Clotting Propensity of Surface-Treated Membranes in a Hemodialysis Set-up That Avoids Systemic Anticoagulation

The development of biocompatible membranes, aiming to limit the inflammatory response, oxidative stress, and coagulability during hemodialysis, has been an important step in reducing dialysis-related adverse outcomes. This includes a reduction in the risk of clotting of the extracorporeal circuit, thus enabling hemodialysis with a reduced dose or even without systemic anticoagulant drugs in patients with an increased bleeding risk. In this article, we summarize the in vitro research and clinical evidence on the antithrombotic properties of vitamin E- and heparin-coated membranes.

Risk for excessive anticoagulation during hemodialysis is associated with type of vascular access and bedside coagulation testing: Results of a cross-sectional study

Background

Recommendations and practice patterns for heparin dosing during hemodialysis show substantial heterogeneity and are scantly supported by evidence. This study assessed the variability in unfractionated heparin (UFH) dosing during hemodialysis and its clinical and biological anticoagulatory effects, and identified explanatory factors of heparin dosing.

Methods

Cross-sectional study assessing UFH dosing, coagulation tests - activated partial thromboplastin time (aPTT) and activated clotting time (ACT) before dialysis start, 1 h after start and at treatment end (4 h) - and measurement of residual blood compartment volume of used dialyzers.

Results

101 patients, 58% male, with a median dialysis vintage of 33 (6-71) months received hemodialysis using a total UFH dose of 9,306 ± 4,079 (range 3,000-23,050) IU/session. Use of a dialysis catheter (n = 56, 55%) was associated with a 1.4 times higher UFH dose (p < 0.001) irrespective of prior access function. aPTT increased significantly more than ACT both 1 h and 4 h after dialysis start, independent of the dialysis access used. 53% of patients with catheter access and ACT ratio < 1.5, 1 h after dialysis start had simultaneous aPTT ratios > 2.5. Similar findings were present at 1 h for patients with AVF/AVG and at dialysis end for catheter use. No clinically significant clotting of the extracorporeal circuit was noted during the studied sessions. Dialyzer's blood compartment volume was reduced with a median of 9% (6-20%) without significant effect of UFH dose, aPTT or ACT measurements and vascular access type.

Conclusion

UFH dose adaptations based on ACT measurements frequently result in excessive anticoagulation according to aPTT results. Higher doses of UFH are used in patients with hemodialysis catheters without evidence that this reduces dialyzer clotting.

Time-resolving characterization of molecular weight retention changes among three synthetic high-flux dialyzers

BACKGROUND

Toxin removal capacity (i.e. performance) of a dialyzer is not constant but diminishes during treatment, as the adsorption of proteins to the membrane provides an additional barrier to uremic solutes. We investigated time-resolving molecular weight retention changes among synthetic high-flux dialyzers and compare the results with recent data from a randomized controlled trial.

METHODS

In plasma recirculation experiments over 240min, sieving coefficients (SC) for β2-microglobulin, myoglobin and albumin were determined for the FX CorAL (Fresenius Medical Care), ELISIO (Nipro) and xevonta (B. Braun). Molecular weight retention (MWR) curves were generated and the shifts over 120min were characterized. Effective pore radius was determined, and the predicted albumin loss was compared with clinical data.

RESULTS

SC decreased over time for all dialyzers (mean relative decrease across all dialyzers: β2-microglobulin: 8.0% (120min); myoglobin: 56.6% (240min); albumin: 94.1% (240min)). FX CorAL (7.3%, 52.6% and 91.1%) and ELISIO (7.7%, 51.0% and 93.8%) showed a lower decrease than xevonta (9.0%, 66.2% and 97.4%). For all dialyzers, MWR curves shifted towards lower molecular weight, with the lowest shift for FX CorAL (by 0.23nm at SC50%, 120 min) and highest for xevonta (0.50nm). FX CorAL had the highest slope over time and the smallest decrease in the effective pore radius (2min: 2.31nm, 120min: 2.08nm). Predicted albumin loss over 4h was highest for xevonta (609.3mg) and comparable between ELISIO (283.6mg) and FX CorAL (313.3mg).

