Chapter 55: Coagulation Disorders

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 ...