In vitro study of r-hirudin permeability through membranes of different haemodialysers.

BACKGROUND: After introducing the specific thrombin inhibitor recombinant hirudin (r-hirudin) into clinical practice in cases of heparin-induced thrombocytopenia (HIT, type II) the possibility of its use as an anticoagulant during haemodialysis treatment in HIT II patients is being discussed more frequently. On the one hand, the efficient, safe and routine use of r-hirudin during haemodialyses, including the maintenance of a therapeutic blood level, presupposes that no r-hirudin will leave the circulation by passing through the dialyser membrane. On the other hand, it is important to have dialysers whose permeability to r-hirudin allows its efficient removal from the human body because, to date, no antidote is commercially available in cases of dangerously high blood concentrations of r-hirudin. METHODS: An in vitro circulation model was used to study the r-hirudin permeability of some low- and high-flux dialysers. As r-hirudin-containing vehicles, both albumin-containing saline solution and bovine blood were circulated in the blood space of the system for 2 h. Transmembrane r-hirudin passage was tested by measuring r-hirudin concentration both in the blood and dialysate space fluids using the ecarin clotting time (ECT). RESULTS: Low-flux dialysers with membranes made from polysulfone or regenerated cellulose proved to be almost impermeable to r-hirudin. In contrast, other low-flux membranes were partly permeable to r-hirudin (e.g. Hemophan) or even almost completely permeable (e.g. cellulose acetate). All high-flux dialysers tested were permeable to r-hirudin. CONCLUSIONS: Only low-flux dialysers with polysulfone or regenerated cellulose membranes proved to be suitable for r-hirudin use in routine haemodialysis therapy. Other low-flux, and all high-flux, capillaries are permeable to r-hirudin and offer the possibility of lowering toxic r-hirudin concentrations after overdosing.     

Washout of water-soluble vitamins and of homocysteine during haemodialysis: effect of high-flux and low-flux dialyser membranes

Aim:   Vitamin deficiencies are common in patients with end-stage renal disease (ESRD) owing to dietary restrictions, drug–nutrient interactions, changes in metabolism, and vitamin losses during dialysis. The present study investigated the levels of serum and red blood cell (RBC) folate, plasma pyridoxal-5'-phosphate (PLP), serum cobalamin, blood thiamine, blood riboflavin, and plasma homocysteine (tHcy) before and after haemodialysis treatment.
Methods:   Vitamin and tHcy blood concentrations were measured in 30 patients with ESRD before and after dialysis session either with low-flux ( n  = 15) or high-flux ( n  = 15) dialysers.
Results:   After the dialysis procedure, significantly lower concentrations of serum folate (37%), plasma PLP (35%), blood thiamine (6%) and blood riboflavin (7%) were observed. No significant changes were found for serum cobalamin or for RBC folate. There were no differences in the washout of water-soluble vitamins between treatments with low-flux and high-flux membranes. Furthermore, a 41% lower concentration in tHcy was observed. The percentage decrease in tHcy was significantly greater in the patients treated with high-flux dialysers (48% vs 37%; P  < 0.01). The percentage change during dialysis was significantly inversely related to the molecular weight of the vitamins measured ( r  =−0.867, P  < 0.01).
Conclusion:   This study showed significantly lower blood or serum levels of various water-soluble vitamins after dialysis, independently of the dialyser membrane. The monitoring of the vitamin status is essential in patients treated with high-flux dialysers as well as in patients treated with low-flux dialysers.     

Removal of high-molecular-weight solutes during high-efficiency and high-flux haemodialysis

BACKGROUND.: Although urea clearance is often increased during high-efficiencyand high-flux haemodialysis to compensate for short treatmenttimes, the impact of these treatment modalities on the removalof larger uraemic toxins has not been thoroughly investigated. METHODS.: We compared solute removal rates for five haemodialysis treatmentstrategies in vitro using neutral dextrans (molecular radiibetween 15 and 50 Å) as marker macromolecules. Removalrates were assessed by the decrease in dextran concentrationwithin the reservoir of a model circuit using outdated humanplasma as the test solution. Results for high-efficiency haemodialysis(CA 110 dialyser at a blood flow rate of 400 ml/min and TAF175dialyser at a blood flow rate of 300 ml/min) and high-flux haemodialysis(CT190G dialyser at a blood flow rate of 300 ml/min and F60dialyser at a blood flow rate of 300 ml/min) were compared withthose for conventional haemodialysis (CA110 dialyser at a bloodflow rate of 200 ml/min). RESULTS.: Dextran clearances were dependent on the dialyser employed,and they decreased with molecular size and time for each treatmentstrategy. Removal rates were greatest using the CT190G and F60dialysers, intermediate for the TAF175 dialyser, and lowestfor the CA110 dialyser at either blood flow rate. CONCLUSIONS.: The results of this study demonstrate that increasing bloodflow rates alone to increase urea clearance may not provideadequate removal of high-molecular-weight solutes. The use ofhigh-flux or large surface area, high-efficiency dialysers aremore effective in maintaining the removal of high-molecular-weightsolutes when treatment time is shortened.     

