HEMODYNAMICS LECTURE 2: Hemostasis & thrombosis Flashcards

1
Q

What is the purpose of endothelial cells in hemostasis?

A

Express anticoagulant or procoagulant factors to regulate clotting

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2
Q

Where do platelets originate?

A

Megakaryocytes in bone marrow

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3
Q

What are the two pathways of the coagulation cascade?

A

Intrinsic and extrinsic

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4
Q

How is the intrinsic pathway activated?

A

Contact with collagen

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5
Q

How is the extrinsic pathway activated?

A

Contact with tissue factor (thromboplastin) following tissue injury

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6
Q

Where do the intrinsic and extrinsic pathways converge?

A

Factor Xa

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7
Q

What is the key event of the common coagulation cascade?

A

The conversion of fibrinogen to fibrin

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8
Q

What converts fibrinogen into fibrin?

A

Thrombin

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9
Q

What are 2 vital cofactors in the coagulation cascade?

A

Calcium and vitamin K

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10
Q

What is PT, and what does it measure?

A

Prothrombin time, measures clotting time in extrinsic and common pathways

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11
Q

How is the PT test done?

A

Add tissue factor, phospholipids, and Ca++ to citrated plasma

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12
Q

What is aPTT, and what does it measure?

A

Activated partial thromboplastin time, measures clotting time in intrinsic and common pathways

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13
Q

How is the aPTT test done?

A

Add negative charge, phospholipids, and Ca++ to plasma

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14
Q

What is TT, and what does it measure?

A

Thrombin time, measures function and level of fibrinogen in blood

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15
Q

How is the TT test done?

A

Add thrombin to plasma

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16
Q

Which clotting time is usually the fastest?

A

PT

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17
Q

Which clotting time is usually the slowest?

A

aPTT

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18
Q

What is a normal platelet count?

A

150000-450000 plt/mcL

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19
Q

What is a low platelet count called?

A

Thrombocytopenia

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20
Q

What is a high platelet count called?

A

Thrombocytosis

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21
Q

What are the three components of virchow’s triad?

A
  1. Endothelial injury
  2. Abnormal blood flow
  3. Hypercoagulability
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22
Q

How does endothelial injury lead to thrombosis?

A

Loss of endothelial cells or imbalance of pro-and anti-coagulation factors can lead to abnormal blood flow or hypercoagulability

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23
Q

How does abnormal blood flow lead to thrombosis?

A

Turbulence or stasis can lead to endothelial injury or hypercoagulability

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24
Q

What are two kinds of hypercoagulability?

A

Primary (genetic)
Secondary (acquired through e.g. OCP, pregnancy, HRT, cancer, aging, smoking, obesity)

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25
Q

What are thrombi composed of?

A

Platelets, RBCs, WBCs, fibrin

26
Q

What is the term for the alternating bands of light platelets and fibrin with darker red blood cells?

A

Lines of Zahn

27
Q

Why are arterial thrombi most commonly found in the aorta and its major branches?

A

High pressure and turbulence

28
Q

What is an example of endothelial damage in large arteries that can lead to thrombosis?

A

Ruptured atherosclerotic plaque

29
Q

What is an example of abnormal blood flow in large arteries that can lead to thrombosis?

A

Aneurysm

30
Q

What is an example of hypercoagulability in large arteries that can lead to thrombosis?

A

Polycythemia

31
Q

Where do venous thrombi normally develop?

A

In the deep veins of the legs in the sinuses above valves

32
Q

What are two main causes of venous thrombi?

A
  1. Reduced venous return
  2. Hypercoagulability
33
Q

Why are 50% of DVTs asymptomatic?

A

Because collateral vessels form

34
Q

Why does DVT cause PE?

A

Because the lungs contain the first microvasculature the embolism will encounter

35
Q

What are 4 things that may happen to a thrombus?

A
  1. Dissolution
  2. Propagation
  3. Embolization
  4. Organization and recanalization
36
Q

What is organization and recanalization of the thrombus?

A

Invasion by connective tissue and blood vessel formation through the thrombus

37
Q

What 3 classes of drugs are used to treat or prevent thrombus?

A
  1. Anticoagulants
  2. Antiplatelets
  3. Thrombolytics
38
Q

Which group of drugs block the liver enzyme required for vitamin K activation?

A

Coumarins (e.g. warfarin)

39
Q

Which drug activates antithrombin to block thrombin from converting fibrinogen into fibrin?

A

Heparin

40
Q

Which group of drugs either inhibit thrombin or factor Xa?

A

Direct oral anticoagulants (DOACs)

41
Q

What are 2 examples of antiplatelet drugs?

A

Aspirin, thromboxane inhibitors

42
Q

What are 2 examples of thrombolytic drugs?

A

Streptokinase, tissue plasminogen activator (tPA)

43
Q

What are 3 risks of thrombosis treatment?

A
  1. Bleeding
  2. Vascular calcification due to vitamin K inactivation
  3. Embolization
44
Q

What is the term for a sudden, insidious onset of widespread fibrin thrombi in the
microcirculation?

A

Disseminated intravascular coagulation (DIC)

45
Q

Why does DIC cause uncontrolled bleeding?

A

It uses up all the platelets and clotting factors

46
Q

What are 4 treatments for pulmonary embolism?

A
  1. Prevention, e.g. anticoagulants
  2. Inferior vena cava filter
  3. Thrombolytics
  4. Embolectomy
47
Q

What kind of embolism may occur after skeletal or soft tissue injuries (e.g. CPR) and burns?

A

Fat or marrow embolism

48
Q

What kind of embolism may occur due to surgical incision, intravascular catheters, laparoscopic procedures, chest wall injuries, or scuba diving?

A

Air embolism

49
Q

What causes amniotic fluid embolism?

A

Amniotic fluid containing fetal epithelial cells and lanugo enters maternal circulation through open uterine and cervical veins

50
Q

What will happen to an infarct if it is not fatal?

A

Scar tissue formation

51
Q

Why are infarcts mostly caused by arterial thrombosis?

A

Because when a vein is occluded then the body is able to divert the blood to collateral vessels

52
Q

Name 2 ways to classify infarcts

A
  1. Colour
  2. Presence of infection
53
Q

What kind of infarcts occur in organs rich in blood supply?

A

Hemorrhagic (red) infarcts

54
Q

Name 2 examples of organs that hemorrhagic infarcts occur

A

Lungs, small intestine

55
Q

Explain the mechanism of hemorrhagic infarcts

A

Affected loose necrotic tissue fills with blood from surrounding blood vessels

56
Q

What kind of infarcts occur in solid organs with end-arterial circulation?

A

Anemic (pale) infarcts

57
Q

Name 3 examples of organs that may be affected by anemic infarcts

A

Heart, spleen, kidney

58
Q

Explain the mechanism of anemic infarcts

A

The only artery supplying the organ with blood is occluded. Blood cannot accumulate from surrounding vessels as the organ tissue is dense/solid

59
Q

Why do brain infarcts typically result in liquefactive necrosis?

A

Because neurons contain proteolytic enzymes that are released upon cell death

60
Q

What are 4 factors the affect the development of an infarct?

A
  1. Nature of blood supply (single or dual)
  2. Rate of occlusion development
  3. Cells’ vulnerability to hypoxia
  4. Patient’s SpO2