Comparison of cellulose diacetate and polysulfone membranes in the outcome of acute renal failure. A prospective randomized study.

BACKGROUND: Whether the nature of haemodialysis (HD) membranes can influence the outcome of acute renal failure (ARF) remains debatable. Recent studies have suggested that dialysis with bioincompatible unsubstituted cellulosic membranes is associated with a less favourable patient outcome than dialysis with biocompatible synthetic membranes. Since we generally use a modified cellulosic membrane with substantially lower complement- and leukocyte-activating potential than cuprophane, for dialysis of patients with ARF, and because there are no data in the literature regarding the influence of modified cellulosic membranes on the outcome of patients with ARF, we compared the outcome of ARF patients dialysed either with cellulose diacetate or with a synthetic polysulfone membrane. We also investigated the potential role of permeability by comparing membranes with high-flux versus low-flux characteristics. METHODS: This prospective, randomized, single centre study included 159 patients with ARF requiring HD. Patients were stratified according to age, gender, and APACHE II score and then randomized in chronological order to one of three dialysis membranes: low-flux polysulfone, high-flux polysulfone and meltspun cellulose diacetate. RESULTS: Aetiologies of ARF and the prevalence of oliguria were similarly distributed among the three groups. There was no significant difference between the three groups for survival (multivariate Cox's proportional hazards model, P=0.57), time necessary to recover renal function (P=0.82), and number of dialysis sessions required before recovery (P=0.86). Multivariate analysis showed that survival was significantly influenced only by the severity of the disease state (APACHE III score, P<0.0001), but not by the nature of the dialysis membrane (P=0.57) or the presence of oliguria (P=0.24). CONCLUSIONS: Among patients with ARF requiring HD survival and recovery time are not significantly influenced by the use of either meltspun cellulose diacetate or the more biocompatible high-flux or low-flux polysulfone. Dialysis using modified cellulose membranes is just as effective as dialysis using synthetic polysulfone membranes, but at a lower cost. In addition, the flux of the membrane did not influence patient outcome.     

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.     

Hirudin elimination by hemofiltration: a comparative in vitro study of different membranes

BACKGROUND: Recombinant hirudin (r-hirudin) is a highly specific and selective thrombin inhibitor. Since 1997, it has been approved for the treatment of heparin-induced thrombocytopenia (HIT type II). Renal function impairment drastically prolongs the elimination half-life time. In cases of bleeding or overdosage, there is currently no antidote available. Hemofiltration has been reported to be useful in r-hirudin elimination. In this study, we determined sieving coefficients (SCs) and drug clearances for two different hemofilters currently used in clinical medicine and intensive care. METHODS: We developed an in vitro postdilution hemofiltration model using 500 ml heparinized (2 IU unfractionated heparin/ml) fresh human blood and bicarbonate substitution fluid. The investigated membranes were high-flux polysulfone F50 (1.0 m2, Fresenius) and AN69 Nephral 200 (1.05 m2, Hospal Cobe). After equilibration, a bolus of Lepirudin was injected into the postfilter port to achieve a r-hirudin blood level of approximately 15 microg/ml. Serial blood and ultrafiltrate samples were taken for the determination of hirudin levels (chromogenic assay) and control parameters. SC and clearances were calculated according to standard formulae. RESULTS: The observed SCs and clearances differed significantly between F50 and Nephral 200 (0.60+/-0.17 and 21.0+/-5.9 ml/min, respectively, vs. 0.44+/-0.09 and 15.5+/-3.0 ml/min, respectively; P = 0.001). The determination of prothrombin fragments showed no coagulation activation during the experiments. The hematocrit values remained stable. CONCLUSIONS: Our data show that r-hirudin can be eliminated by hemofiltration. The elimination obviously depends on the membrane material with high-flux polysulfone being more effective than AN69. These findings may be important in cases of overdosage and for r-hirudin dosage guidelines in continuous hemofiltration.     

