There are two techniques commonly used to prevent blood coagulation in CRRT: heparin and citrate. Heparin increases the activity of antithrombin, a circulating protease inhibitor. Since the patient is systemically anti-coagulated, there is a risk of uncontrolled hemorrhage; however, the anticoagulation effects are monitored by periodically measuring activated clotting time. Due to the ease of monitoring, lower cost and personal experience, most veterinary facilities uses heparin as an anticoagulant.Click here for heparin protocol.

The use of citrate as an anticoagulant has also been described. As blood leaves the patient, citrate is infused. The citrate chelates serum calcium, which is an important enzyme cofactor at several steps in the clotting cascade and this renders the blood unable to clot. Before the blood is returned to the patient, calcium chloride is added to return serum calcium to physiologic levels. Citrate therapy has the advantage of providing local anticoagulation in the circuit without systemic effects on the patient. However, there is a significant risk of hypocalcemia and metabolic alkalosis. In addition, use of citrate requires periodic calcium and acid base monitoring which can be costly. Click here for citrate protocol