Removal capacity of different high-flux dialyzers during postdilution online hemodiafiltration

The Changes in Relative Blood Volume during Dialysis Are Characterized by Ultrafiltration Rate and Predialysis Blood Test Values

INTRODUCTION

Continuous monitoring of relative blood volume (percentage BV) in hemodialysis (HD) is critical for determining dry weight and preventing intradialytic hypotension. However, the cause of the BV variation remains unknown. This research aimed to examine factors that influence the percentage BV.

METHODS

We devised a formula based on coefficients ("a," "τ," and "b") to predict changes in percentage BV. "a" denotes a significant decrease in percentage BV in the early stages of HD. "τ" represents the transition from early to late phase of HD. "b" denotes the slope of the decrease in percentage BV in the late phase of HD. We measured the percentage BV in 18 patients with end-stage renal disease. The coefficients were estimated by fitting experimental data from patients using a least squares optimization algorithm. A correlation analysis of these parameters and patient predialysis data was performed.

RESULTS

Ultrafiltration rate (UFR) was found to be negatively correlated with "b" (r = -0.851, p < 0.01). However, UFR was not significantly related to "a." Predialysis serum total protein level was negatively correlated with "a" (r = -0.531, p = 0.042). Predialysis serum albumin and predialysis sodium were not significantly correlated with "a" and "τ." Plasma osmolarity did not have a significant relationship with "a" and "τ."

DISCUSSION/CONCLUSION

UFR influenced the decrease in percentage BV in the late phase but did not influence the decrease of percentage BV in the early phase. "a" was associated with predialysis serum total protein level but not with plasma osmolality or predialysis sodium. This implies that colloid oncotic pressure is important for plasma refilling immediately after dialysis begins. During the change of percentage BV, the decrease in the early phase of dialysis was not related to UFR, but related to other parameters, especially predialysis total protein level. A decrease in the late phase of dialysis is related to UFR.

Removal performance of pre- and post-dilution online hemodiafiltration using identical hemodiafilters in the same patients

Online hemodiafiltration (OHDF) for renal replacement therapy has two modes: pre- (pre-OHDF) and post-dilution OHDF (post-OHDF). To elucidate the precise differences between the two modes, a clinical study was performed using the same polysulfone hemodiafilters in the same patients. Eight patients were treated with ABH™-22PA for 6 weeks: 3 weeks of pre-OHDF (with substitution volumes of 24, 36, and 48 L) and 3 weeks of post-OHDF (6, 8, and 10 L). The reduction ratios of urea, uric acid (UA), creatinine (CRE), inorganic phosphorus (iP), beta-2-microglobulin (β2-MG), and alpha-1-microglobulin (α1-MG) were evaluated. The removal amounts of β2-MG, α1-MG, and albumin were also evaluated by analyzing the spent dialysis fluids. The types and numbers of adverse events (AEs) and device malfunctions were recorded. The reduction ratios of urea, UA, CRE, iP, and β2-MG were comparable among all conditions, while that of α1-MG tended to be slightly higher in post-OHDF than in pre-OHDF. The removal amounts of α1-MG and albumin in pre-OHDF and post-OHDF were significantly greater with the maximum substitution volume than with the minimum volume. However, the selective removal indices, which were obtained by dividing the amount of α1-MG removed by the albumin level, tended to be slightly higher in pre- than in post-OHDF. No device-related AEs or device malfunctions occurred in either mode. No significant differences in inflammatory responses, evaluated by high-sensitivity C-reactive protein and interleukin-6, were observed. This study provides removal performance and safety data regarding the application of ABH-22PA for pre- and post-OHDF.

Performance and Hemocompatibility of a Novel Polysulfone Dialyzer: A Randomized Controlled Trial

Background

High-flux dialyzers effectively remove uremic toxins, are hemocompatible to minimize intradialytic humoral and cellular stimulation, and have long-term effects on patient outcomes. A new dialyzer with a modified membrane surface has been tested for performance and hemocompatibility.

