Lecture 7 - Platelets Flashcards Preview

Clinical Pathology Exam 1 > Lecture 7 - Platelets > Flashcards

Flashcards in Lecture 7 - Platelets Deck (112):
1

Fibrin formation after vascular injury causes vessel wall to

vasoconstrict and activate hemostasis process

2

Fibrin formation after vascular injury causes vessel wall to

vasoconstrict and activate hemostasis process

3

platelets form an initial unstable platelet plug also during __

primary hemostasis

4

__ form definitive hemostatic plug in secondary hemostasis by making a stable fibrin clot

coagulation factors

5

Sites of extramedullary hematopoeisis where platelets may arise

1. lungs
2. spleen
3. liver

6

__ are the precursors to platelet cells

megakaryocytes

7

4 factors that can contribute to abnormal platelet concentrations

production
consumption
destruction
redistribution (shifting of platelets to/from circuation)

8

most platelet production occurs in the

BM

9

__ is when platelets are removed from circulation during normal maintenance or during accelerated states such as thrombotic dz and vasculitis

consuption

10

Destruction of platelets occurs by macrophages in the __ and __

spleen and liver

11

platelets can sequester in the __ and this redistribution may reduce circulating platelet mass, contraction may increase it

spleen

12

explain the 4 steps of primary hemostasis (platelet "bricks")

1. adhesion
2. shape change
3. granule release
4. aggregation

13

4 things found in platelet DENSE granules that are released after binding which activate more platelets

1. ADP
2. ATP
3. Serotonin
4. Ca++

14

3 things found in platelet ALPHA granules

1. adhesion proteins - von willebrand factor
2. growth factors
3. coagulation proteins

15

platelets have what types of granules

dense and alpha - contain different things

16

What granules contain von willebrand's factors

alpha granules

17

__ stimulates megakaryocyte and platelet production

thrombopoeitin

18

what is the most useful ddx/gold standard for evaluating platelets

peripheral blood film! estimate #, look for clumps, observe morphology (megaplatelet, degranulated?)

19

challenging to get accurate platelet counts in __ and __

cats (large and clumpy)
horses (clump in EDTA, use citrate)

20

Platelet indicies are similar to RBC indicies

MPV, PDW, PCT, MPC (mean platelet content)

21

how do you evaluate megakaryocyte number

BM cytology

22

cat platletes

larger with higher MPV (mean platelet volume)
sensitive to activation (clumping, degranulate)

23

Platelets are estimated on 100x in the __, to estimate platelets use formula

monolayer
estimated platelet count/mcL = average count in 10 fields x 20,000

24

average amount of platelets on 100x field for dogs/cats __, horses __

8-12/field
6/field

25

platelets in reptiles/avian are called

thrombocytes

26

what dog breeds normally have a low platelet count and can be mislabeled as thrombocytopenia

cavalier king charles spaniels (hereditary macrothrombocytopenia)
greyhounds
norfolk terriers
maltese

27

severe thrombocytopenia in most breeds is

28

what do you need to worry about with a p that has severe (

spontaneous bleeding/hemorrhage

29

what can cause severe thrombocytopenia

marrow dz, destruction

30

what can cause mild and moderate thrombocytopenia

marrow dz or consumption

31

clinical signs of severe thrombocytopenia are associated with

SC and mucosal bleeding (petechiation, purpura, ecchymosis, epistaxis, gingival bleeding, melena, hematemesis/uria) and prolonged bleeding after trauma (blood draw)

32

if a patient has severe thrombocytopenia can you draw blood

yes, but do it from small vessels and hold off for longer than normal. Do not do other invasive procedures (cystocentisis) and put them somewhere atraumatic/ can't bump or injury

33

3 signs of peripheral (outside marrow) thrombocytopenia

1. increased DESTRUCTION
2. increased CONSUMPTION
3. abnormal DISTRIBUTION

34

If there is a problem in the marrow causing thrombocytopenia what might you see

decreased PRODUCTION

35

If there is thrombocytopenia with decreased production what might you see in other cells

other cell lines involved

36

5 things that cause decreased production of platelets

1. immune mediated or idiopathic
2. marrow replacement (neoplasia or fibrosis)
3. infectious dz
4. drugs and toxicities (bracken fern)
5. radiation

37

with thrombocytopenia how would you expect normal BM to repsond

Hyperplasia of megakaryocytes (but wit decreased production there is reduced or abscent megakaryocytes)

38

other abnormalities depending on underlying cause for decreased production of platelets

1. other cell lines decreased too
2. morphological abnormalities
3. abnormal cells in circulation (neoplasia, fibrosis)

