Haemostasis is a physiological process of blood clotting and dissolution of the clot, followed by the repair of injured tissue. It results from interplay of vascular endothelium, platelets, coagulation factors, anti-coagulation mechanisms and fibrinolytic system. The fluidity of blood in the absence of injury is maintained by the balance between pro-coagulant pathway, and the mechanisms that inhibit the pro-coagulant pathway. Imbalance between the two mechanisms, for example during clinical illnesses or preoperative period, predisposes a patient to either bleeding or thrombosis. To stop bleeding after injury, a complex process is initiated within seconds. After vasoconstriction, which reduces blood flow, begins the first phase of haemostasis –primary haemostasis. The primary haemostasis leads to the formation of initial platelet plug. Activated platelets adhere …show more content…
Degradation of fibrin is termed fibrinolysis. The fibrinolytic pathway is a complex physiological pathway controlled by action of a series of cofactors, inhibitors, receptors. Dysregulation of this pathway is associated with different pathologies (e.g. coagulopathies, disseminated intravascular coagulation (DIC) or congenital bleeding disorders). Degradation of fibrin is performed by serine protease plasmin, which is present in blood as a proenzyme, plasminogen, and needs to be activated by tissue plasminogen activator (tPA) and urokinase. Disturbance in haemostasis with abnormal bleeding may be caused by thromocytopenia, platelet function disorder, or defects in blood coagulation. Vascular disorders might also cause a bleeding. To get an accurate diagnosis, which is crucial for successful treatment, the haemostatic function has to be examined. The information about the haemostatic function can by gained using a number of laboratory tests to assess platelet and coagulation