Hemostasis (Ch. 22)-- Definition First Flashcards

Exam 2

1
Q

Actin & Myosin contract → Fibrin strands pulled toward platelet plug → Clot retraction → Plasma (liquid) squeezed out of clot → Clot shrinks

A

Fourth Step of Hemostasis

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2
Q
  • Autosomal dominant coagulation disorder
    • Deficiency or defect in vWf
  • Mild-moderate bleeding

Treatment– DDAVP (Desmopressin Acetate) an analog of ADH/Vasopressin

A

von Willebrand Disease

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3
Q
  • Platelet count out of range
  • Abnormal platelet function
  • Coagulation factor dysfunction
  • Loss of blood vessel integrity
A

Causes of Blood Disorders

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4
Q

Activation, adhesion & aggregation of platelets → Platelet plug

Damaged vessel → Activation of platelets

Endothelial cells → vWf → Binds platelet receptors (GPIIb/IIa) to vessel wall → Adhesion

Platelets release mediators (ADP & TXA2) → Aggregation

A

Second Step of Hemostasis

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5
Q
  • X-linked recessive coagulation disorder
    • Factor VIII deficiency
      • Works w/ vWf to promote adhesion
  • S/S
    • Mild
      • Bleeding w/ trauma/injury
    • Severe
      • Spontaneous, uncontrolled bleeding

Treatment– Factor VIII replacement therapy

A

Hemophilia A

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6
Q
  • 3 Stages
    • Vascular constriction
      • Vessel spasm → Blood flow
    • Platelet Plug (unstable)
      • Platelets play a major role
    • Blood coagulation (stable)
      • Clotting factors (CF) play a major role
  • End result
    • Fibrin (CF Ia)
      • Rope-like substance wraps around platelet plugs
      • Structural basis of clot
    • Blood becomes gel-like
      • Traps RBCs in clot
    • Clot & fibrous tissue grow together
      • Seal hole in vessel wall
A

Mechanisms of Hemostasis

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7
Q
  • Factor I to XII
    • Synthesized in liver (mostly)
    • Factor X
      • Beginning of final common pathway
    • Factor VIII
      • Not present in hemophilia
    • Factor I (Fibrinogen)
    • Factor Ia (Fibrin)
    • Factor II (Prothrombin)
    • Factor IIa (Thrombin)
    • Factor IV (Calcium)
  • Vitamin K
    • Required to make CF II, VII, IX, & X
A

Plasma Clotting Factors

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8
Q

Thrombocytopenia (platelets < 150,000/uL) → Bleeding disorder

d/t– Drug-induced, Malignancies, Immune response, Pooling of platelets in the spleen (sequestration)

Manifestation– Petechiae (platelet count < 20,000/uL in small vessels)

A

Low Platelet Count

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9
Q

Requires Ca2+

  • Intrinsic pathway
    • Inside vessel wall
      • Ex: Atherosclerosis
    • Slow
      • 1-6 min.
    • Begins in circulation
    • Factor XII activated
  • Extrinsic Pathway
    • Outside wall of the vessel
      • Ex: Gunshot wound
    • Faster
      • 15 sec.
    • Factor III activated
  • Final Common Pathway
    • Both pathways converge @ Factor X
      • Factor II → IIa (Prothrombin → Thrombin)
      • Factor I to Ia (Fibrinogen → Fibrin)
A

Clotting Cascade

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10
Q

Impaired platelet function → Bleeding disorder

d/t– ASA/NSAID use (ASA irreversibly ⇣ TXA2 activity), Adhesion disorder (von Willebrand disease)

A

Thrombocytopathia

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11
Q

Clotting Cascade:

Factor XII activated → Intrinsic pathway (slow, begins in circulation)

Factor III activated → Extrinsic pathway (fast, exposed tissue)

Factor X activated → Final common pathway → Fibrinogen (H2O soluble) → Fibrin (H2O insoluble)

A

Third Step of Hemostasis

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12
Q

Endothelial cells → tPA → Plasminogen → Plasmin (active) → Digestion of fibrin strands → Clot dissolution (Fibrinolysis)

