Adsorption of Nafamostat Mesilate by Hemodialysis Membranes

The adsorption of the anticoagulant nafamostat mesilate (FUT-175) by five different hemodialysis membranes was studied in vivo and in vitro. In vivo, FUT-175 was adsorbed strongly by a polyacrylonitrile (AN69) membrane and slightly by another polyacrylonitrile (J-PAN) membrane but not by Cuprophan (CU), hemophan (HE), or polymethylmethacrylate (PMMA) membranes during hemodialysis performed in 4 patients in whom FUT-175 was used as an anticoagulant. Only during hemodialysis using the AN69 membrane did FUT-175 not induce a significant prolongation of celite-activated coagulation time. In vitro studies showed that FUT-175 was adsorbed by the AN69, J-PAN, and PMMA membranes but not by the CU and HE membranes. Methylene blue, a dye that possesses a cationic portion in its chemical structure, stained AN69, J-PAN, and PMMA membranes. Since FUT-175 also possesses a cationic portion, we conclude that FUT-175 is adsorbed by negatively charged membranes via an ionic bond and is unsuited for use as an anticoagulant in hemodialysis using an AN69 membrane because of that membrane's marked capacity to adsorb FUT-175.     

Influence of hemodialysis membrane type on pentosidine plasma level, a marker of "carbonyl stress".

Influence of hemodialysis membrane type on pentosidine plasma level, a marker of "carbonyl stress." BACKGROUND: The accumulation of advanced glycation end products (AGEs) in uremia has been ascribed to the retention of carbonyl precursors of AGEs. Pentosidine plasma level has been identified as a surrogate marker of carbonyl precursors ("carbonyl stress"). The influence of hemodialysis (HD) membrane type and residual diuresis on carbonyl stress has not been studied. METHODS: We measured protein-linked and free plasma pentosidine (a surrogate marker of carbonyl stress) by high-performance liquid chromatography in patients on HD with low-flux cellulose (N = 29), high-flux polysulfone (PS; N = 57), polymethylmethacrylate (PMMA) (N = 25), and AN69 (N = 15). RESULTS: Both protein-linked and free pentosidine were similar on low-flux cellulose, high-flux PMMA, and AN69, but were lower (P < 0.01) on high-flux PS. Pentosidine levels were virtually identical on Fresenius and Asahi PS in Japanese and Belgian patients. By multivariate analysis, only the type of HD membrane and residual diuresis proved to be independent determinants (P < 0.001) of pentosidine levels. During a single HD session, the clearance of free pentosidine was similar with all membranes. In three patients who were switched from AN69 to PS, the protein-linked pentosidine level dropped to the control level after resumption of the AN69 membrane. CONCLUSIONS: Both HD membrane type and residual diuresis are independent determinants of pentosidine plasma level, which is a marker of carbonyl stress.     

Hemocompatibility in Hemodialysis and Erythropoietin Therapy

Abstract: Two studies designed to investigate the effect of recombinant human erythropoietin (rHuEPO) treatment of anemia in chronic dialysis patients on hemocompatibility were conducted. Study 1, whose main aim was to establish whether treatment with rHuEPO enhances coagulation activation during dialysis, included 15 patients before rHuEPO therapy at a mean hematocrit (HCT) of 22.3% and then during therapy at a HCT of 29.3%. The plasma concentrations of the thrombin-antithrombin III complex were not higher during rHuEPO therapy than before it when performing hemodialysis with a Cuprophan membrane. No significant difference was demonstrated either in the values of activated clotting times (Hemochron), thrombocyte or white blood cell counts (Coulter S + II), or in plasma C5a concentrations (ELISA) established during dialysis sessions before and during rHuEPO therapy. In Study 2, which focused primarily on the question of whether or not rHuEPO therapy increases thrombocyte activation during hemodialysis, 8 patients on chronic dialysis were examined both before therapy at a mean HCT value of 22.1% and during rHuEPO therapy at a HCT of 31.5%, invariably during dialysis with either a Cuprophan or polyacrylonitrile (AN69HF) membrane. The plasma concentrations of beta-thromboglobulin (ELISA) did not differ between the examinations made during rHuEPO and before rHuEPO therapy; however, statistically significant differences were found between dialysis sessions involving Cuprophan and AN69HF membranes. No significant difference between examination before and during rHuEPO was demonstrated in activated clotting time nor thrombocyte and white blood cell counts in this study either. The authors conclude that rHuEPO therapy does not enhance coagulation activation during hemodialysis, does not have an effect on thrombocyte activation, and does not influence complement activation and changes in white blood cell counts.     

