it possible to provide an adequate dialysis dose that is consistently given to haemodialysis (HD) patients. The aim of this study was to compare dialysis dose (Kt/V) using four different methods and their sensitiveness to a reduction in clearance. METHODS Six patients were monitored on-line with ultraviolet (UV)-absorbance at a wavelength of 297 nm in three consecutive dialysis sessions during 1 week. During the last treatment, the clearance was reduced by approximately 25% by decreasing the blood flow. For the determination of UV-absorbance, a spectrophotometer was connected to the fluid outlet of the dialysis machine with all spent dialysate passing through a flow cuvette. The equilibrated Kt/V (eKt/V) estimated by UV-absorbance was compared with eKt/V from the ionic dialysance method using the on-line clearance monitor (OCM) and the appurtenant software dose-calculation tool DCTool (Fresenius Medical Care, Germany), eKt/V calculated from the dialysate-urea slope and with eKt/V from pre- and post-dialysis blood-urea samples as reference. RESULTS The study demonstrates that the sensitiveness to clearance reduction is similar in the four methods compared for eKt/V. When the different methods were compared, the mean eKt/V of UV-absorbance was 1.21 +/- 0.20, blood 1.30 +/- 0.21, dialysate 1.32 +/- 0.21 and OCM (using the DCTool) 1.31 +/- 0.21. The standard deviation was of the same magnitude. CONCLUSION The UV-method gives a similar response to clearance reduction compared with the other methods when comparing dialysis dose. The high sampling rate by continuous monitoring of UV-absorbance allows evaluation of the clearance process during dialysis and gives immediate feedback to on-line adjustments.
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Affiliation(s)
- Fredrik Uhlin
- Department of Nephrology University Hospital, Linköping, S-58185 Linköping, Sweden.
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Waniewski J. Mathematical modeling of fluid and solute transport in hemodialysis and peritoneal dialysis. J Memb Sci 2006. [DOI: 10.1016/j.memsci.2005.11.038] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Jaroszyński AJ, Głowniak A, Sodolski T, Załuska W, Widomska-Czekajska T, Ksiazek A. Effect of haemodialysis on signal-averaged electrocardiogram P-wave parameters. Nephrol Dial Transplant 2005; 21:425-30. [PMID: 16221710 DOI: 10.1093/ndt/gfi175] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND The P-wave signal-averaged electrocardiogram (SAECG) is a non-invasive technique considered to indicate an increased risk for paroxysmal atrial fibrillation. The study was designed to evaluate the effect of the haemodialysis (HD) process on SAECG parameters in the group of selected HD patients. METHODS Forty-seven HD patients (without relevant cardiac diseases) were included. SAECGs were performed pre- and post-dialysis together with evaluating extracellular body water (ECW) by using bioimpedance and biochemical measurements. For each SAECG, filtered P-wave duration (FPD) and root mean square voltage of the final 20 ms of filtered P-wave (RMS20) were established. RESULTS The duration of either pre- or post-dialysis FDP was higher in HD patients than in the control group (P<0.001 and P = 0.005, respectively). The voltage of either pre- or post-dialysis RMS20 was reduced in HD patients compared with controls (P<0.001 in both cases). HD induced a decrease in the duration of the FDP and a significant increase in the voltage of RMS20 (P<0.001 in both cases). Stepwise multiple regression identified independent predictors of pre- and post-dialysis FDP as: (1) age; (2) pre- and post-dialysis ECW/kg body weight, respectively and; (3) pre- and post-dialysis haemoglobin levels, respectively. In the case of RMS20, we did not find any independent predictors either pre- or post-dialysis. CONCLUSIONS Our study revealed that P-wave SAECG parameters are abnormal in a significant portion of HD patients and improved with HD process. We have also demonstrated that patients' age, volume status as well as the presence of anaemia are important factors influencing P-wave SAECG parameters in HD patients.