Adequacy of haemodiafiltration

In this study we have evaluated the influence of blood and ultrafiltration flow rate on the performance of five different high-flux membrane dialysers during haemodiafiltration. On the basis of clearance data we optimised the haemodiafiltration schedule of six uraemic patients to maintain an adequate midweek blood urea nitrogen concentration, while reducing the treatment time from 285 +/- 23 min to 210 min. After a follow-up of 6 months, we observed no difference in the clinical tolerance or in the biochemical parameters, compared to those found during the preceding haemodialysis period. Our data confirm the suggestions of other authors that haemodiafiltration is an effective alternative to conventional haemodialysis.     

Free serum leptin but not bound leptin concentrations are elevated in patients with end-stage renal disease.

BACKGROUND: Leptin is a 16-kDa protein that is thought to be a regulator of food intake and body weight. Although total serum leptin levels have been reported to be elevated in obese and normal weight patients with end-stage renal disease (ESRD), it is not known whether serum-free leptin concentrations are also increased in patients with ESRD with no apparent nutritional problems. Furthermore, there are no data on how different dialysis modes (high-flux haemodiafiltration and low-flux dialysis) influence serum leptin subfractions. METHODS: We measured fasting serum free and bound leptin levels in three groups of male subjects: patients on haemodiafiltration with high flux dialysers (n=11), patients on haemodialysis with low-flux dialysers (n=17) and healthy age (61+/-8 years) and BMI (23.8+/-3.1 kg/m(2)) matched control subjects (n=28). Both leptin components were determined before and after a single dialysis session. RESULTS: Body mass indices were correlated with serum free leptin levels in both patients (r=0.69, P<0.001) and controls (r=0.77, P<0.001). Mean (SD) serum free leptin levels were significantly higher in ESRD patients than in control subjects (91+/-33 vs 41+/- 21 pmol/l; P<0.01). Bound leptin levels did not differ in both groups (0.67+/-0.12 vs 0.56+/-0.11 nmol/l, NS). Elevated serum-free leptin levels in ESRD patients could be reduced by haemodiafiltration with high-flux membranes, but not with low-flux haemodialysis membranes.The former led to a reduction of initial serum free leptin values to 76+/-17% (P<0.01), whereas bound leptin remained unaffected. CONCLUSION: Serum-free leptin levels are elevated in ESRD without any apparent effect on body weight. In contrast, serum bound leptin levels remain stable, thus central feedback regulation via the bound form of the hormone may serve as an alternative explanation in the regulation of food intake and energy expenditure in chronic patients on haemodialysis with no apparent nutritional problems.     

Reduction of circulating microemboli in the subclavian vein of patients undergoing haemodialysis using pre-filled instead of dry dialysers.

BACKGROUND: Chronic microembolization that can be demonstrated by pulsed Doppler ultrasound may give rise to pulmonary side-effects during haemodialysis by direct vessel obstruction, increased complement activation or platelet aggregation. The objective of the present investigation was to study whether the use of pre-filled instead of dry dialysers would help to minimize the number of microemboli. METHODS: The study cohort consisted of 23 patients undergoing maintenance haemodialysis. Using a 2 MHz pulsed ultrasound device, the subclavian vein downstream to the dialysis fistula was investigated for 10 min during the dialysis session. The ultrasound examination was performed twice during two successive dialysis sessions, using a pre-filled or a dry dialyser in randomized order. RESULTS: In all patients investigated, numerous microembolic signals (MES) could be observed in the subclavian vein. Treatment with pre-filled dialysers was associated with significantly less MES (82 +/- 94) as compared with dry dialysers (268 +/- 296; P = 0.002). CONCLUSIONS: In comparison to dry dialysers, the use of pre-filled dialysers leads to a significant reduction in microembolization, which may prevent repeated damage to the pulmonary vasculature and, thus, cause less pulmonary damage.     