Methods

This multicenter, prospective, randomized, crossover study involved the application of the new polysulfone-based FX CorAL 600 (Fresenius Medical Care, Bad Homburg, Germany), the polyarylethersulfone-based Polyflux 170H (Baxter Healthcare Corporation, Deerfield, IL), and the cellulose triacetate–based SureFlux 17UX (Nipro Medical Europe, Mechelen, Belgium), for 1 week each, to assess the noninferiority of the FX CorAL 600’s removal rate of β2-microglobulin. Performance was assessed by removal rate and clearance of small- and medium-sized molecules. Hemocompatibility was assessed through markers of complement, cell activation, contact activation, and coagulation.

Results

Of 70 patients, 58 composed the intention-to-treat population. The FX CorAL 600’s removal rate of β2-microglobulin was noninferior to both comparators (P<0.001 versus SureFlux 17UX; P=0.0006 versus Polyflux 170H), and superior to the SureFlux 17UX. The activation of C3a and C5a with FX CorAL 600 was significantly lower 15 minutes after treatment start than with SureFlux 17UX. The activation of sC5b-9 with FX CorAL 600 was significantly lower over the whole treatment than with SureFlux 17UX, and lower after 60 minutes than with the Polyflux 170H. The treatments with FX CorAL 600 were well tolerated.

Conclusions

FX CorAL 600 efficiently removed small- and medium-sized molecules, showed a favorable hemocompatibility profile, and was associated with a low frequency of adverse events in this study, with a limited patient number and follow-up time. Further studies, with longer observation times, are warranted to provide further evidence supporting the use of the new dialyzer in a wide range of therapeutic options, and for long-term treatment of patients on hemodialysis, to minimize the potential effects on inflammatory processes.

Distinct Solute Removal Patterns by Similar Surface High-Flux Membranes in Haemodiafiltration: The Adsorption Point of View

INTRODUCTION

Haemodialysis (HD) allow depuration of uraemic toxins by diffusion, convection, and adsorption. Online haemodiafiltration (HDF) treatments add high convection to enhance removal. There are no prior studies on the relationship between convection and adsorption in HD membranes. The possible benefits conferred by intrinsic adsorption on protein-bound uraemic toxins (PBUTs) removal are unknown.

METHODS

Twenty-two patients underwent their second 3-days per week HD sessions with randomly selected haemodialysers (polysulfone, polymethylmethacrylate, cellulose triacetate, and polyamide copolymer) in high-flux HD and HDF. Blood samples were taken at the beginning and at the end of the treatment to assess the reduction ratio (RR) in a wide range of molecular weight uraemic toxins. A mid-range removal score (GRS) was also calculated. An elution protocol was implemented to quantify the amount of adsorbed mass (Mads) for each molecule in every dialyser.

RESULTS

All synthetic membranes achieved higher RR for all toxins when used in HDF, specially the polysulfone haemodialyser, resulting in a GRS = 0.66 ± 0.06 (p < 0.001 vs. cellulose triacetate and polyamide membranes). Adsorption was slightly enhanced by convection for all membranes. The polymethylmethacrylate membrane showed expected substantial adsorption of β2-microglobulin (MadsHDF = 3.5 ± 2.1 mg vs. MadsHD = 2.1 ± 0.9 mg, p = 0.511), whereas total protein adsorption was pronounced in the cellulose triacetate membrane (MadsHDF = 427.2 ± 207.9 mg vs. MadsHD = 274.7 ± 138.3 mg, p = 0.586) without enhanced PBUT removal.

DISCUSSION/CONCLUSION

Convection improves removal and slightly increases adsorption. Adsorbed proteins do not lead to enhanced PBUTs depuration and limit membrane efficiency due to fouling. Selection of the correct membrane for convective therapies is mandatory to optimize removal efficiency.