Angiogenin: a novel inhibitor of neutrophil lactoferrin release during extracorporeal circulation

Degranulation of polymorphonuclear leukocytes (PMNL) occurs during extracorporeal circulation. A degranulation-inhibiting protein identical to angiogenin was recently isolated from high-flux dialyzer ultrafiltrate. This protein inhibits the release of lactoferrin and metalloproteinases from PMNL in vitro. In the present study, we investigated end-stage renal disease patients undergoing regular hemodialysis treatment with either high-flux dialyzers (n = 51) or low-flux dialyzers (n = 44), and chronically uremic patients undergoing hemodiafiltration (n = 30). Hemodialysis therapy with low-flux polysulfone or cellulose triacetate membranes caused no or only minimal reduction (相似文献   

Influence of dialysis procedure, membrane surface and membrane material on iopromide elimination in patients with reduced kidney function

Haemodialysis for the elimination of contrast medium in patients with advanced renal failure is a common procedure. Even though sufficient elimination with the use of regular low-flux membranes is documented, large differences in results have been reported in prior investigations. We, therefore, compared Cuprophan and polysulfone dialysers with different surface areas to haemofiltration with different amounts of substitution fluid in 40 patients with compromised renal function after coronary angiography. Plasma iodine concentrations were measured by fluorescent excitation analysis. At constant blood flow rates of 200 ml/min, Cuprophan membranes with 1. 3 m(2) surface area had a clearance rate of 87 ml/min, whereas polysulfone membranes of comparable size displayed a significantly higher clearance rate of 147 ml/min. Polysulfone membranes with 1.8 m(2) surface area showed a small but insignificant increase in the iodine clearance (162 ml/min), while Cuprophan membranes displayed an increase in clearance rates (121 ml/min). Additional ultrafiltration led to a further increase in the plasma clearance of both membranes and reduced urinary iodine excretion. Haemofiltration was comparable to haemodialysis in terms of efficacy and thus represents an alternative method. Clearance of iopromide during haemodialysis with polysulfone membranes is higher than with Cuprophan membranes. Elimination rates can be further increased by additional ultrafiltration. Haemofiltration is comparable to haemodialysis regarding contrast medium elimination.     

Enhanced long-term reduction of plasma leptin concentrations by super-flux polysulfone dialysers.

BACKGROUND: Hyperleptinaemia in chronic haemodialysis (CHD) patients has been associated with malnutrition, which is an independent predictor of morbidity and mortality in this patient group. METHODS: To assess the influence of HD on plasma leptin, 10 CHD patients were crossover randomized to low-flux polysulfone (PS: F 6HPS), high-flux PS (F 60S), super-flux PS (F 500S) or super-flux cellulose-tri-acetate (CTA: Tricea 150G) for 12 weeks each. Blood samples were collected at the start of the study and each 12-week period. In addition, the relationship between patient characteristics, inflammation and leptin was analysed. RESULTS: At baseline, all groups showed similar leptin concentrations (mean 33.6+/-21.7 ng/ml). After a single HD session, a significant (P<0.01) decrease was observed with all three high permeable devices (Tricea 150G -52.7+/-6.4%; F 60S -63.1+/-5.7%; F 500S -68.7+/-8.2%), whereas leptin remained stable with low-flux PS. After 12 weeks, a marked increase was observed with low-flux PS (week 1, 30.4+/-23.0; week 12, 40.5+/-5.4 ng/ml, P = 0.05), no change with super-flux CTA and high-flux PS (Tricea 150G week 1, 29.4+/-23.7; week 12, 32.0+/-27.9 ng/ml, P = ns; F 60S week 1, 36.0+/-31.8; week 12, 33.0+/-31.2 ng/ml, P = ns), and a significant decrease with super-flux PS (week 1, 38.3+/-33.0; week 12, 29.5+/-31.9 ng/ml, P = 0.02). The change in leptin after 12 weeks was significantly different between super-flux PS, and both low-flux PS (P = 0.009) and super-flux CTA (P = 0.01). Besides interleukin-6 (IL-6) at the start of the study (P = 0.006), no correlations were observed between patient characteristics, parameters of inflammation and plasma leptin levels. CONCLUSIONS: Apart from low-flux PS, plasma leptin decreased considerably with all three high permeable dialysers after a single HD session. In the long run, leptin levels were lower with high-flux PS than with low-flux PS. Moreover, after switching from high-flux PS to super-flux PS (but not super-flux CTA), an additional decrease in leptin was observed. Apart from IL-6 at the start of the study, neither patient characteristics nor inflammatory parameters correlated with plasma leptin levels in this patient group.     

Clinical manifestations of AB-amyloidosis: effects of biocompatibility and flux.

