Sorbents in Acute Renal Failure and End-Stage Renal Disease: Middle Molecule and Cytokine Removal

Effect of the oxygenic groups on activated carbon on its hemocompatibility

In this research, the effect of the oxygenic groups on activated carbon on its hemocompatibility was studied by liquid-phase oxidation to introduce oxygenic groups on its surface and subsequent heat treatment under a nitrogen environment to remove these groups. Hemocompatibility was assessed through coagulation, hemolysis, platelet adhesion, and protein adsorption using rabbit blood samples. Results showed that an increasing presence of oxygenic groups improved hemocompatibility, evidenced by enhanced coagulation, reduced hemolysis, better platelet adhesion, and decreased fetal bovine serum protein adsorption. Conversely, the removal of oxygenic groups diminished hemocompatibility, except for coagulation when groups were removed at 250 ℃ for 15 min. Therefore, this research presents a promising route to enhance the hemocompatibility of activated carbon, offering insights into surface modification for improved biomaterial design.

Application of Extracorporeal Apheresis in Treatment of COVID-19: a Rapid Review

Spread of a novel coronavirus infection in 2019 caused by SARS-CoV-2 virus has become a real threat to public health all around the world. The new pandemic required the mobilization of all resources for effective treatment of COVID-19 patients. Extracorporeal apheresis methods were suggested as an addition to the therapy of severe COVID-19 patients, especially when there is a threat of cytokine storm. Cytokine storm has a complex and not fully understood mechanism, and it can result in the multiple organ failure syndrome, associated with high mortality. The main cytokines that play the key role in the cytokine storm are IL-6, IL-10, and TNF-alpha. Removal of the target pro-inflammatory cytokines from the bloodstream can be beneficial in reducing the risk of complications as well as the mortality rate. We describe and compare different methods of extracorporeal apheresis: hemoadsorption, selective plasma filtration, and plasma exchange therapy in the context of their potential use in COVID-19 treatment.

Uremic Toxins and Blood Purification: A Review of Current Evidence and Future Perspectives

Accumulation of uremic toxins represents one of the major contributors to the rapid progression of chronic kidney disease (CKD), especially in patients with end-stage renal disease that are undergoing dialysis treatment. In particular, protein-bound uremic toxins (PBUTs) seem to have an important key pathophysiologic role in CKD, inducing various cardiovascular complications. The removal of uremic toxins from the blood with dialytic techniques represents a proved approach to limit the CKD-related complications. However, conventional dialysis mainly focuses on the removal of water-soluble compounds of low and middle molecular weight, whereas PBTUs are strongly protein-bound, thus not efficiently eliminated. Therefore, over the years, dialysis techniques have been adapted by improving membranes structures or using combined strategies to maximize PBTUs removal and eventually prevent CKD-related complications. Recent findings showed that adsorption-based extracorporeal techniques, in addition to conventional dialysis treatment, may effectively adsorb a significant amount of PBTUs during the course of the sessions. This review is focused on the analysis of the current state of the art for blood purification strategies in order to highlight their potentialities and limits and identify the most feasible solution to improve toxins removal effectiveness, exploring possible future strategies and applications, such as the study of a synergic approach by reducing PBTUs production and increasing their blood clearance.

Recirculating peritoneal dialysis system using urease-fixed silk fibroin membrane filter with spherical carbonaceous adsorbent

The chronic kidney disease (CKD) patients are undergoing continuous ambulatory peritoneal dialysis (CAPD). However, there are some constraints, the frequent exchange of the dialysate and limitation of outside activity, associated with CAPD remain to be solved. In this study, we designed the wearable artificial kidney (WAK) system for peritoneal dialysis (PD) using urease-immobilized silk fibroin (SF) membrane and polymer-based spherical carbonaceous adsorbent (PSCA). We evaluated this kit's removal abilities of uremic toxins such as urea, creatinine, uric acid, phosphorus, and β2-microglobulin from the dialysate of end-stage renal disease (ESRD) patients in vitro. The uremic toxins including urea, creatinine, uric acid, and phosphorus were removed about 99% by immobilized SF membrane and PSCA filter after 24 h treatment. However, only 50% of β2-microglobulin was removed by this filtering system after 24 h treatment. In vivo study result shows that our filtering system has more uremic toxins removal efficiency than exchanged dialysate at every 6 h. We suggest that recirculating PD system using urease-immobilized SF membrane with PSCA could be more efficient than traditional dialysate exchange system for a WAK for PD.