Adsorption of Human Recombinant Erythropoietin on Dialysis Membranes In Vitro

Abstract: The adsorptive characteristics of 5 dialysis membranes for recombinant human erythropoietin (EPO) were studied in vitro in a closed circuit system. For 120 min, EPO added with bovine serum was significantly adsorbed by polymethylmetacrylate (PMMA) and polyacry–lonitrile (PAN) membranes but not by Cuprophan, ethylene vinyl alcohol (EVAL), or polysulfone (PS) membranes. In addition the EPO adsorptive rate, as well as that of β₂–microglobulin (β₂–MG), was greater with a PMMA membrane than with a PAN membrane. EPO was not detected in the ultrafiltrate at 15 min with 5 membranes. These results indicate that EPO was eliminated by membrane adsorption only with some dialysis membranes.     

Effects of a vitamin E-bonded membrane and of glutathione on anemia and erythropoietin requirements in hemodialysis patients

BACKGROUND: The oxidative damage of RBC membranes in hemodialysis (HD) patients increases red blood cell (RBC) susceptibility to hemolysis and impairs cell survival. Reduction of the oxidative stress might lead to better control of anemia and reduction of the erythropoietin (rhEPO) dose. METHODS: We studied 38 stable HD patients, given a mean dose of rhEPO of 104+/-65 U/kg BW/week, at baseline and during antioxidant treatment with either a full or a 50% dose of EPO. Antioxidant treatment involved the combined use of glutathione, GSH (1200 mg i.v. at the end of each dialysis session) and a vitamin E-bonded HD membrane, CL-E. RBC and reticulocyte counts were done monthly. RBC survival (51Cr T/2) was assayed in 18 patients before and after the end of the study. Oxidative status was determined in 10 patients by measuring plasma concentrations of malondyhaldeide-4-hydroxynonenal (MDA-4HNE), reactive oxygen molecular species (ROMs), and oxydized-LDL (oxLDL) as indices of oxidative stress, alpha-tocopherol and total thiols as single antioxidants, and TAS as a marker of total antioxidant plasma activity. RESULTS: Antioxidant treatment significantly reduced the high basal plasma concentrations of MDA4HNE and oxLDL, and significantly increased those of alpha-tocopherol, whereas TAS and thiols were unmodified. These changes lasted after the reduction of EPO. Anemia significantly improved with treatment, due to a significant increase in RBC survival. A close direct linear relationship was detected between plasma levels of vitamin E and hemoglobin. CONCLUSIONS: Adequate control of oxidative stress achieves better control of anemia in HD patients. Since several antioxidant systems are impaired in uremia, the combined use of the CL-E membrane and GSH seems to be the best antioxidant therapy so far, with significant saving of the rhEPO dose.     

Long-Term Results of Dialysis Therapy with a Highly Permeable Membrane

A five-year study of short-term dialysis using highly permeable polyacrylonitrile membrane AN 69 was started in March 1973 to compare the effects of AN 69 and Cuprophan membrane (CM). The time of dialysis was calculated for each patient on the basis of vitamin B₁₂ clearance of the dialyzer and the residual glomerular filtration rate. For the study, 101 patients (38,555 dialysis sessions) who had been dialyzed for more than six months were selected. They were divided into three groups: Group I (n = 31) patients treated with AN 69 only; Group II (n = 31) patients treated with CM; Group III (n = 39) patients treated first with the CM and then with AN 69. Patients treated with AN 69 had higher levels of plasma urea but no particular metabolic disturbances were observed. The dialysis sessions were significantly better tolerated with AN 69 than with CM, however, the main advantage of using AN 69 is the shortening of dialysis time. The duration of dialysis was 9.5 ± 0.2 hours per week with AN 69 and 16.4 ± 0.2 hours per week with CM. Shortening of dialysis time permits better social rehabilitation of the patients. The shorter dialysis was not associated with any recognizable side effects that could be demonstrated by routine clinical and biological analysis.     

