Convection flow optimization in online hemodiafiltration

Abstract

Objective: to evaluate the dependence of the magnitude of convection flow in online hemodiafiltration (OLHDF) on ultrafiltration control method and patients’ individual characteristics. Materials and methods. The study included 36 stable dialysis patients (20 male and 16 female). The substitution rate was conducted manually based on transmembrane pressure (TMP). In some cases, devices with automatic filtration rate control unit AutoSub plus were used. The filtration rate (FR), TMP, blood flow rate (Qb), specific filtration rate (SFR, m/l/min/mm Hg^–1 ) were recorded. Results. The maximum SFR in various patients ranged from 0.51 to 0.80 ml/min/mm Hg^–1 ; average value was 0.62 ± 0.07 ml/min/mm Hg^–1 . There was significant correlation of SFR with hemoglobin level (r = –0.55). SFR reduced during hemodiafiltration (on average – by 23 ± 4%). SFR was significantly affected by Qb (r = 0.70). Maximum SFR was achieved with a TMP of 140–220 mm Hg; with TMP over 250 mm Hg, a decrease in SFR was noted, an increase in Qb was required for further increase in FR. Individual stability of SFR was noted during serial observations; fluctuations in a particular patient did not exceed 10%. Substitution volume for the HDF session was 18.0 ± 3.3 L, the FR/Qb ratio was 24.7 ± 5.2%. Substitution volume of 21 L was not achieved in 17 of 36 patients. The use of automatic FR adjustment system made it possible to increase the substitution volume (SV) by 12–18%. Conclusion. Achieving maximum convection volume in OLHDF requires individualizing treatment parameters. The use of FR automatic control allows maximum possible convection flow.