[On-line sequential hemodiafiltration (HDF-OL-S): a new therapeutic option]

on line haemodiafiltration provides the greatest clearance for low and high-molecular weight uremic toxins, which is associated with a lower risk of mortality in our patients. Nowadays, there's increasing evidence about the need of achieving at least 20 litters ultrafiltration in postdilution mode and 70% reduction of beta-2-Microglobulin (B2M), however it requires a vascular access's high blood flow. Unfortunately, we do not succeed in these objectives because of our patients being older, diabetic and with poor vascular access; in this situation high blood flows are more difficult to get at the expense of lower post-dilution exchange volumes. The aim of this study was to assess the efficiency of OL-S-HDF to obtain an equivalent ultrafiltration volume as 20 L in OL-postdilution-HDF (OL-P-HDF). OL-S-HDF initially begins in postdilution mode changing to predilution once the transmembrane pressure (TMP) reached 250 mmHg.

we performed one high-flux HD session (HF-HD), one OL-P-HDF session and one OL-S-HDF session in each of the 16 adult patients who participated during 3 consecutive weeks. We compared the clearance rates of low and middle molecules such as urea, creatinine, B2M, myoglobulin and levels of albumin and haematocrit between the 3 different techniques. We measured the pre-filter pressure (PFP) by a manometer set before the dialyzer.

The main characteristics of the sessions are described in table N1. There wasn't significant difference in Kt/V, urea and creatinine removal between the three techniques. B2M and myoglobulin's clearance rates were significantly higher in both hemodiafiltration modes than in HF-HD (p=0.000), however we didn't find differences between OL-P-HDF and OL-S-HDF. There was a direct correlation between PFP and TMP along the sessions in every technique (p<0.05). We found that PFP was better than TMP to correlate with pre-dialysis levels of albumin and haematocrit and also with the haemoconcentration percentage at the end of the sessions.

This study confirms that OL-S-HDF is as good as OL-P-HDF and it could be a useful technique to treat patients with suboptimal access's blood flow to get to achieve ultrafiltration volumes within the objectives. PFP could offer extra information than TMP.