Effects of the tip structure of temporary indwelling catheters on blood recirculation at various blood flow rates and diameters of the mock blood vessel.

AIMS: The aim of the present study was to determine the effects of the tip structure of the catheters used for hemodialysis on blood recirculation at varying blood flow rates and diameters of the mock blood vessel in a well-defined in vitro experimental system, focusing on reverse connection mode. METHODS: A mock circulatory circuit was created with silicon tubing (15 or 20 mm), a circulatory pump, connected through the catheter to dialysis circuit and dialyzer attached to dialysis machine. The tip of the inserted catheter was fixed to the center of the silicone tube, and 3 L of pig blood was poured into the blood side of the dialyzer and the recirculation rates were measured at blood flow rates of 100, 150, and 200 mL/min. Five types of commercially available catheters were used: (A) Argyle™, (B) Gentle Cath™ (Hardness gradient type), (C) Gentle Cath™, (D) Niagara™, and (E) Power-Trialysis®. RESULTS: In the case of reverse connection mode, (1) the recirculation rates were lower in the catheter with a relatively large side hole (catheter C, 17%), catheters with a greater distance between the end hole and side hole (catheters C and D, 25%), and catheter with a symmetrical tip structure (catheter E, 10%) as compared with those in catheters A and B (40% and 25%); (2) increase of the blood flow rate in the dialysis machine was associated with a reduced recirculation rate; and (3) a wider inner diameter of the mock blood vessel and faster flow rate in the vessel were associated with a reduced recirculation rate. CONCLUSION: The lowest recirculation was observed with the catheter with symmetrical holes, which produces a helical blood flow line that does not intersect with the blood streamline flowing out to the blood supply hole.

Comparison of the effects of pre-dilution and post-dilution online hemodiafiltration on the levels of inflammatory markers, lymphocytes, and platelets.

Online hemodiafiltration (OL-HDF) is a blood purification therapy based on diffusion and ultrafiltration and is classified into two types according to the mode of addition of the substitution fluid: pre-dilution OL-HDF (pre-HDF) and post-dilution OL-HDF (post-HDF); we previously reported that pre-HDF is more biocompatible. However, we used lower blood and substitution flow rates in that study and may not have accurately simulated the treatment conditions used in Europe. In this study, we compared the biocompatibilities of the treatment conditions of pre-HDF, commonly used in Japan, and post-HDF, commonly used in Europe, to determine the most biocompatible treatment conditions. We compared the biocompatibilities of pre-HDF and post-HDF using high blood flow rates and high substitution fluid volumes, and also compared the results with those of our previous study. We enrolled six stable patients undergoing maintenance dialysis at our clinic for this study. After the patients underwent hemodialysis (HD), post-HDF, and pre-HDF treatment, the biocompatibilities (based on the serum levels of high-sensitivity C-reactive protein, interleukin-6, pentraxin-3, ß-thromboglobulin, and soluble P-selectin, and the results of the lymphocyte blastogenesis test using phytohemagglutinin and concanavalin A as mitogens) and removal performances (removal performance for urea, creatinine, ß2-microglubulin [MG], and α1-MG, and albumin leakage) were determined. There were no significant differences in the biocompatibility parameters evaluated among the three treatment modes. Post-HDF was associated with significantly higher removal rates of ß2-MG than HD. Post-HDF was associated with significantly higher removal rate of α1-MG, and also significantly higher albumin leakage, than HD and pre-HDF.

Evaluation of low-volume post-dilution online hemodiafiltration with Japanese high-performance hemodiafilters.

PURPOSE: To assess the removal performance of low-volume post-hemodiafiltration (HDF) with Japanese hemodiafilters and the removal performance with 20 % reduction in the total dialysate flow rate (Qdtotal). METHODS: Subjects were 8 patients undergoing pre-HDF. Study 1: Post-HDF was performed at a blood flow rate (Qb) of 250 mL/min and a total volume of substitution fluid (Vs) of 12 L/session(s) for 4 hrs using Fineflux-210Seco (FIX), ABH-21PA (ABH), and NVF-21H (NVF). We assessed removal efficiency of small molecular solutes, low-molecular-weight-proteins and the amount of albumin loss. Study 2: Post-HDF was performed at Vs of 12 L/s under G-1, Qdtotal of 500 and Qb of 250 mL/min; G-2, Qdtotal of 400 and Qb of 250 mL/min; and G-3, Qdtotal of 400 and Qb of 300 mL/min. Removal efficiency was compared and analyzed between these conditions. RESULTS: Study 1: The results using FIX, ABH and NVF are shown in order. The Kt/V were 1.8, 1.9 and 1.8. The ß2-Microglobulin (MG) removal rate (RR) (%) were 81.2, 83.1 and 82.8, and the α1-MG RR were 37.4, 40.2 and 38.5, respectively. Study 2: The results in G-1, 2 and 3 are shown in order. The Kt/V and the RR of small solutes, were significantly higher in G-3. The ß2-MG RR (%) were 81.2, 80.1 and 81.0, and the α1-MG RR were 37.4, 37.5 and 38.0, respectively. CONCLUSIONS: Low-volume post-HDF performed at Qb of 250 mL/min with Japanese high-performance hemodiafilters exhibited favorable removal efficiency for all solutes. Even with 20 % reduction in Qdtotal, the removal performance was also favorable.