Prometheus: From Legend to the Real Liver Support Therapy

Background

A large number of patients develop liver disease that may evolve into progressive chronic failure. Artificial liver support systems (e.g., MARS and Prometheus) are considered in the framework of the steady increase in the number of patients who could possibly benefit from these blood purification devices. Albumin dialysis and adsorption are now two integrated concepts. The present know-how enabling us to appropriately modify several intrinsic characteristics of the adsorbents - e.g., their chemical nature, the particle and pore size distribution, as well as a larger surface offered to adsorption - has helped in better fine-tuning liver support systems to improve adsorption kinetics and flow characteristics specifically for the intended clinical application. These properties together with an improved biocompatibility have made possible the development of adsorptive techniques for which clearances and total removal rates of target compound would be unthinkable with conventional hemodialysis or hemofiltration. Several adsorptive techniques are already available commercially for the treatment of sepsis and septic shock and of acute liver failure, but controlled studies with clinical end points are still lacking.

Surface-Engineered Blood Adsorption Device for Hyperphosphatemia Treatment

Correspondence: Melanie S. Joy, PharmD, PhD, University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences, Department of Pharmaceutical Sciences, Mail Stop C238, Room V20-4108, 12850 East Montview Blvd, Aurora, CO 80045. Email: Melanie.Joy@ucdenver.edu The research employed surface engineering methods to develop, optimize, and characterize a novel textile-based hemoadsorption device for hyperphosphatemia in hemodialysis-dependent end-stage kidney disease. Phosphate adsorbent fabrics (PAFs) were prepared by thermopressing alumina powders to polyester filtration fabrics and treatment with trimesic acid (TMA). For static experiments, phosphate adsorption capacity in buffer solution, plasma, and blood were evaluated by submersing the PAFs in 100 ml. For dynamic experiments, PAFs were equipped in a device prototype and incorporated in a pump-driven circuit. Phosphates were determined by a colorimetric assay and an Ortho Clinical Diagnostics Vitros 5600 Integrated analyzer. The maximum loading amount of TMA-alumina on PAFs was approximately 35 g/m under 260°C processing temperature. Phosphate adsorption capacity increased with initial concentration. Adsorption isotherms from buffer demonstrated a maximum phosphate adsorption capacity of approximately 893 mg/m at 37.5°C, pH 7.4, with similar results from plasma and whole blood. Measured phosphate concentrations during simulations demonstrated a 42% reduction, confirming the high capacity of the PAFs for removing phosphate from whole blood. Results from the current study indicated that an alumina-TMA treated PAF can dramatically reduce phosphate concentrations from biological samples. The technology could potentially be used as a tunable adsorbent for managing hyperphosphatemia in kidney disease.

A novel approach for blood purification: mixed-matrix membranes combining diffusion and adsorption in one step

Hemodialysis is a commonly used blood purification technique in patients requiring kidney replacement therapy. Sorbents could increase uremic retention solute removal efficiency but, because of poor biocompatibility, their use is often limited to the treatment of patients with acute poisoning. This paper proposes a novel membrane concept for combining diffusion and adsorption of uremic retention solutes in one step: the so-called mixed-matrix membrane (MMM). In this concept, adsorptive particles are incorporated in a macro-porous membrane layer whereas an extra particle-free membrane layer is introduced on the blood-contacting side of the membrane to improve hemocompatibility and prevent particle release. These dual-layer mixed-matrix membranes have high clean-water permeance and high creatinine adsorption from creatinine model solutions. In human plasma, the removal of creatinine and of the protein-bound solute para-aminohippuric acid (PAH) by single and dual-layer membranes is in agreement with the removal achieved by the activated carbon particles alone, showing that under these experimental conditions the accessibility of the particles in the MMM is excellent. This study proves that the combination of diffusion and adsorption in a single step is possible and paves the way for the development of more efficient blood purification devices, excellently combining the advantages of both techniques.

Oxidatively-modified and glycated proteins as candidate pro-inflammatory toxins in uremia and dialysis patients

End stage renal disease (ESRD) patients accumulate blood hallmarks of protein glycation and oxidation. It is now well established that these protein damage products may represent a heterogeneous class of uremic toxins with pro-inflammatory and pro-oxidant properties. These toxins could be directly involved in the pathogenesis of the inflammatory syndrome and vascular complications, which are mainly sustained by the uremic state and bioincompatibility of dialysis therapy. A key underlying event in the toxicity of these proteinaceous solutes has been identified in scavenger receptor-dependent recognition and elimination by inflammatory and endothelial cells, which once activated generate further and even more pronounced protein injuries by a self-feeding mechanism based on inflammation and oxidative stress-derived events. This review examines the literature and provides original information on the techniques for investigating proteinaceous pro-inflammatory toxins. We have also evaluated therapeutic - either pharmacological or dialytic - strategies proposed to alleviate the accumulation of these toxins and to constrain the inflammatory and oxidative burden of ESRD.

