Beta2-microglobulin removal and plasma albumin levels with high cut-off hemodialysis.

PURPOSE: beta2-microglobulin (beta2MG) is pivotal to the pathogenesis of dialysis-related amyloidosis. We compared the effects of high cut-off hemodialysis (HCO-HD) with those of standard high-flux hemodialysis (HF-HD) regarding the concentration and clearance of beta2MG and albumin. DESIGN: We enrolled ten patients with acute renal failure in a double-blind, cross-over, randomized controlled trial. PROCEDURES: Each patient received four hours of HCO-HD (estimated in vivo cutoff 50-60 kDa) and four hours of HF-HD (estimated in vivo cutoff 15-20 kDa) in random order. Statistical methods and outcome measures: As data lacked normal distribution, we used nonparametric statistical analysis. Plasma and dialysate concentrations of beta2MG and albumin were measured at baseline and after four hours of each study treatment. MAIN FINDINGS: We found significantly greater diffusive beta2MG clearances for HCO-HD compared to HF-HD (at the start: 71.8 ml/min vs. 5.1 ml/min; P=0.008 and at the end: 68.8 ml/min vs. 5.7 ml/min; P=0.008). We found a reduction in plasma beta2MG concentrations of -31.6% during HCO-HD compared to an increase by 25.7% during HF-HD; P=0.008. At baseline (HCO-HD: 26.0 g/L vs. HF-HD: 26.5 g/L), and at the end of both treatments, plasma albumin concentrations were comparable (HCO-HD: 25.5 g/L vs. HF-HD: 26.5 g/L; P=0.25). During HCO-HD, albumin clearance was 1.9 ml/min at the start and decreased significantly to 0.8 ml/min at the end; P=0.008. HF-HD had an albumin clearance of 0.01 ml/min. CONCLUSIONS: HCO-HD was more effective in decreasing plasma beta2MG concentrations than standard HF-HD and did not reduce plasma albumin levels. Further studies of HCO-HD in the treatment of dialysis-related beta2MG accumulation appear warranted.

Super high flux hemodialysis at high dialysate flows: an ex vivo assessment.

BACKGROUND AND OBJECTIVES: The removal of cytokines by standard hemofiltration is limited. Super high flux membranes may significantly improve removal even when used in dialysis mode. We sought to measure cytokine clearance using a large surface super high-flux membrane and a standard hemodialysis setting. SETTING: ICU laboratory of a tertiary institution. SUBJECTS: Six healthy volunteers. METHODS: Blood form healthy volunteers was incubated for 4 hours with E. coli endotoxin to stimulate cytokine production. Cytokine containing blood was then circulated through a dialysis circuit at 3 different dialysate flow rates. Blood and dialysate were sampled for cytokine and albumin measurements and calculation of clearances. RESULTS: Super high-flux dialysis achieved high median cytokine clearances (IL-1 clearance of 106 ml/min, IL-6 clearance of 66.8 ml/min, IL-8 clearance of 61.7 ml/min and TNF clearance of 36.1 ml/min). Increasing dialysate flow rate from 300 to 500 ml/min did not significantly increase cytokine clearances. Albumin clearances however were between 2.7 and 5.4 ml/min. CONCLUSIONS: Cytokine dialysis is feasible at high dialysate flow rates yielding high cytokine clearances. Albumin loss, however, is appreciable and may require separate supplementation in the clinical setting.

Beta2-microglobulin clearance with super high flux hemodialysis: an ex vivo study.

BACKGROUND: Beta2m accumulation induces disease in patients with end-stage renal failure (ESRF). Thus, its removal from patients with ESRF appears desirable. Current dialysis technology, however, has limited effectiveness. AIMS: To measure beta2m clearance with a novel super high flux membrane. DESIGN: Ex vivo experimental study. SETTING: Intensive Care Laboratory of Tertiary institution. SUBJECTS: Six volunteers. MEASUREMENTS AND RESULTS: At a blood flow of 300 ml/min, the clearance of beta2-MG increased from 113.5 +/- 38.5 ml/min with a dialysate flow rate of 200 ml/min to 184.8 +/- 61.1 ml/min with a flow rate of 300 ml/min and 195.0 +/- 60.0 ml/min with a 500 ml/min flow rate. The clearance of albumin was 4.5 ml/min with a dialysate flow rate of 200 ml/min, 5.2 ml/min for a flow rate of 300 ml/min and 5.8 ml/min for a flow rate of 500 ml/min. CONCLUSIONS: High levels of beta2m clearance can be achieved with a super high flux membrane while albumin losses remain limited.

Complement components as uremic toxins and their potential role as mediators of microinflammation.

