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High Yield Pathoma > Ch. 4 - Hemostasis and Related Disorders > Flashcards

Ch. 4 - Hemostasis and Related Disorders Flashcards

1
Q

What is goal of primary hemostasis?

A

formation of weak platelet plug

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2
Q

What is the goal of secondary hemostasis?

A

stabilization of platelet plug via coagulation cascade

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3
Q

What is step 1 of primary hemostasis?

A

transient vasoconstriction of blood vessels

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4
Q

What 2 things is transient vasoconstriction mediated by?

A

1) neural stimulation

2) endothelin release from endothelial cells

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5
Q

What is step 2 of primary hemostasis?

A

platelet adhesion to surface of disrupted vessel by binding to GPIb receptor of vWF (which is bound to subendothelial collagen)

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6
Q

What is vWF derived from?

A

Weibel-Palade bodies of endothelial cells and a-granules of platelets

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7
Q

What is step 3 of primary hemostasis?

A

platelet degranulation and release of ADP and TXA1

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8
Q

What is the function of ADP from platelet degranulation?

A

released by platelet dense granules and promotes exposure of GPIIb/IIIa receptor on platelets

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9
Q

What is the function of TXA2 from platelet degranulation?

A

promotes platelet aggregation (derived from cyclooxygenase)

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10
Q

What is step 4 of primary hemostasis?

A

platelet aggregation via GPIIb/IIIa using fibrinogen to form a weak platelet plug

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11
Q

What are the common clinical signs of primary hemostasis disorders?

A
  • Sx of mucosal bleeding
  • epistaxis, hemoptysis, GI bleeding, hematuria, and menorrhagia
  • intracranial bleeding with severe thrombocytopenia
  • Sx of skin bleeding
  • petechiae, ecchymosis, purpura
  • easy burising
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12
Q

What is petechiae a sign of?

A

thrombocytopenia - quantitative disorder

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13
Q

What is a normal platelet count?

A

150-400K/uL

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14
Q

What is a normal bleeding time?

A

2-7 min

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15
Q

What is the pathogenesis of immune thrombocytopenia purpura?

A

autoimmune production of IgG against plaetlet antigens (i.e. GPIIb/IIIa)

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16
Q

What produces the antibodies in ITP and how does that lead to thrombocytopenia?

A

plasma cells in spleen - Ab-bound platelets are consumed by splenic macrophages, resulting in thrombocytopenia

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17
Q

What happens in acute ITP?

A

seen in children weeks after viral or immunization; self limited

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18
Q

What happens in chronic ITP?

A

seen in women of child bearing age; may be primary or secondary

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19
Q

What is a secondary association of ITP?

A

SLE

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20
Q

Why may pregnant women see transient ITP in their offspring?

A

anti-platelet IgG can cross the placenta

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21
Q

What are the labs of ITP?

A
  • low platelet count, <50K/ul
  • normal PT/PTT
  • increased megakaryocytes on bone marrow biopsy
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22
Q

What is the Tx of ITP?

A

corticosteroids

-children respond well; adults may relaps

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23
Q

How can platelet count be raised in symptomatic bleeding of ITP?

A

IVIG administration - short-lived

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24
Q

What is eliminated in refractory cases of ITP requiring splenectomy?

A

source of antibody and site of destruction

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25
Q

What is the basis of microangiopathic hemolytic anemia?

A

pathologic formation of platelet microthrombi in small vessels that shears RBCs causing schistocytes

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26
Q

What is consumed in the formation of microthrombi?

A

platelets

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27
Q

What kind of cell looks like a dented helmet?

A

schistocyte - sheared RBC

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28
Q

What is the defect in TTP?

A

deficiency of ADAMTS13 which cleaves vWF multimers into smaller monomers for degradation –> large, uncleaveed multimers lead to abnormal platelet adhesion

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29
Q

Who is the classic pt of TTP?

A

adult female who produces Ab against ADMTS13

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30
Q

What is HUS due to?

A

endothelial damage by drugs or infection resulting in platelet microthrombi

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31
Q

What bug leads to HUS?

A

E. coli O157:H7 with verotoxin which damages endothelial cells

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32
Q

Who gets E. coli O157:H7?

A

children eating undercooked beef

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33
Q

What are the clinical findings of TTP and HUS?

A
  • skin and mucosal bleeding
  • microangiopathic hemolytic anemia
  • fever
  • renal insufficiency
  • CNS abnormality
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34
Q

What are the predominant problems in HUS vs. TTP?

A

HUS: renal insufficiency
TTP: CNS abnormality

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35
Q

What are the lab findings in HUS and TTP?

