Divert to ULTRA: Differences in infused volumes and clearance in two on-line hemodiafiltration treatments

Background: Mixed diffusive-convective dialysis therapies offer greater removal capabilities than conventional dialysis. The aim of this study was to compare two different on-line, post-dilution hemodiafiltration (HDF) treatments with regard to achieved convective volume and middle-molecule dialysis efficiency: standard volume control (sOL-HDF) and automated control of the transmembrane pressure (TMP) (UC-HDF). Methods: We enrolled 30 ESRD patients (55.9 +/- 14.0 years, 20/10 M/F) in a randomized, prospective, crossover study The patients received a 3-month period of sOL-HDF followed by UC-HDF for a further 3 months, or vice versa, using the same dialysis machine. In sOL-HDF, fixed exchange volumes were set according to a filtration fraction greater than or equal to 25%. In UC-HDF therapy, the exchanged volume was driven by a biofeedback system controlling the TMP and its set point in a double loop. Patients maintained their treatment time, dialyzer, blood flow rate, and anticoagulant regimen unchanged throughout the study. Results: Greater convective volumes were achieved in UC-HDF than in sOL-HDF (23.8 +/- 3.9 vs. 19.8 +/- 4.8 L; p<0.001) with high pre-dialysis Ht value (sOL-HDF 34.0 +/- 4.5% and UC-HDF 34.0 +/- 4.4%; p = 0.91). The average clearance values of)beta 2m and P were higher in UC-HDF than in sOL-HDF (respectively 123 24 vs. 111 +/- 22 ml/min, p<0.002 and 158 +/- 26 vs. 152 +/- 25 ml/min, p<0.05). Moreover, the UC-HDF mode led to a significantly increased rate of call-free sessions from 88% to 97% (p<0.0001). Conclusions: This study showed that the biofeedback module, applied to the automatic control of TMP in on-line HDF, results in higher convective volumes and correspondingly higher beta 2m and P clearances. By making the HDF treatment more automated and less complex to perform, it significantly reduced the staff workload.