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Block 7 Week 4 Colt > Primary Hemostasis > Flashcards

Primary Hemostasis Flashcards

1
Q

Primary hemostasis forms a (blank) which is stabilized by secondary hemostasis

A

weak platelet plug

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2
Q

What are the four steps of primary hemostasis?

A
  1. transient vasoconstriction
  2. platelet adhesion to the surface of the disrupted vessel
  3. Platelet degranulation
  4. Platelet aggregation
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3
Q

What two things mediated the immediate vasoconstriction of a damaged blood vessel?

A

neural stimulation and endothelin

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4
Q

What binds to exposed subendothelial collagen?

A

vWF

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5
Q

Platelets bind to vWF using the (blank) receptor

A

GpIb

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6
Q

vWF is derived from the (blank) bodies of endothelial cells and the (blanks) of platelets

A

Weibel-Palade bodies of endo

a-granules of platelets

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7
Q

PLT adhesion induces a shape change which causes degranulation releasing what three things?

A
  1. ADP
  2. TXA2
  3. GPIIb/IIIa
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8
Q

What is the function of GPIIb/IIIa?

A

promotes PLT aggregation

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9
Q

What is the function of ADP?

A

promotes expression of GpIIb/IIIa

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10
Q

What is the function of TXA2?

A

promotes PLT aggregation

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11
Q

PLTs aggregate via GPIIa/IIIa using (blank) as a linking molecule, forming a PLT plug

A

fibrinogen from the plasma

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12
Q

T/F: the coag cascade is not necessary to stabilize the PLT plug

A

false

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13
Q

disorders of primary hemostasis are due to disorders of what cell type?

A

PLT

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14
Q

what is the most common feature in a primary hemostatic disorder?

A

epistaxis

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15
Q

What is a normal bleeding time?

A

2-7 minutes

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16
Q

Is skin bleeding like petechia associated with thrombocytopenia or a qualitative PLT disorder?

A

thrombocytopenia

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17
Q

What is the most common cause of thrombocytopenia in adults and kids?

A

immune thrombocytopenic purpura (ITP)

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18
Q

What Ab class mediates ITP?

A

IgG

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19
Q

What cells produce the Ig in ITP?

A

plasma cells of the spleen

20
Q

What does the IgG target in ITP?

A

GPIIB/IIIa on PLTs

21
Q

What cells consume the Ab-bound PLTs in ITP?

A

macrophages of the spleen

22
Q

why is splenectomy effective in ITP?

A

removes source of Ab and source of destruction of PLTs

23
Q

T/F: acute ITP is life threatening emergency

A

false; self limited to children after viral infx; resolves within weeks

24
Q

What demographic normally gets chronic ITP?

A

women of childbearing age

25
Q

What disease state is associated with ITP?

A

SLE

26
Q

T/F: newborns will have shortlived thrombocytopenia if the mother has ITP

A

true; IgG can cross the placenta; will resolve once the newborn destroys all the maternal IgG

27
Q

Describe the following labs for ITP:
PLT
PT/PTT
bone marrow biopsy

A

low PLT
nomral PT/PTT: coag cascade not involved!!
increased megakaryocytes on bone marrow biopsy

28
Q

What is the initial Tx for ITP? Is it effective?

A

corticosteroids; adults often relapse

29
Q

How is IVIG used in ITP?

A

used to temp. increases PLTs; just buys you time

30
Q

Why do you get low PLTs in MAHA?

A

PLTs consumed in the formation of small clots

31
Q

What type of RBC abn. will you see on a smear of someone with MAHA? Why?

A

Schistocytes; RBCs are sheared when going past microthrombi

32
Q

MAHA is seen in what two qualitative PLT disorders?

A

TTP and HUS

33
Q

What is the cause of TTP? Explain the mechanism?

A

Decreased ADAMTS13 enzyme which cleaves vWF multimers into single units

34
Q

Is decreased ADAMTS13 levels a congenital or acquired def?

A

acquired strangely enough!; seen in adult females

35
Q

(TTP/HUS) is caused by drugs or infection

A

HUS

36
Q

(TTP/HUS) is caused by E. coli O157:H7 dysentery from undercooked beef

A

HUS

37
Q

What E. coli toxin damages endothelial cells in the kidney and brain in HUS?

A

E. coli verotoxin

38
Q

What are the common clinical findings in TTP/HUS?

A
  1. skin and mucosal bleeding
  2. MAHA
  3. fever
39
Q

What clinical finding lets you know you have HUS and TTP?

A

renal insufficiency

40
Q

What clinical finding lets you know you have TTP and not HUS?

A

CNS abnormalities

41
Q 
What are the lab values for TTP and HUS:
PLT
bleeding time
PT/PTT
Hgb
Peripheral smear
Bone marrow biopsy
A

low PLT
increased bleeding time
nomral PT/PTT; coag cascade not involved!!!
low Hgb aka anemia
schistocytes on smear
increased megakaryocytes on bone marrow biopsy

42
Q

Bernard-Soulier syndrome is due to a genetic (blank) deficiency causing impaIred platelet ADHESION

A

GPIb

43
Q

What finding do you see on smear in Bernard-Soulier syndrome?

A

enlarged PLTs; Big-Suckers

44
Q

Glanzmann thrombasthenia is a genetic (blank) deficiency causing impaired PLT AGGREGATION

A

GPIIb/IIIa

45
Q

Aspiriin irreversibly inhibits COX leading to a lack of (blank) and impairs aggregation

A

TXA2

46
Q

T/F: both adhesion and aggregation are impaired in uremia

A

true

Block 7 Week 4 Colt (9 decks)

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