Hemodiafiltration with online regeneration of the ultrafiltrate

Hemodiafiltration with endogenous reinfusion of the regenerated ultrafiltrate (HFR): towards a convective, diffusive, and adsorptive dialysis

Hemodiafiltration with endogenous reinfusion of the ultrafiltrate (HFR) is a dialysis technique characterized by a resin cartridge with adsorptive properties that combines the mechanisms of diffusion, convection, and adsorption in a single therapeutic regimen. After nearly 20 years of clinical experience with HFR, this article reviews the accumulated evidence with this technique, considering whether adsorption reduction, as a third purification mechanism, should be the next step in the treatment of hemodialysis patients. HFR, beyond producing an extensive removal of uremic toxins, has demonstrated to reduce the loss of nutrients and other physiological components during the dialysis session as compared to online hemodiafiltration, ameliorating the inflammatory state and oxidative stress in this population. In addition to its ease of use, the technique is also highly biocompatible and can be used in patients with a compromised vascular access. Based on these observations, HFR appears to be an especially useful therapy for high-comorbidity patients, including those with frailty, malnutrition, or cardiovascular disease. In this review, we, as a consensus panel of nephrologists experienced with HFR, survey existing literature and summarize our views on when to use this technique, which patients may be best suited for HFR, and how to effectively prescribe and monitor this modality of dialysis in daily clinical practice.

Reconsidering adsorption in hemodialysis: is it just an epiphenomenon? A narrative review

Since the first attempt at extracorporeal renal replacement therapy, renal replacement therapy has been constantly improved. In the field of hemodialysis, substantial efforts have been made to improve toxin removal and biocompatibility. The advent of hemodiafiltration (HDF) and, more recently, of mid cut-off membranes have contributed to management of patients with end-stage renal disease (ESRD). Although several uremic toxins have been discovered, we know little about the clinical impact of their clearance in hemodialysis patients. In addition, a great deal of progress has been made in the areas of filtration and diffusion, but the adsorptive properties of hemodialysis membranes remain under-studied. The mechanism of action of adsorption is based on the attraction between the polymer of the dialysis membrane and the solutes, through hydrophobic interactions, ionic or electrostatic forces, hydrogen bonds or van der Waals forces. Adsorption on the dialysis membrane depends on the membrane surface, pore size, structure and electric load. Its involvement in toxin removal and biocompatibility is significant, and is not just an epiphenomenon. Diffusive and convective properties cannot be improved indefinitely and high permeability membranes, despite their high performance in the clearance of many toxins, have several limitations for long-term use in hemodialysis. This review will discuss why adsorption should be reconsidered and better characterized to improve efficiency and adequacy of dialysis.

The Use of Supra-Hemodiafiltration in Traumatic Rhabdomyolysis and Acute Kidney Injury: A Case Report

Oliguric acute kidney injury due to traumatic rhabdomyolysis can be potentially lethal if the proper medical therapy combined with extracorporeal detoxification is not performed. Different extracorporeal techniques are available to overcome this syndrome. Here, we report the first case of removal of myoglobin and successful recovery from acute kidney injury in an elderly septic patient using supra-hemodiafiltration with endogenous reinfusion technique (HFR-Supra) combined with the medical therapy.

Choosing New Adsorbents for Endogenous Ultrapure Infusion Fluid: Performances, Safety and Flow Distribution

Adsorption may notably contribute to the removal of uremic toxins and to the efficiency of hemodialysis. We examined different uncoated stationary matrixes, charcoals and synthetic resins to establish their adsorptive capacities in relation to low (urea, creatinine) and high molecular weight (β2-microglobulin, myoglobin) compounds in in vitro conditions (steady state and flow-through) using isotonic solutions or uremic ultrafiltrate. Trace metal, particle release analyses and scanning electron microscopy of different adsorbents were performed. Dynamic flow-distribution studies were made using 99Technetium and analysing the different regions of interest by single head γ-camera. We show that adsorbents may differ greatly as to their adsorptive capacity depending on flow rate, nature, and total mass of the compounds to be removed from the ultrafiltrate. These studies suggest a methodological approach for screening stationary matrixes for possible application in hemodialysis.

