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Nefrología (Madrid)

On-line version ISSN 1989-2284Print version ISSN 0211-6995


MADUELL, Francisco et al. On-line haemodiafiltration with auto-substitution: assessment of blood flow changes on convective volume and efficiency. Nefrología (Madr.) [online]. 2015, vol.35, n.1, pp.50-57. ISSN 1989-2284.

Introduction: On-line haemodiafiltration (OL-HDF) is currently the most effective technique and several randomised studies and meta-analyses have seen a reduction in mortality and an association directly related with convective volume is observed. Blood flow (Qb) limits the infusion rate to 25-33 % and is the main limiting factor for reaching an optimum substitution volume. With the recent incorporation of monitors with auto-substitution systems, the aim of the study was to assess the effect of Qb variations on convective volume and purifying capacity. Material and Methods: 23 patients, 17 men and 6 women, were included, with an average age of 65.5 ±10 years, time on dialysis 292.2 ± 15 minutes, which were in the OL-HDF programme with the 5008 Cordiax monitor with auto-substitution. Each patient was analysed over 5 sessions in which only the Qb was changed (250, 300, 350, 400 and 450 ml/min). In each session the substitution volume, total convective volume and parameters of dialysis were measured. The concentration of urea (60 Da), creatinine (113 Da), β2-microglobulin (11,800 Da), myoglobin (17,200 Da), prolactin (23,000 Da), α1-microglobulin (33,000 Da) and α1-acid glycoprotein (40,000 Da) in plasma was measured at the start and end of each session in order to calculate the percentage of reduction of these solutes. Results: The trans-membrane pressure was less, with Qb 250 ml/min. A significant increase in convective volume was observed with the increase in Qb, 23.7, 26.9, 30.2, 32.8 and 35.2 l/session to 250, 300, 350, 400 and 450 ml/min, respectively (P < 0.001), representing a percentage of total purified blood of 33.2, 31.2, 30.2, 28.7 and 27.3 % respectively. The percentages of reduction of urea and creatine progressively increased with Qb, slight differences were observed with β2-microglobulin and myoglobin, and no changes were observed in the larger molecules. Conclusion: For each 50 ml/min increase in Qb, the convective volume increased by between 8 and 12 ml/min. The auto-substitution system strengthens the lowest Qbs in the percentage of convective volume with regards to total purified blood. Qb increases the purifying capacity of small molecules, favouring that of β2-microglobulin and myoglobin, and does not influence molecules of a greater molecular weight.

Keywords : Autosubstitution; Online hemodiafiltration (OL-HDF); Dialysis machine; TMP; Convective volume.

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