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MODULE 15 - Cardiorespiratory and Haematopoietic Disease > PATHOLOGY - Haemostatic Disorders > Flashcards

PATHOLOGY - Haemostatic Disorders Flashcards

1
Q

Describe primary haemostasis

A

Primary haemostasis is when there is damage to the endothelium, triggering vasoconstriction and platelet plug formation. Where there is damage to the endothelium, these damaged endothelial cells release von willebrands factors which come into contact with and bind to the now exposed subendothelial collagen. Circulating platelets bind to these von willebrands factors, activating the platelets which will release ADP and thromboxane A which attract and activate more platelets which will aggregate to form a platelet plug as well as a scaffolding system allowing for the binding of fibrinogen

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2
Q

Describe secondary haemostasis

A

Secondary haemostasis is where the extrinsic coagulation cascade is triggered by exposure of subendothelial tissue factor and the intrinsic coagulation cascade is triggered by exposure of subendothelial collagen. Both of these cascades will trigger the final common pathway which converts prothrombin the thrombin through the action of thromboplastin enzymes, and thrombin converts fibrinogen to fibrin which forms a cross-linked fibrin network to form a clot

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3
Q

Which coagulation factors are involved in the extrinsic coagulation cascade?

A

Factor VII
Factor X

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4
Q

Which coagulation factors are involved in the intrinsic coagulation cascade?

A

Factor VIII
Factor IX
Factor X
Factor XI
Factor XII

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5
Q

Which coagulation factors are involved in the final common pathway?

A

Factor I
Factor II
Factor XIII

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6
Q

Which factors are involved in modulating coagulation?

A

Antithrombin
Tissue factor pathway inhibitor
Protein C - Protein S system

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7
Q

Describe tertiary haemostasis

A

Tertiary haemostasis is the process of fibrinolysis where the presence of fibrin triggers enzyme t-PA which converts circulating plasminogen into plasmin which breaks down the fibrin clot

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8
Q

Which history questions should you consider when investigating a possible haemostatic disorder case?

A

Has the patient had any exposure to anticoagulant rodenticides?
Is the patient regularly wormed?
Is there a history of travel outside of the UK? Has there been tick exposure?
Has the patient been systemically ill in the run up to the bleeding?

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9
Q

What can be indicated by young animals presenting with spontaneous bleeding?

A

Congenital haemostatic disorders

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10
Q

What are the differentials for primary haemostasic disorders?

A

Thrombocytopenia
Thrombocytopathia
Von willebrands disease
Vasculopathies

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11
Q

Which two laboratory tests can you do to investigate primary haemostatic disorders?

A

Manual and automated platelet count
Buccal mucosal bleeding time (BMBT)

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12
Q

What would be an adequate number of platelets when doing a manual platelet count using a blood smear?

A

10 to 15 platelets per x100 power view would be an adequate number of platelets, multiplied by 10^15

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13
Q

What value would be indicative of thrombocytopenia when using an automated analyser for platelet counts?

A

Less than 50 x 10^9/litre

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14
Q

At what value would spontaneous bleeding begin when using an automated analyser for platelet counts?

A

Less than 30 x 10^9/litre

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15
Q

Why is it so important to check the blood smear as well as the automated platelet count value?

A

It is important to check the smear for platelet clumping which could lead to inaccurate values counted by the automated analyser

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16
Q

What should you be aware of when doing automated platelet counts in cats?

A

Cat platelets are approximately the size of erythrocytes and thus the platelets are often miscounted by automated analysers

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17
Q

Which dog breed normally has a low platelet count?

A

Cavalier King Charles Spaniels

This low platelet count is normal for them

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18
Q

What can be tested by doing a buccal mucosal bleeding test (BMBT)?

A

Platelet function

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19
Q

How do you carry out a buccal mucosal bleeding test (BMBT)?

A

Using a gadget to make a uniform incision into the buccal mucosa and time how long is takes for the mucosa to stop bleeding. The bleeding should cease within 2 to 4 minutes

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20
Q

What are six key clinical signs of thrombocytopenia?

A

Petechiation
Ecchymoses
Epistaxis
Gastrointestinal bleeding (i.e. meleana)
Bleeding from gums
Clinical signs associated with haemorrhagic anaemia

Thrombocytopenia is heavily associated with mucosal bleeding

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21
Q

What are four possible causes of thrombocytopenia?

A

Immune-mediated thrombocytopenia (IMTP)
Primary bone marrow disease
Infectious diseases
Increased platelet consumption

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22
Q

What is the signalement for immune-mediated thrombocytopenia (IMTP)?

A

Medium sized dogs usually between 4 - 5 years old

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23
Q

Which breed of dog is predisposed to immune-mediated thrombocytopenia (IMTP)?

A

Cocker Spaniels

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24
Q

What are the typical clinical signs of immune-mediated thrombocytopenia (IMTP)?

