Sieving Coefficients Research Articles

Zirconia encrusted ceramic composite membrane for uremic toxins removal: Fabrication and assessment of biocompatibility

In this study, tubular zirconia composite membranes (ZM1-ZM3) were developed using low-cost tubular substrate which was prepared utilizing naturally available clay materials by an extrusion approach. The zirconia nanoparticles were encrusted on a low-cost tubular substrate using spray pyrolysis technique. The membranes were investigated for their biocompatibility in addition to pore size, chemical stability, water permeability, porosity, contact angle, thermogravimetric (TGA), and X-ray diffraction (XRD). Water permeability, pore size and porosity of optimized membrane (ZM3) were 3.05 × 10-4 ± 0.03 L.m-2.h-1.Pa-1, 119 ± 0.57 nm and 36 ± 0.12 %, respectively. Platelets adhesion and protein adsorption were measured to be 4630 ± 46 platelets.mm-2, and 1.05 ± 0.02 μg.cm-2 respectively, while the activated partial thromboplastin time (APTT) and prothrombin time (PT) were 80 ± 0.51 s and 27 ± 0.26 s, respectively. Complement activation C3 and C4 concentrations were assessed to be 76.2 ± 0.88 mg.dL-1 and 21.57 ± 0.80 mg.dL-1, respectively and hemolysis ratio was 0.31 ± 0.01 %. Moreover, the membrane had a considerable antifouling nature with a flux recovery ratio of 89.22 ± 0.58 %. Protein retention was found to be 81.14 ± 0.58 %, in addition to outstanding sieving coefficients of uremic toxins like urea (0.95 ± 0.005), creatinine (0.93 ± 0.004), and phosphate (0.90 ± 0.004). These findings suggest that the produced tubular zirconia composite membrane has the potency for hemofiltration.

On the Temporal Evolution of Key Hemofilter Parameters-In Vitro Study under Co-Current Flow.

Effective permeability KP, the ultrafiltration coefficient (KUF), the sieving coefficient (SC), and the loss/permeation of proteins (primarily albumin) are key parameters/specifications characterizing hemofilter (HF) performance. However, there are uncertainties regarding their determination. This work aims (a) to demonstrate that the co-current flow (of blood and dialysate) can lead to beneficial unidirectional filtration (from blood/plasma to dialysate) under a fairly uniform local trans-membrane pressure (TMP), unlike the presently employed counter-current flow; (b) to study the temporal evolution of key HF performance parameters under co-current flow, particularly during the important early stage of hemocatharsis (HC). Experiments with human plasma and BSA solutions in co-current flow mode (for which a fluid mechanical model is developed) show a fairly uniform local/axial TMP, which also improves the local/axial uniformity of protein membrane fouling, particularly under (currently favored) high convective flux operation. Due to incipient membrane fouling, a significant temporal variability/decline in the effective KP is observed, and, in turn, of other parameters (i.e., the Kuf, SC, and permeation/mass flux Mm for albumin and total proteins). A satisfactory correlation of the albumin/protein mass flux Mm with permeability KP is obtained, indicating strong inter-dependence. In conclusion, co-current flow, allowing for a fair local TMP axial uniformity, enables the acquisition of accurate/representative data on the evolution of HF parameters, facilitating their interpretation and correlation. The new results provide a basis for exploring the clinical application of the co-current flow.

A Novel Method for Separating Full and Empty Adeno-Associated Viral Capsids Using Ultrafiltration.

Adeno-associated viral vectors (AAVs) are the predominant viral vectors used for gene therapy applications. A significant challenge in obtaining effective doses is removing non-therapeutic empty viral capsids lacking DNA cargo. Current methods for separating full (gene-containing) and empty capsids are challenging to scale, produce low product yields, are slow, and are difficult to operationalize for continuous biomanufacturing. This communication demonstrates the feasibility of separating full and empty capsids by ultrafiltration. Separation performance was quantified by measuring the sieving coefficients for full and empty capsids using ELISA, qPCR, and an infectivity assay based on the live cell imaging of green fluorescent protein expression. We demonstrated that polycarbonate track-etched membranes with a pore size of 30 nm selectively permeated empty capsids to full capsids, with a high recovery yield (89%) for full capsids. The average sieving coefficients of full and empty capsids obtained through ELISA/qPCR were calculated as 0.25 and 0.49, indicating that empty capsids were about twice as permeable as full capsids. Establishing ultrafiltration as a viable unit operation for separating full and empty AAV capsids has implications for developing the scale-free continuous purification of AAVs.

Cystatin C and Kidney Function Recovery in Patients Requiring Continuous KRT for Acute Kidney Injury.

