DIC | Anatomy2Medicine
Disseminated intravascular coagulat

DIC

    • Disseminated intravascular coagulation (DIC)
    • an acute, subacute, or chronic thrombohemorrhagic disorder characterized by the excessive activation of coagulation, which leads to the formation of thrombi in the microvasculature of the body.
    • there is consumption of platelets, fibrin, and coagulation factors
    • there is secondarily, activation of fibrinolysis

 

  • Etiology and Pathogenesis.

 

      • DIC is not a primary disease.

 

  • How is clotting is prevented in normal tissues

 

      • Once clotting is initiated, it is critically important that it be limited to the site of injury.
      • as thrombin is swept away in the bloodstream and encounters normal vessels, it is converted to an anticoagulant through binding to thrombomodulin
      • thrombomodulin (MCQ)
        • it is a protein found on the surface of endothelial cells(MCQ)
        • thrombin-thrombomodulin complex activates protein C
        • protein C is an important inhibitor of two procoagulants, factor V and factor VIII(MCQ)
        • Other activated coagulation factors are removed from the circulation by the liver(MCQ)
      • the blood also contains several potent fibrinolytic factors, such as plasmin. (MCQ)

 

  • Two major mechanisms trigger DIC

 

      • release of tissue factor or thromboplastic substances into the circulation
      • widespread injury to the endothelial cells. (MCQ)
    • Thromboplastic substances – ┬ásources
      • placenta in obstetric complications
      • cytoplasmic granules of acute promyelocytic leukemia cells

 

  • Mucus released from certain adenocarcinomas can directly activate factor X, independent of factor VII. (MCQ)

 

    • Widespread endothelial injury may also be produced by
      • deposition of antigen-antibody complexes (e.g., SLE)
      • temperature extremes (e.g., heat stroke, burns
      • microorganisms (e.g., meningococci, rickettsiae).
    • Even subtle endothelial injury can unleash procoagulant activity by enhancing membrane expression of tissue factor.
    • Among cancers, acute promyelocytic leukemia and adenocarcinomas of the lung, pancreas, colon, and stomach are most frequently associated with DIC. (MCQ)
    • Two effects of DIC
    • widespread deposition of fibrin within the microcirculation

 

  • leads to ischemia of the more severely affected organs

 

      • microangiopathic hemolytic anemia(MCQ)
        • results from the fragmentation of red cells as they squeeze through the narrowed microvasculature. (MCQ)
    • a hemorrhagic diathesis.
      • consumption of platelets and clotting factors

 

  • activation of plasminogen leads to plasmin formation

 

      • Plasmin not only cleaves fibrin, but it also digests factors V and VIII, (MCQ)

 

  • fibrin degradation products inhibit (MCQ)

 

        • platelet aggregation

 

  • fibrin polymerization

 

        • thrombin.
    • Thrombogenic tendency in DIC
      • Thrombi are most often found in the brain, heart, lungs, kidneys, adrenals, spleen, and liver, in decreasing order of frequency,
      • In meningococcemia, fibrin thrombi within the microcirculation of the adrenal cortex are the probable basis for the massive adrenal hemorrhages seen in Waterhouse-Friderichsen syndrome
      • Sheehan postpartum pituitary necrosis is a form of DIC complicating labor and deliver(MCQ)

 

  • In toxemia of pregnancy the placenta exhibits widespread microthrombi, (MCQ)
  • An unusual form of DIC occurs in association with giant hemangiomas(MCQ)

 

  • In general, acute DIC, associated with obstetric complications or major trauma, for example, is dominated by a bleeding diathesis, whereas chronic DIC, such as occurs in cancer patients, tends to present with thrombotic complications. (MCQ)