Hemodiafiltration with endogenous reinfusion with and without acetate-free dialysis solutions: effect on ESA requirement.

BACKGROUND: Hemofiltrate reinfusion (HFR) is a form of hemodiafiltration (HDF) in which replacement fluid is constituted by ultrafiltrate from the patient 'regenerated' through a cartridge containing hydrophobic styrene resin. Bicarbonate-based dialysis solutions (DS) used in routine hemodialysis and HDF contain small quantities of acetate (3-5 mM) as a stabilizing agent, one of the major causes of intradialytic hypotension. Acetate-free (AF) DS have recently been made available, substituting acetate with hydrochloric acid. The impact of AF DS during HFR on Hb levels and erythropoietic-stimulating agent (ESA) requirement in chronic dialysis patients was assessed. PATIENTS AND METHODS: After obtaining informed consent, 30 uremic patients treated by standard bicarbonate dialysis (BHD, DS with acetate) were randomized to treatment in 3-month cycles: first AF HFR, followed by HFR with acetate, and again AF HFR. At the beginning and end of each period, Hb and ESA requirements were evaluated. RESULTS: A significant increase in the Hb level was observed throughout all periods of HFR versus BHD (from 11.1 to 11.86 g/dl; p = 0.04), with a significant decrease of ESA requirements from 29,500 to 25,033 IU/month (p = 0.04). CONCLUSION: Regardless of the presence or absence of acetate in DS, HFR per se allows a significant lowering of ESA dosage versus BHD, while at the same time increasing Hb levels. Taking for granted the clinical impact produced, HFR seems to provide a relevant decrease in end-stage renal disease patient costs.

Hemodiafiltration with post-dilution reinfusion of the regenerated ultrafiltrate: a new on-line technique.

AIMS: All convective hemodiafiltration techniques require a replacement fluid, which must have an adequate electrolytic composition and must be sterile and pyrogen-free. Using an integrated adsorption cartridge, the ultrafiltrate can be "regenerated" and used as a replacement fluid (hemo-filtrate reinfusion; HFR). The aim of this study was to evaluate whether the HFR technique as suggested in its original configuration could be improved by inverting the purification sequence (post-dilution HFR; PDHFR) in order to increase the purification efficiency of the whole system. METHODS: We performed standard HFR in 6 uremic patients during 6 months and, subsequently, during further 6 months, PDHFR. The dialytic efficacy of the two techniques and the filter blood loss were evaluated. Moreover, we studied how both techniques affected cytokine levels. RESULTS: We observed a significant increase of urea extraction and of Kt/V values in PDHFR. An equally significant improvement was observed in regard to the extraction of beta2-m and the blood loss. Furthermore, IL6 and TNFalpha decreased significantly after PDHFR treatment. CONCLUSIONS: HFR has proven to be an easy-to-perform hemodiafiltration technique, capable of resolving the typical problem of the other hemodiafiltration technique, the availability and production of a sterile and ultrapure reinfusion solution. The inversion of its configuration has allowed us to improve three aspects that have characterized, in our experience, the treatments performed in the original geometry: the removal of both urea and beta2-m, and the filter. Finally, it's notable that the decrease in cytokines levels achieved with PDHFR might attenuate the uremic micro-inflammatory state.

[Hemodiafiltration with endogenous reinfusion (HFR): evolution of the method]. / Emodiafiltrazione con reinfusione endogena (HFR): evoluzione della metodica.