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Eloot S, de Vos JY, de Vos F, Hombrouckx R, Verdonck P. Middle molecule removal in low-flux polysulfone dialyzers: Impact of flows and surface area on whole-body and dialyzer clearances. Hemodial Int 2005; 9:399-408. [PMID: 16219061 DOI: 10.1111/j.1492-7535.2005.01159.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Some studies found that the removal of middle molecules has a long-term effect on mortality and, even more, is enhanced by high-flux dialysis. In order to enhance middle molecule removal in a low-flux dialyzer, the present study aimed at investigating the combined impact of dialyzer flows and membrane surface area. Blood and dialysate flows were varied within the clinical range 300-500 and 500-800 mL/min, respectively, while the ultrafiltration rate was kept constant at 0.1 L/hr. Single-pass tests were performed in vitro in a single Fresenius F6HPS dialyzer (3 tests) and serially (5 tests) and parallel (3 tests) connected dialyzers. The blood substitution fluid consisted of dialysis fluid in which radioactive-labeled vitamin B12 (molecular weight 1355 Da) was dissolved. Dialyzer clearance as well as whole-body clearance was calculated from radioactivity concentrations of samples taken from the inlet and outlet bloodline. Adding a second dialyzer in series or parallel ameliorated the overall dialyzer and whole-body clearance significantly, except for the highest applied blood flows of 500 mL/min. Better solute removal was also obtained with higher dialysate flows, while the use of higher blood flows seemed advantageous only when using a single dialyzer. Analysis of the ultrafiltration profiles in the different configurations illustrated that enhancing the internal filtration rate ameliorates convective transport of middle molecules. Adequate solute removal results from a number of interactions, as there are blood and dialysate flows, membrane surface area, filtration profile and concentration profiles in the blood and dialysate compartment.
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Affiliation(s)
- Sunny Eloot
- Institute Biomedical Technology, Ghent University, Gent, Belgium.
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Krisper P, Haditsch B, Stauber R, Jung A, Stadlbauer V, Trauner M, Holzer H, Schneditz D. In vivo quantification of liver dialysis: comparison of albumin dialysis and fractionated plasma separation. J Hepatol 2005; 43:451-7. [PMID: 16023249 DOI: 10.1016/j.jhep.2005.02.038] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2004] [Revised: 02/08/2005] [Accepted: 02/18/2005] [Indexed: 12/22/2022]
Abstract
BACKGROUND/AIMS Artificial liver support represents a potentially useful option for the treatment of severe liver failure. A sufficient 'dose' might be crucial for such treatments to provide a survival benefit. The aim of this study was to compare in vivo efficiency and resulting delivered treatment dose of two commercially available devices that use different therapeutic principles: albumin dialysis (AD, MARS) and fractionated plasma separation (FPS, Prometheus). METHODS Eight patients with acute-on-chronic liver failure were treated alternately with AD and FPS. Thirty-two treatments at identical blood and dialysate flow rates were evaluated. Clearance and reduction ratio (a measure of delivered treatment dose) were compared for bilirubin subfractions, ammonia and urea. RESULTS FPS achieved significantly higher clearance for all measured protein-bound and water-soluble markers. This resulted in significantly higher reduction ratios for FPS compared to AD. Unconjugated bilirubin, a marker for strongly albumin-bound toxins, was influenced only by FPS. CONCLUSIONS FPS provided a higher delivered treatment dose than a matching treatment with AD. Reduction ratios of bilirubin and urea should be reported in clinical studies on liver dialysis, since delivered dose is likely to be linked to the clinical effectiveness of extracorporeal liver support therapies.
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Affiliation(s)
- Peter Krisper
- Division of Nephrology and Hemodialysis, Department of Internal Medicine, Medical University Graz, Auenbruggerplatz 27, A-8036 Graz, Austria.
