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I3 Exam 1 > Platelets - Siegel > Flashcards

Platelets - Siegel Flashcards

1
Q

What leads to platelet release from the megakaryocyte

A

fragmentation of megakaryocyte cytoplasm

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2
Q

Do platelets have a DNA or nucleus?

A

NO

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3
Q

What sorts of proteins are found in platelets?

A

structural, granule, glycoproteins, enzymes

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4
Q

How do platelets join together?

A

form fibrillar bridges between platelet membranes

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5
Q

What sort of coat do platelets have?

A

thick proteoglycan coat

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6
Q

What are the dense granules in the platelet?

A

the energy source

- store ATP, ADP, Ca, serotonin, Mg

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7
Q

What do the alpha granules of platelets contain

A

vWF, factor V, VWF

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8
Q

What proteins serve to keep the vessel walls dilated? (4)

A

prostacycline, nitric acid, ADPase, plaminogen activator

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9
Q

what do endothelial cells secrete with vessel wall injury?

A

procoagulants

  • selectins
  • integrins
  • vWF
  • promote platelet adhesion and vasoconstriction
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10
Q

What are subendothelial substances that are released with vessel wall injury

A

collagen, glycoprotein IIb/IIIa on platelet surface, thrombospondin, fibronectin, tissue factor

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11
Q

What are strong platelet agonists

A

thrombin and collagen

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12
Q

What are weak agonists for platelets

A

ADP and epinephrine

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13
Q

What does an elevated bleeding time mean

A

platelets aren’t function properly or thrombocytopenia

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14
Q

Mucosal bleeding

A

platelet defects

  • easy bruising
  • heavy menstrual periods
  • abnormal period times
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15
Q

What does von Willebrands disease affect

A

platelet function and coagulopathy

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16
Q

What are causes of hypoproliferation in thrombocytopenia

A

radiation, drugs, chemicals, infections, bone marrow dysfunction

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17
Q

What are causes of increased desctruction in thrombocytopenia

A

drug induced, DIC

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18
Q

What is TPO

A

mediator of platelet production, produced in liver

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19
Q

What is the effect of TPO on megakaryocytes

A

more platelet production due to increased maturation

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20
Q

What is the effect of TPO on platelets circulating

A

platelets just absorb the TPO and they are degraded

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21
Q

What are drugs that lead to a decreased production of platelets

A

alcohol, thiazide diuretics, cimetidine, chemotherapy

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22
Q

What are three mechanisms that lead to a decreased survival of platelets

A

autosensitization of platelets

  • hapten penicillin type
  • immune complex deposition
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23
Q

Heparin induced thrombocytopenia

A

UFG can lead to platelets dropping to very low levels

  • can lead to bleeding and thrombotic complications - low platelets but they’re bound together
  • need direct thrombin inhibitors
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24
Q

Immune thrombocytopenia purpura

A
  • low platelet count
  • menorrhagia
  • cutaneous bleeding
  • intracranial hemmorhage
  • no viral infection, no drugs, no congenital
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25
Q

What causes ITP

A

autoantibodies to platelet membrane antigens

26
Q

What is the biggest risk of ITP

A

intracranial hemmorhage

27
Q

What is the pathophysiology of ITP

A

rapid destruction of the spleen and liver

  • suppression of TPO
  • platelets are barely lasting
28
Q

What are the autoantibodies targeting in ITP

A

GP IIb/IIIa and GP Ib/IX

29
Q

What age group is acute ITP found in?

A

2-6 yo, usually after a viral infection

30
Q

Thrombocytopenic purpura

A

thrombocytopenia, CNS symptoms, renal failure

31
Q

What is the mechanism of action for thrombocytopenic purpura

A

antibody blocks the function of VWF cleaving

- no cleaving = increased platelet adhesion without activating coagulation cascade

32
Q

What is therapy for TTP

A

removal of antibody and clearance of multimers

  • plasma exchange
  • steroids
33
Q

What is the lifespan of a platelet

A

8 days

34
Q

What holds the platelet plug together

A

fibrin wraps around to hold the platelet plug

35
Q

What promotes platelet adhesion?