39

most common ddx for anemia is

primary idiopathic

40

most common ddx for thrombocytopenia is

secondary immune-mediated (opposite of anemia)

41

increased destruction is caused by

1. sulfa antibiotics
2. vaccination (modified live)
3. circulating immune complexes (virus, sepsis, neoplasia)
4. anaplasma platys (infects platelets)

42

if give a modified live vaccine how long should you wait before doing anything traumatic to that animal such as surgery

2 weeks (thrombocytopenia occurs 3-10days post vx)

43

if there is increased destruction the platelets will be

severely decreased,

44

with increased destruction outside the marrow the __ may increase

MPV (mean platelet volume)

45

what is the first test you should preform with a thrombocytopenia p

snap test for tick and mosquito born dz

46

__ the platelets are becoming excessively activated due to increased hemostatic activity (platlete agregation and coagulation)

consumption

47

Increased consumption causing thrombocytopenia can cause __, a widepread, uncontrolled activation of coagulation cascade

DIC (disseminated intravascular coagulation)

48

4 things that cause increased consumption resulting in thrombocytopenia

1. DIC
2. microangiopathic dz (hemangiosarc)
3. vasculitis or endocarditis
4. envenomations

49

__ alone usually does not result in significant thrombocytopenia

blood loss (should NOT be on differential list!)

50

Secondary thrombocytosis (increased platelets) can be caused by

1. Fe def anemia
2. cushing's dz
3. chronic inflammation
4. post-spenecotmy
5. vinca alkaloids
6. rebound from acute hemorrhage

51

__ is abnormal platelet function, there are platelets but they don't function correctly (it's similar to having thrombocytopenia)

thrombopathia

52

if thrombopathia or thrombocytopenia are suspected what test should you do

check blood film for platelet #s

53

after checking blood film with suspected thrombopathia or thrombocytopenia what next

test coagulation factors (before doing bleeding test like BMBT)

54

After blood film and coagulation factors have been tested for thrombopathia what next

Buccal mucosal bleeding test (BMBT) - Measures the primary hemostatic platelet plug formation time

55

If BMBT is greater than 4 mins what are your concerns

thrombocytopenia, platelet defect (thrombopathia), vascular defect

56

what can cause abnormal platelet function (thrombopathia)

1. increased fibrin degradation products inhibit platelet (DIC, fibrionlysis dz)
2. Drugs (NSAIDS)
3. Renal failure
4. hyperglobulinemia
5. immune mediated thrombocytopenia somtimes
6. congenital cause (von willebrand's dz)

57

what is the most common congenital dz (causes thrombopathy)

von willebrand's dz

58

platelets form an initial unstable platelet plug also during __

primary hemostasis

59

__ form definitive hemostatic plug in secondary hemostasis by making a stable fibrin clot

coagulation factors

60

Sites of extramedullary hematopoeisis where platelets may arise

1. lungs
2. spleen
3. liver

61

__ are the precursors to platelet cells

megakaryocytes

62

4 factors that can contribute to abnormal platelet concentrations

production
consumption
destruction
redistribution (shifting of platelets to/from circuation)

63

most platelet production occurs in the

BM

64

__ is when platelets are removed from circulation during normal maintenance or during accelerated states such as thrombotic dz and vasculitis

consuption

65

Destruction of platelets occurs by macrophages in the __ and __

spleen and liver

66

platelets can sequester in the __ and this redistribution may reduce circulating platelet mass, contraction may increase it

spleen

67

explain the 4 steps of primary hemostasis (platelet "bricks")

1. adhesion
2. shape change
3. granule release
4. aggregation

68

4 things found in platelet DENSE granules that are released after binding which activate more platelets

1. ADP
2. ATP
3. Serotonin
4. Ca++

69

3 things found in platelet ALPHA granules

1. adhesion proteins - von willebrand factor
2. growth factors
3. coagulation proteins

70

platelets have what types of granules

dense and alpha - contain different things

71

What granules contain von willebrand's factors

alpha granules

72

__ stimulates megakaryocyte and platelet production

thrombopoeitin

73

what is the most useful ddx/gold standard for evaluating platelets

peripheral blood film! estimate #, look for clumps, observe morphology (megaplatelet, degranulated?)

