- Ionized calcium is essential for many stages of both coagulation and platelet plug formation
- Multiple roles in coagulation pathway (Calcium is known as Factor IV):
- Required for the activation of factors VII, IX and X
- Acts as a co-factor in the conversion of prothrombin (II) to thrombin (IIa) – binds to the tenase enzyme where it acts as a catalyst speeding up the reaction
- Important in platelet activation and aggregation:
- Increase in intracellular calcium upon stimulation activates a number of calcium-dependent enzymes and regulated release of active substances
- Standard anticoagulant solutions contain citrate which chelates calcium ions and efficiently prevents clotting
