Data on the in vitro elution of substances from three types of polysulfone membrane dialyzers as well as a non-polysulfone cellulose triacetate membrane dialyzer evaluated using ultraviolet absorption

We evaluated the influences of the priming process (washing with saline), saline circulation conditions, and saline incubation on the in vitro elution of substances from three types of polysulfone (PSu) membrane dialyzers sterilized using gamma irradiation [NV-15X (Toray Industries, Inc.)], autoclaving [RENAK-PS1.6 (Kawasumi Laboratories, Inc.)], or in-line steam [FX-140J (Fresenius Medical Care)] methods as well as a non-PSu cellulose triacetate (CTA) membrane dialyzer [FB-150U(NIPRO)]. The effect of priming was evaluated by circulating 1000 mL of saline through the dialyzers at a rate of 100 mL/min and measuring the elution level of the substances by determining their ultraviolet (UV) absorption at 220 nm using spectrophotometry. All the tested dialyzers showed that the elution of the substances decreased as per the order of sample collection. Primed dialyzers were used in the subsequent experiments. Circulating saline through the primed membrane dialyzers at a flow rate of 100 mL/min caused time-dependent elution of substances from all the tested dialyzers; increasing the flow rate to 200 mL/min did not have a significant effect on the time-dependence or elution amount at each time point (0–8 h). The elution was also evaluated after incubating the membrane dialyzers with saline for 24 h. A co-submitted article (Sato et al., 2021) detailed the preparation of the identical experimental circuits, as well as the influences of saline washing, saline circulation conditions, and saline incubation on the elution of the hydrophilic agent polyvinylpyrrolidone (PVP) from each dialyzer using the Müller method, which can enable specific detection of PVP (Müller, 1968). The relative elution levels of PVP among the dialyzers and the experimental conditions were different from those of substances determined using UV (220 nm) absorption. Our data might be used for further development of experiments for identifying non-PVP substances eluted from dialyzers by providing information regarding the conditions of the elutions and types of dialyzers from which they are eluted.

Simple method to make a supersaturated oxygen fluid

Intravenous oxygenation has demonstrated significant increase in partial pressure of oxygen (PO₂) in animal models. A highly dissolved oxygen solution might be able to provide a sufficient level of oxygen delivery to the tissues and organs in patients with hypoxia. However, conventional fluid oxygenation methods have required the use of original devices. If simpler oxygenation of a solution is possible, it will be a useful strategy for application in clinical practice. We simply developed its administration by injection of either air or oxygen gas into conventional saline. We determined the PO₂ values in the solutions in comparison with conventional saline in vitro. To examine the effects of the administration of the new solutions on the blood gas profile, we diluted bovine blood with either conventional or the new solutions and analyzed PO₂, oxygen saturation (SO₂) and total oxygen content. PO₂ levels in the blood and new solution mixture significantly increased with each additional injected gas volume. Significant increases in the PO₂ and SO₂ of the bovine blood were found in those blood samples with the new solution, as compared with those with the control solution. These results suggest that this solution promotes oxygen delivery to the hypoxic tissue and recovery from hypoxia. This method is simpler and easier than previous methods.

Asymmetric triacetate membrane keeps high water flux during ultrafiltration: in vitro study

Membrane fouling is a primary challenge encountered during the administration of hemodialysis (HD) and hemodiafiltration (HDF). A high-flux membrane is suitable for dialyzer reuse, since it is used repeatedly. Water flux is a benchmark used to assess the effectiveness of the dialysis membrane during treatment and it is usually evaluated to determine whether membrane fouling has occurred. Polysulfone (PS) membrane has good biocompatibility and solute permeability; however, polyethersulfone (PES) is often used as a hemodiafilter membrane because of better hydrophilicity compared to PS. We evaluated water flux across hemodiafilters using newly developed asymmetric triacetate (ATA) and PES as conventional membranes in vitro. Water flux of across ATA and PES membranes significantly decreased 30 min after the start of the experiments and thereafter showed stabilization. Water flux across the ATA membrane consistently showed significantly higher values of greater than 100 mL/m²/h/mmHg, compared to lower values observed across the PES membrane. These results suggest that the ATA membrane has a potential use not only for HDF, but also for long-time therapies of HD and HDF.

Efficacy of Biofilm Removal From Hemodialysis Piping

Background

Central dialysate fluid delivery systems (CDDS) are used by dialysis centers in Japan, and although these systems are effective at delivering dialysate, they have a complex piping network with numerous sites where contamination can develop. In Japan, cleaning disinfectants have been clinically evaluated based on endotoxin levels and bacterial counts, but there have been no published studies evaluating the biofilm removal efficacy of these agents at the electron microscope level.

