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NOTES: Heme/Onc > 250/252 - Too Much Bleeding > Flashcards

250/252 - Too Much Bleeding Flashcards

Coagulation and interited bleeding, Thrombocytopenia

1
Q

How can a patient with a factor deficiency have normal PT/PTT?

A

PT and PTT only become abnormal when coagulation factors drop below 30-40%

=> Mild deficiencies can have normal PT and PTT

Measure specific clotting factor deficiencies if clinical suspicion is high

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2
Q

Describe the amplification loop of the coagulation cascade

A

Initially, a small amount of thrombin is produced

Thrombin further activates V, VIII, XI

Results in lots of thrombin

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3
Q

What is the only thrombocytopenia that will have platelets that are too small?

A

Wiscott-Aldrich

Defect in WAS gene; responsible for stabilizing actin cytoskeleton

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4
Q

What clotting factor activates prothrombin -> thrombin?

A

Xa

  • Factor Xa and factor Va form a complex (mediated by calcium) that cleaves prothrombin (factor II) to thrombin (factor IIa).*
  • Small amounts of prothrombin are activated by factor Xa alone. The resulting thrombin activates factor V, which then builds the complex with factor Xa, activating more thrombin in the process.*
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5
Q

Deficiency of which clotting factor will result in elevated PT with normal PTT?

A

F VII

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6
Q

What are the endogenous inhibitors of Factor Va and VIIIa? (2)

A

Activated protein C

with cofactor protein S

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7
Q

Which factor deficiency is most likely to present with bleeding a few days after surgery?

A

Factor XI deficiency

Hemophilia C

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8
Q

What are the treatments for hemophilia C?

A

Fresh frozen plasma

Anti-fibrinolytic agents

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9
Q

What is the most likely diagnosis in an adult patient, on no relevant medications, who has:

  • Isolated thrombocytopenia
  • Normal blood smear
  • Increased megakaryocytes on bone marrow biopsy
A

Immune thrombocytopenia purpura: type of thrombocytopenia involving the formation of autoantibodies against platelets.

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10
Q

List 2 treatment options for immune thrombocytopenia purpura (ITP)

A

According to boards…

  • IVIG
  • Corticosteroid

In real life, usually observe unless pt is bleeding or at high risk

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11
Q

Which clotting factor is deficient in:

  • Hemophilia A:
  • Hemophilia B:
  • Hemophilia C:
A
  • Hemophilia A: FVIII
  • Hemophilia B: FIX
  • Hemophilia C: FXI
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12
Q

What procoagulant factors are inhibited by tissue factor pathway inhibitor (TFPI)? (2)

A

Factor Xa

TF/Factor VIIa

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13
Q

What endogenous substance initiates breakdown of a fibrin clot?

What are the subsequent steps?

A

tPA initiates

Activates plasminogen -> plasmin

Plasmin breaks down the fibrin clot

Results in D-dimer formation

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14
Q

List the 2 major mechanisms of platelet destruction pathologies:

A
  • Antibodies
    • HIT
    • Drug-induced thrombocytopenia
    • Infection-related / immune
  • Thrombotic microangiopathies (mechanical destruction?)
    • DIC
    • TTP
    • HUS
    • HELLP
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15
Q

What is the mechanism and outcome of:

  • Primary hemostasis:
  • Secondary hemostasis:
A
  • Primary hemostasis:
    • Vasoconstriction and platelet aggregation -> Platelet plug
  • Secondary hemostasis:
    • Coagulation cascade -> Fibrin clot
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16
Q

What is the treatment for vWF disease?

A

Desmopressin

vWF concentrate

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17
Q

What duration defines each of the following thrombocytopenias?

  • Acute:
  • Persistent:
  • Chronic:
A
  • Acute: < 3 months from dx
  • Persistent: 3-12 months since dx
  • Chronic: >12 months since dx

Each time interval indicates time that platelet count has been low

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18
Q

Which laboratory test is abnormal in a patient with severe hemophilia A?

A

PTT

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19
Q

When is immune thrombocytopenia purpura treated?

A

Significant bleeding

High risk for traumatic bleeding
(toddlers, sports, phsysical demand)

Caused by antibodies against GpIIb/IIIa

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20
Q

Describe the pathophysiology of heparin-induced thrombocytopenia (HIT)

A
  • IgG antibodies are made against the heparin-platelet factor 4 complex
  • IgG-heparin-PF4 immune complex bind to platelets
  • -> platelet activation and aggregation
  • -> consumption of platelets AND formation of thrombi (clotting)

Tx: Remove heparin, give direct thrombin inhibitor

21
Q

What are the endogenous inhibitors of thrombin? (2)

A

Antithrombin

Thrombomodulin

22
Q

What are the two most commonly mutated proteins in hereditary hemorrhagic telangiectasia?

A

Endoglin or ALK-1 gene

HHT: hereditary, systemic vasculopathy characterized by telangiectasia on the skin and mucosa, particularly in the area of the face (nose, lips, tongue)

23
Q

Which clotting factor cross-links fibrin

A

Factor XIII (Fibrin stabilizing factor)

24
Q

What is the most likely cause of prolonged PT or PTT that does NOT correct with a mixing study?