Plasma cystatin C is a reliable marker to estimate kidney function; however, it is unknown whether this remains true in patients receiving continuous kidney replacement therapy (CKRT). Herein, we tested the hypothesis that lower concentrations of plasma cystatin C during the first three days of CKRT would predict kidney function recovery. We performed a retrospective observational study of 72 patients from a 126-patient, single-center CKRT study. We studied two a priori defined cohorts of patients without advanced CKD who had acute kidney injury requiring CKRT (AKI-CKRT): 1) with early kidney function recovery defined as liberation from KRT within seven days of CKRT initiation versus 2) with delayed kidney function recovery defined as receipt of KRT for >21 days or death while on KRT. Subsequent analysis included patients with advanced CKD and intermediate kidney function recovery (liberation between 8 and 21 days). Cystatin C was then measured on stored plasma, urine, and dialysis effluent collected prior to CKRT initiation and on days 1, 2, and 3 of CKRT. Plasma cystatin C was significantly lower in patients with early kidney function recovery in comparison to patients with delayed kidney function recovery on days 1 (1.79 vs. 2.39mg/L), 2 (1.91 vs. 2.38mg/L) and 3 (2.04 vs. 2.67mg/L) of CKRT. Sieving coefficient and CKRT clearance of cystatin C were similar for patients with early and delayed kidney function recovery. The lowest plasma cystatin C concentration on days 1-3 of CKRT predicted early kidney function recovery with an area under the receiver operating curve of 0.77 (P = 0.002), positive likelihood ratio of 5.60 for plasma cystatin C <1.30mg/L, and negative likelihood ratio of 0.17 for plasma cystatin C ≥1.88mg/L. Lower plasma cystatin C concentrations during the first three days of CKRT are associated with early kidney function recovery.

Human Proenkephalin A 119-159 (penKid) in Extracorporeal Therapies: Ex vivo Sieving Coefficient, Diffusive Clearance, and Hemoadsorption Kinetics

Introduction: Enkephalins, endogenous opioid peptides, are involved in the regulation of renal function. One derived molecule, proenkephalin A, also known as penKid, has been demonstrated to be a reliable biomarker for kidney function and its plasma concentration correlates with measured glomerular filtration rate. penKid is used for prediction and diagnosis of AKI and need of renal replacement therapy (RRT). penKid has also been used to predict the successful weaning from RRT in patients with AKI. Whether the concentration of penKid is affected or not by RRT is a controversial point and there are no studies describing the kinetics of the molecule in such conditions. The low molecular weight (4.5 kDa) would imply free removal by the glomerulus and the dialysis membranes. During RRT, this reduction could not be detected in clinical practice due to the complex kinetics involving either low dialytic clearance or increased production in response to impaired kidney function. The aim of this study was to determine the sieving coefficient and the diffusive clearance of the penKid molecule in conditions of in vitro continuous veno-venous hemofiltration (CVVH) and continuous veno-venous hemodialysis (CVVHD), respectively, and also the penKid removal ratio in conditions of in vitro hemoadsorption (HA) using a synthetic microporous resin. Methods: Blood spiked with a lyophilized penKid peptide solved in 20 mm dipotassium phosphate and 6 mm disodium EDTA [pH 8] to reach target concentrations is used as testing solution. In each experiment, the blood batch was adjusted at a volume of 1,000 mL, maintained at 37°, and continuously stirred. Samples were collected from blood, ultrafiltrate, and spent dialysate at different times during the experiments. Sieving, clearance, and removal ratio were calculated. Results: Significant removal of penKid was observed in CVVH (sieving 1.04 ± 0.27), in CVVHD (clearance 23.08 ± 0.89), and in HA (removal ratio 76.1 ± 1% after 120 min). Conclusion: penKid is effectively removed by extracorporeal therapies. In presence of anuria, penKid generation kinetics can be calculated based on extracorporeal removal and volume variation. In steady state conditions, declining values may be the result of an initial renal function recovery and may suggest discontinuation and successful liberation from RRT.