Influence of Blood Flow on Adsorption of β2-Microglobulin onto AN69 Membrane

Abstract: Adsorption onto the dialyzer membrane is a contributing factor to the elimination of β₂-microglobulin (β₂M) from the sera of uremic patients. The purpose of this prospective study was to ascertain the influence of the blood flow rate on adsorption of β₂M onto the polyacrylonitrile (AN69) hollow-fiber dialyzer membrane in 8 pa tients during regular hemodialysis (HD). Blood first passed through a low-flux polysulfone dialyzer and then through an AN69 dialyzer, which was not in contact with the dialysis fluid. During the investigation period (first hour of the HD session), the blood flow rate was 100 ml/min (first part of the study), 200 mumin (second part of the study), and 300 ml/min (third part of the study). Ultrafiltration was not performed during the investigation period. At the start of the HD sessions, the serum concentration of β₂M in the afferent blood line did not differ significantly among the 3 parts of the study. Serum β₂M was measured in samples taken from the afferent and efferent blood lines of the AN69 dialyzer at 5,10, 15, 30, 45, and 60 min. The serum β₂M concentration decreased significantly in blood that had passed through the AN69 dialyzer. This decrease, indicating membrane adsorption, was maximal during the first part and minimal during the third part of study. The decrease in the contact time between the blood and the AN69 could be the underlying cause. The calculated quantities of β₂M adsorbed onto the AN69 membrane (44.2 ± 10.2, 43.2 ± 12.1, and 42.6 ± 17.3 mg) did not differ significantly among the 3 parts of the study. These results suggest that an increase in blood flow rate from 100 to 300 ml/min did not significantly affect the quantity of β₂M adsorbed onto the AN69 membrane.     

Kinetics of 131I-β2 Microglobulin in Hemodialysis Patients: Assessment Using Total Body Counting

Abstract: The kinetics of ¹³¹I-β₂-microglobulin (β₂-M) were studied using external total body gamma counting in a low noise chamber after administration of trace doses of radioactivity (4 μCi) in 14 uremic patients treated by either hemodialysis or hemofiltration. Data were collected over a 1 week period that included 3 dialysis sessions. The following artificial membranes were used: Cuprophan, polyacrylonitrile AN69, polysulfone, polymethylmethacrylate (PMMA), and polyamide. Radiolabeled β₂-M excretion by an extrarenal route was nearly nonexistent. The ¹³¹I-β₂-M half-life was between 2.4 and 8 days, shorter in patients with residual diuresis. A mean removal of 153 ± 33 mg/L of β₂-M was obtained per dialysis session with a highly permeable membrane. A hemofiltration session (25 L exchange per session) was slightly more efficient in removing β₂-M than a 4 h hemodialysis session with the same AN69 highly permeable membrane. The amounts of ¹³¹I-β₂-M binding on the membranes, expressed as β₂-M equivalents, were 0, 16, 54, 58, and 59 mg/m² for Cuprophan, polysulfone, polyacrylonitrile AN69, polyamide, and PMMA, respectively. In conclusion, the decrease of total body gamma counting directly reflected the β₂-M breakdown and removal in hemodialysis patients. Intact β₂-M was removed by convection with synthetic, highly permeable membranes. In addition, membrane adsorption accounted for 15% (polysulfone) to near 100% (PMMA) of the β₂-M removal per session. Adsorption was of the same magnitude regardless of the dialysis technique in use, indicating a membrane saturability process. None of the currently available dialysis procedures based on a 3 sessions per week schedule can balance β₂-M generation.     

Characterization of insulin adsorption behavior of dialyzer membranes used in hemodialysis

Although it has been reported that plasma insulin is removed by hemodialysis (HD), the mechanism for this has not been elucidated. We investigated the mechanism of insulin removal during HD treatment and the characteristics of insulin removal with three high-flux membranes. In our in vivo study, 20 stable diabetic patients on HD were randomly selected for three HD sessions with three different membranes: polysulfone (PS), cellulose triacetate (CTA), and polyester polymer alloy (PEPA). Blood samples were obtained from the blood tubing at the arterial (A) site at the beginning and end of the sixth HD session to investigate insulin reduction in patients. At 1 h after the initiation of dialysis, blood samples were obtained from both the A and venous sites of the dialyzer to investigate the insulin clearance with the different membranes. There was a significant reduction in patients' plasma insulin at each time point with each of the three membranes. The insulin clearance with the PS membrane was significantly higher than that with the CTA and PEPA membranes. Although no difference was observed in the plasma insulin reduction rate between the three membranes in the total subject group, there was a significantly higher reduction rate with the PS membrane in insulin-dependent diabetes mellitus subjects. The clearance of insulin in in vitro tests was significantly higher with the PS and PEPA membranes than with the CTA membrane in both new and clinically used dialyzers. Insulin was not detected in the dialysate or ultrafiltration fluids in either the in vivo or in vitro studies. The mechanism of plasma insulin clearance by HD is mainly by adsorption, and the amount of insulin adsorbed differed depending on the dialyzer membrane used.     