A

VWF - protein that plays an important role in clotting cascade and physiological adhesion of platelets to subendothelial membrane

36
Q

What does prostacycline do

A

leads to vasodilation to make clotting less likely

37
Q

What is the role of collagen with platelets?

A

strong platelet agonist that causes dense granule release

38
Q

what is glycoprotein IIb/IIIa

A

antigens expressed on the platelet surface that helps platelets bind together

39
Q

What is the role of thrombospondin and fibronectin

A

help activate platelets

40
Q

What are examples of mucosal bleeding due to decreased platelet numbers

A

nose bleeds, easy bruising, heavy menstrual bleeding

41
Q

A 25 yo woman presents to office complaining of easy bruising and petechiae but feels well otherwise. platelet count is 10,000 but her Hgb is 12.8 and Hct is 39 and WBC is 5.5

A

normal HgB, Hct, and WBC but LOW platelet count

- most likely diagnosis is immune thrombocytopenia

42
Q

What is happening with TTP

A

not associated with clotting time

  • collection of large VWF multimers, platelets are coming together forming platelet only clots
  • using up platelets faster than the bone marrow can use them
43
Q

A 45 yo woman presents with profound fatigue, fevers, and confusion. A CBC reveals a markedly diminished platelet count and the lab test saw schiztocytes. What would you want to check?

A
  • check the peripheral smear
  • check PT/PTT - checking intrinsic and extrinsic system
  • draw blood cultures
  • check LDH (hemolysis)
44
Q

What are the common symptoms of TTP

A

low platelets, fever, don’t feel well, renal failure, CNS symptoms

45
Q

What is the mechanism of TTP

A
  • Ab blocks function of vWF cleaving protein ADAMTS-13
  • increased level of high molecular vWF multimers
  • increased platelet adhesion without activating coagulation cascade
46
Q

What is the role of ADAMTS-13?

A

it cleaves Vwf and if you have antibodies against it then you can have TTP

47
Q

What is the therapy for TTP?

A

removal of antibody and clearance of multimers

- plasma exchange

48
Q

When would an in-vitro platelet aggregation study be helpful?

A

A patient has normal platelet count and bleeds excessively after a biopsy
- figure out what the problem is if you have a normal platelet count

49
Q

How is a bleeding time study conducted?

A

pumping BP cuff to 40 mm, making a 1 cm cut 1 mm in depth, blotting q 30 sec until bleeding stops

50
Q

What is a normal bleeding time?

A

less than equal to 8 minutes

51
Q

Where is TPO produced

A

liver

52
Q

What does TPO affect

A

platelets and megakaryocytes and promegakaryoctes in the bone marrow

53
Q

What happens when TPO binds to progenitor cells?

A

expansion and maintenance of progenitor cells which leads to more megakaryocytes production

54
Q

What happens when TPO binds magakaryocytes

A

enhancement of megakaryocyte maturation which leads to increased platelet production

55
Q

What happens when TPO binds to platelets

A
  • internalized and degraded within the cytoplasm
  • doesn’t affect function or activity
  • platelet numbers determine available TPO level
56
Q

What do storage pool diseases result in

A

inherited causes of platelet dysfunction

- decrease or absence of dense granules

57
Q

heparin inducted thrombocytopenia

A
  • antibody reaction that leads to reduced platelet count
  • platelets start clotting
  • Elisa test to determine the Ab test
58
Q

What type of heparin is more likely to cause HIT

A

unfractionated heparin

59
Q

preeclampasia

A
  • hypertension
  • platelet levels can drop
  • especially after 30 weeks
60
Q

HELLP syndrome

A
  • hemolysis
  • elevated bilirubin
  • elevated liver enzymes
  • low platelets
61
Q

Neonatal alloimmune thrombocytopenia

A
  • fetal inheritance of platelet isoantigens not present in the mother
  • comes from the dad
  • well infant with very low platelet count
  • intracranial bleeding of the baby
62
Q

What is the treatment for neonatal alloimmune thrombocytopenia

A

infusion of washed maternal platelets

I3 Exam 1 (12 decks)

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