Uremia is associated with a state of immune dysfunction, increasing infection and malignancy rates. Dysregulation of homeostasis may be directly related to abnormal apoptosis regulation, a process which is crucial for the maintenance of the biologic system. Abnormal apoptosis rates (ARs) have been reported in the literature. We performed a longitudinal study over a 10-week period in three groups of uremic subjects-hemodialysis (HD), peritoneal dialysis (PD), and predialysis chronic renal failure (CRF). Our results showed that ARs were consistent over the observed period. Monocytes extracted from HD and CRF subjects had higher ARs compared to PD and controls (HD: 26.06 +/- 8.82; CRF: 26.96 +/- 12.81; PD: 14.77 +/- 5.87; C: 11.42 +/- 4.60) when placed in culture medium. The plasma of HD and CRF subjects when incubated with U937 cells had a stronger apoptogenic potential compared with PD and controls (HD: 26.08 +/- 11.39; CRF: 24.87 +/- 9.07; PD: 12.13 +/- 4.51; C: 11.69 +/- 4.02). Inflammatory markers (C-reactive protein [CRP], procalcitonin) and cytokines (interleukin [IL]-1beta, IL-2, IL-10) had a generally poor correlation except for tumor necrosis factor (TNF)-alpha (p < 0.001). The phagocytic ability of U937 cells when incubated with the various plasma demonstrated impaired response in the HD and CRF subjects (HD: 27.56 +/- 6.67; CRF: 30.24 +/- 9.08; PD: 36.55 +/- 9.80; C: 40.04 +/- 6.98). These results suggest continuous renal purification, such as in continuous ambulatory peritoneal dialysis (CAPD), may have advantages over intermittent therapies in regulating apoptosis and maintaining biologic function and homeostasis.

The main target for low flux hemodialyzers is an efficient low molecular weight solutes clearance. Such efficiency is largely dependent on the optimization of diffusion between blood and dialysis solution. The diffusion process can be impaired if there is a mismatch between blood and dialysate flow distribution in the dialyzer. Thus optimized flow distribution both in the blood and dialysate compartment becomes quintessential for the maximal efficiency of the diffusion process within the hemodialyzer. The present paper describes the distribution of the blood and dialysate flows in a new low flux polysulfone hollow fiber hemodialyzer characterized by a specific undulation of the fibers and a new cutting technology of the fibers for an improved micro-flow condition in the blood compartment headers. Twelve Diacap α Polysulfone LO PS 15 (1.5 sqm) (B.Braun Medizintechnologie, Melsungen Germany) were employed for the study. Six were analyzed in vitro and six were studied in vivo. Blood flow distribution was studied in vitro by dye injection in the blood compartment during experimental extracorporeal circulation utilizing human blood with hematocrit adjusted at 33%. Sequential images were obtained with a helical scanner in a fixed longitudinal section of the dialyzer 1 cm thick. Average and regional blood flow velocities were measured utilizing the reconstructed imaging sequence. The method allowed the calculation of single fiber blood flow (SF Qb) and the mass transfer zone (MTR) definition in digitally subtracted images. The patterns 20–10 and 40–30 were utilized. The same technology was used to evaluate flow distribution in the dialysate compartment after dye injection in the Hansen's connector. Regional dialysate flow was calculated in central and peripheral sample areas of 1 cm2. Six in vivo hemodialysis treatments on patients with end stage renal disease were performed at three different blood flow rates (250–350 and 450 ml/min) in order to measure urea, creatinine and phosphate clearance. Macroscopic and densitometrical analysis revealed that flow distribution was homogeneous in the blood compartment while in the dialysate compartment a slight difference between the peripheral and central regions in terms of flow velocity was observed. This however was not generating channeling phenomena. Urea creatinine and phosphate clearances were remarkably high and so were the Kt/V observed in all sessions, especially in relation to the studied blood flows. In conclusion, a significant blood to dialysate flow match with optimized countercurrent flow condition was observed in the studied hollow fiber hemodialyzers. Such optimization might be due both to the improved dialyzer design at the level of the blood header and to the specific fiber undulation that prevents dialysate channeling.

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