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Eloot S, Torremans A, De Smet R, Marescau B, De Wachter D, De Deyn PP, Lameire N, Verdonck P, Vanholder R. Kinetic behavior of urea is different from that of other water-soluble compounds: The case of the guanidino compounds. Kidney Int 2005; 67:1566-75. [PMID: 15780113 DOI: 10.1111/j.1523-1755.2005.00238.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Although patients with renal failure retain a large variety of solutes, urea is virtually the only currently applied marker for adequacy of dialysis. Only a limited number of other compounds have up until now been investigated regarding their intradialytic kinetics. Scant data suggest that large solutes show a kinetic behavior that is different from urea. The question investigated in this study was whether other small water-soluble solutes, such as some guanidino compounds, show a kinetic behavior comparable or dissimilar to that of urea. METHODS This study included 7 stable conventional hemodialysis patients without native kidney function undergoing low flux polysulphone dialysis (F8 and F10HPS). Blood samples were collected from the inlet and outlet bloodlines immediately before the dialysis session, after 5, 15, 30, 120 minutes, and immediately after discontinuation of the session. Plasma concentrations of urea, creatinine (CTN), creatine (CT), guanidinosuccinic acid (GSA), guanidinoacetic acid (GAA), guanidine (G), and methylguanidine (MG) were used to calculate corresponding dialyzer clearances. A two-pool kinetic model was fitted to the measured plasma concentration profiles, resulting in the calculation of the perfused volume (V(1)), the total distribution volume (V(tot)), and the intercompartmental clearance (K(12)); solute generation and overall ultrafiltration were determined independently. RESULTS No significant differences were observed between V(1) and K(12) for urea (6.4 +/- 3.3 L and 822 +/- 345 mL/min, respectively) and for the guanidino compounds. However, with respect to V(tot), GSA was distributed in a smaller volume (30.6 +/- 4.2 L) compared to urea (42.7 +/- 6.0L) (P < 0.001), while CTN, CT, GAA, G, and MG showed significantly higher volumes (54.0 +/- 5.9 L, 98.0 +/- 52.3 L, 123.8 +/- 66.9 L, 89.7 +/- 21.4 L, 102.6 +/- 33.9 L, respectively; P= 0.004, = 0.033, = 0.003, < 0.001, = 0.001, respectively). These differences resulted in divergent effective solute removal: 67% (urea), 58% (CTN), 42% (CT), 76% (GSA), 37% (GAA), 43% (G), and 42% (MG). CONCLUSION The kinetics of the guanidino compounds under study are different from that of urea; hence, urea kinetics are not representative for the removal of other uremic solutes, even if they are small and water-soluble like urea.
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Affiliation(s)
- Sunny Eloot
- Institute Biomedical Technology, Hydraulics Laboratory, Ghent University, Belgium.
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Waniewski J, Lindholm B. Fractional Solute Removal and KT/V in Different Modalities of Renal Replacement Therapy. Blood Purif 2004; 22:367-76. [PMID: 15297787 DOI: 10.1159/000080033] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/30/2004] [Indexed: 11/19/2022]
Abstract
The efficacy of solute removal by renal replacement therapy can be assessed by the commonly used index of KT/V (the fraction of the volume cleared from a solute). Fractional solute removal (FSR, the fraction of the total amount of the solute that was removed) is an alternative index that may be more appropriate than KT/V for comparison of the efficacy of different treatment modalities. To elucidate the relationship between these two indexes, we propose to discriminate between two notions of clearance: (1) instantaneous clearance K = (solute removal rate)/C(B), where C(B) is solute concentration in blood, and (2) treatment clearance K(T) = (average rate of solute removal per treatment)/C(B), where C(B) is C(B) at the beginning of the treatment. K is the clearance of the purification device (glomeruli, hemodialyzer or hemofilter) and the diffusive mass transport parameter (K(BD), MTAC) for continuous ambulatory peritoneal