During hemodiafiltration (HDF) the increase in the ultrafiltration (uf) rate improves solute convective clearance. Therefore, considerable amounts of reinfusion liquid are necessary, whose quality must be guaranteed. The use of bags or bottles manufactured by industry causes many problems concerning handling (storage, repeated connections) and costs, and last but not least, it exposes the circuits to a contamination risk. Therefore, the technological research into on-line production systems of sterile and ultrapure reinfusion solutions is justified. The increasing interest in the on-line production of reinfusion fluids from the dialysing solution dates back to the 1990s, and the data in the literature are statistically positive concerning the improvement in depurative performances connected to the uf increase. Although, to be objective, a problem still exists, in real-time the absolute guarantee of the sterility and apirogenicity of the solutions produced on-line is impossible. Using a two-chamber filter, it is possible to produce reinfusion fluid from the uf of the patient himself, which has been 'regenerated' by a sorbent bed, in a closed circuit. This action eliminates any sterility problems, whilst, in addition, providing the possibility for good substance reinfusion such bicarbonates and essential and branched-chain aminoacids. This HDF method, hemo-filtrate-reinfusion (HFR), has clinically demonstrated, beyond its ease of execution, a reduction in physiological component loss, a high biocompatibility and an overall action in contrast to MIA syndrome factors, i.e. malnutrition, inflammation and atherosclerosis.

Adsorption in hemodialysis.

The use of sorbents in different blood purification techniques is reviewed. The sorbents used in these therapies are divided into two groups: (1) Adsorption occurs fundamentally because of the hydrophobic properties of the sorbents. In this group, the sorbents used in different dialysis techniques are charcoal and nonionic macroporous resins. (2) Adsorption occurs by chemical affinity, such as ion exchange resins and chemisorbents. Sorbents were initially used in hemoperfusion, which caused many adverse events; later, with the use of coated charcoal, these undesired effects decreased or disappeared, but the adsorptive properties, water control, and acid-base balance still created problems. For these reasons, the use of sorbents in the treatment of chronic renal failure was almost totally discontinued. Little by little, interest in these substances has reappeared, and at present, they have been used in combination with other blood purification techniques such as hemodialysis, hemofiltration, peritoneal dialysis, and finally, hemodiafiltration. Within the various hemodiafiltration techniques, paired filtration dialysis-charcoal is being used to regenerate the ultrafiltrate, which is used as the replacement fluid. Charcoal regenerates the ultrafiltrate and transforms it into a physiological solution with a normal electrolyte composition, calcium, bicarbonate, and glucose, having eliminated the majority of both middle and large molecule uremic toxins. If regeneration is done properly, this replacement fluid is bacteria and endotoxin free. Studies currently are underway on the adsorption of different inflammatory substances in the ultrafiltrate, which could lead to improvement in the biocompatibility of the system.

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.

The role of technology in hemodialysis.

The evolution of hemodialysis therapy has been characterized over the years by the search for reliable devices and supplies, for more efficient treatments and finally for a more tolerable therapy in long term dialysis patients. In this view, three steps can be identified: a) the first step was the creation of safe and reliable vascular access, dialyzers and machines. This step led to the birth of modern dialysis and treatment personalization was the logical consequence. Each patient is a single entity and he requires a specific therapy prescription and delivery. From this concept the search for adequacy and better outcomes has been generated, with the inevitable consequence that newer techniques were explored in the attempt to perform a more efficient and clinically tolerated dialysis therapy. b) The second step was the attempt to consider the intratreatment variations as possible source for dialytic morbidity. In this view, efforts were made to pre-set ultrafiltration and dialysate sodium profiles in the machine to counterbalance the negative effects of uncontrolled water and solute removal. However, this approach failed to provide significant results, because ultrafiltration and sodium profiles were predetermined and no adaptations could be made if the designed profile was inadequate. c) The third step in the evolution of dialysis was the understanding that on-line signals from the machine and from the patients were required in order to prepare and carry out the adequate response and variation of treatment parameters. For this reason a series of sensors have been developed including urea and blood volume sensors which are offering the most important signals from the patient. In this way, accurate responses could be made during treatment and from a simple manual feedback, we have today a completely automatic form of biofeedback. The question that now arises is where to find the financial resources to afford the upcoming technology. Another question is whether this new technology should be for everybody in routine dialysis or it should be designed for specific conditions. In other words, are these toys for nice experimental studies and speculations or are they tools to improve dialytic outcomes and morbidity? Probably, technology cannot be stopped in its evolution. What is exceptional today will probably be part of the routine of tomorrow. It seems that we are struggling more with the complex physiology of human body than with mechanical or electronic problems that certainly find their solution before or after. The increasing use of computers and the evolution of the applied software will certainly help in reducing the costs and improving the performances of our newer dialysis devices.