Oxalate clearance by haemodialysis--a comparison of seven dialysers.

BACKGROUND: In patients with primary hyperoxaluria (PH) and oliguric end-stage renal disease, oxalate removal is largely dependent on the clearance by dialysis. Data on the oxalate clearance of newer dialyser types are scarce or absent. Therefore, we measured oxalate clearances of seven dialysers in a single 52-year-old female patient with PH. Since haemodiafiltration (HDF) has been advocated to increase oxalate clearance, we also assessed the effect of different pre-dilution flows. The goal of the study was to select the dialyser and pre-dilution flow combination with the highest oxalate clearance. METHODS: Oxalate clearances were assessed by simultaneously taking afferent blood and efferent dialysate samples at 30, 60, 120 and 180 min after the start of haemodialysis. Blood flow and dialysate flow were 350 and 500 ml/min, respectively. All dialysers were tested at a pre-dilution flow of 2 l/h. Six dialysers were also tested at either a pre-dilution flow of 4.5 l/h or without HDF, depending on the ultrafiltration coefficient of the dialyser. RESULTS: Oxalate clearances differed markedly between the tested dialysers, ranging from 144+/-10 to 220+/-12 ml/min. The highest oxalate clearances were achieved with HdF100S (219+/-10 ml/min) and Sureflux FB-210U (220+/-12 ml/min) at a pre-dilution flow of 2 l/h. Higher pre-dilution flows (2 l/h vs no HDF or 4.5 vs 2.0 l/h) yielded similar oxalate clearances. CONCLUSION: The highest oxalate clearances were achieved with a high-flux polysulfone and a cellulose triacetate dialyser with a large surface area. Higher pre-dilution flows did not augment oxalate clearance.     

Effect of vitamin-E-modified dialysers on dialyser clotting, erythropoietin and heparin dosage: a comparative crossover study

We performed a crossover study to compare the effects of different dialysis membranes on 20 patients with frequent dialyser clotting and requiring > or = 5,000 units of heparin per dialysis session. Low-flux dialysers are C15NL (cellulose - Terumo) and E15NL (vitamin-E-coated - Terumo) while high-flux dialysers were F60 (polysulphone) and EE15NL (vitamin-E-coated - Terumo). Ten patients underwent dialysis for 2 months with C15NL then switched to E15NL for 2 months. Similarly, the other 10 patients were started on the high-flux dialyser F60 and then switched over to EE15NL for 2 months. The following parameters were measured at the beginning of the study, 2 weeks, 1 month and then at 2 months: hemoglobin, prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen, protein C, protein S, antithrombin III (ATIII) and factor 12 activity. Dialyser clotting, heparin and erythropoietin requirements were assessed during each dialysis session. There was a significant reduction in clotting with E15NL in comparison to C15NL (22.8 +/- 17 and 44.1 +/- 22.8 (p = 0.0233), respectively). Similarly, heparin requirements were less in the vitamin-E-coated (E15NL) dialysers, 4, 754 +/- 1,427 vs. 6,011 +/- 856 units (p = 0.0281) and erythropoietin usage was also significantly reduced, 4,630 +/- 2,620 vs. 7,850 +/- 4,069 units (p = 0.049). There was a significant increase in hemoglobin with E15NL compared to C15NL, 115 +/- 10.4 vs. 108 +/- 13.1 (p = 0.0343). When the high-flux dialysers were compared there was a tendency towards less dialyser clotting with the EE15NL compared to F60, though this did not achieve statistical significance (p = 0.0561). We could not demonstrate any significant changes between the different dialysers with regards to PT, PTT, fibrinogen factor 12 activity, protein C, protein S and ATIII. In conclusion, we have shown that the use of vitamin-E-modified dialysers is associated with less clotting in patients with persistent clotting problems. In addition, this was associated with less heparin and erythropoietin requirements.     