Plasma Mitochondrial DNA Clearance by Continuous Venovenous Haemofiltration in Critically Ill Patients

ObjectiveMitochondrial DNA (mtDNA) reportedly has diagnostic and predictive value in critically ill patients. This study evaluated the diagnostic and predictive value of mtDNA in patients undergoing continuous venovenous haemofiltration (CVVH).MethodsWe consecutively enrolled 41 patients who were treated with CVVH from September 2018 to December 2019. Prefilter, postfilter, and ultrafiltrate samples were collected before the initiation of CVVH (T0) and 6 and 12 h after CVVH. The total mass removal rate (Mtr), total mass adsorption rate (Mad), plasma clearance (PC), and sieving coefficient (SC) were calculated based on the mass conservation principle.ResultsThe plasma mtDNA concentration in patients at T0 prefilter was higher than that in healthy volunteers [13.77 (12.45–15.86) vs. 1.24 (1.15–1.34) ng/mL, P < 0.001]. Prefilter, but not postfilter or ultrafiltrate, mtDNA decreased during CVVH (P = 0.02), with a total CVVH clearance of 25.9%. The postfilter and ultrafiltrate mtDNA levels were lower than the prefilter level at each time point (P < 0.05 for all). The Mtr, Mad, PC, and SC did not change over time (P > 0.05 for all).ConclusionsPlasma mtDNA in critically ill patients was significantly affected by CVVH.Trial registration: Retrospectively registered on 20 August 2019 at ClinicalTrials.gov (NCT04083482).

#2548 In vitro evaluation of proenkephalin kinetics in hemofiltration and hemodialysis

Abstract Background and Aims Proenkephalin A 119-159 (penKid) is a stable surrogate marker for enkephalins (endogenous opioids regulating kidney function). PenKid plasma concentration correlates to GFR and increases in AKI, for this reason it can be used for prediction and diagnosis of AKI (even subclinical forms) and need of RRT. Furthermore, it seems to be also a reliable biomarker to predict the successful liberation from RRT and may therefore aid in the successful weaning of patients from RRT. PenKid has the perk of maintaining stable its concentration during RRT, suggesting that is barely filtered, in contrast to other biomarkers. However, with its small size of 4.5 kDa, penKid can be assumed to be freely filtered through the glomerulus and dialysis membranes. To address the issue about stable penKid plasma concentrations in RRT (no extracorporeal removal or increased production in response to impaired kidney function), we planned ex vivo experiments simulating different conditions of RRT. The aim of this study is to determine the sieving coefficient and the diffusive clearance of the penKid molecule in conditions of in vitro continuous veno-venous hemofiltration (CVVH) and continuous veno-venous hemodialysis (CVVHD), respectively. Method The lyophilized peptide was solved in 20 mM Dipotassium phosphate, 6 mM Disodium EDTA [pH 8], avoiding concentrations higher than 1 mg/mL. The compound was diluted in 50 mL of plasma to ensure homogeneous distribution. For each experimental modality, a batch of blood of 1000 mL with adjusted hematocrit at 30% and albumin concentration of 3 g% was utilized. Blood was spiked with lyophilized synthetic penKid to achieve two target concentrations of 150 and 500 pmol/L in CVVH and CVVHD modalities, respectively. Blood was adjusted for a volume of 1000 mL, maintained at 37° and continuously stirred during the experiments. CVVH was performed with blood flow (QB) = 150 mL/min and ultrafiltration rate (QUF) = 20 mL/min to reproduce a filtration fraction of 20%. The ultrafiltrate was reinfused in the venous line to maintain initial volume. This allowed to define convective clearance and solute sieving coefficient in pure convective mode. CVVHD was performed with QB = 150 mL/min and dialysate flow (QD) = 35 mL/min (Net QUF = 0 mL/min). This allowed the calculation of diffusive clearance. A polysulfone dialyzer (AV1000 FMC, Bad Homburg, Germany) was utilized. Samples were taken at 10, 30, 60 minutes from the initiation of the circulation, in both modalities. Results Initial penKid concentrations in blood corresponded to the desired targets in all the experiments. Sieving coefficients displayed values between 0.69 and 1.5 and they appear to remain stable over time (Fig. 1). Diffusive clearance displayed values between 35 and 15.7 mL/min. Values appear to present a slight decrease over time (Fig. 2). The observed variability can be attributed to several factors: difference in plasma protein interference in various moments of the experiments, difference in concentration of penKid in plasma water versus plasma or blood, variability in the sample measurements. Conclusion Significant removal of penKid can be obtained by extracorporeal therapies both in convection (CVVH) and diffusion (CVVHD). Further investigation is needed to assess if these findings are confirmed during in vivo treatments in which penKid kinetics is affected by generation, elimination and changes in distribution volume.