Verapamil versus amlodipine in proteinuric non-diabetic nephropathies treated with trandolapril (VVANNTT study): design of a prospective randomized multicenter trial.

Angiotensin converting enzyme inhibitors (ACEI) are the most effective antiproteinuric agents and should be used as first-line drugs in both diabetic and non-diabetic proteinuric nephropathies. The role of calcium channel blockers (CCB) is much more controversial. In diabetic patients verapamil and diltiazem seem more effective than dihydropyridines in reducing urinary protein excretion, and have additive effects with ACEI, but little is available on chronic treatment of non-diabetic nephropathies for non-dihydropyridine CCBs. To test whether the combination of verapamil 180 mg or amlodipine 5 mg with trandolapril 2 mg reduces urinary protein excretion more than trandolapril 2 mg alone, we planned a prospective, randomized, double-blind, multicenter trial. The secondary aims are to evaluate the effects of both treatments on the selectivity of proteinuria and check their safety. Consecutive patients aged between 18 and 70 years with non-diabetic proteinuria > or =2 g/24 h and plasma creatinine < 3 mg/dl or creatinine clearance > or = 20 ml/min are asked to participate. After a four-week run-in during which previous antihypertensive therapy is withdrawn, a single dose of trandolapril 2 mg is given once a day in open conditions for four weeks. At the end of this period patients are randomly assigned to receive once a day, in a double blind fashion, either trandolapril 2 mg and verapamil 180 mg [plus a placebo], or trandolapril 2 mg plus amlodipine 5 mg. They are monitored after one, two, five and eight months.

Hemodiafiltration without replacement fluid. An experimental study.

Paired filtration dialysis (PFD) is the only hemodiafiltration (HDF) technique in which the ultrafiltrate is continuously available but not mixed with the dialysate. As is the case during all convective or predominantly convective techniques, use of a replacement fluid is necessary in an amount equal to the difference between the ultrafiltrate and the desired patient weight loss. This replacement fluid must have an adequate electrolytic composition (Na+, Ca++, and buffer), and must be sterile and pyrogen free. Using an uncoated adsorbent charcoal cartridge (130 g), the ultrafiltrate obtained in PFD was regenerated, eliminating both the small (except for urea, glucose, and phosphates) and medium-to-large solutes but not the electrolytes and bicarbonate. This verified the ultrafiltrate's possible use as replacement fluid. This technique experimentally studied during 24 standard PFD sessions, with a total mean ultrafiltrate of 9,950 +/- 860 ml, allowed a replacement solution to be obtained with the following mean +/- SD composition: pH 7.467 +/- 0.122, HCO3- 27.0 +/- 2.12 mmol/L, Na+ 137.4 +/- 2.6 mmol/L, K+ 4.1 +/- 0.83 mmol/L, Ca++ 1.12 +/- 0.19 mmol/L, urea 68.3 +/- 16.2 mg/dl, creatinine 0.08 +/- 0.02 mg/dl, uric acid 0.05 mg/dl, phosphates 2.77 +/- 0.71 mg/dl, beta-2 microglobulin 0.5 +/- 0.4 mg/L, and atrial natriuretic peptide 4.41 +/- 5.6 pg/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-base balance determination on ultrafiltrate in two-chamber technique hemodiafiltration (PFD).