CONCLUSIONS

Substantial differences in the temporal performance profile of dialyzers exist. The present approach allows characterization of dialyzer permeability changes over time using standard, clinically relevant protein markers.

Real-World Performance of High-Flux Dialyzers in Patients With Hypoalbuminemia

There is little research on factors that influence the choice of dialyzer in patients undergoing hemodialysis. In patients at risk for poorer outcomes, including those with hypoalbuminemia, understanding how this choice impacts clinical parameters could inform patient management. The objective of this real-world analysis was to evaluate the use and performance of four single-use (i.e., nonreuse [NR]), high-flux Optiflux dialyzers with varying surface areas (F160NR [1.5 m2], F180NR [1.7 m2], F200NR [1.9 m2], and F250NR [2.5 m2]) in patients (N = 271) with baseline hypoalbuminemia (≤3.5 g/dl) receiving hemodialysis at a medium-sized dialysis organization. Thrice weekly, in-center dialysis was delivered for 6 months without adjustments to the hemodialysis prescription. Larger dialyzers were more frequently used in men, patients with higher body mass indices, and those with diabetes. Increases in serum albumin from baseline (month 1) to month 6 (p < 0.05) were observed with all dialyzer sizes. A mean increase in hemoglobin of 0.31 g/dl was also observed (p < 0.001). Among patients exhibiting increased serum albumin levels (n = 177), reductions in the neutrophil-to-lymphocyte ratio, a marker of inflammation, were observed (mean: 0.90; p < 0.001). These results support the use of high-flux dialyzers in patients with hypoalbuminemia.

Improved hemocompatibility of polysulfone hemodialyzers with Endexo® surface modifying molecules

Anticoagulation therapy is widely used to reduce clotting during hemodialysis (HD), but may cause adverse effects in end-stage kidney disease patients. A new hemodialyzer with a membrane modified by surface modifying molecule was developed to improve hemocompatibility that aimed to reduce the need for anticoagulation during dialysis treatments. We compared membrane surface characteristics and in vitro hemocompatibility of the new hemodialyzer to the standard polysulfone (PSF) hemodialyzer membrane. Scanning electron microscopy, contact angle measurement (68° ± 3° test vs. 41.6° ± 6° control), and X-ray photoelectron spectrometry measurement for fluorine atomic % (7.4% ± 0.4% test vs. not detectable control), showed that the membrane surface was modified with surface modifying macromolecule (SMM1) but maintained membrane structure and surface hydrophilicity. Zeta potential of the blood-contacting surface showed that the absolute surface charge was reduced at neutral pH (-3.3 mV ± 1.1 mV test vs. -15.6 mV ± 1.0 mV control). Platelet count reduction was significantly less for the SMM1-modified dialyzer (40.88% ± 21.89%) compared to the standard PSF dialyzer (62.62% ± 34.13%), along with Platelet Factor 4 (1824.10 ng/ml ± 436.26 ng/ml test vs. 2479.00 ng/ml ± 852.96 ng/ml control). These studies demonstrate the successful incorporation of SMM1 into the new hemodialyzer with the expected results. Our in vitro experiments indicate that the SMM1-modified hemodialyzers could improve hemocompatibility compared to standard PSF hemodialyzers and have the potential to minimize the patient's anticoagulant requirements during HD. Additional research with SMM1 additives incorporated into the entire dialysis circuit and use in a clinical settings are required to confirm these promising findings.

