Bradykinin is a mediator of anaphylactoid reactions during hemodialysis with AN69 membranes

Bradykinin is a mediator of anaphylactoid reactions during hemodialysis with AN69 membranes. Anaphylactoid reactions (AR) are the most feared complications of hemodialysis. Recently, a high incidence of AR has been reported during dialysis with AN69 membranes in patients treated with ACE inhibitors. Plasma levels of C3a, histamine and bradykinin were measured in 12 patients at the onset of AR during dialysis with AN69. We also investigated bradykinin generation in 10 symptom-free patients dialyzed with four different membranes. None of the 12 patients studied during AR displayed excessive complement activation or histamine release. In contrast, high bradykinin plasma levels (2392 53 fmol/ml; mean sem) were observed in all nine patients of whom bradykinin was measured. One patient developed two consecutive episodes of hypersensitivity on AN69 membranes even without taking ACE inhibitors. Bradykinin levels were high in both episodes (5280 and 10467.7 fmol/ml). Furthermore, this patient showed no symptoms and normal bradykinin levels (123.4 fmol/ml) when dialyzed with other membranes. The role of the membrane type in the AR is further substantiated by the observation that AN69 also provoked a significantly higher bradykinin generation (327.6 18 fmol/ml; mean SEM) during symptom-free sessions compared to other membranes like CuprophanR (5.1 7.3), HemophanR (17.2 6.3) and PolysulfoneR (39.7 6.6). Our findings strongly suggest that bradykinin is the principal mediator of AR during hemodialysis with AN69 membranes. To our knowledge it is the first time that data support the hypothesis of a more general role of bradykinin in shock-like symptoms. Furthermore, bradykinin generation must be regarded as a new marker of biocompatibility of extracorporeal treatments

Anaphylactoid reactions during hemodialysis in sheep are ACE inhibitor dose-dependent and mediated by bradykinin

Anaphylactoid reactions during hemodialysis in sheep are ACE inhibitor dose-dependent and mediated by bradykinin. Anaphylactoid reactions (AR) have been attributed to the generation of bradykinin (BK) when AN69 membranes are used together with angiotensin converting enzyme (ACE) inhibitors during hemodialysis. However, conclusive evidence for the involvement of the BK as the mediator of these AR is still lacking. This study examined the degree of contact activation in an animal model caused by three PAN membranes—AN69, PAN DX, and SPAN—and the effects of different doses of the ACE inhibitor enalapril (ENA) and the BK B2-receptor antagonist icatibant on AR during hemodialysis. Six sheep were dialyzed for one hour with or without ENA pre-treatment using the different membranes in random order. Severe AR were observed only during hemodialysis with AN69 dialyzers together with ENA pre-treatment; the severity of AR increased with the ENA dose. Mild hypotension was noted during hemodialysis with AN69 without ACE inhibition and with PAN DX and 20 mg ENA. Compared to pre-dialysis values, maximum generation of BK after blood passage through the dialyzer was found at five minutes: 73-fold (AN69 without ENA), 161-fold (AN69 with 10 mg ENA), 97-fold (AN69 with 20 mg ENA), 108-fold (AN69 with 30 mg ENA), 154-fold (AN69 with 30 mg ENA and 0.1 mg/kg icatibant), 18-fold (PAN DX without ENA), and 42-fold (PAN DX with 20 mg ENA). Elevated BK levels in arterial blood were detected during hemodialysis with AN69 membranes even without ACE inhibition (2.5-fold); pre-treatment with 20 mg ENA further increased arterial BK concentrations (4-fold). Furthermore, a marked decline of prekallikrein and high molecular weight kininogen concentrations was noted for both AN69 and PAN DX membranes. Anaphylactoid reactions during hemodialysis were completely prevented by icatibant even after pre-treatment with ENA and in the presence of high BK concentrations. Concentrations of prekallikrein, high molecular weight kininogen, and BK remained unchanged and no AR were observed during hemodialysis with SPAN and pre-treatment with 20 mg ENA. Our findings confirm that AR during hemodialysis with the negatively charged AN69 membrane are mediated by BK, since they can be prevented by the BK B2-receptor antagonist icatibant

Binding Affinity and Capacity for the Uremic Toxin Indoxyl Sulfate

Protein binding prevents uremic toxins from removal by conventional extracorporeal therapies leading to accumulation in maintenance dialysis patients. Weakening of the protein binding may enhance the dialytic elimination of these toxins. In ultrafiltration and equilibrium dialysis experiments, different measures to modify the plasma binding affinity and capacity were tested: (i), increasing the sodium chloride (NaCl) concentration to achieve a higher ionic strength; (ii), increasing the temperature; and (iii), dilution. The effects on the dissociation constant K-D and the protein bound fraction of the prototypical uremic toxin indoxyl sulfate (IS) in plasma of healthy and uremic individuals were studied. Binding of IS corresponded to one site binding in normal plasma. K-D increased linearly with the NaCl concentration between 0.15 (K-D = 13.2 +/- 3.7 mu M) and 0.75 M (K-D = 56.2 +/- 2.0 mu M). Plasma dilution further reduced the protein bound toxin fraction by lowering the protein binding capacity of the plasma. Higher temperatures also decreased the protein bound fraction of IS in human plasma. Increasing the NaCl concentration was effective to weaken the binding of IS also in uremic plasma: the protein bound fraction decreased from 89% +/- 3% to 81% +/- 3% at 0.15 and 0.75 M NaCl, respectively. Dilution and increasing the ionic strength and temperature enhance the free fraction of IS allowing better removal of the substance during dialysis. Applied during clinical dialysis, this may have beneficial effects on the long-term outcome of maintenance dialysis patients

