Lecture 7 - Platelets Flashcards
1
Q
Fibrin formation after vascular injury causes vessel wall to
A
vasoconstrict and activate hemostasis process
2
Q
Fibrin formation after vascular injury causes vessel wall to
A
vasoconstrict and activate hemostasis process
3
Q
platelets form an initial unstable platelet plug also during __
A
primary hemostasis
4
Q
__ form definitive hemostatic plug in secondary hemostasis by making a stable fibrin clot
A
coagulation factors
5
Q
Sites of extramedullary hematopoeisis where platelets may arise
A
- lungs
- spleen
- liver
6
Q
__ are the precursors to platelet cells
A
megakaryocytes
7
Q
4 factors that can contribute to abnormal platelet concentrations
A
production
consumption
destruction
redistribution (shifting of platelets to/from circuation)
8
Q
most platelet production occurs in the
A
BM
9
Q
__ is when platelets are removed from circulation during normal maintenance or during accelerated states such as thrombotic dz and vasculitis
A
consuption
10
Q
Destruction of platelets occurs by macrophages in the __ and __
A
spleen and liver
11
Q
platelets can sequester in the __ and this redistribution may reduce circulating platelet mass, contraction may increase it
A
spleen
12
Q
explain the 4 steps of primary hemostasis (platelet “bricks”)
A
- adhesion
- shape change
- granule release
- aggregation
13
Q
4 things found in platelet DENSE granules that are released after binding which activate more platelets
A
- ADP
- ATP
- Serotonin
- Ca++
14
Q
3 things found in platelet ALPHA granules
A
- adhesion proteins - von willebrand factor
- growth factors
- coagulation proteins
15
Q
platelets have what types of granules
A
dense and alpha - contain different things
16
Q
What granules contain von willebrand’s factors
A
alpha granules
17
Q
__ stimulates megakaryocyte and platelet production
A
thrombopoeitin
18
Q
what is the most useful ddx/gold standard for evaluating platelets
A
peripheral blood film! estimate #, look for clumps, observe morphology (megaplatelet, degranulated?)
19
Q
challenging to get accurate platelet counts in __ and __
A
cats (large and clumpy)
horses (clump in EDTA, use citrate)
20
Q
Platelet indicies are similar to RBC indicies
A
MPV, PDW, PCT, MPC (mean platelet content)
21
Q
how do you evaluate megakaryocyte number
A
BM cytology
22
Q
cat platletes
A
larger with higher MPV (mean platelet volume)
sensitive to activation (clumping, degranulate)
23
Q
Platelets are estimated on 100x in the __, to estimate platelets use formula
A
monolayer
estimated platelet count/mcL = average count in 10 fields x 20,000
24
Q
average amount of platelets on 100x field for dogs/cats __, horses __
A
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
