Disseminated Intravascular Coagulation (DIC)

Pathophysiology

1) abnormal clotting process that can have as the major symptom(s) bleeding, thrombosis or both 2) a specific triggering process is required to start the cascade by acting on factor 12 (Hageman’s factor) 3) phases of condition are thrombotic, procoagulant consumption, and fibrinolysis 4) this cycle of fibrin formation and lysis results in eventual depletion of coagulation factors and platelets with resulting hemorrhage 5) also contributing to hemorrhage are the hemorrhagic properties of the accumulated fibrin degradation products

Signs and Symptoms

1) varies in severity from subclinical to life-threatening 2) purpura 3) hemorrhage from areas of surgery or venipuncture 4) hemorrhage from mucosal surfaces 5) deposition of microthrombi and vasospasm, causing peripheral acrocyanosis and gangrene in digits, nose, genitalia

Characteristic Test Findings

Laboratory – 1) thrombocytopenia 2) increased PT and PTT 3) increased thrombin time 4) decreased fibrinogen 5) increased fibrin-degradation products (fibrin splits) 6) protein C deficiency (variable) 7) presence of schistocytes and fragmented RBCs (owing to hemolysis)

Histology/Gross Pathology

deposition of small thrombi and emboli throughout microvasculature

Associated Conditions

1) obstetrical complications – placental abruption, amniotic embolism, retained fetus 2) malignancy – mucinous adenocarcinoma, acute leukemias 3) trauma – burns, head injury, frost bite 4) infections – Rocky Mountain spotted fever, Staphylococcus, Streptococcus, gram-negative bacillus, varicella, rubella, malaria, acute histoplasmosis, Vibrio, clostridial 5) other – glomerulonephritis, hemolytic uremic syndrome, sepsis, fat embolism

Biochemistry

trigger in gram-negative infection is release of endotoxin that activates tissue factor intravascularly (also on monocytes)

Treatment

1) treat underlying cause 2) if main manifestation is thrombosis or peripheral cyanosis, heparin infusion is used 3) if main manifestation is bleeding, fresh frozen plasma and platelets are used; if these products do not stop bleeding, use of heparin infusion should be considered (seems paradoxical but may be effective as it blocks cascade at the antithrombin 3 level) 4) in bleeding, use of factor 7 can be considered

Tips for USMLE

1) the major symptom can be either thrombosis or hemorrhage 2) the best lab value to predict bleeding is a decreased fibrinogen level 3) think DIC in the following situation: a 23 year-old woman with toxic shock syndrome from tampon use, bleeding from her nose and around the endotracheal tube, petechiae on her chest, and increased PT, platelets of 38,000 and a decreased fibrinogen level