A
  • thrombocytopenia with increased bleeding time
  • normal PT/PTT
  • anemia with schistocytes
  • increased megakaryocytes on bone marrow biopsy
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36
Q

What are the Tx of HUS and TTP

A

plasmapheresis and corticosteroids, particularly in TTP

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37
Q

What is the defect in Bernard-Soulier syndrome?

A

genetic GP1b deficiency –> platelet adhesion is impaired b/c can’t bind vWF
-blood smear shows mild thrombocytopenia with enlarged platelets

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38
Q

What is a good way to remember enlarged platelets in Bernard-Soulier?

A

Bernard-Soulier –> “Big Suckers”

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39
Q

What is the defect in Glanzmann hrombasthenia?

A

genetic defect in GIIb/IIIa which impairs platelet aggregation

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40
Q

How does ASA impair platelet aggregation?

A

it irreversibly inactivates cyclooxygenase which prevents formation of TXA2

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41
Q

How does uremia disrupt platelet function?

A

impairs adhesion and aggregation

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42
Q

What is the goal of secondary hemostasis?

A

stabilize the weak plug via development of crosslinked fibrin by thrombin

43
Q

What does activation of coagulation cascade require?

A
  1. exposure to activating substance
  2. phospholipid surface from platelet surface
  3. Ca2+ from dense core granules of platelets
44
Q

What are clinical features of secondary hemostasis?

A
  • deep tissue bleeding into muscle and joints

- rebleeding after surgical procedures

45
Q

How is the extrinsic pathway activated?

A

tissue thromboplastin activates factor VII

46
Q

How is the intrinsic pathway activated?

A

subendothelial collagen activates factor XII

47
Q

What factors are in the common pathway?

A

X, V, II, and I

48
Q

What measures intrinsic pathway?

A

PTT (activated by TT)

49
Q

What measures extrinsic pathway?

A

PT (activated by SEC)

50
Q

What is Hemophilia A?

A

genetic FVIII deficiency, XLR (or new mutation)

51
Q

What are the lab findings of Hemphilia A?

A

-increased PTT, normal PT
-decreased FVIII
-normal platelet count and bleeding count
Tx: recombinant FVIII

52
Q

What is coagulation factor inhibitor?

A

acquired Ab against a coagulation factor resulting in impaired factor function; anti-FVIII is most common

53
Q

How do you distinguish coagulation factor inhibitor from hemophilia A?

A
  • PTT does not correct upon mixing normal plasma in pt’s pkasma (mixing study) d/t inhibitor (Ab binds to normal plasma)
  • PTT does correct in hemophilia A
54
Q

What is vWF disease?

A

genetic deficiency in vWF (most commonly AD) - results in problem with platelet adhesion

55
Q

How do pts with vWF disease present?

A

mild mucosal and skin bleeding

56
Q

What are the lab findings of vWF disease?

A
  • increased bleeding time
  • increased PTT (vWF needed for FVIII), normal PT
  • abnormal ristocetin test* (no aggregation of platelets)
57
Q

What is the Tx of vWF deficiency?

A

desmopression: increases vWF release from Weibel-Palade bodies of endothelial cells

58
Q

What happens in Vitamin K deficiency?

A

disrupts function of multiple coagulation factors: II, VII, IX, X, and protein C & S (lack of gamma carboxylation and activation)

59
Q

What activates Vitamin K?

A

epoxide reductase in liver

60
Q

Who does Vitamin K deficiency occur in?

A

newborns, long-term antibiotic therapy, and malabsorption

61
Q

How does liver failure lead to coagulation deficiency and you measure effect of liver failure on coagulation?

A
  • decreased production of coag factors and decreased activation of vitamin K by epoxide reductase
  • liver failure monitored using PT
62
Q

how does large volume transfusion affect secondary hemostasis?

A

dilutes coagulation factors and results in a relative deficiency

63
Q

What happens in heparin-induced thrombocytopenia?

A

heparin forms a complex with platelet factor 4 and makes IgG autoAbs which consume platelets made by the spleen and can lead to thrombosis

64
Q

What are the 2 problems that arise with DIC?

A

1) widespread microthrombi that result in ischemia and infarction
2) consumption of platelets and coag factors that result in bleeding, esp IV sites and mucosal surfaces

65
Q

What are 5 risk factors for DIC?

A

1) obstetric complication
2) sepsis
3) adenocarcinoma
4) acute promyelocytic leukemia
5) rattlesnake bite

66
Q

What are the lab findings of DIC?

A
  • decreased platelet count
  • increased PT/PTT
  • decreased fibrinogen
  • microangiopathic hemolytic anemia (schistocytes)
  • elevated fibrin split prpoducts (D-dimer)*
67
Q

What is D-dimer?

A

the product of fibrin split products (best screening test for DIC)

68
Q

What is the Tx of DIC?

A

blood transfusion and cryoprecipitate

69
Q

What converts plasminogen –> plasmin

A

tPa

70
Q

What does plasmin do?