Improved Phosphate Clearances with Polycarbonate Membranes

Clearance studies of urea, creatinine and inorganic phosphate have been carried out using polycarbonate dialysers on 20 occasions in two patients undergoing routine maintenance haemodialysis. Clearances were calculated using plasma concentrations and both measured blood flow and calculated plasma flow. Urea and creatinine clearances were comparable to those obtained with cellulose-based dialysers, but phosphate clearances were relatively increased, averaging over 70% of urea clearances. All clearances were reduced as TMP values increased, a feature at variance with the usual situat ion with cellulose membranes. Polycarbonate dialysers have the advantage of higher relative phosphate clearances in addition to the other advantages claimed for them.     

Extended daily veno-venous high-flux haemodialysis in patients with acute renal failure and multiple organ dysfunction syndrome using a single path batch dialysis system.

BACKGROUND: In the treatment of acute renal failure in patients with multiple organ dysfunction syndrome (MODS), continuous renal replacement therapies (CRRT) are increasingly used because of excellent volume control in the presence of improved cardiovascular stability. Patients with MODS, however, are frequently catabolic and have a high urea generation rate requiring either cost-intensive high-volume CRRT or additional intermittent haemodialysis to provide adequate clearance of small-molecular waste products. We tested the closed-loop batch haemodialysis system (called Genius((R))) for the treatment of acute renal failure in patients with MODS in the intensive care unit. METHODS: Blood flow and countercurrent dialysate flow were reduced to 70 ml/min. Thus the 75 l dialysate tank of the Genius((R)) system lasts for 18 h of extended single-path high-flux haemodialysis (18 h-HFD) using polysulphous F60 S((R)) dialysers. Blood pressure, body temperature, and venous blood temperature in the extracorporeal circuit (no heating of the dialysate), ultrafiltration rate, serum urea levels, dialyser urea clearance, and total urea removal were monitored. In addition we tested the bacteriological quality of the spent dialysate at the end of 18-h treatments. RESULTS: Twenty patients with acute renal failure and MODS were investigated. Averaged dialyser urea clearance was 59.8 ml/min (equal to 3.6 l/h or 64.8 l/day). Total removal of urea was 14.1+/-6.5 g/day keeping serum levels of urea below 13 mmol/l. Mean arterial pressure remained stable during the 18-h treatments with a mean ultrafiltration rate of 120 ml/h. The temperature in the venous blood tubing dropped by 5+/-0.5 degrees C during the 18-h treatment (0.28 degrees C/h) in the presence of unchanged core temperature in the patients. There was no bacterial growth in 2.5 l of spent dialysate (<0.0004 colony forming units/ml). CONCLUSIONS: Extended high-flux dialysis using the Genius((R)) system combines the benefits of CRRT (good cardiovascular stability, sterile dialysate) with the advantages of intermittent dialysis (high urea clearance, low treatment costs). High efficiency, simplicity and flexibility of the system offers the unique opportunity to use the same dialysis machine for extended time periods (18 h) as well as for shorter intermittent renal replacement therapy in critically ill patients.     

Effect of dialysis flux and membrane material on dyslipidaemia and inflammation in haemodialysis patients.

BACKGROUND: Dyslipidaemia, inflammation and oxidative stress are prominent risk factors that potentially cause vascular disease in haemodialysis patients. Dialysis modalities affect uraemic dyslipidaemia, possibly by modifying oxidative stress, but the effects of dialyser flux and membrane material on atherogenic remnant particles and oxidized low-density lipoproteins (LDL) are unknown. METHODS: We performed a randomized crossover study in 36 patients on haemodialysis to analyse the effect of dialyser flux and membrane material on plasma lipids, apolipoproteins and markers of inflammation and oxidative stress. Stable patients on low-flux dialysis with polysulphone for >/=6 weeks were assigned to high-flux polysulphone or high-flux modified cellulose with similar dialyser surface area and permeability characteristics and crossed over twice every 6 weeks. RESULTS: Thirty patients completed the study per protocol. Treatments with high-flux polysulphone and modified cellulose lowered serum triglyceride (by 20% and 10%, respectively; P<0.05) and remnant-like particle cholesterol by 32% (P<0.001) and 11% (NS) after the first 6 weeks of treatment. Oxidized LDL decreased significantly with high-flux polysulphone, but not with modified cellulose. Apolipoproteins CII and CIII were reduced, whereas the ratio CII/CIII was increased (all P<0.05). Acute-phase proteins and LDL and high-density lipoprotein cholesterol remained unaffected. CONCLUSIONS: This randomized crossover study demonstrates a potent effect of high-flux haemodialysis on uraemic dyslipidaemia. Polysulphone membrane material showed superiority on oxidatively modified LDL, an indicator of oxidative stress in haemodialysis patients.     