Nanoscale Modulation of the Pore Dimensions, Size Distribution and Structure of a new Polysulfone-Based High-Flux Dialysis Membrane

Current haemodialysis therapy modalities such as haemodiafiltration enhance the removal of larger uraemic solutes from the blood of patients on end-stage renal disease. A number of clinical investigations have demonstrated the clinical benefits of such therapies in contributing towards better patient survival rates and an improved quality of life.

A fundamental prerequisite to the application of convective treatment modalities is the availability of appropriate, technologically-advanced high-flux dialysis membranes that are able to eliminate larger uraemic substances with high efficiency but without causing an excessive leakage of useful proteins. A new membrane, Helixone®, has been developed specifically to meet the present-day requirements of high-flux dialysis and haemodiafiltration therapies involving large substitution rates. The application of nanotechnology fabrication principles and procedures has enabled the development of a membrane having highly-defined inner, separating layer surface structures that offer minimal resistance to the removal of large molecular weight substances across the membrane; for the first time, pore size dimensions, pore size distribution and pore geometry have been modulated and controlled at the nanoscale level for Helixone®.

This paper describes the characterisation of the essential structure- and permeation-related parameters of the new membrane using a number of physical analytical techniques.

Uremic Toxicity: Present State of the Art

The uremic syndrome is a complex mixture of organ dysfunctions, which is attributed to the retention of a myriad of compounds that under normal condition are excreted by the healthy kidneys (uremic toxins). In the area of identification and characterization of uremic toxins and in the knowledge of their pathophysiologic importance, major steps forward have been made during recent years. The present article is a review of several of these steps, especially in the area of information about the compounds that could play a role in the development of cardiovascular complications. It is written by those members of the Uremic Toxins Group, which has been created by the European Society for Artificial Organs (ESAO). Each of the 16 authors has written a state of the art in his/her major area of interest.

Effect of On-Line Hemodiafiltration with Endogenous Reinfusion (HFR) on the Calcium-Phosphorus Metabolism: Medium-Term Effects

Aim

The purpose of the study was to examine the effect of hemodiafiltration with endogenous reinfusion (HFR) compared to hemodialysis (HD) on 28 uremic patients with secondary hyperparathyroidism (2HPT) but positively selected for good and stable control of phosphatemia in order to evaluate the independent effects of dialysis treatments on bone turnover metabolism. Methods: The study was divided into 3 periods of observation: a) HD for three months; b) HFR for three months; c) HFR for a further 3 months. We analysed the trend of: whole PTH, 1–84 PTH, 7–84 PTH, alkaline phosphatase and its bone isoenzyme, total and ionised calcium, phosphatemia, dose of phosphate binder agents, β2-microglobulin, CRP. All the variations found were evaluated through mean values ± SD, t-tests, multivariate analysis.

Results

We observed a deceleration in bone turnover characterized by a reduction of the total and bone alkaline phosphatase (IU/mL) from 92.3 ± 82.8 and 35.8 ± 49.8 at the end of HD to 63.4 ± 23.9 and 16.0 ± 8.7 at the end of HFR, respectively, and 1–84 PTH from 317.5 ± 264.6 pg/mL at the end of HD to 287.5 ± 258.9 pg/mL at the end of the 3rd month of HFR. β2-microglobulin was reduced from 32.9 ± 16.1 mg/L at the end of HD to 26.4 ± 8.1 mg/L already at the end of the first three months of HFR. CRP was reduced from 2.5 ± 2.6 mg/dL at the beginning of the study to 1.3 ± 1.7 mg/dL at the end of HFR. There were no differences with regard to: dialytic efficiency, nutritional status, calcemia, phosphatemia (maintained in the K-DOQI range for the entire duration of the study), also thanks to more careful use of phosphate chelating agents.

Conclusion

We are of the opinion that HFR - essentially thanks to the use of ultrapure endogenous infusate - induces a deceleration in bone turnover due to 2PHT. In addition, phosphate substraction in HFR is better compared to HD, thanks to the improvement of the anti-inflammatory conditions by removing the cytokines harmful to bone metabolism and excluding a priori the negative effects related to hyperphosphatemia. (Int J Artif Organs 2006; 29: 1042–52)

Sodium Prescription in the Prevention of Intradialytic Hypotension: New Insights into an Old Concept

Background: Sodium prescription in patients with intradialytic hypotension remains a challenge for the attending nephrologist, as it increases dialysate conductivity in hypotension-prone patients, thereby adding to dietary sodium levels. Methods: New sodium prescription strategies are now available, including the use of a mathematical model to compute the sodium mass to be removed during dialysis as a physiological controller. Results: This review describes the sodium load of patients with end-stage renal disease on chronic hemodialysis (HD) and discusses 2 strategies to remove excess sodium in patients prone to intradialytic hypotension, namely, Profiled HD and the hemodiafiltration Aequilibrium System. Conclusion: The Profiled HD and Aequilibrium System trial both proved effective in counteracting intradialytic hypotension.

