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442 - Clinical Pathology > Hemostasis > Flashcards

Hemostasis Flashcards

(64 cards)

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1
Q

What is primary hemostasis?

A

The formation of platelet plug. Therefore, disorders of primary hemostasis are related to platelet function.

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2
Q

What is secondary hemostasis?

A

Fibrin clot formation. Therefore, disorders of secondary hemostasis are related to the coagulation cascade.

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3
Q

What are the four main steps of hemostasis?

A
  1. Vascular spasm/vasoconstriction
  2. Platelet plug formation (primary hemostasis)
  3. Coagulation (secondary hemostasis)
  4. Clot retraction and fibrinolysis.
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4
Q

What will a CBC show if you have platelet plug formation?

A

It makes the platelet count falsely low on a CBC (fake ass thrombocytopenia).

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5
Q

What are the four steps of primary hemostasis?

A
  1. Platelet adhesion to von Willebrand factor
  2. Shape change
  3. Granule release
  4. Recruitment.
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6
Q

What is the function of von Willebrand factor (vWF)?

A

vWF is present on the subendothelium of injured vessels and acts as a tether for platelets, helping them adhere to the site of injury.

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7
Q

What clinical signs do we see with disorders of primary hemostasis?

A
  • Superficial hemorrhages (petechia (1-2 mm), purpura (3 mm-2 cm), ecchymosis (2-3 cm))
  • Persistent oozing from surgical sites
  • Recurrent epistaxis
  • Melena or hematochezia
  • Urinary tract hemorrhage.
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8
Q

What are the two main disorders of primary hemostasis?

A
  • Thrombocytopenia (decreased platelet numbers, ex. bone marrow issue)
  • Thrombopathia (platelet function disorder).
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9
Q

What is one congenital thrombocytopenia disorder?

A

Inherited macrothrombocytopenia (common in Cavalier King Charles spaniel dogs).

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10
Q

What is a common acquired thrombopathic disorder?

A

FeLV.

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11
Q

What are the three categories of acquired thrombocytopenia?

A
  1. Increased platelet destruction (ex. IMT)
  2. Increased platelet consumption (ex. DIC, vasculitis)
  3. Decreased platelet production (ex. leukemia, myelophthisis, myelofibrosis).
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12
Q

What is myelophthisis?

A

The replacement of normal hematopoietic tissue with abnormal tissue (ex. neoplasia).

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13
Q

What is myelofibrosis?

A

The replacement of normal hematopoietic tissue with fibrous tissue (most often secondary to a primary marrow injury, such as neoplasia, necrosis, or inflammation).

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14
Q

How is thrombocytopenia diagnosed on a blood smear?

A

< 2-3 platelets/hpf would be consistent with thrombocytopenia.

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15
Q

When does primary (immune mediated thrombocytopenia) IMT occur?

A

When antibodies are generated in response to a target self antigen on platelets (+/- megakaryocytes).

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16
Q

When does secondary (immune mediated thrombocytopenia) IMT occur?

A

Occurs with formation of immune complexes on platelet surface (ex. vaccines, drugs, viral disease, neoplasia).

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17
Q

Which viruses can cause decreased platelet production?

A
  • FeLV/FIV
  • Parvovirus
  • Distemper
  • EIA (equine infectious anemia)
  • BVDV (bovine viral diarrhea virus).
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18
Q

What are the three most common causes of severe thrombocytopenia?

A
  • IMT (primary or secondary)
  • Drug induced
  • Decreased platelet production (ex. bone marrow neoplasia or fibrosis).
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19
Q

True or False: Inherited macrothrombocytopenia is associated with hemorrhage.

A

False, it is NOT associated with hemorrhage.

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20
Q

What disease should you suspect in animals with persistent thrombocytopenia and absence of clinical signs?

A

Inherited macrothrombocytopenia.

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21
Q

What is inherited macrothrombocytopenia characterized by on a CBC?

A

Large platelets.

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22
Q

What are the three types of von Willebrand’s (VWD) disorder?

A

Type 1: Low numbers of VWF proteins with normal structure and function.
Type 2: Low numbers of VWF proteins with abnormal structure and function.
Type 3: Markedly reduced to absent VWF protein.

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23
Q

Which type of VWD is the most common?

A

Type 1.

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24
Q

What four diagnostic tests can you do if you suspect primary hemostasis?