Evaluation and comparison of polysulfone TS-UL and PMMA NF-U dialyzers versus expanded hemodialysis and postdilution hemodiafiltration

Toray has created a new generation of dialyzers, the polysulphone (TS) UL series, and polymethylmethacrylate (PMMA) NF-U series, which offer enhanced efficacy over the previous TS-S series and NF-H series. The aim of this study was to evaluate the safety and efficacy of these dialyzer series versus contrasted expanded hemodialysis (HDx) and postdilution hemodiafiltration (HDF). We conducted a prospective study in 12 patients. Each patient underwent six dialysis sessions: FX80 Cordiax in HD, Toraysulfone TS-1.8 UL in HD, Theranova 400 in HDx, polymethylmethacrylate (PMMA) NF-2.1 U in HDF, Toraysulfone TS-2.1 UL in HDF, and FX80 Cordiax in HDF. The removal ratios (RRs) of urea, creatinine, ß₂ -microglobulin, myoglobin, prolactin, α₁ -microglobulin, α₁ -acid glycoprotein, and albumin were compared intraindividually. Dialysate albumin loss was also measured. The RRs for β₂ -microglobulin, myoglobin, prolactin, α₁ -microglobulin, and α₁ -acid glycoprotein were higher with the TS-2.1 UL and FX80 Cordiax dialyzers in HDF than those obtained with HD treatments and NF-2.1 U in HDF. The β₂ -microglobulin, myoglobin, and prolactin RRs were also higher with HDx than those obtained with HD treatments. The myoglobin and prolactin RRs were higher with TS-1.8 UL in HD than those obtained with helixone dialyzers in HD. Dialysate albumin loss was less than 3 g in all situations except in TS-2.1 UL in HDF. The highest global removal score values were obtained with the TS-2.1 UL and helixone dialyzers in HDF. Significant differences were found between all study situations. In conclusion, the new generation dialyzers, Toraysulfone TS Series UL and PMMA NF-U series, show excellent behaviour and tolerance in HD and HDF, representing an upgrade versus their predecessor series. The higher permeability of the TS UL series has been proven with higher efficiency in HD and maximum performance in HDF. The new PMMA NF-U series allows the use of HDF with good efficiency and complete safety.

Slipping Through the Pores: Hypoalbuminemia and Albumin Loss During Hemodialysis

Hypoalbuminemia results when compensatory mechanisms are unable to keep pace with derangements in catabolism/loss and/or decreased synthesis of albumin. Across many disease states, including chronic kidney disease (CKD), hypoalbuminemia is a well-established, independent risk factor for adverse outcomes, including mortality. In the setting of CKD, reduced serum albumin concentrations are often a manifestation of protein-energy wasting, a state of metabolic and nutritional alterations resulting in reduced protein and energy stores. The progression of CKD to kidney failure and the initiation of maintenance hemodialysis (HD) further predisposes an already at-risk population toward hypoalbuminemia such that approximately 60% of HD patients have albumin concentrations <4.0 g/dl. Albumin loss into the dialysate through the dialyzer appears to be a potentially modifiable cause of hypoalbuminemia in some patients. A group of newer dialyzers for maintenance HD-sometimes termed protein-leaking or medium cut-off membranes-aim to improve clearance of middle molecules (vs high flux dialyzers) but are associated with increased albumin losses. In this article, we will examine the impact of dialyzer selection on albumin losses during conventional HD, including the clinical relevance of such losses on serum albumin levels. Data on the clinical relevance of albumin losses during dialysis and current gaps in the evidence base are also discussed.

