Patients, who had previously been randomized in the CONTRAST study, will remain in their respective group and monitoring will continue. The next patients will be randomized in the same way (1: 1) using the same inclusion and exclusion criteria. HDF randomized patients will receive post-dilution standard reinjection (at least 100ml/min or 6 liter/hr). In rare cases, HDF patients can briefly have reinjection on a pre-dilution mode (if heparin need to be avoided for example) and the reinjection flow should be adjusted accordingly (200ml/min).