Objectives

In this study, we used electron microscopy to evaluate the effectiveness of various cleaning disinfectants in removing biofilms from hemodialysis piping.

Methods

Liquid nitrogen was used to sever a section of dialysis piping on which a biofilm had formed during clinical use. Sodium hypochlorite, acetic acid, and peracetic acid were used at stock-solution concentrations as cleaning disinfectants. These disinfectants were tested at room temperature and when heated (80°C). After cleaning and disinfection, biofilm removal from the surface of the piping was evaluated using a scanning electron microscope (SEM).

Results

Sodium hypochlorite did not show good biofilm removal at room temperature or when heated. Acetic acid was more effective at biofilm removal when heated than at room temperature. Peracetic acid was highly effective at biofilm removal at both room temperature and when heated

Conclusions

Cleaning and disinfection using a disinfectant at a high temperature and high concentration effectively removes biofilms from hemodialysis piping. However, long-term exposure to disinfectants may affect the piping material.

Development of an Accident Reproduction Simulator System Using a Hemodialysis Extracorporeal Circulation System

Background:

Accidents that occur during dialysis treatment are notified to the medical staff via alarms raised by the dialysis apparatus. Similar to such real accidents, apparatus activation or accidents can be reproduced by simulating a treatment situation. An alarm that corresponds to such accidents can be utilized in the simulation model.

Objectives:

The aim of this study was to create an extracorporeal circulation system (hereinafter, the circulation system) for dialysis machines so that it sets off five types of alarms for: 1) decreased arterial pressure, 2) increased arterial pressure, 3) decreased venous pressure, 4) increased venous pressure, and 5) blood leakage, according to the five types of accidents chosen based on their frequency of occurrence and the degree of severity.

Materials and Methods:

In order to verify the alarm from the dialysis apparatus connected to the circulation system and the accident corresponding to it, an evaluation of the alarm for its reproducibility of an accident was performed under normal treatment circumstances. The method involved testing whether the dialysis apparatus raised the desired alarm from the moment of control of the circulation system, and measuring the time it took until the desired alarm was activated. This was tested on five main models from four dialyzer manufacturers that are currently used in Japan.

Results:

The results of the tests demonstrated successful activation of the alarms by the dialysis apparatus, which were appropriate for each of the five types of accidents. The time between the control of the circulatory system to the alarm signal was as follows, 1) venous pressure lower limit alarm: 7 seconds; 2) venous pressure lower limit: 8 seconds; 3) venous pressure upper limit: 7 seconds; 4) venous pressure lower limit alarm: 2 seconds; and 5) blood leakage alarm: 19 seconds. All alarms were set off in under 20 seconds.

Conclusions:

Thus, we can conclude that a simulator system using an extracorporeal circulation system can be set to different models of dialyzers, and that the reproduced treatment scenarios can be used for simulation training.

Dialysate with high dissolved hydrogen facilitates dissociation of indoxyl sulfate from albumin

BACKGROUND

Protein-bound toxins such as indoxyl sulfate (IS) are not efficiently removed by conventional hemodialysis (HD).

OBJECTIVES

To improve the removal of IS, we performed an in vitro study to evaluate the effects of high dissolved hydrogen on the dissociation of IS from albumin using simulated HD.

MATERIALS AND METHODS

Wasted dialysate from peritoneal dialysis was concentrated a hundred times using extracorporeal ultrafiltration method. Dialysate with high dissolved hydrogen was made by mixing concentrated dialysis solution and electrolyzed-reduced water. The amounts of free fractions of IS were determined by high performance liquid chromatography.

RESULTS

IS was significantly dissociated from albumin using dialysate with high dissolved hydrogen compared with conventional dialysate (P < 0.05).

CONCLUSIONS

Effective removal of IS is expected using a dialysate with high dissolved hydrogen.

Dialysis and quality of dialysate in southeast asian developing countries

Background

The number of dialysis patients has been increasing in Southeast Asia, but statistical data about these patients and on the quality of dialysates in Southeast Asian dialysis facilities are still imprecise. For this study, dialysis-related statistical data were collected in Southeast Asia.

Methods

A survey of the quality of dialysates was carried out at 4 dialysis facilities in Vietnam and Cambodia. The dialysis patient survey included the numbers of dialysis facilities and patients receiving dialysis, a ranking of underlying diseases causing the initiation of dialysis, the number of patients receiving hemodialysis (HD)/on-line hemodiafiltration/continuous ambulatory peritoneal dialysis, the number of HD monitoring devices installed, the cost of each session of dialysis (in USD), the percentage of out-of-pocket payments, and the 1-year survival rates of the dialysis patients (in percent). The dialysate survey covered the endotoxin (ET) level and bacterial count in tap water, in water filtered through a reverse osmosis system and in dialysate.