#693 Reversed high-flux SUPRA HFR: a proof of concept pilot study to access the middle molecular weight uremic toxins

Abstract Background and Aims Supra HFR is an extracorporeal purification system in which convection, diffusion, and adsorption act separately. Thanks to a first hemofilter with a sieving coefficient for albumin of 0.02, the endogenous ultrafiltrate is purified by a neutral styrenic resin, then the reconstituted whole blood is led to a second low-flux filter. Recently, an evolution of Supra HFR, called Supra H, has been produced with the innovative second high-flux filter (Bellco, Mirandola, Italy, Kuf &amp;gt; 50 ml/h/mmHg). Aim of the study is a comparison between Supra HFR, Supra H and Supra H used in a reversed configuration, called “reversed Supra H”. The potential advantage of reversed Supra H is to achieve a fine tuning on the removal of medium molecular weight toxins through adsorption acting after the bulky tuning of these molecules with the new high-flux filter (Fig. 1). Method A pilot study was conducted on 4 patients in a cross-over manner. Each patient underwent one session of conventional Supra HFR, one session of Supra H, and one session of reversed Supra H. The median age of the patients was 61 (58-79) years, dialysis vintage was 113 (76-434) months, median blood flow from the vascular access was 300 (270-300) ml/min, dialysis time was 240 (225-240) minutes, and the amount of the endogenous ultrafiltrate (Qinf) produced was kept constant for each patient during the 3 different treatments and was 9.6 (9.2-12) liters. The medium molecular weight toxins studied were β2 microglobulin (β2M), myoglobin and free light chains κ and λ (FLC κ and λ). Albumin removal by all three methods was also studied. The removal of the studied substances was obtained by Reduction Rate per session (RRs) = [(dialysis start value-dialysis end value) / dialysis start value] *100. The dialysis end value was obtained by the stop dialysate flow method and corrected for hemoconcentration according to Schneditz D et al. ASAIO J 2012. Friedman's test was used to analyze the difference between the three groups. Dunn's post-hoc test was conducted to find differences between two groups at a time. Results Regarding the toxic substances studied, the dialysis start values were represented in Table 1. As to the β2M RRs the comparison of Supra HFR vs Supra H vs reversed Supra H was statistically significant in favor of using reversed Supra H (P=0.037), the same result was obtained for the RRs of FLCs κ (P=0.041). Dunn's test showed a significant increase in RRs of FLC κ with reversed Supra H compared with Supra HFR (P=0.040). No significant differences were found for the RRs of myoglobin and FLCs λ although reversed Supra H showed a better trend in the purification of these molecules (Fig. 2). RRs of albumin were similar with these three dialysis techniques. Conclusion The Supra H technique allows an increase in the RRs of tested uremic toxins compared to the RRs obtained by Supra HFR in the conventional version. The reversed Supra H configuration confirms the hypothesis of an even better depurative trend than the other two techniques. The significance of the results is certainly affected by the small number of patients enrolled.

Transglutaminase-mediated stiffening of the glomerular basement membrane mitigates pressure-induced reductions in molecular sieving coefficient by reducing compression

Proteinuria, the presence of high molecular weight proteins in the urine, is a primary indicator of chronic kidney disease. Proteinuria results from increased molecular permeability of the glomerular filtration barrier combined with saturation or defects in tubular protein reabsorption. Any solute that passes into the glomerular filtrate traverses the glomerular endothelium, the glomerular basement membrane, and the podocyte slit diaphragm. Damage to any layer of the filter has reciprocal effects on other layers to increase glomerular permeability. The GBM is thought to act as a compressible ultrafilter that has increased molecular selectivity with increased pressure due to compression that reduced the porosity of the GBM with increased pressure. In multiple forms of chronic kidney disease, crosslinking enzymes are upregulated and may act to increase GBM stiffness. Here we show that enzymatically crosslinking porcine GBM with transglutaminase increases the stiffness of the GBM and mitigates pressure-dependent reductions in molecular sieving coefficient. This was modeled mathematically using a modified membrane transport model accounting for GBM compression. Changes in the mechanical properties of the GBM may contribute to proteinuria through pressure-dependent effects on GBM porosity.

Evaluation of various membranes at different fluxes to enable large-volume single-use perfusion bioreactors.

The growing demand for biological therapeutics has increased interest in large-volume perfusion bioreactors, but the operation and scalability of perfusion membranes remain a challenge. This study evaluates perfusion cell culture performance and monoclonal antibody (mAb) productivity at various membrane fluxes (1.5-5 LMH), utilizing polyvinylidene difluoride (PVDF), polyethersulfone (PES), or polysulfone (PS) membranes in tangential flow filtration mode. At low flux, culture with PVDF membrane maintained higher cell culture growth, permeate titer (1.06-1.34 g/L) and sieving coefficients (≥83%) but showed lower permeate volumetric throughput and higher transmembrane pressure (TMP) (>1.50 psi) in the later part of the run compared to cultures with PES and PS membrane. However, as permeate flux increased, the total mass of product decreased by around 30% for cultures with PVDF membrane, while it remained consistent with PES and PS membrane, and at the highest flux studied, PES membrane generated 12% more product than PVDF membrane. This highlights that membrane selection for large-volume perfusion bioreactors depends on the productivity and permeate flux required. Since operating large-volume perfusion bioreactors at low flux would require several cell retention devices and a complex setup, PVDF membranes are suitable for low-volume operations at low fluxes whereas PES membranes can be a desirable alternative for large-volume higher demand products at higher fluxes.

