Is beta2-microglobulin-related amyloidosis of hemodialysis patients a multifactorial disease? A new pathogenetic approach.

PURPOSE: Beta2-microglobulin amyloidosis (Abeta(2)M) is one of the main long-term complications of dialysis treatment. The incidence and the onset of Abeta(2)M has been related to membrane composition and/or dialysis technique, with non-homogeneous results. This study was carried out to detect: i) the incidence of bone cysts and CTS from Abeta(2)M; ii) the difference in Abeta(2)M onset between cellulosic and synthetic membranes; iii) other risk factors besides the membrane. METHODS: 480 HD patients were selected between 1986 to 2005 and grouped according to the 4 types of membranes used (cellulose, synthetically modified cellulose, synthetic low-flux, synthetic high-flux). The patients were analyzed before and after 1995, when the reverse osmosis treatment for dialysis water was started at our center, and the incidence of Abeta(2)M was compared between the two periods. Routine plain radiography, computer tomography (CT) and nuclear magnetic resonance imaging (MRI) as well as electromyography were used to investigate the clinical symptoms. RESULTS: Bone cysts occurred in 29.2% of patients before 1995 vs. 12.2% after 1995 (p<0.0001). CTS occurred in 24% of patients before 1995 vs. 7.1% after 1995 (p<0.0001). Bone cysts and CTS occurred in older patients, who began dialysis at a late age, with high CRP, low albumin, low residual GFR, and low Hb. Cox regression analysis showed that the risk factor for bone cysts was high CRP (RR 1.3, p<0.01), while albumin (RR 0.14, p<0.0001) and residual GFR (RR 0.81, p<0.0001) were revealed to be protective factors. Cox analysis for CTS confirmed CRP as a risk factor (RR 1.2, p<0.01), and albumin (RR 0.59, p<0.0001) and residual GFR (RR 0.75, p<0.0001) as protective factors. The comparison obtained between membranes did not suggest any protective effect on Abeta(2)M. CONCLUSIONS: The findings that the inflammatory status as well as low albumin and the residual GFR of the uremic patient are predictive of Abeta(2)M lesions suggests that Abeta(2)M has a multifactorial origin rather than being solely a membrane- or technique-related side effect.

Evaluation of hygiene and safety controls for on-line paired hemodiafiltration (PHF).

BACKGROUND: On-line hemodiafiltration is gaining popularity due to increasing evidence of clinical benefits however it also requires strict attention to hygiene and safety as notable quantities of liquid are reinfused into the patient. Although most centers are improving their attention to water quality, a frequent concern is the inadvertent or accidental contamination of water and whether the redundant safety controls are sufficient to protect the patient. In the present study, in order to simulate a worst-case safety condition, we tested in vitro the reliability of paired hemodiafiltration - (PHF), under low, moderate and high bacterial contamination of the water supply. Tests were performed using various bacterial concentrations (range 85-2000 cfu/mL) of Pseudomonas Aeruginosa. Samples were analyzed from different sites throughout the entire on-line hemodiafiltration circuit for bacteria endotoxin, fungus and ability to stimulate whole blood production of TNFalfa. RESULTS: In the in vitro contamination study, with the three bacterial concentrations tested at various points of the circuit, bacteria were below the level of detection and endotoxins were < 0.01 UE/mL. Addition of dialysate samples taken after the first stage of microfiltration, as well as after the first and second stage of ultrafiltration and incubated with whole blood were not associated with stimulated production of TNFalfa . CONCLUSIONS: PHF appeared to be a safe and feasible method for on-line hemodiafiltration even in the unforeseen presence of bacterial contamination of the feed water or water distribution system.

[Safety controls in a new hemodiafiltration on line technique (PHF)]. / Controlli di sicurezza in una nuova tecnica di emodiafiltrazione on-line (PHF).

