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IHO Week 6 (Final) > General Principles of Hemostasis - Krafts > Flashcards

General Principles of Hemostasis - Krafts Flashcards

1
Q

What is hemostasis a balance between?

A

Pro-Clotting (plugs up holes in blood vessels) and Anti-Clotting (keeps clotting under control)

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2
Q

What are the 3 factors in pro-clotting?

A

1) Vascular Constriction
2) Platelets to plug up the hole
3) Fibrin from Fibrinogen cascade

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3
Q

What happens when the blood vessel constricts?

A

Blood loss decreases

Platelets and factors meet (brings them closer together

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4
Q

What is primary hemostasis?

A

Platelets form a plug in the hole

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5
Q

What is secondary hemostasis?

A

Fibrinogen cascade

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6
Q

What happens when the platelets form a plug?

A 
Proteins are exposed
Platelets adhese
Granules release contents
Platelets aggregate
Phospholipids are exposed
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7
Q

What happens when the fibrin seals up the plug?

A

Tissue factor is exposed
Cascade begins and makes fibrin
Fibrin solidifies plug

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8
Q

Where is Tissue Factor NOT normally found?

A

In the blood

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9
Q

When the first platelet finds a site of injury, what does it do?

A

Adhesion to the hole and release of granules

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10
Q

When the subsequent platelets find the initial platelet, what do they do?

A

Aggregation of platelets

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11
Q

How is the inhibition of the coagulation cascade in order to stop a clot from forming?

A

TFPI (Tissue Factor Pathway Inhibition)
ATIII (Anti-Thrombin III)
Proteins C and S (Cascade Brakes!)

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12
Q

How are clots broken down?

A

t-PA

Plasmin

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13
Q

What is seen in the vicinity of a clot being remodeled?

A

Chunks of fibrin from busting down the clot

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14
Q

In the membrane of a platelet, what are the glycoproteins associated with disease?

A

Phospholipids (active coag factors)
GP Ia (binds collagen)
GP Ib (binds vWF)
GP IIb-IIIa (binds fibrinogen)

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15
Q

What is the whole point of the cascade to a clot?

A

Make Fibrin

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16
Q

Fibrinogen is converted to fibrin by what?

A

Thrombin

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17
Q

Prothrombin is converted to thrombin by what?

A

Factor Xa

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18
Q

When the extrinsic pathway is exposed to tissue factor, what factor does it bind to?

A

VIIa

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19
Q

Where does tissue factor come from?

A

Hidden cells exposed during injury
Microparticles floating in blood
Endothelial cells and monocytes (during inflammation)

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20
Q

What activates X –> Xa?

A

TF-VIIa complex

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21
Q

When Xa is made by using tissue factor, it immediately shuts off what?

A

Extrinsic Pathway

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22
Q

What activates factor XI –> XIa?

A

Thrombin

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23
Q

What does XIa activate?

A

IX –> IXa

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24
Q

What cofactor is used to further activate and speed up the intrinsic pathway?

A

VIIIa binds to IXa

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25
Q

What converts VIII –> VIIIa, V —> Va, and VII –> VIIa?

A

Thrombin

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26
Q

What are the key factors in the extrinsic pathway?

A

Tissue Factor and VIIa

*SEXtrinsic Pathway (simple)

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27
Q

What are the key factors in the intrinsic pathway?

A

Factors IXa and VIIIa

*SINtrinsic Pathway (busy)

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28
Q

What are the two things that you can do to prevent clotting?

A

1) Remodel the clot

2) Stop the fibrin cascade

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29
Q

What are FDPs and where do they come from?

A

Fibrin Degradation Products come from busting up a fibrin clot

30
Q

Where does t-PA work?

A

Plasminogen —> Plasmin to bust up the clot into Fibrin Degradation Products

31
Q

How is a clot formed?

A

Fibrinogen –> Fibrin –> CLOT

32
Q

Protein C cleaves what?

A

Va and VIIIa

33
Q

Anti-thrombin III effects what?

A

VIIa, IXa, XIa, Xa, and thrombin

34
Q

Tissue Factor Pathway Inhibitor (TFPI) mediates what interaction?

A

Xa turning off the extrinsic pathway

35
Q

What are we looking for in the morphology of platelets?

A

Size and Granulation

36
Q

What is a normal platelet count?

A

150,000-450,000 x 10^6/L

37
Q

What is a Template Bleeding Time?

A

Used to evaluate platelet response to vascular injury

38
Q

How do you perform a Template Bleeding Time test?