BACKGROUND: Highly permeable biocompatible dialysis membranes may postpone the development of AB-amyloidosis, but the relative contribution of enhanced flux or reduced inflammation by highly biocompatible membranes and sterile dialysis fluid remains unknown. METHODS: In this retrospective investigation, 89 patients with end-stage renal disease maintained on regular haemodialysis for at least 10 years and treated with one type of dialysis membrane exclusively were selected for analysis. They were divided into three groups: low-flux, bioincompatible cellulose (I), low-flux, intermediately biocompatible polysulphone or PMMA (II), or high-flux, highly biocompatible polysulphone or AN69 (III). In addition, the patients were analysed according to the microbiological quality of the dialysis fluid, which had been tested regularly and was classified either as standard or as intermittently contaminated. The clinical manifestations indicative of AB-amyloidosis, namely, carpal tunnel syndrome, arthropathy and bone cysts, were diagnosed after recruitment. RESULTS: Clinical symptoms were most pronounced in group I, intermediate in group II, and lowest in group III. Patients treated with intermittently contaminated dialysis fluid showed a higher prevalence of AB-amyloidosis than patients with less contaminated dialysis fluid. Logistic regression analysis demonstrated that the flux characteristics of the dialyser and the microbiological quality of the dialysis fluid as well as the biocompatibility of the dialyser were independent determinants of AB-amyloidosis. CONCLUSION: It would be prudent clinical practice to employ high-flux biocompatible membranes in conjunction with ultrapure dialysis fluid for the treatment of end-stage renal disease patients who need to remain on long-term 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.     

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.     

Impact of hemodialysis membrane and permeability on neutrophil transmigration in vitro

BACKGROUND/AIM: The impact of dialysis membrane permeability on neutrophil transmigration properties in vitro was examined in the present study. This issue has not been fully scrutinized before. METHODS: We studied the capacity of neutrophils collected from a group of dialysis patients randomly treated with cuprophan, low- or high-flux polysulfone, to transmigrate in vitro through a membrane covered with fibronectin (a main constituent of the endothelial basement membrane). The hemodialysis-induced quantitative changes in expression of adhesion molecules were examined in parallel. RESULTS: At the end of dialysis, neutrophils collected from patients treated with high-flux polysulfone dialyzers had a significantly higher transmigration index than neutrophils from patients treated with low-flux polysulfone membrane (p < 0.01) or cuprophan membrane (p < 0.01), and approached the level of transmigration observed in neutrophils collected from healthy controls. In the groups treated with low-flux polysulfone and cuprophan dialyzers, the transmigration capacity was significantly lower (p < 0.02) compared to neutrophils from healthy subjects. We also noted that differences between low- and high-flux polysulfone dialysis, in the context of transmigration properties, were not mirrored by changes in adhesion phenotype, which strengthens the view that there is no strict relationship between these two features. CONCLUSION: The study demonstrates that high-flux polysulfone dialysis, as opposed to low-flux polysulfone and cuprophan treatment, improves the transmigration properties of circulating neutrophils, despite similar effects on adhesion molecule phenotypes. A plausible mechanism is that potentially toxic middle range molecules that inhibit neutrophil migration are more efficiently eliminated during high-flux polysulfone dialysis, but this explanation requires further support.     

Differences in the permeability of high-flux dialyzer membranes for bacterial pyrogens

