On-line Regeneration Research Articles

Effects on inflammatory and nutritional markers of haemodiafiltration with online regeneration of ultrafiltrate (HFR) vs online haemodiafiltration: a cross-over randomized multicentre trial

HFR [double chamber haemodiafiltration (HDF) with reinfusion of regenerated ultrafiltrate] is a novel dialytic method which combines the processes of diffusion, convection and adsorbance. In this technique an adsorbent cartridge of resin and charcoal may regenerate the ultrafiltrate suggesting its use as an endogenous substitution fluid. The aim of this multicentre randomized cross-over study was to compare HFR to online HDF in terms of inflammatory and nutritional parameters. After a 1 month run-in period of standard bicarbonate dialysis (HD) with a synthetic membrane, 25 chronic dialytic patients were randomized (A-B or B-A) to be treated by HFR (A) with a two-chamber filter (SG 8 Plus - high permeability Polysulphone HF 0.7 m2 + SMC 1.95 sqm; Bellco, Mirandola, Italy) or by online sterile bicarbonate HDF. Each study period of 4 months was separated by 1 month of HD and the entire length of the study was 10 months. CRP levels were measured by a highly sensitive nephelometric assay (Dade, Behring) with a sensitivity of 0.1 microg/ml. Cytokine concentrations were determined by EIA [Interleukin (IL) 6, Biosource, USA and IL-10 Bender MED-Systems, Vienna]. The sensitivity thresholds were < 5 pg/ml for IL-6 and < 8 pg/ml for IL-10. Serum leptin was determined with a ELISA method (Biosource, USA). All parameters were determined monthly in patients starting a midweek dialytic session. Plasma CRP and IL-6 were significantly reduced during the 4 months of HFR and HDF: CRP from 8.0 +/- 3.2 to 5.6 +/- 3.4 mg/l with HFR (P < 0.05) and from 9.4 +/- 4.3 to 5.9 +/- 3.9 mg/l with HDF (P < 0.05). IL-6 decreased from 14.8 +/- 6.3 to 10.1 +/- 3.2 with HFR (P < 0.02) and from 12.1 +/- 4.2 to 9.6 +/- 3.7 with HDF (P = ns) with a percentage decrease after 4 months of 32% with HFR vs 21% with HDF. During the 1 month wash-out period with HD, CRP increased from 5.7 +/- 3.6 to 8.7 +/- 3.9 mg/l (P < 0.01) and IL-6 from 10 +/- 3.4 to 13.5 +/- 5.2 pg/ml (P < 0.01). A significant increase in IL-10 was detected either in HFR (from 4.8 +/- 2.1 to 6.89 +/- 1.7 pg/ml) and in HDF (from 3.3 +/- 1.7 to 8.95 +/- 4.3 pg/ml; P < 0.05) after 4 months. No significant variation in serum leptin levels were observed during the study. CRP and IL-6 were highly correlated (r = 0.54; P < 0.001) as was serum albumin and prealbumin (r = 0.39; P < 0.001). Serum albumin was negatively correlated with CRP (r = -0.26; P < 0.01) and IL-6 (r = -0.19; P < 0.05); serum prealbumin was correlated with IL-6 (r = 0.37; P < 0.001) and with CRP (r = 0.24; P < 0.01). Haemodiafiltration with online regeneration of ultrafiltrate and online HDF are highly biocompatible techniques and no significant difference between HFR and online HDF was observed in terms of reduction of inflammatory markers. Further studies with a longer follow-up are needed to evaluate the clinical relevance of the online endogenous reinfusion to counteract the chronic inflammatory state of the uraemic patient.

Clean analytical methodology for the determination of lead with Arsenazo III by cyclic flow-injection analysis

A clean analytical methodology, where the sample determined and the reagent used are both toxic, has been proposed. A cation exchange mini-column was incorporated after the flow-through cell for on-line regeneration of the main reagent and the accumulation of heavy metal ions. The method involves the spectrophotometric determination of lead with Arsenazo III, the accumulation of lead onto the cationic exchanger, and subsequent regeneration of the chromogenic reagent, which makes the system reversible and the reagents reusable. The developed method provides a satisfactory way to cut down on the toxic reagent consumption and the produced volume of waste, an important step towards the zero emissions research initiative concept. The excellent repeatability and reproducibility, and the simplicity of this method are well suited for continuous measurements. The method was successively applied to the assay of lead in high-octane gasoline.

