Guest Editor's Introduction: This paper was presented at the 26th ASAIO Congress held in April 1980. It was printed in Trans. Am. Soc. Artif. Intern Organs, Volume 26, page 406–411, 1980, and reprinted here with permission. This is the first clinical paper dealing with double filtration plasmapheresis. The plasma separator was made using Kuraray's polyvinyl alcohol hollow fiber, and Kuraray's plasma fractionator was made of ethylene vinyl alcohol hollow fibers. Seven patients afflicted with various diseases were treated by this method for 2 to 10 sessions. This procedure required supplemental infusion of albumin solution.

Renal replacement therapy with dialyzers capable of enhanced internal filtration (IF) can be an alternative to standard hemodiafiltration, as it provides convective solute removal comparable to that of hemodiafiltration by a simple procedure. In this study, we clinically evaluated the effect of the hollow fiber length in the dialyzer, a crucial factor influencing the rate of IF, by comparing two commercial dialyzers (BS-1.6U, BS-1.6UL, Toray, Japan) which differed in the fiber length, but had the same surface area and inner diameter of their hollow fibers. We showed that in the dialyzer with the longer fibers, the pressure profile along the dialyzer was significantly altered, and the solute clearance tended to be increased. In addition, we successfully quantified the IF rate with a Doppler ultrasound in the experimental circuit, by measuring the blood flow velocities along the bundle of fibers. We showed that the changes in the blood flow velocity were more marked in the dialyzer with the longer fibers; the calculated IF rates in the dialyzers with the shorter and longer fibers were 11.1 mL/min and 37.7 mL/min, respectively, which seemed to be compatible with the solute clearances. This simple and readily applicable method is expected to be useful in the development of modified dialyzers to fully exploit the benefits of IF in renal replacement therapy.

Background: Adverse reactions, such as anaphylactoid shock, have been reported to occur frequently with the use of polysulfone (PSf) membrane dialyzers. Polyvinylpyrrolidone (PVP) elution from the membrane may be a key factor in these reactions. In this paper, we discuss the problems in the evaluation of PVP elution from PSf membrane dialyzers sterilized by gamma-ray irradiation. Methods and Results: PVP concentrations in the filling solutions in some wet-type PSf membrane dialyzers are measured by Müller's method as a standard measurement method. The PVP concentrations in autoclave (AC)-sterilized dialyzers were one order of magnitude higher than those in the solutions in dialyzers sterilized by gamma-ray irradiation. Because it is difficult to determine the PVP concentrations in the filling solutions sterilized by gamma-ray irradiation by Müller's method, single-fractionated-component PVP solutions with fractionated components of PVP (K90 or K30) were prepared and the PVP concentrations of the solutions before and after gamma-ray irradiation were determined. The results indicated that the PVP concentrations in the solutions could be determined by Müller's method before irradiation, whereas PVP was undetectable in the solution after irradiation. For single-fractionated-component PVP solutions with K90 and K30, the changes in the structure of PVP before and after gamma-ray irradiation were analyzed by high-performance liquid chromatography (HPLC). The single-fractionated-component PVP solutions with K90 and K30 had a broad peak at retention times of 15 and 19 min, respectively, prior to the gamma-ray irradiation, whereas both solutions showed a similar sharp peak at a retention time of 23 min after the irradiation. Based on these results, it is surmised that PVP is degraded by irradiation to yield PVP degradation products of low molecular weight. Furthermore, nuclear magnetic resonance (NMR) spectroscopy for PVP K90 solution was performed to confirm the signals from the vinylpyrrolidone (VP) skeletal structures. Signals from the VP skeletal structures were detected before the gamma-ray irradiation but disappeared after the irradiation. Thus, it appears that the degradation products of PVP without VP skeletal structures cannot be detected by Müller's method. Conclusions: The measurement of PVP concentrations by Müller's method is inappropriate for the evaluation of PVP elution from PSf membrane dialyzers sterilized by gamma-ray irradiation.

Continuous recirculating peritoneal dialysis (CRPD) was introduced to enhance solute removal efficiency in conventional peritoneal dialysis (PD) therapies such as continuous ambulatory peritoneal dialysis (CAPD). In CRPD, a portion of the dwell dialysate in the patient's peritoneal cavity is drained through a double-lumen catheter and purified by an extracorporeal dialyzer. In this study, solute removal characteristics and safety of CRPD are examined in ex vivo and clinical studies. Recirculation dialysis experiments using nine dogs (13.6 +/- 2.5 kg of body weight) were carried out for 240 min in the ex vivo study, whereas another seven dogs (12.1 +/- 2.8 kg) received conventional peritoneal dialysis (CPD) (120 min dwelling x 2) and six additional dogs (11.9 +/- 2.7 kg) received a Tidal PD (20 min dwelling x 12; 50% of tidal volume ratio) as controls. The ex vivo study revealed that CRPD has a higher efficiency for solute removal than CPD and is equivalent to Tidal PD. In the BUN reduction rate, the 19.4 +/- 5.5% in 240 min CRPD (n = 9) was significantly higher (p< 0.05) than the 3.5 +/- 3.6% in 240 min CPD (n = 7) and equivalent to the 17.3 +/- 4.7% in 240 min Tidal PD (n = 6). Continuous recirculating peritoneal dialysis maintained a low UN level in the peritoneal cavity due to dialysis with an extracorporeal dialyzer. This tendency was also seen in creatinine removal. In the clinical study, CRPD (n = 10) and CPD (n = 5) treatments were used in three renal failure patients. Higher solute removal efficiency was shown in CRPD than in CPD treatments, and the urea peritoneal clearance was 14.1 +/- 4.4 ml/min in CRPD (n = 10), significantly higher (p < 0.05) than the 7.3 +/- 2.1 ml/min in CPD (n = 5). No fibrin formation occurred during CRPD treatments.

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