Association between free light chain levels, and disease progression and mortality in chronic kidney disease

Immunoglobulin free light chains (FLCs) form part of the middle molecule group of uremic toxins. Accumulation of FLCs has been observed in patients with chronic kidney disease (CKD). The aim of the present study was to measure FLC levels in patients at different CKD stages and to assess putative associations between FLC levels on one hand and biochemical/clinical parameters and mortality on the other. One hundred and forty patients at CKD stages 2-5D were included in the present study. Routine clinical biochemistry assays and assays for FLC kappa () and lambda () and other uremic toxins were performed. Vascular calcification was evaluated using radiological techniques. The enrolled patients were prospectively monitored for mortality. Free light chain and levels were found to be elevated in CKD patients (especially in those on hemodialysis). Furthermore, FLC and levels were positively correlated with inflammation, aortic calcification and the levels of various uremic toxins levels. A multivariate linear regression analysis indicated that FLC and levels were independently associated with CKD stages and 2 microglobulin levels. Elevated FLC and levels appeared to be associated with mortality. However, this association disappeared after adjustment for a propensity score including age, CKD stage and aortic calcification. In conclusion, our results indicate that FLC and levels are elevated in CKD patients and are associated with inflammation, vascular calcification and levels of other uremic toxins. The observed link between elevated FLC levels and mortality appears to depend on other well-known factors

Clinical performance comparison of two medium cut-off dialyzers

Introduction Medium-cut-off (MCO) dialyzers may beneficially impact outcomes in patients on hemodialysis. Methods In a randomized, controlled trial in maintenance hemodialysis patients, the new Nipro ELISIO-17HX MCO dialyzer was compared to the Baxter Theranova 400 filter regarding middle molecule removal. Furthermore, the suitability of two assays for free lambda-light chain (λFLC) detection (Freelite vs. N-Latex) was verified. Results ELISIO-HX achieved slightly lower reduction ratios for β2-microglobulin (71.8 ± 6.0 vs. 75.3 ± 5.8%; p = 0.001), myoglobin (54.7 ± 8.6 vs. 64.9 ± 8.7%; p < 0.001), and kappa-FLC (62.1 ± 8.8 vs. 56.3 ± 7.7%; p = 0.021). λFLC reduction ratios were more conclusive with the Freelite assay and not different between ELISIO-HX and Theranova (28.4 ± 3.9 vs. 38.7 ± 13.4%; p = 0.069). The albumin loss of Theranova was considerably higher (2.14 ± 0.45 vs. 0.77 ± 0.25 g; p = 0.001) and the Global Removal ScoreLoss alb largely inferior (30.6 ± 7.4 vs. 82.4 ± 29.2%/g; p = 0.006) to ELISIO-HX. Conclusions The new ELISIO-HX expands the choice of dialyzers for MCO hemodialysis

A multi-center, prospective, open-label, 8-week study of certoparin for anticoagulation during maintenance hemodialysis – the membrane study

Background Adequate anticoagulation is prerequisite for effective hemodialysis to prevent clotting in the extracorporeal circuit. We aimed providing first data on the efficacy and safety of the low-molecular-weight heparin certoparin in this setting. Methods Multicenter, open-label, 8-week trial. Patients received a single dose of 3,000 IU certoparin i.v. with additional titration steps of 600 IU and/or continuous infusion if necessary. Results 120 patients were screened, 109 enrolled (median age 71; range 26–90 years) and 106 available for efficacy analyses. The percentage of unsatisfactory dialysis results at 8 weeks due to clotting or bleeding, was 1.9% (n = 2/106; 95% confidence interval [CI] 0.23–6.65%); no major bleeding. 1.9% had moderate/severe clotting in the lines/bubble catcher and 2.8% in the dialyser at week 8. 15.7 ± 14.3% of the dialysis filters’ visual surface area was showing redness. In subgroups of patients receiving median doses of 3000 ± 0, 3000 (2400–6000) and 4200 (3000–6600) IU, plasma aXa levels at baseline, 4 and 8 weeks were 0.24 [95%CI 0.21–0.27], 0.33 [0.27–0.40] and 0.38 [0.33–0.45] aXa IU/ml at 2 h. $C_{48h}$ was 0.01 [0.01–0.02] aXa IU at all visits. At baseline and 4 weeks $AUC_{0-48h}$ was 2.66 [2.19–3.24] and 3.66 [3.00–4.45] aXa IU*h/ml. In 3.0% of dialyses (n = 83/2724) prolonged fistula compression times were documented. Eight patients (7.34%) had at least one episode of minor bleeding. 4) 85.3% of patients had any adverse event, 9.2% were serious without suspected drug relation; and in 32 patients a drug-relation was suspected. Conclusions Certoparin appears effective and safe for anticoagulation in patients undergoing maintenance hemodialysis