Correction of the acid-base balance in uremic patients during hemodiafiltration (HFD) may be biased by an inadequate monitoring of pH and blood gases. HDF performed with the two-chamber technique (PFD) generates pure ultrafiltrate (uf) unmixed with dialysate. We carried out 84 determinations of HCO3- levels in 15 different PFD patients by measuring the pH and pCO2 of the uf, then correlated the values with those simultaneously evaluated on arterial blood with standard methods. The mean HCO3- levels (mmol/L) were 23.21 +/- 2.49 in blood samples and 25.54 +/- 3.07 in uf, with a mean difference of -2.33 +/- 1.46. Statistical analysis gave: t = 13.5 (p = O) (one-sample analysis), r = 0.86 (p = 0) (linear regression analysis) and a good agreement between the two clinical measurements (81 out of 84 data points fell within the 95% confidence interval) (Bland-Altman analysis). In conclusion, we suggest that during HDF performed with the two-chamber technique, the patient's HCO3- level can be monitored on the uf without blood sampling.

Use of the ultrafiltrate obtained in two-chamber (PFD) hemodiafiltration as replacement fluid. Experimental ex vivo and in vitro study.

PFD (Paired Filtration Dialysis) is the only hemodiafiltration (HDF) technique in which the ultrafiltrate (UF) is continuously available not mixed with the dialysate. As with all convective or prevailingly convective techniques, a replacement fluid is necessary in an amount equal to the difference between the UF and the desired weight loss. This replacement fluid (R) must have an adequate electrolytic balance (Na+, Ca++, and buffer), and must be sterile and pyrogen-free. Using an uncoated adsorbent charcoal cartridge, we "regenerated" the UF obtained in PFD, eliminating the small (except for urea, which was later eliminated by diffusion in the dialyzing section of the PFD system) and the medium-to-large molecules (vit B12 and myoglobin in vitro and beta-2-microglobulin (B2m) and (hANP) in vivo), but not the electrolytes and the endogenous bicarbonate, so as to verify its possible use as R. This technique, experimentally performed in 12 patients under HDF treatment with standard PFD, with a total mean UF of 9650 +/- 875 ml and the use of 130 g of uncoated charcoal, produced a solution with the following composition: Na+ 135.4 +/- 2.4 mmol/l, K+ 3.4 +/- 1.23 mmol/l, Ca++ 1.18 +/- 0.14 mmol/l, HCO3- 26.7 +/- 2.3 mmol/l, phosphates 2.88 +/- 0.81 mg/dl, urea 63 +/- 14 mg/dl, creatinine 0.08 +/- 0.02 mg/dl, uric acid 0.05 +/- 0.0 mg/dl, beta-2 microglobulin 0.5 +/- 0.5 mg/l, and hANP 4.15 +/- 5 pg/l.(ABSTRACT TRUNCATED AT 250 WORDS)

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 (beta2-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 gamma-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.

Blood flow distribution in sorbent beds: analysis of a new sorbent device for hemoperfusion.

A new polymer-based sorbent cartridge has been recently developed for enhancing middle molecule removal during hemodialysis. The cartridge (Betasorb, Renaltech, New York, USA) has been designed to be placed in series with the dialyzer in the blood circuit. It is therefore important to evaluate the distribution of flow into the blood compartment of the device in order to assess if the surface of the sorbent is utilized to the best. For this purpose, a special imaging technique was utilized. Cartridges were analyzed during a simulated in vitro circulation at 250 and 350 ml/min of blood flow and 25% and 40% hematocrit. Cartridges were placed in vertical position and a cross longitudinal section 1 cm thick was analyzed in sequence by a helical scanner. Dye was injected into the arterial inlet and the progressive distribution was evaluated by sequential densitometrical measures carried out automatically by the machine. The sequential images analyzed by the scanner demonstrated excellent distribution of the flow in the blood compartment with minimal difference between the central and the peripheral regions of the compartment. In particular the following flow velocity pattern could be observed under the different experimental conditions tested. We may conclude that the cartridge design is adequate and no channelling effects could be detected in the blood compartment. The flow distribution is slightly affected by changes in flow rate and hematocrit showing an optimal utilization of the available surface for molecule adsorption.

[Critical evaluation of dialytic adequacy]. / Esame critico dell'adeguatezza dialitica.

