HEMODYNAMICS LECTURE 2: Hemostasis & thrombosis

Question 1

What is the purpose of endothelial cells in hemostasis?

Answer 1

Express anticoagulant or procoagulant factors to regulate clotting

Question 2

Where do platelets originate?

Answer 2

Megakaryocytes in bone marrow

Question 3

What are the two pathways of the coagulation cascade?

Answer 3

Intrinsic and extrinsic

Question 4

How is the intrinsic pathway activated?

Answer 4

Contact with collagen

Question 5

How is the extrinsic pathway activated?

Answer 5

Contact with tissue factor (thromboplastin) following tissue injury

Question 6

Where do the intrinsic and extrinsic pathways converge?

Answer 6

Factor Xa

Question 7

What is the key event of the common coagulation cascade?

Answer 7

The conversion of fibrinogen to fibrin

Question 8

What converts fibrinogen into fibrin?

Answer 8

Thrombin

Question 9

What are 2 vital cofactors in the coagulation cascade?

Answer 9

Calcium and vitamin K

Question 10

What is PT, and what does it measure?

Answer 10

Prothrombin time, measures clotting time in extrinsic and common pathways

Question 11

How is the PT test done?

Answer 11

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

Question 12

What is aPTT, and what does it measure?

Answer 12

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

Question 13

How is the aPTT test done?

Answer 13

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

Question 14

What is TT, and what does it measure?

Answer 14

Thrombin time, measures function and level of fibrinogen in blood

Question 15

How is the TT test done?

Answer 15

Add thrombin to plasma

Question 16

Which clotting time is usually the fastest?

Answer 16

PT

Question 17

Which clotting time is usually the slowest?

Answer 17

aPTT

Question 18

What is a normal platelet count?

Answer 18

150000-450000 plt/mcL

Question 19

What is a low platelet count called?

Answer 19

Thrombocytopenia

Question 20

What is a high platelet count called?

Answer 20

Thrombocytosis

Question 21

What are the three components of virchow’s triad?

Answer 21

1. Endothelial injury
2. Abnormal blood flow
3. Hypercoagulability

Question 22

How does endothelial injury lead to thrombosis?

Answer 22

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

Question 23

How does abnormal blood flow lead to thrombosis?

Answer 23

Turbulence or stasis can lead to endothelial injury or hypercoagulability

Question 24

What are two kinds of hypercoagulability?

Answer 24

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

Question 25

What are thrombi composed of?

Answer 25

Platelets, RBCs, WBCs, fibrin

Question 26

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

Answer 26

Lines of Zahn

Question 27

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

Answer 27

High pressure and turbulence

Question 28

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

Answer 28

Ruptured atherosclerotic plaque

Question 29

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

Answer 29

Aneurysm

Question 30

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

Answer 30

Polycythemia

Question 31

Where do venous thrombi normally develop?

Answer 31

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

Question 32

What are two main causes of venous thrombi?

Answer 32

1. Reduced venous return 2. Hypercoagulability

Question 33

Why are 50% of DVTs asymptomatic?

Answer 33

Because collateral vessels form

Question 34

Why does DVT cause PE?

Answer 34

Because the lungs contain the first microvasculature the embolism will encounter

Question 35

What are 4 things that may happen to a thrombus?

Answer 35

1. Dissolution 2. Propagation 3. Embolization 4. Organization and recanalization

Question 36

What is organization and recanalization of the thrombus?

Answer 36

Invasion by connective tissue and blood vessel formation through the thrombus

Question 37

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

Answer 37

1. Anticoagulants 2. Antiplatelets 3. Thrombolytics

Question 38

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

Answer 38

Coumarins (e.g. warfarin)

Question 39

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

Answer 39

Heparin

Question 40

Which group of drugs either inhibit thrombin or factor Xa?

Answer 40

Direct oral anticoagulants (DOACs)

Question 41

What are 2 examples of antiplatelet drugs?

Answer 41

Aspirin, thromboxane inhibitors

Question 42

What are 2 examples of thrombolytic drugs?

Answer 42

Streptokinase, tissue plasminogen activator (tPA)

Question 43

What are 3 risks of thrombosis treatment?

Answer 43

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

Question 44

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

Answer 44

Disseminated intravascular coagulation (DIC)

Question 45

Why does DIC cause uncontrolled bleeding?

Answer 45

It uses up all the platelets and clotting factors

Question 46

What are 4 treatments for pulmonary embolism?

Answer 46

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

Question 47

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

Answer 47

Fat or marrow embolism

Question 48

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

Answer 48

Air embolism

Question 49

What causes amniotic fluid embolism?

Answer 49

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

Question 50

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

Answer 50

Scar tissue formation

Question 51

Why are infarcts mostly caused by arterial thrombosis?

Answer 51

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

Question 52

Name 2 ways to classify infarcts

Answer 52

1. Colour 2. Presence of infection

Question 53

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

Answer 53

Hemorrhagic (red) infarcts

Question 54

Name 2 examples of organs that hemorrhagic infarcts occur

Answer 54

Lungs, small intestine

Question 55

Explain the mechanism of hemorrhagic infarcts

Answer 55

Affected loose necrotic tissue fills with blood from surrounding blood vessels

Question 56

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

Answer 56

Anemic (pale) infarcts

Question 57

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

Answer 57

Heart, spleen, kidney

Question 58

Explain the mechanism of anemic infarcts

Answer 58

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

Question 59

Why do brain infarcts typically result in liquefactive necrosis?

Answer 59

Because neurons contain proteolytic enzymes that are released upon cell death

Question 60

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

Answer 60

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