A

Inflate a blood pressure cuff
Make measured incisions
Time how long it takes to stop bleeding with blotting paper

39
Q

What is wrong with the Template Bleeding Time test?

A

Does not measure the coagulation factor, just measures platelet plug formation

40
Q

What does the Closure Time test measure?

A

How quickly platelets occlude small holes in a membrane

41
Q

What is the Closure Time test used for?

A

Aspirin-Related Bleeding

von Willebrand disease

42
Q

What is the Platelet Aggregation test?

A

Used to find platelet function abnormalities

43
Q

How do you perform a Platelet Aggregation test?

A

Add aggregating agents to patient’s sample to see if platelets aggregate
Measure the DECREASE in sample turbidity

44
Q

How does a coagulation lab test work?

A

Draw blood into citrate tube
Spin tube, decant plasma
Add reagents to plasma
Watch for formation of fibrin

45
Q

What does the Prothrombin Time (PT) test measure?

A

Extrinsic Pathway - how long it takes to make fibrin

Plasma + Thromboplastin

46
Q

What do we measure in the Extrinsic Pathway?

A

Factor VII

  • Made by liver
  • Needs Vitamin K to work
  • Decreased by Coumadin
  • Short half-life
47
Q

What coagulation factors need Vitamin K to work?

A

Factor II, VII, IX, and X

48
Q

What kinds of things would increase the Prothrombin time (or prolong the clotting time)?

A
  • Decreased VII, X, V, II, I
  • Coumadin
  • Heparin
  • Disseminated Intravascular Coagulation (DIC)
49
Q

When should you order a Prothrombin Time (PT) test?

A

NEVER!

Order INR instead

50
Q

What is an INR?

A

A corrected Prothrombin Time (PT) test

51
Q

When should you order an INR?

A
  • Assess Liver Function
  • Monitor Coumadin Therapy
  • Diagnose DIC
  • Assess Pre-OP Status
52
Q

What does the Partial Thromboplastin Time (PTT) test measure?

A

Intrinsic Pathway

Plasma + Phospholipid

53
Q

What is another name for Partial Thromboplastin Time (PTT)?

A

Activated Partial Thromboplastin Time (APTT)

54
Q

What kinds of things would increase the Partial Thromboplastin Time (or prolong the clotting time)?

A 
Hemophilia A (Missing Factor VIII)
Hemophilia B (Missing Factor IX)
DIC
Heparin
Inhibitors
55
Q

When should you order a PTT?

A
  • Investigate a history of abnormal bleeding
  • Monitor heparin therapy
  • Diagnose DIC
  • Diagnose an anti-phospholipid antibody
  • Assess Pre-OP Status
56
Q

What does the Thrombin Time test measure?

A

Conversion of Fibrinogen to Fibrin
Plasma + Thrombin
(Ignores the Intrinsic and Extrinsic Pathways)

57
Q

What kinds of thinks would increase Thrombin Time?

A

Decreased Fibrinogen

Increased Fibrin Degradation Products

58
Q

When should you order a Thrombin Time?

A

When the PTT is prolonged and you want to rule out a fibrinogen problem (VERY rare!)

59
Q

If you have a prolonged PTT, but the TT is normal, what test would you order to figure out if it is an intrinsic or extrinsic problem?

A

PTT Mixing Study

60
Q

What are the factors in the PTT Mixing Study?

A

Pooled Plasma + Patient Plasma + Phropholipid

61
Q

What are the outcomes of the PTT Mixing Study?

A

If PTT corrects: some factor is missing

If PTT doesn’t correct: an inhibitor is present

62
Q

What does a Fibrin Degradation Product Assay measure?

A

Fibrin Degradation Products (including D-dimers)

VERY VERY Sensitive

63
Q

When Fibrin is forming a clot, what factor cross-links the fibrin?

A

Factor XIII

64
Q

How is Fibrinogen broken down to FDPs?

65
Q

How is Cross-Linked Fibrin broken down and what is it broken down to?

A

Plasmin

D-dimers

66
Q

When are FDPs increased?

A

Thrombi

Minor Clotting

67
Q

When should you order an FDP assay?

A

To rule OUT a clot

68
Q

What does a Fibrinogen Assay measure?

A

Fibrinogen

69
Q

When is Fibrinogen decreased?

A

DIC (using up all coag factors)

Massive bleeding

70
Q

When should you order a Fibrinogen level?

A
  • Diagnose DIC

- Follow patients with massive bleed

IHO Week 6 (Final) (11 decks)

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