Background: Hemodiafiltration (HDF) is associated with a lower incidence of neuropathy, carpal tunnel syndrome, joint pain, and partial correction of anemia. HDF with on-line-prepared substitution fluid (OL HDF), as compared with conventional hemodialysis, increases the treatment tolerance and, as compared with standard HDF, avoids storage problems and allows a higher substitution volume at low cost. Methods: Thirty-two hemodialysis patients treated by OL HDF for at least 9 months were studied. Hemoglobin, hematocrit, iron metabolism, serum albumin, dialysis dose and dry body weight were determined under a settled condition with regular hemodialysis 3 months before the transfer to OL HDF. The same parameters were analyzed 3, 6 and 9 months after the beginning of the new treatment modality. Results: During OL HDF, hemoglobin values significantly increased in patients without addition of recombinant human erythropoietin (rHuEPO): baseline vs. 6 months 11 ± 1.7 vs. 12 ± 1.8 g/dl (p < 0.01); baseline vs. 9 months 11 ± 1.7 vs. 12 ± 1.6 g/dl (p < 0.05). In patients on a maintenance dose of rhuEPO, this could be significantly reduced, while the target hemoglobin levels were maintained (10.6 ± 0.9 g/dl): baseline 99.8 ± 50.4 U/kg/week, 3rd month 76.2 ± 43 U/kg/week, 6th month 64.3 ± 37 U/kg/week, and 9th month 59.4 ± 38.6 U/kg/week (p = 0.007, p = 0.0006, and p = 0.0007, respectively, vs. baseline). Iron metabolism, dialysis dose, dry body weight and serum albumin levels did not significantly change during the follow-up period. Further, a stability of the rHuEPO supplementation was observed in 14 patients followed up for 24 months. Conclusions: OL HDF influences anemia and rHuEPO dose. It allows considerable anemia correction in patients without rHuEPO treatment, while it significantly reduces rHuEPO doses in those on rHuEPO treatment as compared with standard hemodialysis. The rHuEPO costs are consequently reduced.

The aim of the present study was transmembrane pressure (TMP) modulation in high-volume mixed hemodiafiltration (HDF) to optimize efficiency and minimize protein loss. The optimal flow/pressure conditions in on-line mixed HDF assisted with a feedback control of TMP were defined in this prospective randomized study in order to obtain maximal efficiency in solute removal while minimizing potential side effects. Two different TMP profiles in mixed HDF were compared in 12 unselected patients who underwent two study periods of 2 weeks each in cross-over randomized sequence: (A) constant TMP at around 300 mmHg and (B) profiled TMP, in which TMP was slowly increased from a low initial value to the maximal value. In both procedures, the mean volume exchange was 10.6+/-1.4 l/h. Mean filtration fraction was 53%. Instantaneous beta2-microglobulin (beta2-m) clearance was higher at the start of the session with profiled TMP (207+/-35 vs 194+/-28 ml/min, P<0.005), whereas no differences were found at the end (135+/-19 vs 132+/-19 ml/min). Profiled TMP resulted in a higher mean beta2-m clearance of the session (97.0+/-15.4 vs 87.8+/-18.3 ml/min, P<0.01), in lower albumin loss in the first 30 min (0.62+/-0.14 vs 0.98+/-0.18 g, P<0.0001), and, in the whole session (3.98+/-1.19 vs 5.24+/-0.77 g, P<0.001), in higher dialyzer ultrafiltration coefficients and lower resistance indexes. This study showed that the TMP feedback modulation in mixed HDF was highly effective in maintaining very high ultrafiltration rates and filtration fractions, and minimized potential side effects as a result of the improved preservation of membrane permeability and more favorable dialyzer pressure regimen.

Mixed HDF was the most efficient technique in the highest range of safe operating conditions. In mid-dilution HDF, high pressures generated inside the dialyser compromised membrane permeability and limited the total infusion rate, resulting in an overall reduction in solute removal.

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Dialysis access procedures and complications are an important cause of morbidity and hospitalization for chronic hemodialysis patients. Subjects over 65 years old have a higher incidence of co-morbid factors (diabetes mellitus, atheros clerosis, neoplasms, heart failure), therefore the correct choice in terms of timing and type of permanent access is extremely important. As elbow fistulas are often complicated by heart failure and PTFE grafts have a higher risk of thrombosis, we decided to evaluate the success rate of distal fistula as primary dialysis access in elderly patients. We carried out a retrospective study to identify survival predictors and actual vascular network saving. Between January 1991 and September 2000, 277 vascular access procedures were performed on 198 elderly patients (age 65 or older). The first anastomosis was positioned as peripherally as possible. In cases of patients with poor peripheral vasculature or three co-morbid factors, vascular access was first created at the origin of radial artery (Toledo-Pereyra fistula). Survival (Kaplan - Meyer analysis) was significantly higher for Toledo-Pereyra fistulas compared to wrist and snuff-box ones, in spite of the presence of a high incidence of co-morbid factors. We conclude that Toledo-Pereyra fistula is an efficient primary choice in elderly patients.