AIMS: The increasing use of high-flux membranes for hemodialysis has raised concerns that patients dialyzed with these membranes may be at higher risk of being exposed to cytokine-inducing bacterial substances in the dialysate than patients dialyzed with low-flux membranes. We investigated the permeability of various high-flux membranes for both purified E. coli lipopolysaccharide (LPS) as well as for LPS derived from Stenotrophomonas (Sten.) maltophilia. MATERIALS AND METHODS: An in vitro dialysis circuit with saline in the blood compartment of 3 dialyzers containing different membranes (polysulfone, helixone and Diapes) was employed. The dialysate was challenged with increasing doses of sterile filtrates derived from Sten. maltophilia cultures or with purified LPS from E. coli. Samples from the blood compartment were tested for cytokine induction (IL-1beta, IL-6 and TNF) in mononuclear cells as well as for LPS by limulus amebocyte lysate test (LAL). RESULTS: IL-6 induction above sterile controls (< 0.02 ng/ml IL-6) was observed by samples from the blood side of DIAPES dialyzers (1.2 +/- 0.7 ng/ml IL-6) after challenging the dialysate with 4.1 +/- 3.6 U/ml E. coli LPS (9.9 +/- 4.5 ng/ml IL-6). In contrast, at the same challenge dose no significant IL-6 induction above sterile controls was observed by blood side samples of polysulfone (0.15 +/- 0.07 ng/ml) and helixone (0.09 +/- 0.05 ng/ml) dialyzers. Increasing the amount of E. coli LPS in the dialysate further augmented IL-6 induction by blood side samples of Diapes but not of polysulfone and helixone dialyzers. Similar results were obtained for IL-1beta and TNF. After challenging the dialysate with E. coli LPS as well as with cultures of Sten. maltophilia, significantly more LAL reactivity was observed in the blood compartment of Diapes compared to polysulfone and helixone. CONCLUSIONS: There are considerable differences between high-flux membranes regarding their permeability for cytokine-inducing substances from E. coli as well as for LPS derived from E. coli and Sten. maltophilia. Dialyzers that leak CIS under aqueous conditions in vivo should not be used unless the dialysate has passed through an ultrafilter.     

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.     

Permeability of dialyzer membranes to TNF alpha-inducing substances derived from water bacteria.

Pro-inflammatory cytokine-inducing substances derived from cultured E. coli have previously been shown to pass across low-flux regenerated cellulosic dialyzer membranes. In the present study, a sterile filtrate of Pseudomonas maltophilia grown from standard bicarbonate dialysis fluid was used to test the permeability of various dialyzer membranes (regenerated cellulose, cellulose triacetate, polyacrylonitrile, polysulfone and polyamide) to TNF alpha-inducing bacterial substances. Pyrogen-free tissue culture medium (MEM) was recirculated for 60 minutes in the dialysate compartment of a closed-loop dialysis system, then P. maltophilia filtrate was added and recirculation was continued for a further hour. Samples from the dialysate (MEM) and the blood side (containing 10% human plasma in MEM) were incubated with donor mononuclear cells (MNC) for 18 hours and TNF alpha release was measured in MNC supernatants by radioimmunoassay. Five minutes after the addition of P. maltophilia filtrate, mean TNF alpha-inducing activity in the dialysate increased from (mean +/- SEM) 0.10 +/- 0.02 to 18.2 +2- 1.5 (ng/2.5 x 10(6) MNC/18 hr). TNF alpha-inducing activity in the blood side increased with regenerated cellulose from 0.10 +/- 0.01 to 4.57 +/- 1.55 (N = 8; P less than 0.001); with cellulose triacetate from 0.20 +/- 0.05 to 0.44 +/- 0.10 (N = 5; P less than 0.05), and with polyacrylonitrile from 0.10 +/- 0.02 to 1.16 +/- 0.45 (N = 5; P less than 0.03). No increased TNF alpha-inducing activity was observed in the blood side of polysulfone (N = 5) or polyamide dialyzers (N = 5).(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Highly permeable membranes in dialysis: Optimal therapy design

Summary: Considering the removal potential of diffusion and convection in relation to the size of uraemic toxins, it is evident that we should not rely solely on diffusion to purify the blood, as is the case in the most common form of dialysis, haemodialysis with low-flux membranes. In order to remove more of the larger uraemic toxins, we need to use more convective transport in dialysis therapy. the use of high-flux membranes is increasing and approximately 25% of all dialysis treatments are performed with these membranes. They are characterized by high permeability to water, but for good convective transport they should also have generous and stable sieving properties. the convective transport provided by these membranes when used in a haemodialysis set-up is limited to the desired weight loss and the uncontrolled ultrafiltration which is compensated by backfiltration. to better use the potential of a high-flux membrane, the ultrafiltration should be greatly increased, as in haemodiafiltration (HDF) and haemofiltration (HF). the large volumes of fluid, free from bacteria and pyrogen, which are required for these therapies can be provided by special multi purpose treatment systems. On-line preparation of bicarbonate-containing fluid that can be used for substitution is a safe, practical and cost-effective method. In addition to high clearance of solutes over a wide molecular weight range, the convective therapies provide good haemodynamic stability in response to fluid removal during dialysis.     