The AN69 ST haemodialysis membrane under conditions of two different extracorporeal circuit rinse protocols a comparison of thrombogenicity parameters.

BACKGROUND: Thrombogenicity is an important parameter of haemodialysis (HD) membrane biocompatibility. The surface of the polyacrylonitrile AN69 ST membrane is coated with a polyethylenimine. This modification allows heparin adsorption. The binding of heparin to the membrane surface occurs during priming of the extracorporeal circuit (ECC) by rinsing it with saline and heparin. Our aims were to assess and compare the thrombogenicity of the AN69 ST membrane under conditions of two extracorporeal circuit (ECC) rinse protocols-with and without unfractionated heparin (UFH). METHODS: In a prospective, crossover and randomized study, we examined 10 patients during HD after ECC preparation with either rinse protocols. Prior to HD and at 15, 60 and 240 min, we determined plasma levels of the thrombin-antithrombin complexes (TAT), platelet factor 4 (PF4), heparin concentration (antiXa) and thrombocyte count. Systemic anticoagulation was performed using UFH. RESULTS: During HD after ECC rinse without UFH, there was a significantly earlier and more marked increase in TAT compared with UFH-containing rinse (P <0.05). Using Spearman coefficient, we demonstrated a significant correlation between TAT and antiXa at 60 min (r = -0.534) and 240 min (r = -0.538). A comparison of the TAT/antiXa ratios between rinses at 60 min revealed a significantly higher increase in TAT following UFH-free rinse (P <0.05). There was no difference in PF4 between the rinses. Platelet count did not change significantly during HD using either rinse protocol. CONCLUSION: Based on plasma TAT levels, ECC priming with an UFH-containing solution reduces the thrombogenicity of the AN69 ST membrane. There is no significant difference between both types of priming concerning PF4 and thrombocyte count.     

Lack of plasma interleukin-1 beta or tumor necrosis factor-alpha elevation during unfavorable hemodialysis conditions.

Plasma interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) were determined by ELISA in 17 healthy controls, 23 HD patients, 10 continuous ambulatory peritoneal dialysis patients, and 15 chronic renal failure patients, as well as in 2 HD patients experiencing pyrogenic reactions. Another group of 10 chronic HD patients were dialyzed for 2.5 h, 5 with first-use Cuprophan membranes and 5 with first-use high-flux cellulose triacetate membranes. The mean bacterial and endotoxin concentrations of the dialysate used for HD treatments during the study period were 18,440 +/- 530 CFU/mL (mean +/- SEM) and 976 +/- 205 pg/mL, respectively. Blood specimens were obtained intradialysis and postdialysis for cytokine assay and were incubated to augment cytokine production. There was no difference in plasma IL-1 beta or TNF-alpha concentrations among the healthy controls, continuous ambulatory peritoneal dialysis patients, chronic renal failure patients, or HD patients. Neither cytokine increased significantly during or after HD. Two patients experiencing pyrogenic reactions had plasma TNF-alpha concentrations of 537 and 413 pg/mL, compared with matched controls of 6 and 0 pg/mL. Il-1 beta concentration did not differ from controls. We conclude that: (1) plasma IL-1 beta and TNF-alpha are not chronically elevated in chronic renal failure, continuous ambulatory peritoneal dialysis, or HD patients; (2) HD with new Cuprophan or cellulose triacetate membranes and high concentrations of dialysate endotoxin and bacteria does not cause elevation of circulating IL-1 beta or TNF-alpha; and (3) pyrogenic reactions might be mediated by TNF-alpha.     