Effect of hemodiafiltration with endogenous reinfusion on overt idiopathic chronic inflammation in maintenance hemodialysis patients: a multicenter longitudinal study

Chronic inflammation is widely diffuse in maintenance hemodialysis (MHD) patients and is associated with poor survival. Hemodiafiltration with endogenous reinfusion (HFR) is a dialysis technique, highly biocompatible, able to adsorb proinflammatory cytokines and to decrease amino acids and antioxidants loss. These features could be helpful in MHD patients affected by idiopathic chronic inflammation, but this issue remains to be elucidated. We performed a multicenter longitudinal study to assess the effect of the switching from bicarbonate HD to HFR in patients with serum C-reactive Protein (CRP) > 5 mg/L coupled with albumin <4.0 g/dL in the last 6 months. We enrolled 24/176 (14%) patients, of which 20 patients were assessed at 4 months and 18 completed the study. We excluded 11 patients with evident causes of inflammation. At baseline, serum levels of CRP (18.7[7.0-39.4] mg/L) and albumin (3.5[3.3-3.7] g/dL) were significantly correlated (r = -0.49; P = 0.028). The effect on CRP and albumin was almost evident in the first 4 months and remained stable until to eighth month. A strict correlation (R = -0.49; 0.040) between percentage change of CRP (-35%) and albumin (+14%) after 8 months of HFR. These effects were associated with the reduction of IL-6, IL-1β, and TNF-α and the increment of pre-albumin and leptin, whereas the serum levels of Branched Chain Amino Acid (BCAA) remained unchanged. In MHD patients affected by idiopathic chronic inflammation the switching from BHD to HFR is associated with improvement of inflammation. Whether these favorable effects may modify the outcomes of these high-risk patients needs to be confirmed by studies ad hoc.

Evidence that p-cresol and IL-6 are adsorbed by the HFR cartridge: towards a new strategy to decrease systemic inflammation in dialyzed patients?

Introduction

Hemodialysis (HD) and hemodiafiltration clear only with a low efficiency the plasma from interleukin-6 and p-cresol, two protein-bound uremic toxins associated with high cardiovascular risk in end stage renal disease. HFR Supra is a double-chamber hemodiafiltration system in which the ultrafiltrate returns to the patient after its regeneration through a resin cartridge that binds hydrophobic and protein-bound solutes. In the present study, we evaluated whether the HFR cartridge can also bind total p-cresol and IL-6 and remove them from the ultrafiltrate.

Methods

We compared the levels of IL-6 and p-cresol in ultrafiltrate samples collected at the inlet (UF_in) and at the outlet (UF_out) of the cartridge at the start or at the end of a 240 min HFR session in 12 inflamed chronic HD patients. The pro-inflammatory activity of the ultrafiltrate samples was also determined by evaluating the changes that they induced in IL-6 mRNA expression and protein release in peripheral blood mononuclear cells from 12 healthy volunteers. IL-6 and p-cresol circulating levels were also assessed in peripheral plasma blood samples collected before and after HFR and, for comparison, a control HD.

Results

p-Cresol and IL-6 were lower in UF_out than in UF_in both at the start and at the end of the HFR session, suggesting that they were retained by the cartridge. IL-6 mRNA expression and release were lower in PBMC incubated with UF_out collected at the end than with UF_in collected at the start of HFR, suggesting that passage through the cartridge reduced UF pro-inflammatory activity. Plasma total p-cresol decreased by about 53% after HFR, and 37% after HD. IL-6 circulating values were unmodified by either these dialysis procedures.

Conclusions

This study shows that the HFR-Supra cartridge retains total p-cresol and IL-6 in the ultrafiltrate and lowers plasma total p cresol but not IL-6 levels.