A

Fifth Step of Hemostasis

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13
Q

Clotting/Stoppage of Blood Flow

Red blood cells trapped in fibrin meshwork (semisolid clot)

Clot=Thrombus

  • Normal
    • Blood vessel seals to stop bleeding
  • Abnormal
    • Thrombosis
      • Inappropriate formation of blood clots
    • Hemorrhage
      • Failure to form a blood clot in the presence of bleeding
A

Hemostasis

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14
Q
  • Bleeding
  • Petechiae
  • Oozing from puncture sites
  • Severe hemorrhage
  • Hypoxia & organ damage
    • Microemboli obstruct blood vessels
      • Renal, circulatory, or respiratory failure
        • Convulsions
        • Coma

Treatment– Manage primary disease, Replace clotting components (Factor VIII, FFP (fresh-frozen plasma), platelets, cryoprecipitate), Heparin

A

Clinical Manifestations of Disseminated Intravascular Coagulation (DIC)

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15
Q

Major role in platelet adhesion & blood clotting

  • von Willebrand Factor (vWf) Synthesis
    • Required for blood clotting
    • Cell wall integrity disrupted → vWf → Aggregation
  • Promote blood flow
    • Block platelet adhesion
    • Inhibit coagulation
    • Clot lysis
A

Endothelial Cells

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16
Q
  • PT/INR
    • Prothrombin time
      • Time (sec.) it takes for blood to clot
      • Extrinsic pathway
  • PTT
    • Partial prothrombin time
      • Time (sec.) it takes for blood to clot
      • Intrinsic pathway
  • ⇡ PT/PTT/INR
    • Clotting too slow
    • ⇡ Risk of hemorrhage
  • ⇣ PT/PTT/INR
    • Clotting too fast
    • ⇡ Risk of clotting
A

Blood Coagulation Clinical Assessment (“Coags”)

17
Q
  • Anuclear fragment of megakaryocyte
  • Originate from myeloid stem cells
    • Life span: 8-12 days
    • Normal levels: 150,000-400,000 cells/uL
  • Thrombopoietin
    • Hormone that stimulates thrombocyte proliferation
      • Released from liver & kidneys
  • Function
    • Aggregate → Blood coagulation & Vessel repair
  • Components
    • Glycoprotein Ilb/Ila (GPIIb/IIa)
    • ADP
    • Serotonin
    • Thromboxane (TXA2)
    • Actin/Myosin II
    • Alpha & Delta Granules
      • Secrete mediators
A

Platelets (Thrombocytes)

18
Q

INJURYVasoconstriction/Vessel Spasm → ⇣ Blood flow from rupture

Nerve reflexes & Humoral factors → Short vessel spasm

Platelets → TXA2 → ⇡ Aggregation & Vasoconstriction

A

First Step of Hemostasis

19
Q

Widespread coagulation and bleeding due to underlying disorder

d/t– Obstetric complication, Malignant neoplasms, Systemic infections (Sepsis), Severe trauma, Surgery, Burns (extrinsic pathway), Endothelial or tissue injury (intrinsic pathway)…

  • MASSIVE activation of clotting pathway
    • Excessive thrombin generation
      • Fibrinogen converted to fibrin via thrombin
      • Fibrin deposited in capillaries
      • Systemic microvascular clots
  • Vicious cycle (steps 3-5 repeat)
    • Clotting, dissolution (bleeding), clotting, dissolution (bleeding)…
  • Uncontrolled, excessive bleeding
    • All clotting factors have been used up
A

Disseminated Intravascular Coagulation (DIC)

20
Q
  • Endogenous anticoagulants
    • Released simultaneously w/ blood clot formation
      • Inactivate clotting factors
        • Antithrombin III
        • Proteins C & S
      • Plasminogen (proenzyme) → Plasmin (active)
        • Converted by tissue plasminogen activator (tPA)– AKA “clot buster”
        • Plasmin digests fibrin strands & degrades clot
A

Fibrinolysis (Clot Dissolution)