The Dialyzer Identification Code (DIC): A filter characteristics codification for dialyzer choice in renal replacement therapy

The dialyzer is the core element of extracorporeal blood purification therapies where several processes take place depending on specific membrane characteristics. To date, the filter choice requires preliminary knowledge of all its characteristics as they cannot be easily deduced from the commercial trade name, hence the difficulty in identifying easily equivalent dialyzers and clearly comparing single-filter characteristics. The choice of improper dialyzers for a specific treatment can determine a less-effective blood purification and potentially harmful treatments. We aimed to propose a univocal and standardized alphanumeric string to summarize essential filter properties in the Dialyzer Identification Code (DIC). DIC clearly describes device characteristics and allows to compare different dialyzer performances without resorting to the technical data sheets. Therefore, the presence of the DIC on every device facilitates information retrieval on the dialyzer, its intended use, and can facilitate matching the dialysis modality to correct dialyzers achieving a personalized renal replacement therapy. The standard filter characteristics codification by the DIC may further optimize correct extracorporeal blood purification prescriptions and the use of equivalent filters from different providers avoiding treatment inefficiency, clinical complications, and improving patient safety.

Ex vivo lung perfusion with perfusate purification for human donor lungs following prolonged cold storage

Background

Ex vivo lung perfusion (EVLP) has developed as the most effective technique for estimating marginal donor lungs. This study attempted to extend the EVLP running time to 12 hours with a dialyzer rather than periodically replacing the perfusate.

Methods

Human donor lungs rejected by the clinical lung transplantation (LTx) team were obtained. After cold storage lasting 18-24 hours, lungs were randomly assigned to 2 groups: a control group and a perfusate purification (PP) group. The control group underwent EVLP in the traditional way, while a dialyzer was added into the circuit as a bypass in the PP group. The effects on lung function, microenvironment, inflammatory response, and cell death were evaluated.

Results

A total of 8 rejected donor lungs were obtained and each group was assigned to 4 cases of EVLP. Three cases were prematurely terminated because of serious lung edema and decreased lung function. There were no significant differences in airway pressure, pulmonary artery pressure, and oxygen concentration between the two groups in the first 8 hours. The pH in the control group was significantly lower than that in the PP group, and the levels of potassium and lactate were significantly higher than those in the PP group. Inflammatory markers increased in both groups, while IL-6 and IL-10 were higher in the PP group in the first 6 hours. Hematoxylin and eosin (HE) staining revealed lung injuries in both groups, but no significant difference was noted in the HE-stained slides. There were significantly more TUNEL-positive cells in the control group (69.5%±4.0%) than in the PP group (47.5%±3.9%) (P=0.000).

Conclusions

Using the modified method of EVLP reduces the high cost caused by exchanging perfusion fluid per hour and could prolong the normothermic preservation time of donor lungs.

Multipoint dilution hemofiltration: A new technology for maximum convective clearance

Convection-based renal replacement therapies (RRTs) have the potential to improve patient outcomes when compared to diffusion-based RRT such as hemodialysis (HD), but have limited clearance rates. We propose and characterize multipoint dilution hemofiltration (MPD-HF), a purely convective blood purification technology which removes the fundamental filtration limit associated with convective RRT resulting in clearance rates on par with HD. In MPD-HF, filtration of liquid and solutes occurs along the length of the hollow fibers that convey the blood, and substitution fluid is pushed into the fibers at multiple points along their length. Since multiple filtration and dilution steps are contained within one pass of the blood through the hollow fiber, the fraction of fluid that can be filtered may be increased to allow a high clearance rate that removes a wide range of toxins. In vitro tests yielded an average steady-state filtrate fraction of 68%, exceeding commercial HDF cartridge filtrate fractions by a factor of approximately 3. The molecular weights of molecules cleared spans up to the cutoff of 66 kDa for albumin.

Evaluation of Different Dialyzers and the Impact of Predialysis Albumin Priming in Intermittent Hemodialysis With Reduced Anticoagulation

Introduction

Systemic anticoagulation is widely used in routine clinical hemodialysis, but can be contraindicated in specific settings. Anticoagulant-free treatment regimens are prone to failure even in chronic intermittent hemodialysis. We quantified fiber blocking in settings of reduced anticoagulation to assess performance of different dialyzers and the potential benefit of albumin priming.