Cardiovascular disease is the major cause of death in end-stage renal disease (ESRD) patients. There is growing evidence that atherogenesis is an inflammatory rather than a purely degenerative process leading to a state of microinflammation. This raises the issue of whether treatment modalities of ESRD contribute to the microinflammatory state. One potential candidate in this context is the complement system. Here we consider three potential pathways linking complement activation to progression of atherosclerosis: (1) complement activation on artificial surfaces depends on their physicochemical characteristics, the effect of which is amplified because of the accumulation of complement factor D; (2) the exposure of ESRD patients to endotoxin creates a microinflammatory state, and this may amplify complement-induced damage; exposure to endotoxin may result from frequent infections because of the impairment of host-defense mechanisms or from transfer of bacterial contaminants across dialysis membranes into the blood stream; and (3) direct transduction of proinflammatory signals from blood-material interactions to the vascular system. We conclude that the complement system is an important candidate system in the genesis of microinflammation and accelerated atherogenesis in ESRD. We advance the hypothesis that the generation of proinflammatory signals, in which the complement system appears to be involved--both through systemic and local activation--plays a role in the development of late complications of uremia, including coronary heart disease. This hypothesis provides a rationale to maximize the biocompatibility of the dialysis procedure, that is, selection of nonactivating materials, use of ultrapure dialysis fluid, and--still theoretical--high-flux dialysis to remove factor D.

Molecular adsorbent recycling system (MARS): clinical results of a new membrane-based blood purification system for bioartificial liver support.

The use of xenogenic or genetically engineered cell types in bioartificial liver support systems requires separation methods between the patients' blood and the liver support bioreactors that guarantee the sufficient transfer of pathophysiologically relevant substances but prevent complications. The present paper describes a new membrane separation system that is nearly impermeable to proteins but enables the exchange of water soluble and protein bound toxins by a special membrane and a recycled protein containing dialysate. Because the full range of toxins in hepatic failure has still not been identified, the value of this membrane separation method was evaluated clinically. Thirteen patients suffering from life threatening hepatic failure who had not responded to state of the art therapy were treated with this device, the molecular adsorbent recycling system (MARS). The overall survival rate was 69%. All patients showed positive response to the therapy, indicating that the presented membrane separator combines therapeutic effectivity with the highest safety criteria for the patient by cutting the exchange of substances below the level of proteins.

Sterile versus non-sterile dialysis fluid in chronic hemodialysis treatment.

As the quality of water in the dialysis fluid varies considerably, and in view of the fact that endotoxin or active derivatives can cause acute side effects in patients, the dialysis fluid must be sterile. Therefore, we introduced ultrafiltration of dialysis fluid before entering the dialyzer. Fifteen patients, (ten women, five men) were treated for 4 weeks with nonsterile, and then with sterile dialysis fluid. The bacterial loading in the dialysis fluid before hemodialysis was 1.34 X 10(5)/ml, and after hemodialysis 2.9 X 10(3)/ml; the endotoxin concentration was high and varied between less than 1 EU/ml and greater than 10 EU/ml before and after hemodialysis. After ultrafiltration of the dialysis fluid by a polyamide hollow fiber membrane, all samples were free of bacteria and the concentration of endotoxin was lower than the detectable limit (less than 0.03 and less than 0.5 EU/ml). With ultrafiltration of dialysis fluid we can obtain sterile dialysate, which is endotoxin free. Interleukin-1 and tumor necrosis factor in the patients with ultrafiltration was significantly lower than without ultrafiltration.

Evaluation of a new polyamide membrane (Polyflux 130) in high-flux dialysis.

Removal of beta 2-microglobulin has become a major objective of dialysis therapy. The present study was performed to evaluate both compatibility and elimination capacity for beta 2-microglobulin of a newly developed high-flux polyamide membrane (Polyflux 130) during hemodialysis. The degree of leukopenia was moderate (-22%) and comparable with Polysulfone 600 (-25%). C3a desarg generation had a tendency to be lower with the Polyflux 130 membrane, and C5a desarg formation was identical with both types of membranes. As for degranulation of polymorphonuclear leukocytes, plasma elastase levels increased by 209% with Polyflux 130 and by 160% with Polysulfone 600 membranes. Likewise, plasma lactoferrin values rose during hemodialysis by 233% (Polyflux 130) and 160% (Polysulfone 600). The differences between membranes, however, were statistically not significant. There was a sharp drop in the serum levels of beta 2-microglobulin during dialysis with both membranes (Polyflux 130: -46%; Polysulfone 600: -48%). Accordingly, sieving coefficients were calculated to be 0.77 +/- 0.06 for Polyflux 130 and 0.80 +/- 0.06 for the Polysulfone 600 membrane. Both membranes were capable to remove large quantities of beta 2-microglobulin, amounting to 235 +/- 11 and 250 +/- 10 mg/4 h of dialysis for Polyflux 130 and Polysulfone 600, respectively.

Do the effects of adventitious deafness include disordered speech?

The popular clinical prediction is that adventitious deafness will result in deterioration of speech sound production; consequently, a recommendation of speech conservation training is thought to be warranted in these cases. This prediction usually follows from a theory that counts feedback (particularly auditory feedback) as important in the maintenance of normal speech. The results of this study, designed to examine the speech of five adventitiously deafened adults matched with a group of normal controls, do not support the prediction of speech deterioration. Even so, judges were able to differentiate deafened from normally hearing speakers. Some possibilities are considered that could account for the identity of the deafened speakers in the absence of clinically significant speech disorder, and clinicians are encouraged to reevaluate their assumptions concerning this population.