Differences in Dialysis Efficacy Have Limited Effects on Protein-Bound Uremic Toxins Plasma Levels over Time

The protein-bound uremic toxins para-cresyl sulfate (pCS) and indoxyl sulfate (IS) are associated with cardiovascular disease in chronic renal failure, but the effect of different dialysis procedures on their plasma levels over time is poorly studied. The present prospective, randomized, cross-over trial tested dialysis efficacy and monitored pre-treatment pCS and IS concentrations in 15 patients on low-flux and high-flux hemodialysis and high-convective volume postdilution hemodiafiltration over six weeks each. Although hemodiafiltration achieved by far the highest toxin removal, only the mean total IS level was decreased at week three (16.6 &plusmn; 12.1 mg/L) compared to baseline (18.9 &plusmn; 13.0 mg/L, p = 0.027) and to low-flux dialysis (20.0 &plusmn; 12.7 mg/L, p = 0.021). At week six, the total IS concentration in hemodiafiltration reached the initial values again. Concentrations of free IS and free and total pCS remained unaltered. Highest beta2-microglobulin elimination in hemodiafiltration (p &lt; 0.001) led to a persistent decrease of the plasma levels at week three and six (each p &lt; 0.001). In contrast, absent removal in low-flux dialysis resulted in rising beta2-microglobulin concentrations (p &lt; 0.001). In conclusion, this trial demonstrated that even large differences in instantaneous protein-bound toxin removal by current extracorporeal dialysis techniques may have only limited impact on IS and pCS plasma levels in the longer term

Determination of Advanced Glycation End Products in Serum by Fluorescence Spectroscopy and Competitive ELISA

Peer Reviewe

Enhancement of solute clearance using pulsatile push-pull dialysate flow for the Quanta SC+: A novel clinic-to-home haemodialysis system.

BACKGROUND AND OBJECTIVE:The SC+ haemodialysis system developed by Quanta Dialysis Technologies is a small, easy-to-use dialysis system designed to improve patient access to self-care and home haemodialysis. A prototype variant of the standard SC+ device with a modified fluidic management system generating a pulsatile push-pull dialysate flow through the dialyser during use has been developed for evaluation. It was hypothesized that, as a consequence of the pulsatile push-pull flow through the dialyser, the boundary layers at the membrane surface would be disrupted, thereby enhancing solute transport across the membrane, modifying protein fouling and maintaining the surface area available for mass and fluid transport throughout the whole treatment, leading to solute transport (clearance) enhancement compared to normal haemodialysis (HD) operation. METHODS:The pumping action of the SC+ system was modified by altering the sequence and timings of the valves and pumps associated with the flow balancing chambers that push and pull dialysis fluid to and from the dialyser. Using this unique prototype device, solute clearance performance was assessed across a range of molecular weights in two related series of laboratory bench studies. The first measured dialysis fluid moving across the dialyser membrane using ultrasonic flowmeters to establish the validity of the approach; solute clearance was subsequently measured using fluorescently tagged dextran molecules as surrogates for uraemic toxins. The second study used human blood doped with uraemic toxins collected from the spent dialysate of dialysis patients to quantify solute transport. In both, the performance of the SC+ prototype was assessed alongside reference devices operating in HD and pre-dilution haemodiafiltration (HDF) modes. RESULTS:Initial testing with fluorescein-tagged dextran molecules (0.3 kDa, 4 kDa, 10 kDa and 20 kDa) established the validity of the experimental pulsatile push-pull operation in the SC+ system to enhance clearance and demonstrated a 10 to 15% improvement above the current HD mode used in clinic today. The magnitude of the observed enhancement compared favourably with that achieved using pre-dilution HDF with a substitution fluid flow rate of 60 mL/min (equivalent to a substitution volume of 14.4 L in a 4-hour session) with the same dialyser and marker molecules. Additional testing using human blood indicated a comparable performance to pre-dilution HDF; however, in contrast with HDF, which demonstrated a gradual decrease in solute removal, the clearance values using the pulsatile push-pull method on the SC+ system were maintained over the entire duration of treatment. Overall albumin losses were not different. CONCLUSIONS:Results obtained using an experimental pulsatile push-pull dialysis flow configuration with an aqueous blood analogue and human blood ex vivo demonstrate an enhancement of solute transport across the dialyser membrane. The level of enhancement makes this approach comparable with that achieved using pre-dilution HDF with a substitution fluid flow rate of 60 mL/min (equivalent to a substitution volume of 14.4 L in a 4-hour session). The observed enhancement of solute transport is attributed to the disruption of the boundary layers at the fluid-membrane interface which, when used with blood, minimizes protein fouling and maintains the surface area