Current dialyzer classification in Japan and mortality risk in patients undergoing hemodialysis

Dialyzers are classified into five types based on their β2-microglobulin clearance rate and albumin sieving coefficient: Ia, Ib, IIa, and IIb. In addition, a new classification system introduced a type S dialyzer. However, limited information is available regarding the impact of dialyzer type on patient outcomes. A cohort study was conducted using data from the Japanese Society for Dialysis Therapy Renal Data Registry database. Total 181,804 patients on hemodialysis (HD) were included in the study, categorized into four groups (type Ia, IIa, IIb, and S). The associations between each group and two-year all-cause mortality were assessed using Cox proportional hazard models. Furthermore, propensity score-matching analysis was performed. By the end of 2019, 34,185 patients on dialysis had died. After adjusting for all confounders, the risk for all-cause mortality was significantly lower in the type IIa, and S groups than in the type Ia group. These significant findings were consistent after propensity score matching. In conclusion, our findings suggest that super high-flux dialyzers, with a β2-microglobulin clearance of ≥ 70 mL/min, may be beneficial for patients on HD, regardless of their albumin sieving coefficient. In addition, type S dialyzers may be beneficial for elderly and malnourished patients on dialysis.Trial registration number: UMIN000018641

Improved sieving coefficient in perfusion cell culture with reduced effective filtration length of hollow fibers.

The hollow fiber filter is the primary cell-retention device used in high-density perfusion cell culture and often used in an alternating tangential flow (ATF) configuration. The limited commercially available diaphragm pumps for ATF prevent utilization of vertical space when scaling beyond 500 L. Stacking hollow fiber filters coupled with viscous cell culture imposes vacuum pressure exceeding facility capabilities. Additionally, the longer filter assembly increases the hold-up volume and exceeds the diaphragm pump's fluid exchange capacity. The conventional tangential flow filtration (TFF) configuration circumvents this issue by exchanging culture from the bioreactor and cell-retention device in a unidirectional recirculation loop; however, the increased filter length when scaled up exacerbates the TFF's inherent issue with product retention from Starling flow. Stacking commercially available 20 cm TFF filters to make up the similar single-module length TFF used for the platform 3 and 50 L perfusion process at 41.5 and 65 cm, respectively, attempts to reduce fouling caused by Starling flow. The permeate of a single-module filter is partitioned into short independent segments through serially stacked filters, each harvested separately. By partitioning the permeate, the sieving coefficient increased for both 3 and 50 L scales. Reduction of Starling flow was confirmed with lower total hydraulic membrane resistance throughout the culture. This work demonstrates a method for increasing sieving coefficient and filter capacity by stacking TFF filters with independent permeate streams.

Anakinra Removal by Continuous Renal Replacement Therapy: An Ex Vivo Analysis.

Patients with sepsis are at significant risk for multiple organ dysfunction, including the lungs and kidneys. To manage the morbidity associated with kidney impairment, continuous renal replacement therapy (CRRT) may be required. The extent of anakinra pharmacokinetics in CRRT remains unknown. The objectives of this study were to investigate the anakinra-circuit interaction and quantify the rate of removal from plasma. The anakinra-circuit interaction was evaluated using a closed-loop ex vivo CRRT circuit. CRRT was performed in three phases based on the method of solute removal: 1) hemofiltration, 2) hemodialysis, and 3) hemodiafiltration. Standard control samples of anakinra were included to assess drug degradation. University research laboratory. None. Anakinra was administered to the CRRT circuit and serial prefilter blood samples were collected along with time-matched control and hemofiltrate samples. Each circuit was run in triplicate to assess inter-run variability. Concentrations of anakinra in each reference fluid were measured by enzyme-linked immunosorbent assay. Transmembrane filter clearance was estimated by the product of the sieving coefficient/dialysate saturation constant and circuit flow rates. Removal of anakinra from plasma occurred within minutes for each CRRT modality. Average drug remaining (%) in plasma following anakinra administration was lowest with hemodiafiltration (34.9%). The average sieving coefficient was 0.34, 0.37, and 0.41 for hemodiafiltration, hemofiltration, and hemodialysis, respectively. Transmembrane clearance was fairly consistent across each modality with the highest during hemodialysis (5.53 mL/min), followed by hemodiafiltration (4.99 mL/min), and hemofiltration (3.94 mL/min). Percent drug remaining within the control samples (93.1%) remained consistent across each experiment, indicating negligible degradation within the blood. The results of this analysis are the first to demonstrate that large molecule therapeutic proteins such as anakinra, are removed from plasma with modern CRRT technology. Current dosing recommendations for patients with severe renal impairment may result in subtherapeutic anakinra concentrations in those receiving CRRT.

