The proposed study seeks to determine the appropriate balance between the removal of undesirable small molecular substances (urea, creatinine, phosphate) and large molecular substances (ß2-m) and the retention of important substances (e.g.albumin) for the Baxter Xenium XPH dialyzer type under defined therapeutic conditions of olHDF primarily concerning filtration flow rates in relation to blood flow/plasma water flow rates. Furthermore the possibility of the removal of certain protein-bound substances shall be investigated together with the impact of increasing ultrafiltration on the parameters of the micro-inflammation.

The new high flux dialyser membrane Xenium XPH 210 from Baxter will show an considerably increased removal of ß2-Microglobulin with olHDF in post dilution mode together with a markedly increased removal of small molecules (urea, creatinine, phosphate). The loss of albumin will depend on the treatment modalities. However, the albumin permeability is tolerable over the whole range of total filtration rate selected and applied to the patients.

Together with the albumin loss into the filtrate/dialysate a small amount of albuminbound substances is detectable.

Parameters of micro-inflammation can be influenced by an increasing convective part of the treatment.

Inclusion Criteria:

• Patients who have signed an informed consent form.
• Patients between 18 and 75 years.
• Patients who have been treated with hemodialysis for more than three months.
• Patients who are treated three times a week for 4-5 hours.
• Patients who are usually treated with high-flux dialyzers.
• Patients who are on a stable anticoagulation and erythropoetin regimen.
• Patients whose hematocrit is over 28 %.
• Patients having no vascular access related problems.

Exclusion Criteria:

• Patients not meeting the inclusion criteria.
• Patients who are in a poor nutritional status as judged by the investigator.
• Patients in a gravid state.
• Patients with an unstable clinical condition (e.g. cardiac or vascular instability).
• Patients whose life expectancy is less than 12 months.
• Patients with a positive anamnesis for the first use syndrome.
• Patients with known coagulation problems.
• Patients who receive hemodialysis via a single dialysis needle or central venous catheter.
• Patients participating in another study that may interfere with the outcome of the present study.