Switch from Bicarbonate Hemodialysis to Hemodiafiltration with Online Regeneration of the Ultrafiltrate (HFR): Effects on Nutritional Status, Microinflammation, and β2‐Microglobulin

Hemodiafiltration (HFR) with on-line regeneration of the ultrafiltrate, a technique of hemodiafiltration in which the ultrafiltrate passes through a cartridge containing uncoated charcoal, has been shown to be safe, simple, and well tolerated and has been claimed to improve nutritional status or to prevent its deterioration while decreasing the inflammatory response via a reduced production of proinflammatory cytokines. The purpose of the present prospective study was to ascertain whether HRF improves the nutritional status, reduces microinflammation, and decreases serum beta2-microglobulin levels in patients with end-stage renal disease (ESRD). Eight patients, four males and four females, with a mean age of 49.4 +/- 16.8 years, stable on hemodialysis over a period of 8.7 +/- 6.1 years and on standard 4-4.5 h three-times-a-week bicarbonate hemodialysis, were switched to three-times-a-week, 4-h HFR. At baseline and every two months for 12 months at mid-week, serum levels of urea, creatinine, albumin, total cholesterol, C-reactive protein, fibrinogen, complement, ferritin, beta2-microglobulin, intact parathyroid hormone (PTH), hemoglobin concentrations, and hematocrit and the EPO weekly dose were determined. At baseline and at the end of the study, the Malnutrition Inflammatory Score (MIS) was calculated. Nutritional and inflammatory parameters remained constant during the 12-month period of the study. After 12 months of HFR, the MIS trended to be lower, but the difference was not statistically significant. Serum beta2-microglobulin and PTH levels remained constant during all time intervals. Neither hematocrit nor hemoglobin changed over the course of the study as well as the weekly EPO dose. The change from bicarbonate hemodialysis to HFR was safe and well tolerated but was not associated with an improvement of nutritional and inflammatory parameters or a reduction of serum beta2-microglobulin levels.

Evaluation and optimization of an on-line admicelle-based extraction-liquid chromatography approach for the analysis of ionic organic compounds.

Admicelles-based solid-phase extraction (SPE) was on-line coupled with liquid chromatography/electrospray ionization/ion trap mass spectrometry, and it was proposed for the extraction of ionic organic compounds based on the formation of surfactant-analyte ion pairs. The approach was illustrated by studying the preconcentration of quaternary ammonium herbicides (quats) on sodium dodecyl sulfate (SDS) admicelles produced on alumina. Optimization of the parameters affecting SPE were studied on the basis that admicelles are dynamic entities in equilibrium with the aqueous phase. Some general guidelines could be established for method development from the results obtained. Factors influencing on-line operation were elucidated. On-line regeneration of the sorbent in each run was easily achieved by disruption of SDS admicelles with methanol and posterior coating of the alumina with SDS. The recovery of quats from drinking water samples were found quantitative for paraquat, diquat, and difenzoquat and above to 70% for chlormequat and mepiquat. Concentration factors of about 250, using sample volumes of 50 mL, were achieved. The detection limits ranged from 10 to 30 ng/L. The approach developed permits compliance with the directives of the European Community for drinking waters (100 ng/L) and goes deeply into the basis of solid-phase extractions that use surfactant-coated mineral oxide as sorbents.

Enhanced dissolution of hematite in reductive-complexing formulation under regenerative mode

The citric acid–EDTA–ascorbic acid (CEA) formulation used for the dissolution of hematite ( α-Fe 2O 3) powder results in a major portion of the dissolved iron as Fe(III)–EDTA (∼80%). Since Fe(III)–EDTA does not dissociate on the cation-exchange resin due to its high stability, the on-line regeneration of EDTA during the dissolution process becomes difficult. The results reported in this study show how, in such a situation, regeneration of EDTA is made possible by introducing carbon steel coupons of known surface area in the dissolution formulation. In these powder dissolution studies, we demonstrate the enhanced dissolution of α-Fe 2O 3 (more than the stoichiometric amount) in dilute CEA formulation by adopting a regenerative mode of dissolution. The powder dissolution study reported in this work is to simulate the application of dilute chemical formulation for the chemical decontamination of a system wherein the base metal (stainless-steel)-aided dissolution is absent e.g., primary system of BWRs/PWRs. A typical case study evaluation is carried out to estimate the approximate surface area of carbon steel required to be exposed in the real system application.