2526. Ex Vivo Assessment of Sulbactam-Durlobactam (SUL-DUR) Clearance during Continuous Renal Replacement Therapy (CRRT)

Abstract Background Optimal dosing of antibiotics in patients on CRRT is complicated by factors that can influence drug adsorption and clearance including filter type, CRRT mode, effluent rate (ER), and the drug’s properties itself. SUL-DUR is a novel combination antibiotic under development for management of Acinetobacter baumannii infections. We sought to characterize SUL and DUR adsorption and transmembrane clearance (CLTM) in an ex vivo CRRT model. Methods CLTM was determined in hemofiltration (CVVH) and hemodialysis (CVVHD) modes using the Prismaflex M100 and HF1400 hemofilter sets. One liter of heparinized bovine blood was allowed to circulate in the Prismaflex CRRT system for 10 minutes. SUL and DUR were then added to achieve a plasma concentration of 30 mg/L, the average maximum concentration achieved in humans following SUL-DUR 1g/1g q6h as a 3h infusion. Pre-filter blood, post-filter blood and effluent samples were collected at 0, 10, 30, and 60 minutes to determine SUL and DUR concentrations. Combinations of filters, modes, and replacement fluid were tested in triplicate at effluent rates of 1, 2 and 3 L/h. The sieving coefficient (SC) for CVVH and the saturation coefficient (SA) for CVVHD were calculated to determine CLTM. Adsorption was measured through a closed loop system bypassing effluent elimination. Multiple linear regression was used to determine SUL and DUR CLTM as a function of ER, filter, and mode. Results SUL and DUR adsorption was minimal at 10% for both drugs. Mean ± standard deviation initial SUL and DUR concentrations were 28.6 ± 2.5 and 27.4 ± 1.9 mg/L, respectively. The overall mean SC/SA across different modes, filters, and ERs was 1.0 and 0.9 for SUL and DUR, respectively. Multiple linear regression demonstrated that the ER was the primary driver (p&amp;lt; 0.001) of CLTM for both drugs based on the equations: SUL CLTM (L/h) = -0.0123 + (1 x ER), R2 = 0.998; DUR CLTM (L/h) = 0.0346 + (0.91 x ER), R2 = 0.958. Conclusion SUL and DUR were efficiently cleared by both CVVH and CVVHD through M100 and HF1400 filters. The clearance of both drugs during CRRT was dependent primarily on the ER. When incorporated into established population pharmacokinetic models, these data can be used to estimate CLTM and devise dosing recommendations for SUL-DUR for patients requiring CRRT. Disclosures Xiaoyi Ye, MD, Sanofi Genzyme: Honoraria David P. Nicolau, PharmD, Allergan: Advisor/Consultant|Allergan: Grant/Research Support|Cepheid: Advisor/Consultant|Cepheid: Grant/Research Support|Merck: Advisor/Consultant|Merck: Grant/Research Support|Pfizer: Advisor/Consultant|Pfizer: Grant/Research Support|Shionogi: Advisor/Consultant|Shionogi: Grant/Research Support|Tetraphase: Advisor/Consultant|Tetraphase: Grant/Research Support|Venatorx: Advisor/Consultant|Venatorx: Grant/Research Support|Wockhardt: Advisor/Consultant|Wockhardt: Grant/Research Support Joseph L. Kuti, PharmD, bioMeriuex Inc.: Grant/Research Support|Entasis Therapeutics: Grant/Research Support|Merck &amp; Co, Inc: Grant/Research Support|Shionogi Inc: Advisor/Consultant|Shionogi Inc: Grant/Research Support|Shionogi Inc: Honoraria