Trial Registration

ClinicalTrials.gov NCT01865773

Inflammation and oxidative stress in patients on hemodiafiltration

BACKGROUND

Chronic inflammation and oxidative stress are common features in hemodialysis patients. However, research results on the long-term influence of hemodiafiltration (HDF) on oxidative stress and inflammation are limited.

METHODS

We studied changes of inflammatory and oxidative stress biomarkers in 9 stable patients on post-dilution HDF for 9 months. Total antioxidant capacity (TAC), reactive oxygen metabolites (d-ROMs) and superoxide dismutase (SOD) measured by spectrophotometry were used as oxidative stress biomarkers. High-sensitivity CRP (hs-CRP) and IL-6 measured by ELISA were used as inflammation biomarkers.

RESULTS

d-ROMs showed significant reduction at 3 months (323.0 +/- 81.9 vs. 275.0 +/- 62.0 U, p < 0.008) and remained low (267.9 +/- 45.8 U) to the end of the study. At the end of the study there was a significant increase in TAC levels (1.3 +/- 0.1 vs. 1.4 +/- 0.1 mmol/l, p < 0.03), while SOD rise did not reach statistical significance (13.1 +/- 9.8 vs. 18.7 +/- 9.4 U/ml, p = 0.06). hs-CRP values at the end of the study decreased significantly (16.3 +/- 11.4 vs. 6.0 +/- 5.1 microg/ml, p < 0.02), while IL-6 levels showed a non-significant reduction (16.9 +/- 9.3 vs. 12.0 +/- 7.3 pg/ml, p = 0.2).

CONCLUSION

Our results suggest that post-dilution HDF for 9 months suppresses oxidative stress by rapid lowering of d-ROMs and improves antioxidant capacity by increasing TAC, while it reduces inflammation by decreasing hs-CRP.

In vivo removal of high- and low-molecular-weight compounds in hemodiafiltration with on-line regeneration of ultrafiltrate

BACKGROUND

Current methods of renal replacement therapy, combining convection and diffusion, are largely unsatisfactory in removing uremic toxins. Adsorption is a third mechanism that has been applied in extracorporeal therapy. This study evaluates the impact of hemodiafiltration with on-line regeneration of ultrafiltrate, a new two-step integrated sorbent system, on in vivo removal of a wide spectrum of solutes with different molecular weights.

METHODS

Pre- and post-dialysis concentrations of small, medium-size, and large molecules were determined in ten patients undergoing regular hemodiafiltration treatments with on-line regeneration of the ultrafiltrate. We also analyzed, at different times of the same dialysis session, the inlet and outlet ultrafiltrate; the latter had been regenerated by the sorbent cartridge and was used as reinfusion liquid. The mean dialysis time was 260 +/- 21.2 min with a blood flow of 361 +/- 33.3 ml/min and a reinjection volume of 3.6 +/- 0.2 l/h.

RESULTS

Urea, creatinine and phosphate reduction ratio were respectively 69.8 +/- 8.2, 61.9 +/- 5.5, and 40.2 +/- 17.3%. Removal of medium-size markers such as calcitonin, osteocalcin, beta2-microglobulin, cystatin C, myoglobin and prolactin varied between 24 and 60%. The percentage of reduction for retinol binding protein and alpha1-microglobulin was negligible and we were unable to demonstrate any removal of alpha1-acid glycoprotein, pre-albumin, and albumin in the regenerated ultrafiltrate.

CONCLUSION

The hemodiafiltration with on-line regeneration of ultrafiltrate is a new hemodialysis system, which allows uremic toxin removal over a wide molecular-weight spectrum.

New Method for Phosphate Kinetics Estimation during Hemodialysis and On-Line Hemodiafiltration with Endogenous Reinfusion

AIM

The purpose of this study was to optimize the operative and analytical methodologies to a more exact determination of intradialytic kinetics of the phosphates (P) tested in hemodialysis (HD) and in on-line hemodiafiltration with endogenous reinfusion (HFR - Hemo Filtrate Reinfusion).

METHODS

The mass balance measurements of urea and P were carried out in 18 clinically stable HD patients. The effective blood flow (Qb) was measured with a Transonic monitor. The plasma was deproteinized with 10% trichloroacetic acid to prevent breakdown of the proteins and the consequent pseudohyperphosphatemia. Subsequently the supernatant containing the ultrafiltrable phosphates was made to react with a solution of ammonium molybdate for a spectrophotometric reading.