Pervaporation Membranes That Are Highly Selective for Acetic Acid over Water

Supported liquid membrane pervaporation (SLMPV) is a pervaporation process for separating volatile organic compounds (VOCs) from their dilute aqueous solution. It simultaneously integrates extraction of the VOCs from the aqueous solution with flash distillation of the VOCs from the organic phase. By using a liquid membrane consisting of reactive extractants, pervaporation of primarily acetic acid from its aqueous solutions was studied. Limited studies of butyric acid were also done. Among various extractants tested, trioctylamine (TOA) and tridodecylamine demonstrated better performances. The SLM is permselective for acetic acid and butyric acid. The acetic acid selectivity can be as high as 33 for a feed of 1 M at 60°C, an order of magnitude higher than that obtained by any solid polymeric membrane reported in the literature. The simple SLM system demonstrated long-term stability; for example, decreases of about 30% in both pervaporation flux and selectivity were observed over an operational period of 500 h. A new technique of continuous on-line regeneration of the LM during operation maintains completely stable operational performance.

Repetitive determination of calcium ion and regeneration of a chromogenic reagent using chlorophosphonazo III and an ion exchanger in a circulatory flow injection system.

The spectrophotometric determination of Ca2+ with chlorophosphonazo III (CPN) has been carried out by a circulatory flow injection (FI) method. A cation-exchange mini-column for the on-line regeneration of the main reagent was incorporated in this FT system, allowing a repetitive determination of Ca2+. A solution of 4.0 x 10(-5) M CPN in a 0.05 M acetate buffer (pH 5.0) in a single reservoir (50 ml) was continuously circulated at a constant flow rate of 1.5 ml min(-1). Into the stream, an aliquot (20 microl) of a sample containing Ca2+ was quickly injected by means of a 6-way valve. The complex formed was monitored spectrophotometrically at 670 nm in the flow system. Then, the stream passed through a cation-exchange column, which was introduced after the flow-through cell. A successful ligand-exchange reaction of Ca2+ between the CPN reagent and a cation exchanger, as well as a simultaneous regeneration of the free reagent took place. The stream then returned to the reservoir. The regeneration and recycling of the CPN reagent allowed as many as 300 repetitive determinations of 2.5 mg l(-1) Ca2+ solutions with the same 50 ml circulating solution.

Hemodiafiltration with online regeneration of the ultrafiltrate

The concept of regeneration of dialysis fluids and of ultrafiltrate in particular has been recently revisited. Hemodiafiltration with online regeneration of the ultrafiltrate allows the concomitant infusion of sodium, calcium, and bicarbonate. Here, we studied the adsorptive characteristics of an integrated two-step sorbent system relative to different solutes present in the ultrafiltrate: sodium, calcium, phosphate, bicarbonate, uric acid, creatinine, and beta2-microglobulin. In vitro studies were performed in order to differentiate the relative roles for each sorbent (mineral-activated charcoal or hydrophobic resin) in adsorbing a given solute. Ex vivo studies were performed in order to evaluate the presence of cytokines (interleukin-1 beta and tumor necrosis factor-alpha), of cytokine (interleukin-1 beta and tumor necrosis factor-alpha)-inducing activities, and of the cytokine release in response to exogenous bacterial lipopolysaccharide by normal whole blood incubated with ultrafiltrate samples obtained at 15, 120, and 240 minutes after the start of treatment. The results of the present studies show the presence of immunomodulatory substances in the ultrafiltrate and the significant (P < 0.01) increase in the lipopolysaccharide-induced release of both interleukin-1 beta and tumor necrosis factor-alpha. The biological relevance of the ultrafiltrate and the possible relevance of the online, endogenous reinfusion are discussed.

Lipid apheresis: from a heroic treatment to routine clinical practice.

Lipid apheresis has developed from a heroic treatment into a routine clinical therapy and currently is the major indication for performing extracorporeal plasma therapy. Whereas it was once reserved for patients with homozygous familial hypercholesterolemia, today it has a place in the secondary prevention of severe coronary heart disease when low-density lipoprotein (LDL)-cholesterol level exceeds 150 mg/dl, despite conservative treatment, in any type of primary hypercholesterolemia. Unselective plasma exchange has been replaced by a variety of selective procedures. The efficacy of the treatment can be maximized by combining LDL apheresis with the use of cholesterol synthesis enzyme inhibitors. Clinical studies have shown that drastic cholesterol reduction can result in regression of coronary atherosclerosis as well as in reduced cardiac morbidity and mortality. Technical progress comprises improved selectivity, online regeneration of adsorbers, and LDL adsorption from whole blood. Recently, a new LDL hemoperfusion procedure was successfully tested in a clinical pilot study; blood is passed directly over a lipid sorbent without prior plasma separation. If this system is demonstrated to be safe and effective in clinical Phase III trials, a further qualitative step in the rapid development of LDL apheresis will have made.