A

Signs of a primary haemostatic disorder
Anaemia

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25
What causes anaemia in immune-mediated thrombocytopenia (IMTP)?
Immune-mediated thrombocytopenia (IMTP) causes spontaneous bleeding throughout the body which can cause anaemia
26
What is Evan's syndrome?
Evan's syndrome is a very rare syndrome where immune-mediated thrombocytopenia (IMTP) presents concurrently with immune-mediated haemolytic anaemia (IMHA)
27
How do you diagnose immune-mediated thrombocytopenia (IMTP)?
- Detect thrombocytopenia on a platelet count - tends to have a very low platelet count of less than 30 x 10^9/litre - Exclude any other causes of thrombocytopenia
28
How do you manage and treat patients with immune-mediated thrombocytopenia (IMTP)?
Gentle handling is very important Blood transfusion *(if severly anaemic)* Immunosuppressive therapy Low dose vincristine Omeprazole
29
What can you administer to immune-mediated thrombocytopenia (IMTP) patients that are refractory to immunosuppressive treatment?
Human intravenous immunoglobulins
30
Why would you administer low dose vincristine to patients with immune-mediated thrombocytopenia (IMTP)?
Vincristine stimulates platelet release from the bone marrow
31
Why would you administer omeprazole to patients with immune-mediated thrombocytopenia (IMTP)?
Immune-mediated thrombocytopenia (IMTP) can cause severe gastrointestinal bleeding and since steroids are being administered as immunosuppressive therapy, they can cause gastrointestinal ulceration which can also cause bleeding. Omeprazole protects the GI tract from ulceration
32
What is the prognosis for patients with immune-mediated thrombocytopenia (IMTP)?
Immune-mediated thrombocytopenia (IMTP) causes spontaneous bleeding which can eventually cause death
33
What would be a key indicator of thrombocytopenia caused by primary bone marrow disease?
If other cell lines are affected, i.e. there is a pancytopenia or bicytopenia, this can indicate primary bone marrow disease
34
Which infectious agent can cause thrombocytopenia?
Anaplasmsa ## Footnote Anaplasma can be carried by ixodes ricinus and dermacentor reticulatus ticks so it is important to consider tick history
35
List two examples of things that can cause increased platelet consumption and thrombocytopenia
Disseminated intravascular coagulation (DIC) Severe blood loss
36
What are some of the clinical signs of von willebrands disease? | Remeber von willebrands is congenital
Prolonged bleeding at surgical sites *i.e. after neutering* Prolonged bleeding at oestrus Prolonged bleeding after losing deciduous teeth Clinical signs associated with haemorrhagic anaemia
37
How do you diagnose von willebrands disease?
Normal platelet count Normal coagulation tests Prolonged buccal mucosal bleeding test (BMBT) Send a sample to an external lab to test for reduced von willebrands
38
Which breed of dog is predisposed to von willebrands disease?
Dobermans
39
How do you treat and manage von willebrands disease?
Desmopressin (DDAVP) Cryoprecipitate
40
When is cryoprecipitate particularly good for managing von willebrands disease?
Cryoprecipitate is a portion of plasma rich in von willebrands factors which can be useful to administer prior to surgery in patients with von willebrands disease
41
What are the differentials for secondary haemostasic disorders *(also known as coagulopathies)*?
Anticoagulant rodenticide toxicity Hepatic failure Haemophilia
42
What are clinical signs of a coagulopathy?
Haematomas Haemoarthrosis Bleeding into body cavities *(i.e. haemoabdomen, haemothorax)* Haemorrhagic anaemia
43
Which three laboratory tests can you do to investigate secondary haemostatic disorders/coagulopathies?
Prothrombin time (PT) Activated partial thromboplastin time (aPTT) Fibrinogen levels
44
What is evaluated by a prothrombin time (PT) test?
Extrinsic coagulation cascade Final common pathway Coagulation factor VII
45
What is evaluated by an activated partial thromboplastin time (aPTT)?
Intrinsic coagulation cascade Final common pathway Coagulation factors VIII, IX, XI, XII
46
What is the mechanism of action for anticoagulant rodenticides?
Anticoagulant rodenticides are slowly absorbed by the gastrointestinal tract and mechanically inhibit an enzyme which is crucial for the production of vitamin K1, a necessary component for clotting factors II, VII, IX and X. When the production of these clotting factors in the liver is inhibited, prothrombin cannot be adequately converted to thrombin, and coagulopathy results
47
What are the clinical signs of anticoagulant rodenticide poisoning?
Clinical signs associated with a coagulopathy May be anaemic May be thrombocytopenic
48
Which laboratory tests should you do to diagnose anticoagulant rodenticide poisoning?
Prolonged prothrombin time (PT) Prolonged activated partial thromboplastin time (aPTT)
49
(T/F) Thrombocytopenia caused by blood loss would **not** have an automated platelet count of less than 50 x 10^9/litre
TRUE.
50
How to you treat/manage patients with anticoagulant rodenticide poisoning?
Vitamin K1 IV fluid therapy Whole blood transfusion if severely anaemic Fresh frozen plasma transfusion to replace coag factors
51
Which liver diseases can cause coagulopathies?