dialysis (CAPD). For all modalities of renal replacement therapy: FSR = K(T)T/V, and K(T) generally decreases with the treatment time. For purification of a single compartment with a constant volume, V, using an open loop system (i.e. with no recirculation or dwelling of dialysis fluid, as in hemodialysis (HD), hemofiltration (HF) or in the native kidney), FSR is a function of only one lumped, nondimensional parameter, KT/V(B), where V(B) is the distribution volume of the solute within the body. In contrast, if closed loop systems are applied, as for example in HD with recirculation of dialysis fluid (RD) or in peritoneal dialysis, FSR depends on two lumped, nondimensional parameters: KT/V(B) and KT/V(D), where V(D) is the volume of dialysis fluid. It is necessary to discriminate between K and K(T) for analysis of dialysis dose. For HD and HF, FSR is a function of KT/V, whereas KT/V alone does not allow calculation of FSR for CAPD and RD. The current practice of using K(T)T/V for CAPD but KT/V for HD and HF leads to confusion because of the inconsistency in the interpretation of the quantitative prescription of dialysis dose. The application of FSR, instead of KT/V, for all treatment modalities may solve this dilemma. Furthermore, K(T)T/V (currently used only for CAPD) is equal to FSR for all treatment modalities. Both FSR and K(T) may be generalized to describe the total solute removal per treatment cycle composed from a few treatment sessions. A few different definitions of the adequacy parameters for the treatment cycle are formulated and discussed.
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Affiliation(s)
- Jacek Waniewski
- Divisions of Baxter Novum and Renal Medicine, Karolinska Institute, Stockholm, Sweden
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Ikizler TA, Sezer MT, Flakoll PJ, Hariachar S, Kanagasundaram NS, Gritter N, Knights S, Shyr Y, Paganini E, Hakim RM, Himmelfarb J. Urea space and total body water measurements by stable isotopes in patients with acute renal failure. Kidney Int 2004; 65:725-32. [PMID: 14717948 DOI: 10.1111/j.1523-1755.2004.00439.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND Knowledge of urea volume of distribution (Vurea) in patients with acute renal failure (ARF) is critical in order to prescribe and monitor appropriate dialytic treatment. We have recently shown that in ARF patients, Vurea estimation by urea kinetic modeling is significantly higher than total body water (TBW) by anthropometric estimation. However, these estimates of Vurea and TBW have not been validated by isotopic methods, considered as reference measurement standards. METHODS In this study, we measured Vurea by [13C]urea and TBW by deuterium oxide (D2O) in 21 patients with ARF (14 males, 7 females, age 62.0 +/- 10.6 years old, 83% Caucasian, 17% African American) at three different centers. These measurements were compared to TBW estimates from anthropometric and bioelectrical impedance (BIA) measurements. RESULTS Our results show that Vurea by [13C]urea (51.0 +/- 11.7 L) is significantly higher than TBW estimated by all other methods (TBW by D2O: 38.3 +/- 9.8 L, P < 0.001; TBW by BIA: 45.7 +/- 15.7 L, P= 0.08; TBW by Watson formula: 38.3 +/- 7.3 L, P < 0.001; TBW by Chertow formula: 39.3 +/- 7.8 L, P= 0.002, all versus Vurea). Despite significant overestimation of the absolute value and considerable variation, Vurea significantly correlated with TBW by BIA (r= 0.66, P < 0.01) and TBW by D2O (r= 0.5, P= 0.04). There was also significant correlation between D2O and BIA determined TBW (r= 0.8, P < 0.001). CONCLUSION In terms of useful guidelines to prescribe a specific dose of dialysis in patients with ARF, conventional estimates of TBW as surrogates for Vurea should be used with caution. We propose that these conventional estimates of TBW should be increased by approximately 20% (a factor of 1.2) to avoid significant underdialysis.
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Affiliation(s)
- T Alp Ikizler
- Vanderbilt University Medical Center, Division of Nephrology, Nashville, Tennessee 37232-2372, USA.
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