Methods

This crossover study included 10 patients performing 4 hours of hemodialysis at midweek in 7 different settings: that is, using Solacea 19H and FX800, both with regular and half dose of anticoagulation, Evodial 1.3 without systemic anticoagulation, and FX800 (half dose) and Evodial (no anticoagulation) when primed with a human albumin solution. Dialyzer fiber blocking was visualized in the dialyzer outlet potting using a 3-dimensional computed tomography (CT) scanning technique on micrometer resolution.

Results

No sessions had to be prematurely interrupted because of circuit clotting. The relative number of open fibers post dialysis was not influenced by the reduction of anticoagulation in the Solacea making this dialyzer superior in fiber patency in this setting above both the FX800 with reduced anticoagulation and the Evodial with no anticoagulation. Furthermore, no differences in relative number of open fibers were found in the FX800 and Evodial dialyzers with versus without albumin priming.

Conclusion

In situations in which reduced anticoagulation is indicated, the asymmetric triacetate ATA Solacea dialyzer outperforms a dialyzer with a conventional polysulfone membrane (FX800) or with the heparin-coated polyacrylonitrile membrane (Evodial). The use of human albumin to prime the dialysis circuit did not improve dialyzer patency.

High-permeability alternatives to current dialyzers performing both high-flux hemodialysis and postdilution online hemodiafiltration

Most high-flux dialyzers can be used in both hemodialysis (HD) and online hemodiafiltration (OL-HDF). However, some of these dialyzers have higher permeability and should not be prescribed for OL-HDF to avoid high albumin losses. The aim of this study was to compare the safety and efficacy of a currently used dialyzer in HD and OL-HDF with those of several other high permeability dialyzers which should only be used in HD. A prospective, single-center study was carried out in 21 patients. Each patient underwent 5 dialysis sessions with routine dialysis parameters: 2 sessions with Helixone (HD and postdilution OL-HDF) and 1 session each with steam sterilized polyphenylene, polymethylmethacrylate (PMMA), and medium cut-off (MCO) dialyzers in HD treatment. The removal ratios (RR) of urea, creatinine, ß₂ -microglobulin, myoglobin, prolactin, α₁ -microglobulin, α₁ -acid glycoprotein, and albumin were compared intraindividually. A proportional part of the dialysate was collected to quantify the loss of various solutes, including albumin. Urea and creatinine RRs with the Helixone-HDF and MCO dialyzers were higher than with the other 3 dialyzers in HD. The β₂ -microglobulin, myoglobin and prolactin RRs with Helixone-HDF treatment were significantly higher than those obtained with all 4 dialyzers in HD treatment. The β₂ -microglobulin value obtained with the MCO dialyzer was also higher than that obtained with the other 3 dialyzers in HD treatment. The myoglobin RR with MCO was higher than those obtained with Helixone and PMMA in HD treatment. The prolactin RR with Helixone-HD was significantly lower than those obtained in the other 4 study sessions. The α₁ -microglobulin and α₁ - acid glycoprotein RRs with Helixone-HDF were significantly higher than those obtained with Helixone and PMMA in HD treatment. The albumin loss varied from 0.54 g with Helixone-HD to 3.3 g with polyphenylene. The global removal score values ((Urea_RR + β₂ -microglobulin_RR + myoglobin_RR + prolactin_RR + α₁ -microglobulin_RR + α₁ -acid glycoprotein_RR - albumin_RR )/6) were 43.7% with Helixone-HD, 47.7% with PMMA, 54% with polyphenylene, 54.8% with MCO and 59.6% with Helixone-HDF, with significant differences. In conclusion, this study confirms the superiority of OL-HDF over HD with the high-flux dialyzers that allow both treatments. Although new dialyzers with high permeability can only be used in HD, they are in an intermediate position and some are very close to OL-HDF.