Influence of different hemodialysis membranes on red blood cell susceptibility to oxidative stress

Oxidative stress is crucial in red blood cell (RBC) damage induced by activated neutrophils in in vitro experiments. The aim of the study was to evaluate whether the bioincompatibility phenomena occurring during hemodialysis (HD) (where neutrophil activation with increased free radical production is well documented) may have detrimental effects on RBC. We evaluated RBC susceptibility to oxidative stress before and after HD in 15 patients using Cuprophan, cellulose triacetate, and polysulfone membrane. RBC were incubated with t-butyl hydroperoxide as an oxidizing agent both in the presence and in the absence of the catalase inhibitor sodium azide. The level of malonaldehyde (MDA), a product of lipid peroxidation, was measured at 0, 5, 10, 15, and 30 min of incubation. When Cuprophan membrane was used, the MDA production was significantly higher after HD, indicating an increased susceptibility to oxidative stress in comparison to pre-HD. The addition of sodium azide enhanced this phenomenon. Both cellulose triacetate and polysulfone membranes did not significantly influence RBC susceptibility to oxidative stress. Neither the level of RBC reduced glutathione nor the RBC glutathione redox ratio changed significantly during HD with any of the membranes used. The RBC susceptibility to oxidative stress was influenced in different ways according to the dialysis membrane used, being increased only when using the more bioincompatible membrane Cuprophan, where neutrophil activation with increased free radical production is well documented. The alterations found in this study might contribute to the reduced RBC longevity of HD patients where a bioincompatible membrane is used.     

Role of contact system activation in hemodialyzer-induced thrombogenicity.

BACKGROUND: The contact system is generally believed to be the main trigger of the coagulation cascade during extracorporeal circulation. However, the extent of contact activation, its role for intradialytic thrombin generation as well as the influence of different dialyzer membranes have not been well established. METHODS: In a novel full-scale ex vivo recirculation dialysis model, we investigated the thrombogenicity of three widely used hemodialyzers (Cuprophan Renak RA15-U, Polysulfone F6HPS and AN69XT Nephral 200). The activation of the contact system was evaluated using a newly developed ELISA for factor XIIa-C1-inhibitor complexes. Additionally, we determined free FXIIa (ELISA), thrombin-antithrombin (TAT) complexes, platelet factor 4 (PF4), complement activation (C5a), granulocyte elastase and blood cell counts. The findings in blood from normal volunteers were compared with factor XII-deficient blood. RESULTS: With normal blood AN69 exhibited the highest thrombogenicity in comparison to Cuprophan and Polysulfone, as assessed by TAT generation and platelet consumption. AN69 caused a rapid increase of the FXIIa-C1-inhibitor complexes and of free FXIIa. Despite significant TAT generation with Cuprophan and Polysulfone free FXIIa remained unchanged and the FXIIa-C1-inhibitor complexes stayed below the detection limit. With factor XII-deficient blood Polysulfone exhibited the same TAT generation, whereas the thrombogenicity of AN69 was greatly reduced. CONCLUSIONS: Our data challenge the common assumption that activation of the contact system with generation of FXIIa is the main trigger for coagulation and thrombus formation in hemodialysis. Only the negatively charged AN69 membrane with enhanced thrombogenicity strongly induced contact activation.     

Platelet-Leukocyte Aggregates During Hemodialysis: Effect of Membrane Type

Hemodialysis is associated with the formation of platelet-leukocyte aggregates. Whether this phenomenon is hemodialysis (HD) membrane dependent is unclear. To evaluate this process, we examined respectively platelet activation (anti-CD41, anti-CD62, and antifibrinogen monoclonal antibodies [MoAb] binding), leukocyte activation (CD11b expression), and the appearance of platelet specific antigens on leukocytes as an index of platelet-leukocyte aggregation during HD using 3 different membrane materials, Cuprophan, Hemophan, and polysulfone. Flow cytometric techniques and specific MoAb were used. All parameters were assayed 5 min after initiation of HD to avoid the confounding variable of leukopenia and resultant cell subpopulation analysis. Platelet activation (anti-CD62 and antifibrinogen binding) occurred only with Cuprophan. All 3 membranes induced equivalent increases in CD11b expression on neutrophils and similarly increased the binding of anti-CD41 to neutrophils, reflecting an increment in the formation of platelet neutrophil aggregates. However, only Cuprophan induced an increase in anti-CD62 binding to neutrophils, suggesting that the aggregated platelets linked to neutrophils were activated. Increased anti-CD41 binding by monocytes was similarly observed with all 3 membranes. However, only polysulfone induced an increase in CD11b expression and fibrinogen binding to monocytes. We conclude that while the formation of platelet leukocyte aggregates appears to be a universal phenomenon in HD occurring with a variety of membrane types, subtypes of this phenomenon consisting of activated platelets and fibrinogen binding may be membrane dependent. This phenomenon may serve as a new biocompatibility parameter and may shed light on some of the biologic consequences of hemodialysis.     

