Table 12.12 . Of these, DIC is most often associated with sepsis, obstetric complications, malignancy, and major trauma (especially to the brain). The initiating events in these conditions are multiple and often interrelated. For example, in obstetric conditions, tissue factor derived from the placenta, retained dead fetus, or amniotic fluid enters the circulation; however, shock, hypoxia, and acidosis often coexist and can lead to widespread endothelial injury. Trauma to the brain releases fat and phospholipids, which act as contact factors and thereby activate the intrinsic arm of the coagulation cascade.
Whatever the pathogenic mechanism, DIC has two consequences. First, there is widespread fibrin deposition within the microcirculation. The associated obstruction leads to ischemia in the more severely affected or vulnerable organs and hemolysis as red cells are traumatized while passing through vessels narrowed by fibrin thrombi (microangiopathic hemolytic anemia). Second, because of the depletion of platelets and clotting factors and the secondary release of plasminogen activators, there is a superimposed bleeding tendency. Plasmin cleaves not only to fibrin (fibrinolysis) but also to factors V and VIII, thereby reducing their concentration further. In addition, fibrinolysis creates fibrin degradation products. These inhibit platelet aggregation, have anti-thrombin activity, and impair fibrin polymerization, all of which contribute to the hemostatic failure (
Fig. 12.30 http://ebooksmedicine.net
Fig. 12.30 Pathophysiologyofdisseminatedintravascularcoagulation.Massive tissue destruction Activation of plasmin Microangiopathic hemolytic anemia Proteolysis of clotting factors Fibrin split products Inhibition of thrombin, platelet aggregation, and fibrin polymerization Endothelial injury Platelet aggregation Consumption of clotting factors and platelets Sepsis Fibrinolysis Bleeding Ischemic tissue damage Vascular occlusion Widespread microvascular thrombosis
Table 12.12 Major Disorders Associated With Disseminated Intravascular Coagulation
Carcinomasofpancreas,prostate,lung,andstomachAcutepromyelocyticleukemia
Acuteintravascularhemolysis,snakebite,gianthemangioma,shock,heatstroke,vasculitis,aorticaneurysm,liverdisease
Release of tissue factor