Hepcidin Removal during Continuous Renal Replacement Therapy

Introduction: Patients with acute kidney injury (AKI) or end stage kidney disease (ESKD) may require continuous renal replacement therapy (CRRT) as a supportive intervention. While CRRT is effective at achieving solute control and fluid balance, the indiscriminate nature of this procedure raises the possibility that beneficial substances may similarly be removed. Hepcidin, an antimicrobial peptide with pivotal roles in iron homeostasis and pathogen clearance, has biochemical properties amenable to direct removal via CRRT. We hypothesized that serum hepcidin levels would significantly decrease after initiation of CRRT. Methods: In this prospective, observational trial, we enrolled 13 patients who required CRRT: 11 due to stage 3 AKI, and 2 due to critical illness in the setting of ESKD. Plasma was collected at the time of enrollment, and then plasma and effluent were collected at 10:00 a.m. on the following 3 days. Plasma samples were also collected from healthy controls, and we compared hepcidin concentrations in those with renal disease compared to normal controls, evaluated trends in hepcidin levels over time, and calculated the hepcidin sieving coefficient. Results: Plasma hepcidin levels were significantly higher in patients initiating CRRT than in normal controls (158 ± 60 vs. 17 ± 3 ng/mL respectively, p < 0.001). Hepcidin levels were highest prior to CRRT initiation (158 ± 60 ng/mL), and were significantly lower on day 1 (102 ± 24 ng/mL, p < 0.001) and day 2 (56 ± 14 ng/mL, p < 0.001) before leveling out on day 3 (51 ± 11 ng/mL). The median sieving coefficient was consistent at 0.82–0.83 for each of 3 days. Conclusions: CRRT initiation is associated with significant decreases in plasma hepcidin levels over the first 2 days of treatment regardless of indication for CRRT, or presence of underlying ESKD. Since reduced hepcidin levels are associated with increased mortality and our data implicate CRRT in hepcidin removal, larger clinical studies evaluating relevant clinical outcomes based on hepcidin trends in this population should be pursued.

Structure design and performance study on anticoagulant-separation dual functional PVC plasma separation membrane

It is necessary to inject anticoagulant continuously during plasma exchange therapy due to the poor anticoagulant performance of the plasma separation membrane. However, it can easily lead to a risk of bleeding or thrombosis. Herein, a novel anticoagulation-separation dual functional polyvinyl chloride (PVC) plasma separation membrane structure is proposed. The small molecular itaconic acid was grafted onto the PVC plasma separation membrane, which can bind Ca2+ in blood to extend coagulation time. When blood flows through the membrane, the blood coagulation time will be prolonged. Meanwhile, plasma containing toxins can be filtrated from the inside of the membrane to the outside. Toxins are removed from human blood effectively. The results proved that itaconic acid was grafted on the PVC plasma separation membrane without reducing membrane pores, membrane sieving coefficient, membrane flux, and membrane tensile strength, successfully. The maximum pores of the adopted anticoagulant-separation dual function PVC plasma separation membrane were 0.30 µm. The bovine serum albumin sieving coefficient reached 95 %. The flux exceeded 300 L·m−2·h−1. The tensile strength was above 4 MPa. Meanwhile, it exhibited excellent hemocompatibility by suppressed bovine serum albumin adsorption, platelets adsorption, erythrocytes adsorption, hemolysis, and strengthened anticoagulant activity. Thus, the anticoagulation-separation dual functional PVC plasma separation membrane designed in this work may have a great clinical application prospect.

Two-Dimensional Theoretical Analysis and Experimental Study of Mass Transfer in a Hollow-Fiber Dialysis Module Coupled with Ultrafiltration Operations.

This research theoretically and experimentally develops a hollow-fiber dialysis module coupled with ultrafiltration operations by introducing a trans-membrane pressure during the membrane dialysis process, which can be applied to the waste metabolic end products in the human body for improving the dialysis efficiency. The solutes were transported by both diffusion and convection from the concentration driving-force gradient between retentate and dialysate phases across the membrane, compared to the traditional dialysis processes by diffusion only. A two-dimensional modeling of such a dialysis-and-ultrafiltration system in the hollow-fiber dialysis module was formulated and solved using the stream function coupled with the perturbation method to obtain the velocity distributions of retentate and dialysate phases, respectively. The purpose of the present work is to investigate the effect of ultrafiltration on the dialysis rate in the hollow-fiber dialyzer with ultrafiltration operations. A highest level of dialysis rate improvement up to about seven times (say 674.65% under Va=20 mL/min) was found in the module with ultrafiltration rate Vw=10 mL/min and membrane sieving coefficient θ=1, compared to that in the system without operating ultrafiltration. Considerable dialysis rate improvements on mass transfer were obtained by implementing a hollow-fiber dialysis-and-ultrafiltration system, instead of using the hollow-fiber dialyzer without ultrafiltration operation. The experimental runs were carried out under the same operating conditions for the hollow-fiber dialyzers of the two experimental runs with and without ultrafiltration operations for comparisons. A very reasonable prediction by the proposed mathematical model was observed.

Use of ultrafiltration/diafiltration for the processing of antisense oligonucleotides.