Oxalate removal by daily dialysis in a patient with primary hyperoxaluria type 1.

BACKGROUND: Dialysis patients with primary hyperoxaluria are exposed to risks and hazards associated with calcium oxalate salt deposition in body tissues, since regular dialysis treatment does not adequately correct hyperoxalaemia. The purpose of this study was to evaluate oxalate mass removal using various dialysis modes in a patient suffering from primary hyperoxaluria type 1 (PH1). METHODS: Oxalate kinetics during daily haemodialysis was compared with that of standard haemodialysis (STD HD) and haemodiafiltration (HDF) using high flux dialysers (FB 170 H and FB 210 U, Transdial, Paris, France). All dialysis sessions lasted for 4 h. Blood was withdrawn and spent dialysate was collected in plastic bags every hour to evaluate mass removal. Oxalate concentration in plasma and in spent dialysate was determined by an enzymatic method. Oxalate generation, distribution volume and tissue deposition were calculated using single-pool models adapted from previous studies. RESULTS: Although no significant difference was found in mass removal per session between dialysis strategies and dialyser types, weekly mass removal with daily HD was about 2 times greater than with STD HD or HDF. Even when daily HD was performed, the oxalate generation rate-mass removal ratio (G/R ratio) remained at a value of approximately 2. CONCLUSION: Although daily HD sessions led to a substantial increase in weekly oxalate removal, all three types of renal replacement therapy were insufficient to compensate for estimated oxalate generation. To eliminate sufficient amounts of oxalate generated in PH1 patients, at least 8 h of daily dialysis with a high-flux membrane would probably be required. Renal replacement therapy for PH1 patients needs be improved further.     

Effect of dialyser membrane pore size on plasma homocysteine levels in haemodialysis patients.

BACKGROUND: Hyperhomocysteinaemia is a putative risk factor for atherothrombotic cardiovascular disease in the haemodialysis population. High-dose vitamin B therapy does not entirely normalize elevated plasma total homocysteine (tHcy) levels in haemodialysis patients. Alternative therapies to reduce tHcy further are therefore required. Modifications of the dialysis regimen may result in a better removal of Hcy. We examined the effect of dialyser membrane pore size on tHcy levels in vitamin-replete chronic haemodialysis patients. METHODS: Forty-five haemodialysis patients were dialysed during 4 weeks with a low-flux, a high-flux and a super-flux membrane, in random order. Pre-dialysis tHcy was determined at baseline and every 4 weeks. In 18 patients, plasma tHcy before and after dialysis and dialysate tHcy concentrations were measured. RESULTS: Pre-dialysis tHcy decreased significantly during 4 weeks super-flux dialysis (-14.6 +/- 2.8%), whereas it remained stable during high-flux (+0.5 +/- 2.4%) and low-flux dialysis (+1.7 +/- 3.2%). The homocysteine reduction ratio was not different for the three membranes: 0.39 +/- 0.03 for the super-flux, 0.47 +/- 0.02 for the high-flux and 0.39 +/- 0.02 for the low-flux dialyser. The amount of Hcy recovered in the dialysate during a single dialysis session was also similar: 117.5 +/- 3.6 micro mol during super-flux, 95.3 +/- 11.5 micro mol during high-flux and 116.5 +/- 11.6 micro mol during low-flux dialysis. CONCLUSION: Super-flux dialysis significantly lowers tHcy in chronic haemodialysis patients. Improved removal of middle-molecule uraemic toxins with inhibitory effects on Hcy-metabolizing enzymes, rather than better dialytic clearance of Hcy itself, may explain the beneficial effect of the super-flux membrane.     

Increase of C-reactive protein serum values following haemodialysis

In this study serum C-reactive protein values were measured to prove the induction of an acute-phase response during the haemodialysis procedure in end-stage renal disease patients. C-reactive protein values were measured with a sensitive enzyme-linked immunosorbent assay to detect values below the detection limit of standard assays. Predialysis C-reactive protein serum values in 17 patients on regular haemodialysis with cuprophan dialysers were greater than those of 18 normal controls (P less than 0.001). In the same group of haemodialysis patients serum C-reactive protein values 24 h after haemodialysis were significantly greater than predialysis values (P less than 0.001). These results suggest that acute-phase proteins are induced during haemodialysis, probably due to cytokine release during the haemodialysis procedure.     

