Randomised Study of High-flux Haemodialysis and Haemodiafiltration

The most common forms of renal replacement therapy currently in use are high flux haemodialysis (HF-HD) and haemodiafiltration (HDF). Although these techniques appear similar to the patient, there are important differences in what happens to the blood as it travels through the dialysis machine. During HDF, the machine controls hydrostatic pressure across the dialyser to remove additional water together with toxins from the blood and this fluid volume is continually replaced with an ultra-pure solution. HDF has a theoretical advantage removing more waste substances, especially larger molecules, from the blood than HF-HD which may be of benefit to the patient in the medium to long term.Despite the theoretical advantages, trials have so far been unable to find any significant difference in death rates or the development of health problems among patients on HDF or HF-HD. It is therefore important to examine other factors which may help doctors and patients to decide which treatment to use. The investigators have designed a study which aims to answer three main questions: 1. Does HDF make patients feel better? 2. Is blood pressure more stable on HDF in comparison with HF-HD? 3. Are Phosphate levels and other blood parameters better controlled with HDF than HF-HD? The investigators will do this by randomly assigning patients on HF-HD to receive 2 months of either HF-HD or HDF with as equivalent treatment prescriptions as possible and without the patient knowing which treatment they are receiving. After two months the patients will switch to the alternative form of dialysis for a further two months. During the study the investigators will ask the patients how long it took them to recover from the preceding session of dialysis, assess the frequency of symptomatic low blood pressure and also perform blood tests at set intervals to measure specific blood parameters.