A systemic anticoagulation is often required to prevent circuit and filter clotting in ICU patients undergoing continuous renal replacement therapy (CRRT). A regional citrate-based anticoagulation (RCA) does not induce a systemic anticoagulation and prolongs the filter lifespan, but metabolic side-effects have been associated with this therapy. We conducted a randomized controlled trial with patients requiring CRRT to determine whether RCA using a balanced predilution replacement fluid is more effective than heparin in terms of renal replacement delivered dose and safety profile.