Effect of permeability on indices of haemodialysis membrane biocompatibility.

BACKGROUND: Increases in plasma anaphylatoxins frequently are used as an index of haemodialysis membrane biocompatibility; however, their plasma levels may be influenced by the loss of anaphylatoxins into the dialysate compartment. METHODS: We compared the generation and compartmental distribution of anaphylatoxins, C3a and C5a, in a high flux and a low flux polysulfone membrane dialyser when whole human blood was recirculated through an in vitro haemodialysis circuit. RESULTS: Plasma C3a levels in high flux polysulfone (2.31 +/- 0.81 microg/ml) and low flux polysulfone (3.02 +/- 0.98 microg/ml) dialysers were comparable after 120 min (P = NS). In contrast, dialysate C3a in high flux polysulfone (0.65 +/- 0.31 microg/ml) accounted for 37.5 +/- 7.0% of the total detected (plasma + dialysate) C3a mass in the dialysers, while dialysate C3a in low flux polysulfone dialysers (0.01 +/- 0.01 microg/ml) accounted for only 0.3 +/- 0.3% of the total mass (P < 0.05; high flux vs low flux). Anaphylatoxin C5a was undetectable in the dialysate compartment of either dialyser examined. CONCLUSIONS: Our results indicate that anaphylatoxins readily traverse certain high flux dialysis membranes; consequently, plasma C3a levels may not accurately reflect the C3-activating potential of these membranes.     

Removal of contrast media by different extracorporeal treatments.

BACKGROUND: Although the capability of extracorporeal treatments after administration of contrast media to prevent radiocontrast-induced nephropathy is controversial, haemodialysis is performed in many institutions after radiographic procedures. There are conflicting reports on the efficacy of different dialysers and treatment modalities to remove contrast media. METHODS: We compared the contrast medium-removing ability of different extracorporeal treatments in a randomized trial. Thirty-nine patients on chronic renal-replacement therapy or with chronic renal failure were randomized to receive low-flux haemodialysis (Low-HD, n=10), high-flux haemodialysis (High-HD, n=10), online haemodiafiltration (HDF, 10 litre substitution, n=10) and online haemofiltration (HF, 18 litre substitution, n=9) after administration of contrast medium during routine radiological procedures. Plasma concentrations of contrast medium (iopromide or iomeprol) were measured by energy-dispersive X-ray fluorescence analysis. RESULTS: The extraction ratio for contrast media was 0.64+/-0.1 for Low HD (P<0.05 vs. High-HD and vs. HDF), 0.74+/-0.1 for High-HD (P<0.05 vs. HF), 0.81+/-0.1 for HDF (P<0.05 vs HF), and 0.62+/-0.1 for HF. Mean extracorporeal plasma clearances were 82+/-2 for Low-HD (P<0.05 vs. High-HD and vs HDF), 100+/-2 for High-HD, 115+/-4 for HDF (P<0.05 vs. HF), and 86+/-5 ml/min for HF. CONCLUSIONS: We conclude that HDF and High-HD remove contrast media more effectively than Low-HD and HF during the time of each treatment session. However, whether this is also true for the overall elimination of contrast media by these different procedures needs to be addressed in future studies, by a precise assessment of the drug time course after the session.     

