Calcium ion (Coagulation factor IV) (Ca2+)

Calcium ions, historically designated as Coagulation Factor IV, serve as an indispensable cofactor in both the intrinsic and extrinsic pathways of the blood coagulation cascade (Source: StatPearls). They facilitate the binding of vitamin K-dependent clotting factors, including Factors II, VII, IX, and X, to negatively charged phospholipid surfaces on platelets and endothelial cells through gamma-carboxyglutamic acid (Gla) residues (Source: Journal of Biological Chemistry). This binding is essential for the formation of enzyme-cofactor complexes, such as the tenase and prothrombinase complexes, which ultimately lead to thrombin generation and fibrin clot formation (Source: NCBI). In clinical practice, calcium is targeted primarily through chelation by agents like sodium citrate or EDTA to prevent blood clotting in vitro for laboratory testing and blood storage (Source: Wikipedia). Conversely, calcium supplementation using calcium gluconate or calcium chloride is used therapeutically to manage hypocalcemia-induced coagulopathy or to neutralize the effects of citrate during massive blood transfusions (Source: NIH). Proper regulation of calcium levels is critical, as deviations can lead to either excessive bleeding or life-threatening thrombotic events.

Other names

Factor IVCoagulation factor IVCa++Divalent calcium cation

Chelation of calcium ions prevents the assembly of coagulation factor complexes on phospholipid membranes, thereby inhibiting the cascade. Supplementation restores the necessary concentration for clotting.