Therapeutic effect of high-efficiency online hemodiafiltration for recurrent restless legs syndrome in dialysis patients.

Two dialysis patients developed recurrent restless legs syndrome. The clinical courses and the association between the α1-microglobulin removal rate and the therapeutic effects of hemodiafiltration were analyzed. Case 1: a middle-aged woman was switched from predilution online hemodiafiltration to hemodialysis, following which the α1-microglobulin removal rate decreased from 39.1 to 29.9%. A month later, the severe restless legs syndrome occurred. The treatment was then switched to high-efficiency hemodiafiltration and 2 weeks later, these symptoms were resolved. The α1-microglobulin removal rate increased to 41.9%. Her symptoms recurred 5 years later with severity; thus, the hemodiafiltration treatment conditions were changed. Under revised conditions, the α1-microglobulin removal rate was 42.6%, and her symptoms were alleviated. Continuation of high-efficiency hemodiafiltration led to the resolution of the syndrome at 1 month after recurrence. Case 2: a middle-aged man on hemodialysis developed the restless legs syndrome in the second year of treatment. The α1-microglobulin removal rate was 23.8%. After switching to a month-long high-efficiency hemodiafiltration with a removal rate of ≥ 40%, his symptoms were resolved. However, the syndrome recurred after a year with severity. The symptoms were alleviated using various measures. The hemodiafilters were changed, and hemodiafiltration with an α1-microglobulin removal rate of ≥ 40% was continued; 2 months later, his symptoms resolved. High-efficiency online hemodiafiltration is an effective therapeutic strategy for restless legs syndrome in dialysis patients. We found, for the first time, that target removal efficiency is an α1-microglobulin removal rate of 40% or higher.

Continuous hemofiltration model using porcine blood for comparing filter life.

The purpose of the present study was to establish a continuous hemofiltration model using porcine blood to compare filter life. Continuous hemofiltration (CHF) experiments were performed using an in vitro hemofilter evaluation system utilizing porcine blood containing trisodium citrate in addition to nafamostat mesilate as anticoagulants. The lifetime of the hemofilter was evaluated using the transmembrane pressure and the pressure drop across the hemofilter at varying trisodium citrate concentrations. The porcine blood used in this experiment was considered to be in a slightly hypercoagulable state because of the continuous contact with non-biological materials and calcium inflow from substitution fluid. Blood containing 7 or 8 mM of trisodium citrate and nafamostat mesilate could be effectively used to compare the lifetimes of hemofilters utilized under the same conditions. In this CHF model using porcine blood, the plugging of the hollow fibers occurred shortly after the plugging of the membrane pores. In conclusion, a CHF model using porcine blood can be established by adjusting the concentration of trisodium citrate added to the blood.

Evaluation of the Biocompatibility of Dialysis Membranes.

BACKGROUND: Improvements in the biocompatibility of dialysis membranes have reduced biological responses elicited by blood-membrane interactions. In this article, recent technological developments in dialysis membranes with regard to biocompatibility and recent progress in the evaluation of the biocompatibility of dialysis membranes are reviewed. SUMMARY: The focus of investigation into dialysis membranes in recent years has focused on not only membrane materials, but also their surface textures, which have been changed, for example, by coating with vitamin E or by changing the amount and type of hydrophilizing agents used. Research and development is directed at altering the chemical and physical properties of membrane surfaces to suppress biological responses that are particularly elicited as a result of platelet activation. To develop membranes with excellent biocompatibility, biocompatibility should be evaluated on a like-for-like basis under conditions that are similar to those in clinical settings. Evaluation using actual dialyzers can be performed using porcine blood, platelet-rich plasma isolated from porcine blood (and platelet-rich plasma with leukocytes), or suspension of neutrophils isolated from porcine blood or cultured human monocytes. KEY MESSAGES: Highly biocompatible dialysis membranes can be developed when the overall correlations among biological reactions are examined by integrating all data on biological responses elicited by blood-membrane interactions or mutual interactions among blood cells.

Effects of increased surface coverage of polyvinylpyrrolidone over a polysulfone hemofilter membrane on permeability and cell adhesion during continuous hemofiltration.

The purpose of the present study was to evaluate the adhesiveness of blood cells and the solute removal performance change of modified polysulfone membranes which have increased polyvinylpyrrolidone (PVP) coverage over their surface. Continuous hemofiltration (CHF) experiments for 24 h were carried out using an ex vivo hemofilter evaluation system to compare a modified polysulfone hemofilter (SHG) with the conventional polysulfone hemofilter (SH). The 25 and 50 % cutoff values of the sieving coefficient of dextran after CHF and the protein concentration in the filtrate was higher in SHG, indicating that less fouling occurred in the SHG membrane. Adhesion of blood cells after 24 h of CHF was significantly higher in the case of SH than in the case of SHG. Blood cell adhesion and membrane fouling were reduced with the use of a polysulfone membrane modified with increased PVP coverage over the surface.