Regional Citrate Anticoagulation: A Tale of More Than Two Stories

Abstract

Calcium is a key clotting factor and several inorganic molecules that bind to calcium have been found to reduce the clotting propensity of blood. Citrate, a calcium chelator, is used for blood transfusion as well as for maintaining patency of the extracorporeal circuit known as regional citrate anticoagulation (RCA). The amount of citrate should be chosen such that ionized calcium concentrations in the extracorporeal circuit are reduced enough to minimize propagation of the coagulation cascade. The dialytic removal of the calcium-citrate complexes combined with reduced ionized calcium concentrations make necessary calcium supplementation of the blood returning to the patient. This can be achieved in different ways. In classical RCA, citrate and calcium are infused in the afferent and efferent tubing, respectively, whereas the dialysate does not contain calcium. This setup has been shown to be highly efficacious with a very low clotting propensity. Strict monitoring of blood electrolytes is required. Alternatively, the use of a high calcium dialysate leads to calcium loading obviating the need of a separate calcium infusion pump. Main advantages are a simplified delivery of RCA and less fluctuation of systemic calcium concentrations. Nowadays, citric acid is sometimes added to the acid concentrate as replacement for acetic acid. Differences and similarities between RCA and citrate-containing dialysate are discussed. RCA is an excellent alternative to heparin for patients at high risk of bleeding.