Filtration of native and glycated beta2-microglobulin by charged and neutral dialysis membranes

BACKGROUND: It has been postulated that protein glycation and formation of advanced glycation end products (AGE) are among toxic factors in chronic uremia, whether the renal disease is of diabetic or nondiabetic origin. In this setting, AGE-modified beta2-microglobulin (beta2m) may favor dialysis beta2m-related dialysis amyloidosis. Consequently, efficient removal of modified beta2m by highly permeable dialysis membranes is as important as removal of native beta2m to postpone the development of dialysis amyloidosis. METHODS: To define the role of dialysis membrane surface electronegativity on plasma protein transfer, an in vitro model was used to test the interactions of native and glycated beta2m with various highly permeable dialysis membranes. An experimental circuit with minidialyzers was used. The neutral high-flux polysulfone membrane (PS), the electronegative polymethylmetacrylate membrane (PMMA), the electronegative AN69 membrane and a modified AN69 membrane, the surface of which was neutralized with polyethyleneimine (AN69-PEI), were tested using both native beta2m and the more acidic glycated beta2m. Protein mass transfer and binding to the membrane were measured. RESULTS: Mass transfer of glycated beta2m was significantly decreased through all membranes tested when compared with native beta2m. This result was due to the increased molecular weight of beta2m, which became less permeable to porous membranes, whereas adsorption of both native and glycated beta2m to membranes, due to ionic interactions, decreased similarly with AN69 and AN69-PEI, but remained unchanged with PS and PMMA. Moreover, surface neutralization of AN69 membrane did not alter its core binding capacity, since beta2m absorption accounted for 98 and 97% and glycated beta2m for 83.7 and 81.4% of the protein removed with AN69 and AN69-PEI, respectively. CONCLUSION: Clearance of glycated beta2m through highly permeable neutral and negatively charged membranes was lower than that of native beta2m, reflecting a decreased sieving coefficient for the neoformed higher molecular weight and conformationally altered molecule. The binding capacity of the neutral PS was roughly half that of the charged membranes. Neutralizing surface electronegativity of the AN69 membrane with PEI did not alter its binding capacity. These results suggest that it would be useful for dialysis protocols to include comparative studies of both serum native and modified beta2m in order to prevent beta2m-amyloidosis.     

Hemodialysis Urea Rebound and Membrane Biocompatibility: Accuracy of Kt/V Estimations

Abstract: To date, the magnitude, causes, and factors that govern urea rebound are not clearly defined. This study was undertaken to determine the possible influence of the biocompatibility of dialyzer membrane on urea rebound and to assess the participation of rebound in the calculation of Kt/V-urea by different methods. Blood urea samples were obtained before, and at 2, 30, and 60 min posthemodialysis in 8 patients undergoing dialysis with 2 different membranes, Cuprophan and polyacrylonitrile (24 sessions with each membrane). Urea rebound was documented in all patients. The degree of rebound was large,20%, and it was achieved within 30 min after the end of dialysis. Urea rebound was observed with both Cuprophan and polyacrylonitrile membranes, without significant differences. Kt/V-urea significantly decreased (p < 0.001) by all methods when urea rebound was incorporated. We conclude that urea rebound is clinically very important and is not influenced by the biocompatibility of the dialyzer membrane. This phenomenon must be taken into account in the calculation of Kt/V; otherwise, it might be overestimated.     