A
  • CBC with platelet count
  • Evaluate blood smear for giant platelets (don’t forget to look for platelet clumps)
  • BMBT (see other card on this)
  • Bone marrow aspirate.
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25
What diagnostic test should you do if you don't have time to wait for bloodwork results, but you suspect VWD?
BMBT (buccal mucosal bleeding time test). Cut the lip of the suspected animal and report bleeding time. It should be less than 4 mins.
26
What diagnostic test should you do if your platelet counts are normal on the CBC, but you still suspect VWD?
BMBT (buccal mucosal bleeding time test).
27
When is the BMBT test not performed?
It is not performed in cases of thrombocytopenia! (will likely be prolonged with platelet counts < 70 x 109/L).
28
Which two disorders does a bone marrow aspirate help distinguish between?
IMT and myeloproliferative disease.
29
A von Willebrand factor antigen assay (vWF:Ag) will be less than ________ percent in bleeding dogs.
25% (can often even be 15%!).
30
What stimulates fibrin formation?
Tissue factor
31
Which coagulation factor(s) are in the common pathway?
Factors X, V, II (2, 5, 10) and fibrinogen
32
Which coagulation factor(s) are in the intrinsic pathway?
Factors XII, XI, IX, VIII (8, 9, 11, 12)
33
Which coagulation factor(s) are in the extrinsic pathway?
Factor VII (7)
34
What converts fibrinogen to fibrin?
Thrombin
35
The majority of coagulation factors are made in the ______________ in an ______________ form.
Liver, inactive
36
What coagulation pathway is the only one that is physiologically relevant?
Extrinsic pathway
37
What factors in the coagulation cascade require Vitamin K?
2, 7, 9, 10
38
Which forms of coagulation factors are functional?
The carboxylated ones. Carboxylation is required for them to be active in coagulation. Carboxylase is Vitamin K dependent.
39
What do rodenticides inhibit?
Vitamin K
40
The extrinsic pathway is activated by _____________
Tissue factor
41
What does the common pathway result in the formation of?
The formation of thrombin which can then turn fibrinogen into fibrin
42
What are three tests you can run to evaluate secondary hemostasis?
1. ACT (activated clotting time) 2. PT (prothrombin time) 3. aPTT (activated partial thromboplastin)
43
Which coagulation pathway(s) does the ACT test evaluate?
Intrinsic and common
44
Which coagulation pathway(s) does the aPTT test evaluate?
Intrinsic and common
45
Which coagulation pathway(s) does the PT test evaluate?
Extrinsic and common
46
Describe the ACT test.
The activated clotting time test measures the time required for the formation of a visible clot to form. Different species have different times. ACT is usually not prolonged unless coagulation factors are <10% of normal activity. ## Footnote Evaluates the intrinsic and common pathway.
47
Describe the PT test.
The prothrombin time test is performed using a coagulometer and measures the time required to form a fibrin clot in citrated plasma after the addition of thromboplastin, tissue factor, and Ca. ## Footnote Evaluates the extrinsic and common pathways.
48
Describe the aPTT test.
Performed using a coagulometer, it measures the time required to form a fibrin clot in citrated plasma after addition of an activator (ex. silica) and Ca.
49
What are important things to note when collecting samples to test secondary hemostasis?
1. Take the blood as atraumatically as possible 2. Use blue top tubes that contain sodium citrate 3. Fill the tube to the appropriate line or you will not have the proper blood to anticoagulant ratio of 9:1 4. Mix tube well
50
What will happen if you under fill your blue top tubes?
You will have way too much anticoagulant and will have falsely prolonged coagulation times
51
What is the most common cause of coagulopathy in vet med?
Anti-Vitamin K anticoagulants (rodenticide)
52
What are the two categories of coagulation disorders?
1. Coagulation factor deficiency 2. Coagulation factor inhibition
53
Why would we give heparin to a patient with DIC?
Heparin is an anticoagulant, so we can try to limit the formation of clots in patients with DIC
54
How do you treat rodenticide poisoning?
Administer Vitamin K
55
What are two anti-vitamin K anticoagulants that cattle can ingest?
Moldy sweet clover or sweet vernal grass
56
Ingestion of rodenticides would cause what kind of results in an ACT, PT, and aPTT?
It would cause an increased clotting time in all three tests since Vitamin K is involved in every coagulation pathway
57
Pathology in which organ could cause a coagulation factor deficiency?
Hepatic disease. Remember most of these clotting factors are made in the liver
58
What species get Hemophilia A?
Cats, dogs, cattle, horses
59
Hemophilia A is a deficiency of what factor?
Factor VIII (A kinda sounds like 8)
60
Hemophilia B is a deficiency of what factor?
Factor IX
61
What species get Hemophilia B?
Dogs and cats
62
A patient with Hemophilia B would have prolonged clotting in which tests?
ACT and aPTT ## Footnote remember that Factor IX is in the intrinsic pathway.
63
A diagnosis of hemophilia is typically made when factor activity is less than ___________
30%
64
A patient with Hemophilia A would have prolonged clotting in which tests?
ACT and aPTT ## Footnote remember that Factor VIII is in the intrinsic pathway.

442 - Clinical Pathology (5 decks)

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