RESULTS

The mean urea mass transfer in HD was 16.9 g/session and in HFR 15.4 g/session. The mean P mass transfer in HD was 726 mg/session and in HFR 679 mg/session. Nevertheless, in HFR a significant difference was verified between the clearances of P, between the plasma water side (122.4 +/- 30.8 ml/min) and the dialysate side (105.9 +/- 19.4 ml/min).

CONCLUSION

As far as the P mass transfer is concerned, the data obtained is able to be superimposed with that described in the literature during HD, while in HFR it is possible to hypothesize a high efficiency, thanks to an increased output of P in relation to the phenomenon of adsorption which, although is limited, contributes to the transfer of the total mass. Based on this study and re-examining the literature on P kinetics, there is space for methodological improvement both on the operating front with careful determination of the effective Qb, and on the chemical front overcoming the inaccuracy of automatic analyzers in determining the plasma P owing to possible overestimation of phosphatemia and poor sensitivity in measuring the lower levels of P present in the dialysate and/or ultrafiltrate.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Sequential convective therapies (SCT): a prospective study on feasibility, safety, adequacy and tolerance of on-line hemofiltration and hemodiafiltration in sequence

Sequential dialysis techniques (i.e pure ultrafiltration followed by dialysis) have been used in the past, due to their capability to remove large volumes of fluids without inducing hemodynamic instability. The disadvantages of inadequate efficiency and lack of technology lead to the decline of such methods. Hemofiltration (HF) and hemodiafiltration (HDF) are recently being utilized in a greater proportion thanks to on-line fluid preparation systems. Each process (HF and HDF) has its own benefits in the removal of small, medium and high-molecular weight substances and in hemodynamic stability. Sequential convective therapies (SCT) such as hemofiltration-hemodiafiltration in sequence (HF-HDF) may combine the benefits and eliminate the disadvantages of each method and should be studied in order to explore their potential application in modern dialysis. Furthermore they can be easily applied nowadays, due to the development of new sophisticated dialysis machines. In order to evaluate the feasibility, safety, efficiency and tolerance of different SCT methods we studied 3 schedules: SCT1: 1h pre-dilution HF followed by 3h of post-dilution HDF (in the HF mode we lost 25% of the total fluid that had to be removed). SCT2: 1h pre-dilution HF followed by 3h of post-dilution HDF (in the HF mode we lost 50% of the total fluid that had to be removed). SCT3: 2h pre-dilution HF followed by 2h of post-dilution HDF (in the HF mode we lost 50% of the total fluid that had to be removed). We studied 6 chronic hemodialysis patients using the same machine (AK200 ULTRA), with on-line fluid preparation system and the same type of dialyzer (Polyflux 210). SCT schedules were compared to on-line HF, on-line HDF and high flux dialysis performed with the same dialyzers. The treatments resulted safe, easy, feasible and well tolerated with an improved hemodynamic response to high volume convective therapies. Adequacy of treatment was satisfactory in all SCT schedules while middle molecular weight solute clearance and removal resulted higher in treatments with higher convective component. SCT might represent an interesting option for the future especially in patients with hemodynamic instability and requirements for interventions during treatment.

Switch from Bicarbonate Hemodialysis to Hemodiafiltration with Online Regeneration of the Ultrafiltrate (HFR): Effects on Nutritional Status, Microinflammation, and beta2-Microglobulin

BACKGROUND

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).

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Controversies and Issues in Hemodiafiltration Therapy

Hemodiafiltration appears to be the most effective technique of renal replacement therapy but several drawbacks are not counterbalanced by significant advantages. Although optimal transfer for both small and middle molecules can be achieved, there is no difference in mortality risk between HDF and HD patients. The infusion of a large amount of dialysate containing residual acetate of 2-7 mmol/l could lead to impaired cardiac contractile functions and carbonyl stress whereas loss of amino acids and water-soluble vitamins along with high UF rate could lead to malnutrition. Moreover, as substitution fluid is prepared on-line, contaminated fluid could be inadvertently infused to patients. Stringent maintenance rules are required for the production of sterile and non-pyrogenic dialysis solutions. Finally, daily hemodialysis could be the most promising mode of renal replacement therapy since it leads to a more stable 'milieu interieur' than other techniques whatever the mode of solutes removal when performed three times a week.

[Renal replacement therapy in the future]

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