Removal of chelated aluminium during haemodialysis using polysulphone high-flux dialysers

Polysulphone high-flux dialysers were used for removal of chelated aluminium in desferrioxamine-treated patients on maintenance haemodialysis. When compared with charcoal haemoperfusion in series with a cuprophane dialyser, the same aluminium clearance was obtained (34% of blood flow). During 4 h of haemodialysis serum aluminium was reduced to the concentration seen before desferrioxamine infusion. We conclude that high-flux polysulphone dialysers remove chelated aluminium as efficiently as does charcoal haemoperfusion, and at a lower cost.     

Treatment of hirudin overdosage in a dialysis patient with heparin-induced thrombocytopenia with mixed hemodialysis and hemofiltration treatment

We report a patient who developed type II heparin-induced thrombocytopenia (HIT) and accidentally received a recombinant hirudin (r-hirudin) overdosage. Treatment with hemodialysis (HD) using high-flux polysulfone dialyzer and hemofiltration was performed. Length of treatment was adjusted, monitoring activated partial thromboplastin time (aPTT) to 1.5-2.5 times the mean of the normal range. She developed deep venous thrombosis and occlusion of vascular access. Only after cessation of heparin lock catheter, platelet count began to increase. After one year of treatment with acenocoumarol and additional low-dose r-hirudin, neither bleeding nor thrombotic episodes have been reported.     

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.     

A comparison of dialysers with low-flux membranes: significant differences in spite of many similarities

The solute removal characteristics and haemocompatibility of low-flux dialysers containing Cuprophan^m, cellulose acetate, polymethylmethacrylate (PMMA), and polycarbonate-polyether (Gambrane^m) membranes were compared in a multicentre cross-over clinical trial. While all four dialysers provided comparable removal of urea and creatinine, the dialyser containing PMMA membrane showed a reduced ability to remove phosphate compared to that containing Cuprophan membrane. Significant {beta}2-microglobulin removal was obtained with the dialyser containing Gambrane membrane, whereas the other three dialysers had no impact on plasma {beta}2-microglobulin concentrations. The ability to activate complement, measured as changes in the plasma concentrations of C3a des Arg and the terminal complement complex, and to produce leukopenia was greater for the dialyser containing Cuprophan membrane than for the other three. The ability to activate complement and cause leukopenia was not consistent among the remaining three dialysers and the degree of leukopenia could not be predicted from the level of complement activation. Neutrophil degranulation, as indicated by the release of elastase-&agr;1-proteinase inhibitor, occurred to a greater extent with the dialysers containing Cuprophan and Gambrane membranes. None of the dialysers was overtly thrombogenic as judged by changes in platelet count and plasma concentrations of the thrombin-antithrombin III complex. Our results demonstrate that although there are many similarities between dialysers containing low-flux membranes, there are also significant differences. These differences may enable improvements in therapy, while allowing continued use of low-flux dialysers.     

Removal of plasma porphyrins with high-flux hemodialysis in porphyria cutanea tarda associated with end-stage renal disease.

Plasma porphyrin levels are markedly increased in patients with porphyria cutanea tarda (PCT) associated with end-stage renal disease. Conventional hemodialysis (CHD) with lower blood flow rates (less than 250 mL/min) and cuprophan or cellulose acetate membranes is ineffective in removing significant amounts of porphyrins in this condition. Changes in plasma porphyrin levels and porphyrin clearances during hemodialysis with higher blood flow rates and more-permeable, high-efficiency cellulose acetate and high-flux polysulfone dialyzers were evaluated in a chronic hemodialysis patient with PCT and markedly elevated plasma porphyrins. The polysulfone membrane achieved significantly better fractional porphyrin removal (P = 0.02) and porphyrin clearances (P less than 0.01) than did the high-efficiency cellulose acetate membrane. After conversion from maintenance CHD with a standard cellulose acetate dialyzer to a 4-wk period of high-flux hemodialysis (HFHD) with a polysulfone dialyzer, predialysis plasma porphyrins fell by 37%. After returning to CHD, plasma porphyrins returned to the higher prestudy levels. These observations suggest that HFHD with more permeable membranes and higher blood flow rates removes porphyrins more effectively than does CHD. HFHD may be a useful adjunct to other measures used in treating dialysis patients with PCT.