Flow Injection Renewable Surface Immunoassay: A New Approach to Immunoanalysis with Fluorescence Detection

This paper introduces a new methodology of carrying out heterogeneous immunoassays automatically, using a flow injection technique on a renewable surface. Flow injection renewable surface immunoassay (FIRSI) relies on the use of a minute amount of beads to form a reactive surface, which is interrogated by fluorescence spectrometry. Following the assay, on-line regeneration normally used in flow based immunoassays is avoided by fluidically removing the spent reactive surface and replacing it with a new layer of beads. This allows the monitoring of antibody-antigen binding at its early stages, dramatically increases the sampling frequency of a serial assay, and eliminates the problems associated with a decrease in surface reactivity caused by repetitive use. A model system utilizing anti-mouse IgG1-coated beads and mouse IgG1 protein is used to characterize the method with respect to reproducibility, flow rate, contact time, and amount of beads.

On-line regeneration control for a diesel particulate trap system

Wide applicability of particulate traps on diesel powered vehicles, may be substantially aided by the design and development of improved regeneration control systems. A particularly promising class of on-line regenerable trap systems is supported by engine-based regeneration techniques; the most important of them seems to be engine exhaust throttling. In this paper, various control schemes for the above class of systems are briefly reviewed and a control system based on controlling engine air-to-fuel ratio during regeneration is recommended. Such a control system, that is yet to be developed, is expected to fully exploit the advantages of modern electronic diesel engine management systems, in the direction of supporting a reliable and cost effective trap system.

Therapeutic application of phenylalanine immunoadsorbent with on-line regeneration.

To improve the adsorption capacity of the artificial reticuloendothelial system containing phenylalanine as a ligand, a regeneration method for the adsorbent during plasma perfusion was developed. The adsorbed rheumatoid factor, immunoglobulins, and complements were demonstrated to be elutable from the adsorbent with a 5% glucose solution in vitro. The regeneration method was applied to the treatment of a patient with rheumatoid arthritis. During each plasma perfusion, the adsorbent was regenerated, usually twice, with a 5% glucose solution at a flow rate of 50 ml/min. After each regeneration, the adsorption capacity of the adsorbent was found to be improved by determining the pre- and post-column plasma titers of a rheumatoid arthritis hemagglutination test.

UF6 plasma chemistry reconstitution experiments using high-temperature fluorine

Prior results indicate techniques have been developed for fluid mechanical confinement of high-temperature uranium hexafluoride (UF6) plasma for long test times while simultaneously minimizing uranium compound deposition on the walls. Follow-on investigations were conducted to demonstrate a UF6/argon injection, separation, and reconstitution system for use with rf-heated uranium plasma confinement experiments applicable to UF6 plasma core reactors. A static fluorine batch-type regeneration test reactor and a flowing preheated fluorine/UF6 regeneration system were developed for converting all the nonvolatile uranium compound exhaust products back to pure UF6 using a single reactant. Pure fluorine preheat temperatures up to 1000 K resulted in on-line regeneration efficiencies up to about 90%; static batch-type experiments resulted in 100% regeneration efficiencies but required significantly longer residence times. A custom-built, ruggedized time-of-flight (T.O.F.) mass spectrometer, sampling, and data acquisition system permitted on-line quantitative measurements of the UF6 concentrations down to 30 ppm at various sections of the exhaust system; this system proved operational after long-time exposure to corrosive UF6 and other uranium halides.

Sorbent regeneration of ultrafiltrate as a long-term treatment of end-stage renal failure.

A sorbent system (Redy D 11 cartridge) capable of on-line regeneration of ultrafiltrate during hemofiltration (Amicon 0.5 m2) has been developed and applied on a 3 X 4 hr/week schedule to three patients with end-stage renal failure previously treated for up to six months with hemodialysis. Total experience, to date, is sixteen patient months (three to seven months). Tolerance to fluid removal improved with the new system. Patient well-being and rehabilitation have been maintained. The system offers the potential of hemofiltration without sterile replacement fluid or expensive fluid-balancing machines.