Results

In each of the countries, the most frequent reason for the initiation of dialysis is diabetes mellitus. HD is usually carried out according to the ‘reuse’ principle. The 1-year survival rates are 70% in Myanmar and about 90% in the Philippines and Malaysia. The ET levels in standard dialysates were satisfactory at 2 facilities. The bacterial counts in dialysates were not acceptable at any of the facilities investigated.

Conclusion

There is an urgent need to teach medical workers involved in dialysis how to prepare sterile and ET-free dialysates.

Novel system to detect bacteria in real time in aquatic environments

Bacteria tests are conducted for quality control in many different industries. However, the cultivation method takes a long period of time to obtain results and there are more than a few bacteria that are difficult to cultivate. We have focused on the autofluorescence substance in the bacteria to detect them, and developed a sensor to measure the bacteria in real-time, without any pretreatments or addition of any reagents. This system uses a 405nm laser focused on the sample flowing through the flow-cell in order to detect the fluorescent light from the bacteria as well as scattered light. Fluorescent light and scattered light are separated by a dichroic mirror, and the number of viable particles (bacteria) and that of non-viable particles are obtained. We tested this system using fluorescent polystyrene latex particles and several bacterial strains, and confirmed that it had good detection capability. We believe that this system will become a next-generation bacteria detection system and help the introduction of PAT (process analytical technology) to all areas where real time and on-site detection is needed.

Current situation of endotoxin retentive filter

Most Japanese facilities use central dialysis fluid delivery systems (CDDS). In addition, since high-performance dialysis membranes are frequently used in Japan, the standard recommends that ultrapure dialysis fluid (UPD) should be used for all dialysis modalities at all dialysis facilities. RO produces and endotoxin retentive filters (ETRFs) occupy the most important position for UPD in this CDDS process. But ETRF is not accepted as medical equipment now in Japan. Since the logarithm reduction value (LRV) of ETRFs widely used today may be a desirable 3 for endotoxin (ET) and 7 for bacteria, UPD could be theoretically obtained through the use of ETRFs. However, we have no data of the LRV for ET and bacteria with a both new and used ETRF now. So we must study whether ETRF has this performance by doing an ET and bacterial challenge test in the near future. Also, ETRF will have to be accepted as medical equipment indicating the safety of CDDS.

Sodium sulfite and N-acetylcysteine: new additives to dialysate for inhibiting formation of glucose degradation products and advanced glycation end-products

The present study evaluated the inhibiting effect of various chemicals on the advanced glycation end-product (AGEs) cross-linking caused in protein by glucose degradation products (GDPs). We evaluated a few dozen organic and inorganic chemicals--in addition to previously reported AGE inhibitors, such as thiazolium derivatives and aminoguanidine--for their inhibiting effect. Collagen IV (from human placenta) or human serum albumin (HSA) was incubated with an AGE accelerator and one of the selected chemicals in phosphate buffer solution at 37 degrees C for as long as 14 days. Fluorescence intensity (440 nm) was determined after a given incubation time. Among 36 chemicals tested, 8 new chemicals and 5 previously known AGE inhibitors significantly suppressed the increase in fluorescence intensity seen after incubation of HSA with methylglyoxal. We believe that 6 chemicals may effectively quench GDPs and inhibit AGE cross-link formation, in a manner different from that of aminoguanidine and thiazolium.

Can recovered protein from the CAPD patient's own dialysis effluent substitute for dextrose?

Albumin has been evaluated as an osmotic agent for peritoneal dialysis as being physiologically safe and having modest colloidal osmotic pressure. However its extremely high cost inhibits clinical applications, and hypoalbuminemia is often seen in continuous ambulatory peritoneal dialysis (CAPD) patients, especially those with high peritoneal equilibration test (PET) values and who lose a large quantity of albumin everyday. This study aims at recovering protein from CAPD effluent and reusing it safely at reasonable cost as a substitute for dextrose. The dialysis effluent was collected and concentrated with a semipermeable membrane. Uremic toxins and low-molecular-weight solutes were removed by repeated filtration and water dilution. The concentrate was acidified with hydrochloric acid down to pH 2, thence de-acidified with water dialysis up to pH 5. At this point, the isoelectric point of albumin, at which precipitate was deposited, the precipitate was separated from the supernatant and re-dissolved into electrolyte solution. The acidified concentrate exhaled an unpleasant odor, like that of decayed food. The precipitate solution, however, did not smell at all. The initial ultrafiltration rate of the recovered protein solution was measured and compared with that of dextrose and dextran by using a high-sensitivity differential manometer, one end of which was connected with the test solution cell, and the other with the serum cell. The ends were separated by a semipermeable membrane. The recovered protein solution at 20 g/dL concentration was almost equivalent in initial ultrafiltration rate to the 2.0 g/dL dextrose solution and to 20 g/dL dextran (MW: 75,000 dalton) solution.

