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COAGULATION OVERVIEW

DAMAGE TO VESSEL ENDOTHELIUM ACTIVATES COAGULATION

  • Platelets: form the primary platelet plug (primary hemostasis) and help regulate coagulation.

    • Platelet activation: initiated by the presence of tissue factor (TF).

      • Platelets adhere to the activated endothelium, aggregate, and provide a surface for clot formation.

  • Coagulation cascade: ends with fibrin strand formation, which produces a reinforced cross-linked platelet clot (secondary hemostasis).

    • Intrinsic pathway: Activation of factor XII is the first step in the intrinsic pathway.

    • Extrinsic pathway: Activation of factor VII, along with presence of TF, is the first step in the extrinsic pathway.

    • Common pathway: Activation of factor X then leads to activation of factor II (prothrombin) to factor IIa (thrombin) and finally fibrin formation from fibrinogen. This results in the formation of a cross-linked fibrin clot.

THE MANAGEMENT OF PATIENTS WITH SUSPECTED COAGULATION DISORDERS

DETAILED PATIENT HISTORY

  • History of prolonged or excessive bleeding

  • History of recurrent or severe thrombosis

    • Deep venous thrombosis (DVT)

    • Pulmonary embolus (PE)

    • Stroke

    • Myocardial infarction (MI)

  • History of severe bruising/hematoma formation

  • History of hemarthrosis

  • History of spontaneous mucous membrane bleeding

  • History of prolonged bleeding after surgeries

  • History of heavy menses

  • Medication history

  • Family history of hypercoagulable conditions

PHYSICAL EXAMINATION

  • Location of the process: diffuse vs. localized

  • Signs of thrombosis: arterial vs. venous

  • Depth: superficial (mucocutaneous) vs. deep (intra-articular)

  • Presence of splenomegaly: splenic sequestration vs. underlying liver disease vs. marrow infiltration

  • Presence of liver disease: varices vs. ascites

LABORATORY TESTS

  • Platelet count

  • Prothrombin time (PT)

  • Activated partial thromboplastin time (aPTT)

  • Thrombin time (TT)

  • Fibrinogen level

  • Fibrin degradation products (FDPs)

  • D-dimer

  • Platelet and erythrocyte morphology

CONDITIONS ASSOCIATED WITH SERIOUS BLEEDING

DISSEMINATED INTRAVASCULAR COAGULATION (DIC)

  • Definition: Imbalance between coagulation and fibrinolysis (either may dominate)

    • Abnormal activation of coagulation (due to TF release)

    • Excessive thrombin generation

    • Excessive fibrin thrombi

    • Eventual consumption of clotting factors and platelets (leads to bleeding)

  • Laboratory findings:

    • Prolonged PT, aPTT, TT

    • Decreased fibrinogen and platelets

    • Decreased factors V, VIII, and II (later)

    • Positive D-dimer

  • Underlying conditions associated with DIC:

    • Sepsis

    • Multiple organ dysfunction syndrome (MODS)

    • Acute respiratory distress syndrome (ARDS)

    • Liver disease

    • Shock

    • Multiple trauma

    • Penetrating brain injury

    • Necrotizing pneumonitis

    • Tissue necrosis/crush injury

    • Intravascular hemolysis

    • Thermal injury

    • Freshwater drowning

    • Fat embolism syndrome

  • Treatment: Treat underlying condition

    • Supportive therapy with blood products to stop bleeding:

      • Packed red blood cells (pRBCs)

        • Dose: 10 to 15 mL/kg

        • Pediatric blood volume is approximately 80 mL/kg

      • Cryoprecipitate: higher fibrinogen content than fresh frozen plasma (FFP) or whole blood; aim to increase fibrinogen level ≥100 mg/dL

        • 1 bag of cryoprecipitate per 10 kg body weight, every 8 to 12 hours

      • FFP:

        • Dose: 10 to 15 mL/kg

      • Platelets: maintain platelet counts up to 40,000 to 80,000/mcL of blood

    • Recombinant activated factor VII: indicated during trauma or surgical cases and during severe life-threatening hemorrhage that is ...

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