PURPOSE: On-line hemodiafiltration (HDF) is gaining popularity due to increasing evidence of clinical benefits. The purpose of this study was to test a new on-line technique paired hemodiafiltration (PHF). In addition, we evaluated the PHF system during in vitro contamination. METHODS: Five patients used the PHF technique over a 6-month period. We performed a disinfection protocol and tested for bacteria, endotoxin, halogenated carbons and metals in the feed water, and we tested for bacteria, endotoxins and fungi in the dialysate after different ultrafiltration stages. In vitro tests were performed using three bacterial concentrations of pseudomonas aeruginosa. Samples were analyzed from different sites throughout the entire on-line HDF circuit for bacteria endotoxins, fungus and the ability to stimulate whole blood production of tumor necrosis factor-alpha (TNF-alpha). RESULTS: The bacteriological control from the feeding machine water and at the entrance to the monitors had a bacterial level of <100 CFU/mL. No bacteria were detected in the dialysate and endotoxin levels were <0.03 EU/mL. In the in vitro contamination study, with the three bacterial concentrations tested at various points in the circuit, bacterial and fungi were below the level of detection and endotoxins were <0.03 UE/mL. The addition of dialysate samples taken after the 1st microfiltration stage, as well as after the 1st and 2nd ultrafiltration stage and incubated with whole blood were not associated with stimulated TNF-alpha production. CONCLUSIONS: PHF appeared to be a safe and feasible method for on-line HDF even in the unforeseen presence of the bacterial contamination of the feed water or in the water distribution system.

Oxidant stress in hemodialysis: prevention and treatment strategies.

Oxidant stress has been implicated in a number of pathologies associated with uremia and hemodialysis. These patients have an increased incidence of cardiovascular disease, amyloidosis associated with protein modification, and notable changes in both function and structure of many cellular components. Oxidative reactions most frequently involving free radical intermediates play an important role in these processes and participate both directly and indirectly by further amplification of the inflammatory responses or in activation of signaling cascades mediating proliferation, differentiation, and cell death. Proteins and lipids are susceptible to oxidative degradation. These changes can ultimately alter important structural and functional characteristics and lead to pathological changes. This article addresses some of the diverse mechanisms and pathways involved in these changes, and suggests new therapeutic strategies in preventing oxidative damage.

Coupled plasma filtration-adsorption in a rabbit model of endotoxic shock.

OBJECTIVE: To test the hypothesis that nonselective adsorption by a hydrophobic resin of cytokines and other proinflammatory mediators could improve 72-hr survival in a rabbit model of endotoxic shock. DESIGN: Prospective, randomized, controlled animal trial. SETTING: Animal care facility at a research institution. SUBJECTS: A total of 109 New Zealand white male rabbits. INTERVENTIONS: Anesthetized rabbits were cannulated with indwelling femoral arterial and venous lines. Septic shock was induced by a single intravenous injection of Escherichia coli lipopolysaccharide. The dose was experimentally assessed in 40 rabbits receiving 1.0, 0.5, 0.1, and 0.05 mg/kg body weight to determine LD80 at 72 hrs. Extracorporeal circulation consisted of plasma filtration coupled with passage of the plasma filtrate through a hydrophobic sorbent and reinfusion into the venous line. The extracorporeal treatment lasted for 3 hrs. Rabbits injected with endotoxin (0.05 mg/kg) were submitted to plasma filtration with (19 rabbits) or without (20 rabbits) sorbent adsorption. As controls, rabbits injected with vehicle alone were treated with plasma filtration (ten rabbits) or without (ten rabbits) sorbent adsorption. Ten rabbits were monitored under anesthesia to determine basal survival. MEASUREMENTS AND MAIN RESULTS: Plasma concentrations of endotoxin, bioactive tumor necrosis factor, resin-adsorbed platelet-activating factor, mean arterial pressure, base excess, and white cell count were assessed and a global severity score was established. At 72 hrs, cumulative survival was significantly (p = .0041) improved in septic rabbits treated with coupled plasma filtration-adsorption. Circulating tumor necrosis factor bioactivity remained similar in control and treated rabbits. Biologically significant amounts of platelet activating factor were eluted from the sorbent during the entire treatment time. The severity score inversely correlated with survival (p < .001). CONCLUSIONS: Coupled plasma filtration-adsorption improved survival in a rabbit model of endotoxic shock. Coupled plasma filtration-adsorption may be an extracorporeal treatment capable of removing structurally different inflammatory mediators associated with sepsis.