Proteins adsorbed to a polysulfone hemodialysis membrane under heparin and citrate anticoagulation regimens

The study aim was to compare molecular-level effects (blood-dialyzer interactions) of heparin and citrate anticoagulation using proteome-wide analysis of biofilm adsorbed to dialysis membrane. Ten patients receiving maintenance hemodialysis were examined in a crossover design under three different anticoagulation regimens, namely citrate, heparin, and anticoagulation-free (control). Following a regular hemodialysis session (4 hours, polysulfone membrane), dialyzers were flushed and the surface biofilm eluted by acetic acid. Protein composition of the eluates was determined by 2-dimensional gel electrophoresis and resulting patterns compared between regimens. Proteins responsible for the difference were identified by mass spectrometry. Citrate anticoagulation was associated with significantly less protein adsorption to the membrane than heparin (2.2 [1.1-2.9] mg vs. 6.5 [2.9-11.6] mg, P = 0.009). Among the proteins identified as major discriminators between citrate and the other regimens, fibrin α-chain fragments of molecular weight below 40 kDa prevailed. In these fragments, an analysis of the amino acid sequence has been performed by comparison with the UniProt database. It showed missing α-chain cross-links. On the contrary, heparin prevented adsorption and cleavage of several heparin-binding proteins; especially complement factor H-related protein 3, insulin-like growth factor binding proteins (2, 4, and 5), and chemerin. Compared to heparin, citrate is associated with less protein adsorption and imperfectly crosslinked fibrin clot formation. Membrane adsorptive properties are significantly modified by the anticoagulation regimen.

Anaphylactic reaction to ethylene oxide in a hemodialysis patient

We present the case of a patient who developed a severe systemic allergic reaction during initiation of hemodialysis. The reaction completely resolved by switching the dialysis filter sterilized by ethylene oxide to a steam sterilized filter. Ethylene oxide is used to sterilize heat sensitive medical devices, and although allergic reactions related to ethylene oxide have been reported before, awareness is lacking among providers in the inpatient setting, specifically in the intensive care unit setting.

Comparison of biocompatibility in polysulfone dialysis membranes with different sterilization

INTRODUCTION

Polysulfone (PSf) membrane has been widely used for hemodialysis. A few studies have been reported in which a method of sterilization may affect biocompatibility. In this study, the comparison was made between two PSf membranes in order to evaluate the effect of sterilization from the biocompatibility point of view.

METHODS

We investigated the biocompatibility of the following two dialyzers, that is, APS-11SA (Asahi Kasei medical Co., Tokyo, Japan), sterilized by gamma-ray irradiation, and RENAK PS-1.0 (Kawasumi laboratories, Tokyo, Japan), sterilized by autoclave. Heparin of 40 units/mL was put in a syringe, and test blood was collected from healthy volunteers. Then, the dialyzer and blood circuit were filled with the test blood. Subsequently, the blood was circulated by a roller pump at the rate of 200 mL/min. We measured the platelet counts, CD41 and CD42b platelet surface markers, beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) at 30, 120, and 240 minutes, respectively.

FINDINGS

The platelet counts at 30, 120, and 240 minutes decreased significantly from the initiation of blood circulation in both dialyzers. The average beta-TG and PF4 increased from 61.3 ± 22.1 and 17.0 ± 6.4 ng/mL to 680.7 ± 217.1 and 550.7 ± 116.7 ng/mL with APS-11SA and to 454.3 ± 85.6 and 402.0 ± 58.0 ng/mL with RENAK PS-1.0, respectively. The average expression of CD41 and CD42b in APS-11SA and RENAK PS-1.0 was similar.

DISCUSSION

There are some reports that the gamma-ray irradiation changes the membrane structure of the PSf membrane, crosslinking the polyvinylpyrrolidone (PVP), a hydrophilic agent, on to the membrane. On the other hand, excess amount of PVP may have been eluted during the rinsing procedure in RENAK PS-1.0 because it was sterilized with autoclave. Because both these factors influenced on our results, APS-11SA and RENAK PS-1.0 dialyzers showed excellent blood compatibility.