Measurement of back clearance

With improvement in dialysis membranes, back filtration becomes the focus of study. Because new membranes that remove low molecular weight proteins, such as beta 2-microglobulin by diffusion are now available for clinical use, both back filtration and back diffusion become problems. This paper gives the mass transfer rate of solutes from the dialysate to blood compartment. As markers of toxic or antigenic substances, inulin (MW 5,200), lysozyme (MW 14,300), and alpha-lactoalbumin (MW 14,400) were used. The dialyzers tested were the CLSU-12W, AM-FP10, BK-1.0P, and FB-110U. The UFR controller set the flow rate on the blood side at 200, dialysate at 500, and ultrafiltration (QF) as 0 to 50 ml/min. Under these conditions, the inulin back clearance is 16 (CLSU) to 26 ml/min (FB), even if the QF is 50 ml/min, and is 10 to 34 ml/min for lysozyme at QF = 0 ml/min. Although a substantial amount of solute moves into the blood compartment, back clearance does not drastically decrease with increase in QF. To avoid contamination of the blood side, clean-up techniques for the dialysis line or online protein adsorber should be followed.

Effects of zeta potential on the permeability of dialysis membranes to inorganic phosphate

Some patients on hemodialysis have elevated plasma phosphate values. The chemical and physical properties of dialysis membranes may cause reduced inorganic phosphate clearance, leading to hyperphosphatemia. The zeta potential was determined by a streaming potential method using an electrolytic, aqueous solution to elucidate discrepancies in phosphate ion transport through cellulosic and polymethylmethacrylate membranes. The authors also carried out dialysis experiments at 310K to obtain solute permeability for H32PO4(2-), overall mass transfer coefficient for HPO4(2-), and pure water permeability. This study demonstrates that permeability to inorganic phosphate ion does not vary with zeta potential for cellulosic membranes, but polymethylmethacrylate membranes with highly negative zeta potentials may suppress phosphate removal from patients on hemodialysis.

Nondestructive evaluation by x-ray computed tomography of dialysate flow patterns in capillary dialyzers

It is hard to evaluate dialysate flow patterns inside the fiber bundle of capillary dialyzers. The current study describes a novel determination of dialysate flow by x-ray computed tomography. The authors did steady and nonsteady state tracer experiments with adipiodone to observe the dialysate flow pattern in capillary dialyzers held vertically and horizontally. The hollow fibers were filled with paraffin to avoid permeation of adipiodone from the dialysate to blood compartment. In steady state tracer experiments, adipiodone solution (50 vol%) was injected into the dialysate compartment at a flow rate of 1.5 ml/min. Horizontal sectional dialysate flow patterns were observed every 2 cm from the point of the adipiodone injection. Adipiodone solution flowed along broken and twisted fiber bundles at dialysate flow rates ranging from 200 to 600 ml/min. In nonsteady state tracer experiments, dialysate was switched from pure water to adipiodone solution by solenoid-controlled valves after a steady state was reached, and adipiodone solution (2.4 vol%) was infused into the dialysate compartment for 30 sec at a flow rate of 500 ml/min. Vertical sectional dialysate flow patterns were observed every 2 sec after the start of adipiodone infusion. Values for dialysate flow velocity at the outer and inner regions of the fiber bundle were 3.5 and 0.6 cm/sec for the CA-170, and 1.4 and 0.7 cm/sec for the HF-200 capillary dialyzer, respectively. This study demonstrates the usefulness of x-ray computed tomography in visually and quantitatively determining dialysate flow patterns in capillary dialyzers.

Effects of membrane structure on removal of low molecular weight proteins

Much attention is being devoted to the efficient removal of beta 2-microglobulin from patients on hemodialysis as it may cause amyloidosis. The objective of the present article is to clarify the beta 2-microglobulin removal characteristics of dialysis membranes having varying water contents and pore radii. For membranes of regenerated cellulose, polymethylmethacrylate (PMMA) and ethylenevinyl alcohol (EVA), solute and pure water permeability and water content were determined by the standard methods. Data analysis using a tortuous pore model allows determination of pore radius, surface porosity, and tortuosity, and hence, the sieving coefficient as a function of Stokes radius. Based on the tortuous pore model calculation, little beta 2-microglobulin is removed from patients on hemodialysis by regenerated cellulose and PMMA membranes, but EVA membranes, with a sieving coefficient of 0.5, are capable of removing it. The solute permeability for urea is about 2 orders greater than that for beta 2-microglobulin.