Establishing the relationship between complement activation and stimulation of phagocyte oxidative metabolism in hemodialyzed patients: a randomized prospective study

The present prospective study was conducted in order to establish the relationship between complement activation and stimulation of phagocyte oxidative metabolism observed in long-term hemodialysis (HD) patients during the early phase of dialysis with cellulosic membranes. Two groups of 10 randomized (HD) patients treated with cellulosic (Cuprophan, CUP) or synthetic polyacrilonitrile (PAN AN-69) membranes were studied. Leukocyte counts, C3a antigen plasma concentration and whole blood basal and stimulated chemiluminescence (CL) production were determined in blood samples drawn from the fistula before dialysis (T0) and from both the afferent and efferent lines of the dialyser at 15 min (T15) and at the end (Tend) of the dialysis session. This study confirms that, coincident with the nadir of leukopenia observed at T15, dialysis with CUP but not PAN membranes induces a marked rise in C3a antigen levels and profound alterations in whole blood CL production consisting of a dramatic increase in basal CL and a significant loss in CL response capacity to stimulating agents. It further demonstrates that a direct relationship exists between the variations in C3a antigen plasma levels and whole blood CL production observed in the CUP group of patients from T0 to T15 (delta 15) of dialysis. This relationship is characterized by a positive correlation between delta 15 C3a and delta 15 basal CL levels in afferent and efferent lines, and a negative correlation between delta 15 C3a and delta 15 CL response capacity values in the efferent but not afferent line. In contrast, no significant correlation with the type of dialysis membrane could be demonstrated between the variations in polymorphonuclear neutrophil counts and C3a antigen levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of hemodialysis membranes on the plasma insulin level of diabetic patients on maintenance hemodialysis

AIM: The aim of the present study was to evaluate the alteration in plasma immunoreactive insulin (IRI) concentrations due to hemodialysis (HD) treatment by using three types of membranes in diabetic HD patients. METHOD: We recruited 20 outpatients on maintenance HD with diabetes for this crossover study. HD was performed using membranes made of cellulose triacetate (CTA), polyester-polymer alloy (PEPA), and polysulphone (PS). These membranes were used for 2 weeks (6 HD sessions) in each patient in a randomized order decided by drawing lots. Blood samples were obtained at the beginning and end of the HD session from the blood tubing at the arterial (A) site. At 60 min after the initiation of dialysis, blood samples were obtained from the blood tubing at both the A and venous (V) sites of the dialyzer. RESULTS: The plasma IRI levels decreased significantly at the sites an hour after initiating HD in all membranes. The clearance of IRI was significantly higher in the case of the PS membrane when compared with the CTA and PEPA membranes. CONCLUSIONS: It was concluded that plasma insulin is cleared by HD, and the rate differs for each membrane. Plasma insulin clearance with the PS membrane is higher than that with the PEPA and CTA membranes.     

Role of complement and platelet-activating factor in the stimulation of phagocytosis and reactive oxygen species production during haemodialysis.

BACKGROUND: Neutrophil phagocytic functions have been studied extensively in haemodialysis (HD) patients; however, results are contradictory and the mechanisms that modulate phagocytosis and oxidative burst during dialysis are not completely understood. METHODS: The present study investigated neutrophil functions in a selected population of patients before and during clinical dialysis with cuprophane, and polyacrylonitrile (AN69) membranes. We measured phagocytosis of Escherichia coli and intracellular hydrogen peroxide (H2O2) production by flow cytometry in whole blood. RESULTS: Before dialysis, neutrophils from HD patients showed normal phagocytic capability and H2O2 formation. Phagocytosis of FITC-E. coli was significantly stimulated in cuprophane but not AN69-treated patients. Spontaneous and stimulated H2O2 production was enhanced with both cuprophane and AN69 membranes. We then investigated in vitro the role of complement and platelet-activating factor (PAF) in the activation of neutrophils. Incubation of whole blood with C5a increased phagocytosis but not H2O2 production. On the contrary, the addition of synthetic PAF showed a markedly stimulated H2O2 production without increase in phagocytosis. Moreover, during dialysis with formaldehyde-reused cuprophane, complement activation was abolished and phagocytosis was no longer enhanced, while the stimulation of H2O2 production persisted. In addition, we also excluded a particular role of the membrane itself in the activation of neutrophils. CONCLUSION: We demonstrated that in a selected population of HD patients, neutrophils exhibit normal phagocytic capability and normal intracellular H2O2 production. During dialysis, the stimulation of phagocytosis observed with cuprophane is complement dependent, whereas the enhanced H2O2 production observed with both cuprophane and AN69 membranes might be related to PAF production.