Current status of dosing and quantification of acute renal replacement therapy. Part 2: dosing paradigms and clinical implementation

The dosing and quantification of acute renal replacement therapy has emerged as one of the most pressing issues in the management of critically-ill patients with acute kidney injury. Although there is ongoing debate as to the best marker of uraemic injury in this setting, several landmark studies have identified clearance-related expressions of acute renal replacement therapy dose as important determinants of survival. Part 1 of this review examined the factors affecting the delivery of prescribed acute renal replacement therapy dose. Part 2 summarises and contextualises findings from recent dose-outcome studies, and reviews clinical tools to assist in the prescription and quantification of acute renal replacement therapy dose.

Plasma Interleukin-18 Levels in Hemodialysis Patients: Increased by Dialysis Process and Association with Interleukin-6 and Tumor Necrotic Factor-α

BACKGROUND/AIMS

This study investigated changes of interleukin-18 (IL-18) levels before and after dialysis, and the possible association with other pro-inflammatory cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha).

METHODS

Plasma IL-18 of healthy controls, and pre- and post-dialysis of uremic patients undergoing hemodialysis (HD) were evaluated by ELISA methodology.

RESULTS

Plasma IL-18 levels were significantly increased in patients with maintenance HD (p <0.001) compared to its level in normal subjects. When compared to pre-dialysis levels, a significant increase in plasma IL-18 was measured at the end of HD (p = 0.032). There was a significant correlation among plasma IL-18, IL-6 and TNF-alpha levels in HD patients.

CONCLUSION

Plasma IL-18 concentration was significantly higher in HD patients and was significantly elevated by cellulose-based HD processes. Pre-activation of immunologically active cells may contribute to the association between pre-dialysis IL-18 and post-dialysis IL-6 and TNF-alpha levels.

Assessment of the Stability of an Immunoadsorbent for the Extracorporeal Removal of Beta-2-Microglobulin from Blood

BACKGROUND

Dialysis-related amyloidosis (DRA) is a devastating and costly condition that affects patients with end stage kidney disease. A key feature of DRA is the formation of amyloid fibrils, consisting primarily of beta2-microglobulin. Except for kidney transplantation, conventional kidney replacement therapies, which are based on nonspecific mechanisms, do not adequately address beta2-microglobulin removal. An antihuman beta2-microglobulin single-chain variable region antibody fragment (scFv) was developed to confer specificity to beta2-microglobulin removal during hemodialysis.

METHODS

The scFv was immobilized onto agarose and characterized for beta2m binding capacity, thermal stability at 37 degrees C, regeneration capacity, storage conditions, and sterility.

RESULTS

The beta2-microglobulin binding capacity was 1.3 mg/ml scFv gel. The immunoadsorbent is thermally stable, can be regenerated, stored short-term in 20% ethanol, lyophilized for long-term storage, and withstand process conditions similar to that of a patient's hemodialysis therapy.

CONCLUSIONS

The results support further investigation of immobilized scFvs as a novel tool to remove beta2-microglobulin from blood.

Acute renal failure after lung transplantation: incidence, predictors and impact on perioperative morbidity and mortality

The incidence, predictors and clinical significance of acute renal failure (ARF) after lung transplantation are not well described. We retrospectively collected data on 296 patients transplanted at our center between April 1992 and December 2000; follow-up was extended until December 2002. Patients were initially divided into two groups: ARF (doubling of baseline creatinine within 2 weeks after surgery) and NoARF. The ARF group was subdivided into ARFD (dialyzed) and ARFnD (not dialyzed). The incidence of ARF was 56% (166/296), but most cases were ARFnD (n = 143). Independent predictors of ARFD (n = 23) were: baseline GFR (OR 0.98, CI 0.96-0.99, p = 0.012), pulmonary diagnosis other than COPD (OR 6.80, CI 1.5-30.89, p = 0.013), mechanical ventilation > 1 d (OR 6.16, CI 1.70-22.24, p = 0.006) and parenteral amphotericin B use (OR 3.04, CI 1.03-8.98, p = 0.045). Both ARFnD and ARFD were associated with longer duration of mechanical ventilation, increased hospital stay and increased early mortality. One-year patient survival was 92.3%, 81.8% and 21.7% in the NoARF, ARFnD and ARFD groups, respectively (p < 0.0001). After controlling for important covariates, ARFD remained associated with an increased hazard of dying (HR 6.77, CI 4.00-11.44, p < 0.0001). In conclusion, ARF occurs commonly after lung transplantation and affects important clinical outcomes, especially when dialysis is required.