Relevance of platelet-activating factor in inflammation and sepsis: mechanisms and kinetics of removal in extracorporeal treatments.

Sepsis can be considered a systemic inflammatory response syndrome (SIRS) caused by infection. When an excessive and/or persistent activation of humoral and cellular mechanisms of host defense is present, an exaggerated and generalized activation of inflammatory mechanisms can lead to a multiple organ dysfunction syndrome. Mediators thought to be involved in this syndrome include the major plasma cascade systems (complement, coagulation, and fibrinolytic systems) and soluble cell-derived mediators (cytokines, reactive oxygen species, platelet-activating factor (PAF), arachidonic acid metabolites, and nitric oxide and related compounds). Several findings indicate that among these mediators, PAF may exert an important role in the pathophysiology of septic shock. Evidence is accumulating that in human sepsis this scenario is far more complicated and that removal of inflammatory mediator excess from plasma, rather than blockade of their potentially beneficial local production, might provide a rationale for the use of continuous renal replacement therapy (CRRT). There is an emerging view that CRRT should be considered in the light of broader concept (ie, the use of blood purification for the treatment of sepsis). Recent studies, performed in an experimental model of continuous arteriovenous hemofiltration with exogenous PAF, demonstrated that polysulfone membranes can adsorb substantial amounts of biologically active PAF. These studies also showed that the removal of this mediator occurs by a two-step process involving early adsorption followed by ultrafiltration. Although the removal of cytokines, such as tumor necrosis factor-alpha (TNF-alpha), remains controversial, mainly because of differences in membrane used, operational conditions, and inter- and intra-assay variability, the crucial point is that no evidence has yet been given to show real benefit from CRRT in significantly reducing the plasma concentration of cytokines. The net advantage of CRRT, however, may not only be the removal of cytokines per se, but also the simultaneous elimination of cytokine-inducing substances. Experimental and human studies will be discussed as to whether extracorporeal treatments may remove an excess of circulating cytokines, either by increasing the turnover rate (the so-called high-volume hemofiltration), or by using sorbent systems to regenerate plasma filtrate.

Removal of constitutive and inducible nitric oxide synthase-active compounds in a modified hemodiafiltration with on-line production of substitution fluid: the contribution of convection and diffusion.

Chronic renal failure and the uremic state lead to accumulation of various endogenous inhibitors of nitric oxide synthase. Previous studies on end-stage uremic patients nitric oxide synthase activity in murine vascular endothelium and cytokine-induced macrophage cell lines was shown to be modulated during treatment (Nephrol Dial Transplant 1995; 10: 1386-96). Paired filtration dialysis, a modified hemodiafiltration technique, physically separates convection from diffusion. Plasmas, ultrafiltrates and dialysates from seven uremic patients undergoing paired filtration dialysis performed using ultrapure apyrogen substitution fluid in the absence (first 120 min) or presence (last 120 min) of extracellular fluid reduction were tested for their inhibitory/stimulatory effect on ecNOS, constitutively expressed on t.End 1 cell line, a murine vascular endothelium, or for their inducing effect on iNOS, inducible on J774 cells, a macrophage cell line. On ecNOS, Group 1 (stimulatory, 3/7 patients) markedly enhanced the ecNOS activity as compared to control plasma, whereas group 2 plasma (inhibitory, 4/7 patients) inhibited ecNOS plasma. Post-dialysis plasma samples from all Group 1 and 2 patients showed a marked decrease of the predialysis stimulatory and inhibitory activity, respectively. On iNOS: all patient plasmas stimulated iNOS activity. The UF and particularly the dialysate had a remarkable iNOS inducing effect (Group 1). The substitution fluid obtained at 120 min during treatment in Group 1 and 2 had no effect on NOS activity. No correlation was found between predialysis ecNOS or iNOS activity values with mean systolic or diastolic pressures. These studies suggest a complex balance of ecNOS inhibitors/stimulators and iNOS inducers in uremia. Dialysis may remove ecNOS inhibitors and stimulators by convection and, in the latter case, by diffusion. iNOS inducers are removed during dialysis, suggesting the biocompatibility of the dialysis system with the on-line production of ultrapure substitution fluid.