A

Inhibitor

Specific factor inhibitor or lupus anticoagulant

25
Q

What clotting factor levels define each level of hemophilia?

  • Mild:
  • Moderate:
  • Severe:
A
  • Mild: >5%
  • Moderate: 1-5%
  • Severe: <1%

Factors 30-40% of normal can still have normal PT/PTT

26
Q

Deficiency of which clotting factors (6) will result in elevated PTT with normal PT?

A

HMWK

PK

FXII

FXI

FIX

FVIII

27
Q

What is the inheritance of:

  • Hemophilia A:
  • Hemophilia B:
  • Hemophilia C:
A
  • Hemophilia A: X-linked recessive
  • Hemophilia B: X-linked recessive
  • Hemophilia C: Autosomal recessive
28
Q

Which clotting factor cleaves fibrinogen -> fibrin?

A

Thrombin (Factor II)

29
Q

Describe the bleeding associated with Hemophilia C deficiency

A

Delayed post-surgical bleeding

  • A few days after surgery*
  • FXI is important for the thrombin burst; no FXI -> no burst -> weaker clot*
30
Q

Which part of the clotting cascade is evaluated with PTT?

A

Intrinsic pathway

31
Q

Describe the negative feedback loop that regulates thrombopoietin

A

Thrombopoietin = signal to make more platelets

Thrombopoietin is constituitively expressed in the liver

Thrombopoietin is cleared when it binds to the cMPL receptor on platelets

=> More platelets = less thrombopoietin = less platelet production

32
Q

What is the cause of Aplasia vs. Myelophthisis?

What is the bone marrow doing differently?

A
  • Aplasia = bone marrow is not making platelets
    • Aplastic anemia
    • Myelodysplasia
    • Secondary bone marrow suppression
  • Myelophthisis = Bone marrow is making platelets, but they are not healthy
    • ​Cancer
    • Myelofibrosis
    • Oseoporosis
33
Q

Which coagulation factor deficiency will have normal PT and normal PTT?

A

Factor XIII deficiency

Results in a weak clot that dissolves more easily

34
Q

What is the most common congenital bleeding disorder?

A

Von Willebrand’s disease

35
Q

List 4 causes of secondary ITP

A
  • Lupus
  • Malignancy
  • HIV
  • Hepatitis C

This was a “boards alert” question from this lecure (which I think means it won’t appear on our exam) but figured it might be good to remember

36
Q

What is the difference in presentation between HUS and TTP?

A

HUS:

  • hemolytic anemia
  • thrombocytopenia
  • renal failure

TTP:

  • hemolytic anemia
  • thrombocytopenia
  • renal failure –> Renal failure is usually not as bad in TTP; rarely requires dialysis
  • fever
  • altered mental status
37
Q

List 2 anti-fibrinolytic agents

A

Aminocaproic acid

Tranexamic acid

38
Q

Deficiency of which clotting factors (4) will result in elevated PTT and PT?

A

FX

FV

Prothrombin (FII)

Fibrinogen (FI)

(Common pathway)

39
Q

What is the endogenous inhibitor of Factor XIa?

A

Protease Nexin 2

40
Q

Which thrombocytopenia is caused by antibodies against GP IIb/IIIa?

A

Immune thrombocytopenia purpura (ITP)

Glanzman thrombasthenia = hereditary mutation in GPIIb/IIIa

41
Q

What is the difference in etiology of immune thrombocytopenia purpura in children vs. adults

A
  • Children
    • Usually preceded by a viral illness
    • Self-limited
    • Bleeding is rare
  • Adults
    • Usually idiopathic
    • High relapse rate
    • Treat if platelet count <30,000 or actively bleeding
42
Q

What is the treatment for heparin-induced thrombocytopenia?

A

Discontinue ALL heparin (heparin, enoxaparin, fondaparinux)

Give direct thrombin inhibitor (Agatroban or bivalirudin)

43
Q

List 3 clotting factor deficiencies NOT associated with bleeding?

Which lab abnormality will be present?

A

Contact activation factors

  • Factor XII
  • High-molecular weight kininogen
  • Prekallikrein

Elevated PTT

Results in elevated PTT but no bleeding

44
Q

Which part of the clotting cascade is evaluated with PT?

A

Extrinsic and common

45
Q

Where is von Willebrand Factor stored? (2)

A
  • Endothelial: Weible-Palade bodies
  • Platelets: Alpha granules
46
Q

List 4 manifestations of severe hemophilia A

A
  • Spontaneous joint hemorrhage
  • Intramuscular hemorrhage
  • Intracranial hemorrhage
  • Serious bleeding after trauma or injury

Severe Hemophilia A = <1% of normal FVIII

47
Q

What platelet counts correspond with each level of thrombocytopenia?

  • Mild:
  • Moderate:
  • Severe:
A
  • Mild: 100k-149k
  • Moderate: 50k-99k
  • Severe: <50k
48
Q

List 2 functions of von Willebrand factor

A
  • Bind platelets to the endothelium
  • Binding protein for FVIII
    • vWF carries FVIII; without it, VIII is rapidly degraded
    • Mutation in vWF presents like hemophilia A

NOTES: Heme/Onc (36 decks)

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