Severe/chronic cholestasis End-stage liver disease
52
How can severe/chronic cholestasis cause a coagulopathy?
Cholestasis reduces enterohepatic circulation of bile acids and subsequently reduces the absorption of vitamin K1 in the intestine, which is essential for the production of coagulation factors
53
How can end-stage liver disease cause a coagulopathy?
End-stage liver disease reduces the production of coagulation factors
54
What laboratory tests should you do to diagnose a coagulopathy secondary to liver disease?
Prolonged prothrombin time (PT) Prolonged activated partial thromboplastin time (aPTT) Biochemistry to assess for increased liver enzymes, hyperbilirubinaemia and assess for decreased proteins
55
Why do you get decreased urea and creatinine levels in patients with liver disease?
The liver synthesises urea and creatinine
56
What should you do before any intervention in patients with liver disease?
Before any intervention *(such as surgery)* in patients with liver disease, you should do a PT and aPTT to see if they have a coagulopathy as this will prolong their clotting time following the procedure and you may need to alter your treatment plan
57
How do you treat and manage coagulopathy secondary to liver disease?
Manage/treat the underlying liver disease Vitamin K1 Whole blood transfusion if severely anaemic Fresh frozen plasma transfusion to replace coag factors
58
What are the two classifications of haemophilia?
Haemophilia A Haemophilia B
59
Which coagulation factor is affected by haemophilia A?
Coagulation factor VIII
60
Which coagulation factor is affected by haemophilia B?
Coagulation factor IX
61
Which dog breed is predisposed to haemophilia? | Remember haemophilia is congenital
German Shepherds
62
How do you diagnose haemophilia A and B?
Prolonged activated partial thromboplastin (aPTT) Normal prothrombin time (PT)
63
What is haegman factor deficiency?
Haegman factor deficiency is a condition seen in cats where there is a deficiency in coagulation factor XII deficiency which caused a prolonged aPTT however there is no bleeding associated with this condition
64
Which three laboratory tests can be done to investigate tertiary haemostatic disorders?
D-dimers Fibrin degredation products Thrombo-elastography (TEG) | Has to be done in an external lab
65
What is thrombo-elastography (TEG)?
Thrombo-elastography (TEG) measures whole blood capability to make and sustain clot formation
66
Give an example of a tertiary haemostatic disorder
Hyperfibrinolysis
67
Which dog breed is predisposed to hyperfibrinolysis?
Greyhounds
68
What should you administer to greyhounds prior to surgery and why?
Administer tranexamic acid to greyhounds prophylactically as tranexamic acid is a fibrinolysis inhibitor and will reduce the risk fo excessive bleeding during surgery
69
What are four of the more complex or 'mixed' haemostatic disorder?
Disseminated intravascular coagulation (DIC) Angiostrongylus vasorum infection Sepsis Trauma associated coagulopathy
70
What is disseminated intravascular coagulation (DIC)?
Disseminated intravascular coagulation (DIC) is an acquired syndrome characterised by the dysfunction of the normal regulatory mechanisms of the coagulation and fibrinolysis resulting in an unregulated production of thrombin resulting in the formation of intravascular thrombi and the eventual depletion of platelets and coagulation factors leading to haemorrhage
71
What causes disseminated intravascular coagulation (DIC)?
Disseminated intravascular coagulation (DIC) is caused by widespread endothelial cell damage and the release of thromboplastins which convert prothrombin to thrombin
72
What are the three main causes of disseminated intravascular coagulation (DIC)?
Neoplasia Systemic inflammation Sepsis
73
How do you diagnose disseminated intravascular coagulation (DIC)?
Prolonged prothrombin time (PT) Prolonged activated partial thromboplastin time (aPTT) Platelet count to detect thrombocytopenia Decreased fibrinogen Increased D-dimers Increased fibrin degredation products
74
How do you treat and manage disseminated intravascular coagulation (DIC)?
Treat the underlying cause Supportive care of organs prone to thrombi, ischaemia and haemorrhage Whole blood transfusion Fresh frozen plasma transfusion
75
What is the prognosis for disseminated intravascular coagulation (DIC)?
Very poor prognosis
76
What are the clinical signs of angiostrongylus vasorum infection?
Cough Primary haemostatic disorder Secondary haemostatic disorder
77
How do you diagnose angiostronglylus vasorum infection?
Faecal Baermann's test for L1 larvae *(3 day pooled sample)* Prolonged prothrombin test (PT) Prolonged activated partial thromboplastin time test (aPTT) Thrombocytopenia Low fibrinogen levels | Be aware there may not be haemostatic changes
78
How do you treat and manage angiostrongylus vasorum infections?
Antiparasitic drugs Supportive care for haemorrhage (transfusion) Corticosteroids Tranexamic acid
79
Which antiparasitic drugs can you use to treat angiostrongylus vasorum?
Moxidectin Imadicloprid
80
What is tranexamic acid?
Tranexamic acid is a fibrinolysis inhibitor

MODULE 15 - Cardiorespiratory and Haematopoietic Disease (21 decks)

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