Hemostasis defined

Hemostasis as defined by Virchow in the last century is a fine balance between blood flow, humoral factors, and cellular elements of the vascular system. Today, molecular and... 

Platelet activation by ADP and adenosine triphosphate (ATP) is a key player in hemostasis and thrombosis, Several receptors are involved, and there are a number of drugs that target these receptors (I). The P2XI receptor is an ATP-gated channel but its role is not yet well defined. 

The development of parallel-plate perfusion chambers [67,68] made possible the study of platelet interaction with the extracellular matrix (ECM) generated by cells in culture or with isolated subendothelial components under defined experimental conditions. The use of the ECM produced by human umbilical vein endothelial cells (HUVEC) in culture as adhesive substrate has Su tated the understanding of the mechanisms involved in primary hemostasis [68]. HUVECs are immature and not subjected to flow conditions during their culture, two Ikctors which may influence the reactivity of their ECM towards platelets [69]. Interestingly, the properties and reactivity of the underlying ECM can be modified by exposure of HUVECs to different stimuli, an experimental approach which has fevored the investigation of basic mechanisms of thrombosis [33]. 

In one study changes in hemostasis in surgical patients undergoing massive transfusion occurred in 93% of patients (34). The platelet count was most frequently abnormal. Well-defined hemostatic disorders, for example Die, were detected in 48% of patients. It was suggested that the laboratory abnormalities were induced by massive transfusion. Laboratory monitoring and therapeutic measures directed at any underlying disease have been recommended. 

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