Ultrafiltration/diafiltration (UF/DF) has been the hallmark for concentrating and buffer exchange of protein and peptide-based therapeutics for years. Here we examine the capabilities and limitations of UF/DF membranes to process oligonucleotides using antisense oligonucleotides (ASOs) as a model. Using a 3 kDa UF/DF membrane, oligonucleotides as small as 6 kDa are shown to have low sieving coefficients (<0.008) and thus can be concentrated to high concentrations (≤200 mg/mL) with high yield (≥95%) and low viscosity (<15 centipoise), provided the oligonucleotide is designed not to undergo self-hybridization. In general, the oligonucleotide should be at least twice the reported membrane molecular weight cutoff for robust retention. Regarding diafiltration, results show that a small amount of salt is necessary to maintain adequate flux at concentrations exceeding about 40 mg/mL. Removal of salts along with residual solvents and small molecule process-related impurities can be robust provided they are not positively charged as the interaction with the oligonucleotide can prevent passage through the membrane, even for common divalent cations such as calcium or magnesium. Overall, UF/DF is a valuable tool to utilize in oligonucleotide processing, especially as a final drug substance formulation step that enables a liquid active pharmaceutical ingredient.

Clearance of NT-proBNP and Procalcitonin during Continuous Venovenous Hemodialysis with the Medium Cutoff Filter in Patients with Rhabdomyolysis-Associated Early Acute Kidney Injury

Introduction: In polytrauma patients with AKI continuous venovenous hemodialysis (CVVHD) with medium cutoff membrane filters is commonly adopted to increase the removal of both myoglobin and inflammatory mediators, but its impact on increasing molecular weight markers of inflammation and cardiac damage is debated. Methods: Twelve critically ill patients with rhabdomyolysis (4 burns and 8 polytrauma patients) and early AKI requiring CVVHD with EMIc2 filter were tested for 72 h on serum and effluent levels for NT-proBNP, procalcitonin (PCT), myoglobin, C-reactive protein (CRP), alpha1-glycoprotein, albumin, and total protein. Results: The sieving coefficients (SCs) for proBNP and myoglobin were as higher as 0.5 at the start, decreased to 0.3 at the 2nd h, and then slowly declined to the final value of 0.25 and 0.20 at the 72nd h, respectively. PCT showed a negligible SC at the 1st h, a peak of 0.4 at the 12th h, and a final value of 0.3. SCs for albumin, alpha1-glycoprotein, and total protein were negligible. A similar trend was observed for the clearances (17–25 mL/min for proBNP and myoglobin; 12 mL/for PCT; <2 mL/min for albumin, alpha1-glycoprotein, and total protein). No correlation was found between systemic determinations and filter clearances of proBNP, PCT, and myoglobin. Net fluid loss/hour during CVVHD positively correlated with systemic myoglobin for all patients and NT-proBNP in the burn patients. Conclusion: CVVHD with EMiC2 filter showed low clearances for NT-proBNP and procalcitonin. CVVHD did not significantly affect the serum levels of these biomarkers, which could be adopted in the clinical management of early CVVHD patients.

Elimination of cefotaxime using polysulfone and polyacrylonitrile-derived filters: An in vitro assessment.

Continuous renal replacement therapy (CCRT) efficiently eliminates cefotaxime. To our knowledge, there are no previous in vitro studies dealing with the disposition of cefotaxime. We studied the elimination of cefotaxime by two filters in a model mimicking a session of CRRT using the NeckEpur® technology. The ST150®-polyacrylonitrile filter with the Prismaflex, Baxter-Gambro, and the AV1000®-polysulfone filter with the Multifiltrate Pro, Fresenius, were studied. Continuous filtration used a flowrate of 1 L/h in post-dilution only. Simulated blood flowrate was set at 200 mL/min. Routes of elimination were assessed using the NeckEpur® technology. Cefotaxime concentrations were measured using ultra high-performance liquid chromatography, and tandem mass spectrometry. Two sessions were performed using the ST® filter and three using the AV® filter. Stability of cefotaxime during 6 h was assessed in triplicate with a mean variation of concentrations of 2.4 ± 1.5% at the end of the study. The mean measured initial concentration in the central compartment (CC) for the five sessions was 52.4 mg/L. The mean amount eliminated from the CC at the end of the sessions using the ST150®-polyacrylonitrile and the AV1000®-polysulfone filters were 72% and 73%, respectively. The clearances of cefotaxime from the central compartment (CC) were 1.1 and 1.2 L/h, respectively. The mean sieving coefficient were 0.99 and 0.99, respectively. The mean percentages of the amount eliminated from the CC by filtration/adsorption were 87/13% and 92/8%, respectively. Both adsorption percentages were below 15%. We conclude neither the ST150®-polyacrylonitrile nor the AV1000®-polysulfone filters result in clinically significant adsorption of cefotaxime.