At present it is difficult to define the concept of dialysis adequacy correctly. The paper analyses two of the parameters which are commonly used for this purpose: Kt/V and the behaviour of Beta-2 microglobulin, molecular antipodes for the removal of uremic toxins. A critical analysis is made of the validity of methods to calculate the former and the reliability of the latter. Attention is focused on the fact that an evaluation of dialysis adequacy cannot be limited to theoretical observations regarding the removal of solutes, but must also be integrated by the clinical observation of patients and the commencement of support therapy (pharmacological and/or nutritional and/or physical). In this manner, the adequate treatment of the uremic patients is not entrusted solely to the technological component.

[Hemodiafiltration: choice or necessity in high-efficiency treatment?]. / Emodiafiltrazione: scelta o obbligo nel trattamento ad alta efficienza?

The risks of back-filtration that occur with the use of high hydraulic permeability membranes with haemodialytic techniques in the course of which the difference between forced and necessary ultrafiltration is compensated for by correcting transmembrane pressure in favour of the dialyser compartment. In this way a form of concealed haemodiafiltration is attained in which the replacement fluid is the dialysing solution, annulling, owing to the possible consequences of the transit of bacterial endotoxins into the circulation, all the advantages linked to the use of these membranes. It is concluded by suggesting the implementation of well controlled haemodiafiltration through the careful quali-quantitative evaluation of the replacement fluid.

[Is a monthly biochemical check-up useful more than 2 years after kidney transplantation?]. / E utile un controllo biochimico mensile dopo il secondo anno di trapianto?

Over the course of the years many transplantation centres have altered their pattern of periodical check-ups in patients with stable renal function, in some cases considerably prolonging the intervals. Peripheral centres, which are attended by patients after kidney transplantation, must reconcile the follow-up requirements made by various reference centres. The authors carried out a retrospective evaluation of 39 patients who, at 30-6-1992, had had kidney transplants for more than two years, taking into consideration a series of hematochemical tests indicative of the main functional alterations (creatininemia, hepatic enzymes, hemochrome, cyclosporin assay). In the 31 patients receiving monthly check-ups after the second year, changes in cyclosporinemia were on average significantly more frequent in comparison to variations in other parameters. This finding, together with the need for a careful control of transplant patients, would appear to confirm the value of monthly check-ups. However, the positive experience of some centres which begin to space out periodical check-ups at an early stage and report good organ survival, opposes the previous affirmation. Lastly, it emerges from this study that patients undergoing frequent controls even after the second year of transplantation have significantly lower organ survival.

[Vascular access in hemodialysis. Surveillance and role of percutaneous transluminal angioplasty]. / Accessi vascolari in emodialisi. Sorveglianza e ruolo dell'angioplastica percutanea transluminale.

The function of vascular shunts in hemodialysis plays a vital role for the efficiency and effectiveness of replacement therapy. A study was performed in 147 patients undergoing periodical hemodialysis with distal FAV (no = 86), proximal FAV (no = 33), PTFE grafts (no = 23), Canaud-Tesio catheters (no = 7). A protocol for function evaluation was developed which also included the calculation of overall recirculation (R), that was found to be 10.8 + 7% (using the three blood sample method). In 28/143 patients the monitoring protocol recommended the use of angiography which identified abnormalities in 78% of cases, before the onset of thrombotic phenomena. In particular, surgical radiology was able to resolve 94% of cases in which angiography revealed a stenosis using percutaneous transluminal angioplasty and/or the insertion of one or more stents.

["Clinical clearance" and "weekly clearance" of urea in periodical hemodialytic treatment]. / "Clearance clinica" e "clearance settimanale" dell'urea nel trattamento emodialitico periodico.

Starting from the hypothesis that small molecules are freely diffusible, a simple formula is proposed for the determination of real ureic clearance during dialysis. This automatically allows for all variables (blood flow and flow of the dialysing solution, temperature, physical and/or chemical state of the membrane, level of solute concentration, transmembrane pressure, etc.). On the basis of this formula, a calculation system is also proposed for assessing weekly ureic clearance levels and hence the real efficiency of treatment. This system may also be applied to peritoneal dialysis and permits optimisation of substitutive treatment. It is thus easier to select the best filter and rhythms for each patient.

