Hemostasis I

Question 1

Hemostasis components

Answer 1

• vascular system
• platelet system
• coagulation system
• fibrinolytic system
• coagulation inhibition system

Question 2

Mechanism of hemostasis

Answer 2

1. vascular constriction
2. formation of platelet plug
3. formation of blood clot
4. Fibrinolysis

Question 3

Causes of vascular constriction in hemostasis

Answer 3

1. Platelet-released thromboxane A2

2. nervous system reflex to pain

Question 4

Formation of platelet plug (primary hemostasis)

Answer 4

Injury–> Collagen + VWF + PLTs + fibrinogen

Question 5

How are platelets activated

Answer 5

1. Binding of VWF to GPIb

2. Thrombin, adrenalin, ADP, collagen

Question 6

Activated platelets release?

Answer 6

ADP, thromboxane, Calcium

Question 7

Activation of plts by ADP exposes what receptor?

Answer 7

GPIIb/IIIa

Question 8

Other than ADP, what else leads to GPIIb/IIIa exposure?

Answer 8

thromboxane A2

Question 9

Function of GPIIb/IIIa

Answer 9

Receptor that binds to fibrinogen, linking platelets together

Question 10

Secondary hemostasis

Answer 10

Clot formation

Question 11

Function of thrombin in hemostasis?

Answer 11

Fibrin conversion, platelet activation

Question 12

Name for Factor I

Answer 12

Fibrinogen

Question 13

Name for Factor 2

Answer 13

Prothrombin

Question 14

Name for Factor 3

Answer 14

Tissue factor or thromboplastin

Question 15

Name for Factor 4

Answer 15

Calcium

Question 16

Name for factor 13

Answer 16

Fibrin-stabilizing factor

Question 17

Prothrombin is converted to thrombin by the action of what?

Answer 17

Prothrombin activator

Question 18

fibrinogen is converted to fibrin monomer and eventually fibrin fibers by

Answer 18

Thrombin

Question 19

Fibrin fibers are converted to cross-linked fibrin fibers by the action of what factor?

Answer 19

Factor 13. Fibrin-stabilizing factor

Question 20

Aspirin works on what pathways (site of action) to inhibit the production of?

Answer 20

COXs pathways to inhibit the production of thromboxane A2

Question 21

Extrinsic pathway is activated by?

Answer 21

Tissue factor, which is released into the blood as a result of vascular injury.

Question 22

Primary factor in the extrinsic pathway

Answer 22

Factor 7

Question 23

TF:FVII activates what factor?

Answer 23

Factor ten, and is considered a TENase

Question 24

Intrinsic pathway is activated by?

Answer 24

Trauma to the blood, or exposure to collagen

Question 25

Factors specific to the intrinsic pathway

Answer 25

12, 11, 9, 8

Question 26

Factors of the common pathway

Answer 26

10, 5, 2, 1

Question 27

Final common pathway

Answer 27

where the intrinsic and extrinsic pathway converge, resulting in fibrin formation

Question 28

In the contemporary view of hemostasis coagulation begins with the activation of factors X and IX by?

Answer 28

TF:FVII complex, thus, linking the intrinsic and extrinsic pathway

Question 29

3 Phases of coagulation activation in the contemporary view of hemostasis?

Answer 29

1. Initial phase
2. Amplification phase
3. Propagation phase

Question 30

Initiation phase

Answer 30

Tissue factor exposed–> TF:FVIIa complex –> Activation of FX and FIX–> Generation of small amounts of thrombin FIIa

Question 31

Is the amount of thrombin generated in the initial phase large or small?

Answer 31

small

Question 32

Amplification phase

Answer 32

-conversion from extrinsic to intrinsic thrombin formation by generation of another tenase (FIXa:FVIIIa)

FIXa:FVIIIa increased production of FXa by 50-100x hence amplification, and increased thrombin production

Thrombin creates a positive feedback group

Question 33

Factors thrombin acts on in the positive feedback loop

Answer 33

11–>11a, 8–>8a, 5–>5a

**Thrombin also leads to further PLT activation and aggregation

Question 34

Propagation phase

Answer 34

Thrombin burst –>plt aggregation and the formation of fibrin fibers, which stabilized by FXIIIa into cross-linked fibrin strands, to form a stable network

Question 35

Fibrinolysis

Answer 35

Dissolution of thrombi and maintaining patency of vascular system

Question 36

Fibrinolysis pathway

Answer 36

Plasminogen activated to plasmin which cleaves fibrin

Question 37

Factors that activate plasminogen

Answer 37

Physiologic- tPA, Urokinase

Exogenous- Streptokinase

Question 38

Medications that block plasmin from cleaving thrombin

Answer 38

Amicar

Tranexamic acid

Question 39

Hemophilia A is a deficiency in what factor?

Answer 39

Factor VIII

Question 40

Severe hemophilia

Answer 40

<1% of normal factors

Question 41

Mild hemophilia

Answer 41

> 5% but <40% normal factors

Question 42

Hemophilia B

Answer 42

Factor IX deficiency

Question 43

Treatment for hemophilia

Answer 43

• Replacement of factor
• DDAVP
• sometimes antifibrinolytics

Question 44

because of frequent factor replacement, 30% of patients with hemophilia A develop?

Answer 44

antifactor antibodies

Question 45

Disseminated intravascular coagulation

Answer 45

Thrombohemorragic d/o involving the generation of intravascular thrombin and consumption of procoagulants and platelets

Question 46

Common conditions that cause DIC

Answer 46

Sepsis, obstetric complications, trauma, shock, massive hemolysis, hepatic failure

Question 47

Management of DIC primarily focuses on treating?

Answer 47

the underlying disorder

Question 48

DIC diagnosis

Answer 48

plts 10-20k

• Symptoms of thrombosis
• Bleeding from three unrelated sites
• Lab findings- prolonged clotting times, decreased clotting factors