A

1) cleaves cross-linked fibrin and serum fibrinogen
2) destroys coag factors
3) blocks platelet aggregation

71
Q

What inactivates plasmin?

A

a2-antiplasmin

72
Q

What are disorders of fibrinolysis d/t?

A

plasmin overactivity

73
Q

What are two examples of plasmin overactivity?

A

1) radical prostatectomy - release of urokinase activates plasmin
2) liver cirrhosis - reduced production of a2-antiplasmin

74
Q

How do pts with plasmin overactivity present?

A

increased bleeding that resembles DIC

75
Q

What are the lab findings of fibrinolysis disorders?

A
  • increased PT/PTT
  • increased bleeding time with NORMAL platelet count
  • increased fibrinogen split products WITHOUT D-dimer (no fibrin clots, just overactivity of plasmin)
76
Q

How do you treat fibrinolysis disorders?

A

aminocaproic acid - blocks activation of plasminogen

77
Q

What are 3 causes of endothelial damage?

A

1) atherosclerosis
2) vasculitis
3) elevated levels of homocystine

78
Q

What is a thrombosis characterized by?

A

1) lines of Zahn (alternating lines of RBCs and fibrin)
2) attachment to vessel wall
* both features distinguish thrombus from postmortem clot

79
Q

How do thrombi form in aneurysms?

A

balloon-like dilatation of blood vessel can lead to turbulence of blood flow

80
Q

What do endothelial cells produce to block platelet aggregation?

A

PGI2, NO, and tPA

81
Q

What do endothelial cells produce to block anticoagulation?

A

heparin-like molecule which binds to anti-thrombin III

82
Q

What are the functions of tPA produced by endothelial cells?

A

1) cleaves fibrin and serum fibrinogen
2) destorys coagulation factors
3) blocks platelet aggregation

83
Q

What does thrombomodulin produced by endothelial cells do?

A

redirects thrombin to activate protein C, which inactivates factors V and VIII

84
Q

How is methionine formed?

A

THF-M –> Vit B-M –> homocysteine –> methionine

85
Q

How does Vit B/folate deficiency lead to endothelial damage?

A

elevated levels of homocysteine damage endothelium

86
Q

What are the Sx of cystathionine beta synthase deficiency?

A

vessel thrombosis, MR, lens dislocation and long slender fingers

87
Q

What is defective in Protein C or S deficiency?

A

hypercoagulable state: FV and FVIII overactive

88
Q

What is the pathology of warfarin skin necrosis in presence of Protein C/S deficiency?

A

factors 2, 7, 9, 10, C, and S are inactivated, but C and S are inactivated first leading to hypercoagulable skin leading to warfarin skin necrosis

89
Q

What is Factor V Leiden?

A

mutated form of FV that lacks cleavage deactivation by proteins C and S –> hypercoagulable state

90
Q

What happens to PT in pts with ATIII deficiency who are given heparin?

A

PTT does not rise with standard heparin dosing

91
Q

How are oral contraceptives associated with hypercoagulable state?

A

estrogen induces increased production of coagulation factors

92
Q

What is characteristic of atherosclerotic embolus?

A

cholesterol clefts

93
Q

What is the pathology of fat embolus?

A

associated with bone fractures and soft tissue trauma and presents with dyspnea and petechiae on skin overlying chest

94
Q

Where is gas embolus seen?

A

decompression sckness - presents with joint and muscle pain (bends) and respiratory Sx (chokes)

95
Q

What is Caisson disease?

A

chronic gas emboli - multifocal ischemic necrosis of bone

96
Q

How does amniotic fluid embolus present?

A

shortness of breath, neuro Sx, and DIC

*characterized by squamous cells and keratin debris

97
Q

How does amniotic fluid embolus lead to DIC?

A

amniotic fluid contains tissue thromboplastin

98
Q

Why is PE most often clinically silent?

A

1) lung has dual blood supply

2) embolus is usually small and self-resolves

99
Q

When does pulmonary infarction occur d/t PE?

A

obstruction of large- or medium-sized artery with pre-existing cardiopulmonary compromise
-only 10% of PE cause infarction

100
Q

What tests is useful for PE

A

spiral CT - vascular filling defect in lung

  • LE Doppler US to detect DVT
  • elevated infarct
101
Q

What does PE reveal on gross exam?

A

hemorrhagic wedge-shaped infarct

102
Q

What is a saddle embolus?

A

embolus that blocks both L and R plumonary artery or with significant occlusion of a large pulmonary artery
-death is d/t electromechanical dissociation

103
Q

What gives rise to systemic embolism?

A

thromboembolus that most commonly arises in the L heart and occludes flow to organs, most commonly LE

High Yield Pathoma (4 decks)

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