Proteomics investigation of the changes in serum proteins after high- and low-flux hemodialysis

PURPOSE

This study aimed to use proteomics methods to investigate the changes in serum protein levels after high- and low-flux hemodialysis (HD).

METHODS

Before and after HD, serum samples were obtained from two selected patients who were treated with a Polyflux 140 H high-flux dialyzer and a Polyflux 14 L low-flux dialyzer during two continuous therapy sessions. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was performed to identify the proteins.

RESULTS

A total of 212 and 203 serum proteins were identified after high-flux and low-flux HD, respectively. After high-flux HD, 21 proteins increased, and 132 proteins decreased. After low-flux HD, 87 proteins increased, and 45 proteins decreased. High-flux HD led to a significantly greater reduction in protein levels than low-flux HD (0.73 ± 0.13 vs. 0.84 ± 0.18, p = .00). Among the increased and decreased proteins, the isoelectric point (pI) values mainly ranged from 5 to 7, and the molecular weights (Mws) were mostly smaller than 30 kDa. The serum proteins showed no difference in pI or Mw for high- and low-flux HD. Gene ontology (GO) analysis showed that the detected proteins were related to immune system processes and complement activation.

CONCLUSIONS

Serum protein levels differentially changed after high- and low-flux HD. Long-term effects should be observed in future studies.

Effects of enoxaparin on myeloperoxidase release during hemodialysis

Myeloperoxidase (MPO) is a proteolytic and prooxidant enzyme largely assembled with the vascular wall, and a heparin-binding protein. We studied if low-molecular-weight heparin enoxaparin administered for hemodialysis (HD) anticoagulation causes systemic MPO activation. Plasma MPO levels were measured in patients undergoing maintenance HD with an intravenous bolus of enoxaparin. Patients were retested during HD employing dialyzers with heparin-grafted polyacrylonitrile membrane and no systemic enoxaparin administration. During enoxaparin-anticoagulated HD plasma MPO levels strikingly increased in all patients (8.6-fold at 10 minutes and 3.3-fold at 120 minutes, both P < 0.0001). The increments were directly associated with the enoxaparin dosage and strongly inversely with the predialysis levels of the enzyme. The increase in plasma MPO during systemic heparin-free HD was significantly less pronounced. Enoxaparin administered for HD anticoagulation induces a marked and dose-dependent increase in plasma MPO as a plausibly favorable result of the liberation of the enzyme from the vascular wall.

A high blood level in the venous chamber and a wet-stored dialyzer help to reduce exposure for microemboli during hemodialysis

During hemodialysis (HD), microemboli develop in the blood circuit of the apparatus. These microemboli can pass through the venous chamber and enter into the patient's circulation. The aim of this study was to investigate whether it is possible to reduce the risk for exposure of microemboli by altering of the treatment mode. Twenty patients on chronic HD were randomized to a prospective cross-over study of three modes of HD: (a) a dry-stored dialyzer (F8HPS, Fresenius, steam sterilized) with a low blood level in the venous chamber (DL), (b) the same dialyzer as above, but with a high level in the venous chamber (DH), and (c) a wet-stored dialyzer (Rexeed, Asahi Kasei Medical, gamma sterilized) with a high blood level (WH). Microemboli measurements were obtained in a continuous fashion during 180 minutes of HD for all settings. A greater number of microemboli were detected during dialysis with the setting DL vs. WH (odds ratio [OR] 4.07, 95% confidence interval [CI] 4.03-4.11, P<0.0001) and DH vs. WH (OR 1.18, 95% CI 1.17-1.19, P<0.0001) and less for DH vs. DL (OR 0.290, 95% CI 0.288-0.293, P<0.0001). These data indicate that emboli exposure was least when using WH, greater with DH, and most with DL. This study shows that using a high blood level in the venous chamber and wet-stored dialyzers may reduce the number of microemboli.