[Kinetics of anticoagulation in hemodialysis. Sequential study of single, intermittent and continuous heparinization]. / Cinetica dell'anticoagulazione in emodialisi. Studio sequenziale sull'eparinizzazione unica, intermittente e continua.

A sequential real-time study was run to monitor plasma heparin values following three standard dose protocols during 4-hr dialysis, using an enzymatic method. One group of patients was given a single dose of 7000 IU at the commencement of dialysis, a second group 5000 IU at the start and 2500 IU at the end of the third hour, and a third group 2500 IU at the start and 1500 UI/hr for four hours. Plasma levels were checked every hour and ranged from 0.702 IU/ml (+/- 0.069) (start) to 0.290 IU/ml (+/- 0.079) (end) in the first group, 0.552 (+/- 0.116) to 0.312 (+/- 0.09) in the second, and 0.456 (+/- 0.113) to 0.314 (+/- 0.063) in the third. Correlation of heparin levels with coagulation time led to the establishment of an optimal range of 0.2 to 0.6 IU/ml.

A procedure to teach self-control to children with attention deficit hyperactivity disorder.

This study examined the use of a progressive delay procedure combined with verbal mediation to teach self-control to children with attention deficit disorder. Results showed that when participants were initially given the choice between an immediate smaller reinforcer and a larger delayed reinforcer, all participants chose the smaller reinforcer. When slight delays to obtain a larger reinforcer were instated in conjunction with intervening verbal activity, all participants demonstrated self-control regardless of the content of the verbal activity.

[Bicarbonate balance in hemodiafiltration (HDF): a comparison between two infusion methods of on-line prepared solution]. / Bilancio dei bicarbonati in emodiafiltrazione (HDF): confronto fra due metodiche di reinfusione di liquido prodotto on-line.

PURPOSE: Hemodiafiltration (HDF) has high removal rates of low and middle-high molecular weight uremic toxins. We aimed to understand the efficacy and the safety in correcting on-line HDF acidosis. We compared two infusion methods of on-line prepared solution in HDF: HDF with an infusion solution produced from dialysate (HDF-OL) and HDF with a solution from patient ultrafiltrate after regeneration (HFR). METHODS: Eleven patients (four males, seven females) age 66 +/- 10 yrs, dialysis age 5.0 +/- 1.3 yrs, on anuria had two dialysis methods for the 1st session of the week, one HDF-OL and one HFR in 2 different weeks. In HDF-OL a high-flux polysulphone dialyser 1.8 m2 was used, in HFR a two-stage filter was used: polyetersulfone 0.7 m2 + SMC 1.95 m2 and a sorbent cartridge Selecta plus (Bellco) to regenerate the ultrafiltrate. HCO3- in the dialysis bath was 32 mmol/L. RESULTS: Plasma bicarbonates, before dialysis were 21.6 +/- 2.1 mmol/L on HDF-OL and 21.5 +/- 3.3 on HFR (p=ns), at the end they were 27.5 +/- 1.8 mmol/L on HDF-OL and 27.8 +/- 1.2 mmol/L on HFR (p=ns). On HDF-OL bicarbonates reached a plateau at mid session: 27 +/- 1.2, 27.5 +/- 1.2, 27.5 +/- 1.8 to 120, 180 and 240 min respectively. On HFR the plateau was reached more slowly: 26.1 +/- 1.9, 27.1 +/- 1.4, 27.8 +/- 1.2 with the same times. CONCLUSIONS: HFR-OL and HFR efficaciously corrected acidosis in a 4-h dialysis session. The same results, statistically and clinically, were achieved with infusion solution derived from dialysate and from solution from regenerated ultrafiltrate. In the latter, it was interesting that the global quality of the infusion solution was obtained from a close circuit from the patient ultrafiltrate.