Etiologies

Most cases of acute DIC in the intensive care unit setting are due to sepsis, particularly involving Gram-negative organisms. One of the earliest and most severe forms described occurs with meningococcal septicemia, in which widespread bleeding and shock are associated with bilateral adrenal hemorrhage and a grave prognosis (Waterhouse-Friederichsen syndrome). DIC has since been linked with a wide variety of Gram-positive and Gram-negative infections. Viruses, particularly varicella, cytomegalovirus, the hepatitis viruses, and even HIV, occasionally cause DIC, possibly via immune-complex generation.

DIC may complicate a variety of obstetric conditions (Table...!) in which it develops against the background of the prothrombotic state of pregnancy. In amniotic fluid embolism and placental abruption, release of placental thromboplastins into the maternal circulation is believed to be important in the pathogenesis. Amniotic fluid embolism is manifest by an acute onset of respiratory failure and hypotension followed by coagulopathy and hemorrhagic shock; although rare (about 1 in 50 000 deliveries), the fatality rate is about 80 per cent. In abruptio placentae, the hemostatic disturbance is related to both the shock state and the degree of placental separation; in cases involving large amounts of concealed hemorrhage and fetal death, DIC is invariable and often severe. In contrast, DIC complicating the retained fetus syndrome is typically of a slow progressive type; bleeding is a late feature and is preceded by declining renal function.

DIC may follow various types of trauma. Specific examples include burns, heat stroke, open head wounds, and crush injuries, although hypovolemia of any cause may trigger its development. Acidosis, dehydration, and hypoxia are important contributory factors.

DIC is a recognized complication of hepatic cirrhosis, acute massive hepatic necrosis, and conditions associated with protracted (more than 5 days) intrahepatic or extrahepatic cholestasis. The pathogenesis may involve release of tissue thromboplastins and impaired hepatic clearance of fibrin degradation products and activated coagulation factors.

Other disorders, usually seen outside the intensive care setting, are also associated with DIC. Cancer, particularly involving metastatic and/or mucus-secreting tumors is an important cause; the DIC in such cases is typically of a chronic compensated type. DIC was long believed to be a common complication of acute promyelocytic leukemia; recent work suggests that bleeding is more often due to primary fibrinolysis. Worldwide, important causes of DIC include falciparum malaria and snake venoms. DIC complicating the latter often entails direct activation of specific coagulation factors and the generation of non-coagulable blood.

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