74

challenging to get accurate platelet counts in __ and __

cats (large and clumpy)
horses (clump in EDTA, use citrate)

75

Platelet indicies are similar to RBC indicies

MPV, PDW, PCT, MPC (mean platelet content)

76

how do you evaluate megakaryocyte number

BM cytology

77

cat platletes

larger with higher MPV (mean platelet volume)
sensitive to activation (clumping, degranulate)

78

Platelets are estimated on 100x in the __, to estimate platelets use formula

monolayer
estimated platelet count/mcL = average count in 10 fields x 20,000

79

average amount of platelets on 100x field for dogs/cats __, horses __

8-12/field
6/field

80

platelets in reptiles/avian are called

thrombocytes

81

what dog breeds normally have a low platelet count and can be mislabeled as thrombocytopenia

cavalier king charles spaniels (hereditary macrothrombocytopenia)
greyhounds
norfolk terriers
maltese

82

severe thrombocytopenia in most breeds is

83

what do you need to worry about with a p that has severe (

spontaneous bleeding/hemorrhage

84

what can cause severe thrombocytopenia

marrow dz, destruction

85

what can cause mild and moderate thrombocytopenia

marrow dz or consumption

86

clinical signs of severe thrombocytopenia are associated with

SC and mucosal bleeding (petechiation, purpura, ecchymosis, epistaxis, gingival bleeding, melena, hematemesis/uria) and prolonged bleeding after trauma (blood draw)

87

if a patient has severe thrombocytopenia can you draw blood

yes, but do it from small vessels and hold off for longer than normal. Do not do other invasive procedures (cystocentisis) and put them somewhere atraumatic/ can't bump or injury

88

3 signs of peripheral (outside marrow) thrombocytopenia

1. increased DESTRUCTION
2. increased CONSUMPTION
3. abnormal DISTRIBUTION

89

If there is a problem in the marrow causing thrombocytopenia what might you see

decreased PRODUCTION

90

If there is thrombocytopenia with decreased production what might you see in other cells

other cell lines involved

91

5 things that cause decreased production of platelets

1. immune mediated or idiopathic
2. marrow replacement (neoplasia or fibrosis)
3. infectious dz
4. drugs and toxicities (bracken fern)
5. radiation

92

with thrombocytopenia how would you expect normal BM to repsond

Hyperplasia of megakaryocytes (but wit decreased production there is reduced or abscent megakaryocytes)

93

other abnormalities depending on underlying cause for decreased production of platelets

1. other cell lines decreased too
2. morphological abnormalities
3. abnormal cells in circulation (neoplasia, fibrosis)

94

most common ddx for anemia is

primary idiopathic

95

most common ddx for thrombocytopenia is

secondary immune-mediated (opposite of anemia)

96

increased destruction is caused by

1. sulfa antibiotics
2. vaccination (modified live)
3. circulating immune complexes (virus, sepsis, neoplasia)
4. anaplasma platys (infects platelets)

97

if give a modified live vaccine how long should you wait before doing anything traumatic to that animal such as surgery

2 weeks (thrombocytopenia occurs 3-10days post vx)

98

if there is increased destruction the platelets will be

severely decreased,

99

with increased destruction outside the marrow the __ may increase

MPV (mean platelet volume)

100

what is the first test you should preform with a thrombocytopenia p

snap test for tick and mosquito born dz

101

__ the platelets are becoming excessively activated due to increased hemostatic activity (platlete agregation and coagulation)

consumption

102

Increased consumption causing thrombocytopenia can cause __, a widepread, uncontrolled activation of coagulation cascade

DIC (disseminated intravascular coagulation)

103

4 things that cause increased consumption resulting in thrombocytopenia

1. DIC
2. microangiopathic dz (hemangiosarc)
3. vasculitis or endocarditis
4. envenomations

104

__ alone usually does not result in significant thrombocytopenia

blood loss (should NOT be on differential list!)

105

Secondary thrombocytosis (increased platelets) can be caused by

1. Fe def anemia
2. cushing's dz
3. chronic inflammation
4. post-spenecotmy
5. vinca alkaloids
6. rebound from acute hemorrhage

106

__ is abnormal platelet function, there are platelets but they don't function correctly (it's similar to having thrombocytopenia)

thrombopathia

107

if thrombopathia or thrombocytopenia are suspected what test should you do

check blood film for platelet #s

108

after checking blood film with suspected thrombopathia or thrombocytopenia what next

test coagulation factors (before doing bleeding test like BMBT)

109

After blood film and coagulation factors have been tested for thrombopathia what next

Buccal mucosal bleeding test (BMBT) - Measures the primary hemostatic platelet plug formation time

110

If BMBT is greater than 4 mins what are your concerns

thrombocytopenia, platelet defect (thrombopathia), vascular defect

111

what can cause abnormal platelet function (thrombopathia)

1. increased fibrin degradation products inhibit platelet (DIC, fibrionlysis dz)
2. Drugs (NSAIDS)
3. Renal failure
4. hyperglobulinemia
5. immune mediated thrombocytopenia somtimes
6. congenital cause (von willebrand's dz)

112

what is the most common congenital dz (causes thrombopathy)

von willebrand's dz