What does "online hemodiafiltration" mean?

http://ndt.oxfordjournals.org/content/early/2011/09/19/ndt.gfr491.abstract

First published online: September 19, 2011

Nocturnal, every-other-day, online haemodiafiltration: an effective therapeutic alternative

Francisco Maduell1, Marta Arias1, Carlos E. Durán1, Manel Vera1, Néstor Fontseré1, Manel Azqueta2, Nayra Rico3, Nuria Pérez1, Alexis Sentis1, Montserrat Elena3, Néstor Rodriguez1, Carola Arcal1, Eduardo Bergadá1, Aleix Cases1, Jose Luis Bedini3 and Josep M. Campistol1

Abstract
Background.

Longer and more frequent dialysis sessions have demonstrated excellent survival and clinical advantages, while online haemodiafiltration (OL-HDF) provides the most efficient form of dialysis treatment. The aim of this study was to evaluate the beneficial effects of a longer (nocturnal) and more frequent (every-other-day) dialysis schedule with OL-HDF at the same or the highest convective volume.

Methods

This prospective, in-centre crossover study was carried out in 26 patients, 18 males and 8 females, 49.2 ± 14 years old, on 4–5 h thrice-weekly post-dilution OL-HDF, switched to nocturnal every-other-day OL-HDF. Patient inclusion criteria consisted of stable patients with good vascular access and with good prospects for improved occupational, psychological and social rehabilitation. Patients were randomly assigned into two groups: Group A received the same convective volume as previously for 6 months followed by a higher convective volume for a further 6 months, while Group B received the same schedule in reverse order.

Results.

Nocturnal every-other-day OL-HDF was well tolerated and 56% of patients who were working during the baseline period continued to work throughout the study with practically no absenteeism. The convective volume was 26.7 ± 2 L at baseline, 27.5 ± 2 with the unchanged volume and 42.9 ± 4 L with the higher volume. eKt/V increased from 1.75 ± 0.4 to 3.37 ± 0.9. Bicarbonate, blood urea nitrogen (BUN) and creatinine values decreased, while phosphate levels fell markedly with a 90% reduction in phosphate binders. Blood pressure and left ventricular hypertrophy (LVH) improved and the use of anti-hypertensive drugs decreased. In both groups, BUN, creatinine and β2-microglobulin reduction ratios improved. Different removal patterns were observed for myoglobin, prolactin and α1-acid glycoprotein.

Conclusions

Nocturnal every-other-day OL-HDF could be an excellent therapeutic alternative since good tolerance and occupational rehabilitation, marked improvement in dialysis dose, nutritional status, LVH, phosphate and hypertension control and a substantial reduction in drug requirements were observed. In this crossover study, different removal patterns of large solutes were identified.

So, what exactly does "online hemodiafiltration" mean?