Semipermeable Hollow Fiber Phantoms for Development and Validation of Perfusion-Sensitive MR Methods and Signal Models

Two semipermeable, hollow fiber phantoms for the validation of perfusion-sensitive magnetic resonance methods and signal models are described. Semipermeable hollow fibers harvested from a standard commercial hemodialysis cartridge serve to mimic tissue capillary function. Flow of aqueous media through the fiber lumen is achieved with a laboratory-grade peristaltic pump. Diffusion of water and solute species (e.g., Gd-based contrast agent) occurs across the fiber wall, allowing exchange between the lumen and the extralumenal space. Phantom design attributes include: i) small physical size, ii) easy and low-cost construction, iii) definable compartment volumes, and iv) experimental control over media content and flow rate.

Immunologic function and survival in hemodialysis patients

BACKGROUND

Although the medical determinants of mortality in patients with end-stage renal disease (ESRD) treated with hemodialysis (HD) are well appreciated, the contribution of immunologic parameters to survival in such patients is unclear, especially when variations in age, medical comorbidity and nutrition are controlled. In addition, although dysregulation of cytokine metabolism has been appreciated in patients with ESRD, the association of these parameters with outcomes has not been established. Recently, the type of dialyzer used in patients' treatment has been associated with survival, but the mechanisms underlying these findings, including their immune effects, have not been established. We conducted a prospective, cross-sectional, observational multicenter study of urban HD patients to determine the contribution of immunological factors to patient survival. We hypothesized increased proinflammatory cytokines would be associated with increased mortality, and that improved immune function would be associated with survival.

METHODS

Patients were assessed using demographic and anthropometric indices, Kt/V, protein catabolic rate (PCR) and immunologic variables including circulating cytokine [interleukin (IL)-1, IL-2, IL-4, IL-5, IL-6, IL-12, IL-13 and tumor necrosis factor (TNF)-alpha] levels, total hemolytic complement activity (CH50), and T cell number and function. A severity index, previously demonstrated to be a mortality marker, was used to grade medical comorbidity. A Cox proportional hazards model, controlling for patients' age, severity index, level of serum albumin concentration, dialyzer type and dialysis site was used to asses relative survival risk.

RESULTS

Two hundred and thirty patients entered the study. The mean (+/- SD) age of the population was 54.4 +/- 14.2 years, mean serum albumin concentration was 3.86 +/- 0.47 g/dl, mean PCR was 1.1 +/- 0.28 g/kg/day, and mean Kt/V 1.2 +/- 0.3. Patients' serum albumin concentration was correlated with levels of Kt/V and PCR, and their circulating IL-13 and TNF-alpha levels, but negatively with their circulating IL-2 levels, T-cell number and T-cell antigen recall function. T-cell antigen recall function correlated negatively with PCR, but not Kt/V. There was no correlation of any other immune parameter and medical or demographic factor. Immune parameters, were all highly intercorrelated. Mean level of circulating cytokines in HD patients were in all cases greater than those of a normal control group. There were few differences in medical risk factors or immune parameters between patients treated with different types of dialyzers. After an almost three-year mean follow-up period, increased IL-1, TNF-alpha, IL-6, and IL-13 levels were significantly associated with increased relative mortality risk, while higher levels of IL-2, IL-4, IL-5, IL-12, T-cell number and function, and CH50 were associated with improved survival. The difference in survival between patients treated with unmodified cellulose dialyzers and modified or synthetic dialyzers approached the level of statistical significance, but there were no differences in levels of circulating cytokines between these two groups.

CONCLUSIONS

Higher levels of circulating proinflammatory cytokines are associated with mortality, while immune parameters reflecting improved T-cell function are associated with survival in ESRD patients treated with HD, independent of other medical risk factors. These factors may serve as markers for outcome. The mechanism underlying the relationship of immune function and survival, and the effect of interventions to normalize immune function in HD patients should be studied.