The study will evaluate the benefit of early initiation of CRRT in the initial phase of severe sepsis in patients admitted to the ICU. Primary evaluated end-point is 28-day mortality. Secondarily evaluated end-point is length of ICU-stay, length of stay in hospital, duration of mechanical ventilation. There are two groups. One group of participants with early CRRT initiation and another group with late CRRT initiation. Reference group no CRRT.