Beta(2)-microglobulin clearance decreases with Renalin reuse

The HEMO study revealed that beta(2)-microglobulin clearance decreases over time with Renalin reuse in the high-flux group. It was suggested that the reuse of polysulfone or cellulose triacetate high-flux dialyzers with Renalin (without bleach) results in degradation of the high-flux capacity. At our haemodialysis unit (Vila Real, Portugal) we reused dialyzers until January 2000 (limited to 10 reuses), with an automatic machine Renatron (Renal Systems, Minntech. All of our 31 patients who started with postdilution haemodiafiltration on-line (HDFol) were always dialyzed with F-80 polysulfone (Fresenius). The reposition rate was 10 litres/session until 1998 and 20 litres/session thereafter. Reuse techniques were abandoned in our country in January 2000 following an EEC directive. Thereafter, we have decided to maintain HDFol with the same dialyzers without reuse. The mean beta(2)-microglobulin predialysis values did not decrease over time until reuse was terminated (1995 with low-flux haemodialysis: 25.4 +/- 6.4 microg/l; 1997: 24.7 +/- 6.6 microg/l; 1998: 29.2 +/- 8.9 microg/l; 1999: 33.7 +/- 4.7 microg/l) whereas beta(2)-microglobulin clearances were reasonable with HDFol (1998: 56.4 +/- 25.9 ml/min; 1999: 47.9 +/- 16.4 ml/min). After stopping reuse we have noticed that predialysis beta(2)-microglobulin values decreased (2000: 23.0 +/- 3.9 microg/l) in accordance with beta(2)-microglobulin clearance duplication (2000: 84.1 +/- 25.0 ml/min; p < 0.01). It is our opinion that the reuse of polysulfone dialyzers with Renalin should be abandoned in the field of high-flux haemodialysis. It causes deterioration in the beta(2)-microglobulin clearance and probably interferes with the high-flux haemodialysis benefits, namely the reduction of dialysis-related amyloidosis.     

Effect of dialysis on serum/plasma levels of free immunoglobulin light chains in end-stage renal disease patients.

BACKGROUND: Free immunoglobulin light chains (FLCs) have previously been shown to be uraemic toxins. In this work we investigated the effect of haemodialysis and haemodiafiltration on the level of FLCs in serum/plasma of uraemic patients. METHODS: Serum/plasma proteins were separated by non-reducing SDS-PAGE and transferred to a nitro-cellulose membrane. FLCs were detected by specific antibodies and an enhanced chemiluminescence detection system. The FLC concentrations were calculated. We studied 15 healthy subjects, 10 patients with chronic renal failure, 71 patients undergoing haemodialysis treatment and 33 patients treated with haemodiafiltration. Different membranes were compared: low- and high-flux polysulfone membranes, low- and high-flux cellulose triacetate membranes, high-flux polymethylmethacrylate and polyacrylonitrile membranes. RESULTS: Chronic renal failure patients showed elevated FLC concentrations as compared with controls. In haemodialysis or haemodiafiltration patients these values were even higher. This was mainly due to an increased concentration of FLC of the lambda-type. The treatment modality per se did not influence the FLC concentrations. Only haemodialysis or haemodiafiltration with the polymethylmethacrylate membrane lead to a significant reduction in FLC concentrations; however, these did not reach control levels. We did not observe differences in FLC levels between patients with different underlying diseases, nor did we find a correlation between age or the duration of the dialysis treatment and FLC concentrations. We found a positive correlation between FLC concentrations at the beginning of dialysis treatment and the amount of IgLCs removed during treatment. However, the average FLC level after treatment did not reach control values. CONCLUSIONS: Currently available haemodialysis or haemodiafiltration treatments are unable to normalize the elevated serum/plasma levels of FLCs in end-stage renal disease patients.     

Serum aluminium level in the veneto chronic haemodialysis population: cross-sectional study on 1,026 patients

A total of 1,026 patients undergoing haemodialysis as the only chronic treatment were studied in all the dialysis units of the Veneto region, Italy. Aluminium was determined in water, dialysis fluids, and patients' serum. Aluminium mean concentration was 9.1 micrograms/l in tap water and 13.3 and 15.7 micrograms/l in bicarbonate and acetate haemodialysis fluids, respectively. Patients' serum aluminium mean level was 52.0 micrograms/l with the following frequency distribution: 59.2% below 60 micrograms/l, 25.5% between 60 and 100 micrograms, and 15.3% above 100 micrograms/l. The mean serum aluminium level was higher in patients undergoing haemodialysis with aluminium concentration in fluids over 10 micrograms/l. This was true also in patients not receiving aluminium hydroxide. Furthermore, we found higher average serum aluminium in those treated with aluminium hydroxide more than 3 g/day. No relationship was found between serum aluminium and sex, age, dialytic age, parathyroid hormone, and vitamin D treatment. Moreover, the patients with serum aluminium above 100 micrograms/l had higher serum alkaline phosphatase and lower mean cell volume values. Thus, in our haemodialysis population aluminium overloading occurred in spite of low concentration in water and fluid, and it was a result more of fluid pollution (over 10 micrograms/l) than aluminium hydroxide ingestion (over 3 g/day).