An alternative to heparin is citrate, which allows regional anticoagulation of the circuit and the filter without an effect increasing the risk of bleeding for the patient. Anticoagulation with citrate is more complex, nurses need to follow a strict protocol.. Several small studies have shown that regional anticoagulation with citrate is associated with less bleeding and a longer filter survival. The use if citrate is however associated with a greater risk of metabolic complications, if the protocol is not strictly followed. Primary aim of the present study is to show in a larger group of intensive care patients whether the use of regional anticoagulation with citrate is safe compared to systemic anticoagulation with the low molecular weight heparin nadroparin.