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IHO Week 6 > Principles of Hemostasis > Flashcards

Principles of Hemostasis Flashcards

1
Q

2 pathways of clotting

A

Extrinsic

Intrinsic

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2
Q

Pro clotting

A

plugs up holes in vessels

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3
Q

anti clotting

A

keeps clotting under control

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4
Q

primary hemostasis

A

formation of platelet plug

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5
Q

secondary hemostasis

A

forming of fibrin meshwork

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6
Q

First step in pro clotting cascade

A

blood vessels constrict - blood loss decreases and platelets and factors meet

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7
Q

What happens when platelets form a plug

A 
proteins are exposed
platelets adhese
Granules release contents
platelets aggregate
phospholipids are exposed
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8
Q

Why is phospholipid exposure so important?

A

Coag factors need phospholipids to adhere to surface of endothelium

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9
Q

Fibrin

A

Seals up plug

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10
Q

What happens when TF is exposed?

A

Cascade begins, makes fibrin

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11
Q

General mechanism?

A
  • Platelets see subendothelium and stick
  • Layer of platelets adhese, flatten out and release granules
  • Granules attract other platelets
  • phospholipids exposed on newly activated surface
  • Coag factors come and sit down
  • fibrin made
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12
Q

What busts up fibrin

A

FDPs

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13
Q

Clotting cascade inhibition mediated by?

A

TFPI
ATIII
Proteins C and S

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14
Q

Clot lysis mediated by?

A

t-PA

Plasmin

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15
Q

Granules in platelets

A

a (firbrinogen, vWF)

d (serotonin, ADP, Ca)

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16
Q

Membrane of platelets contain

A

phospholipids (bind coag factors)
GP Ia (collagen)
GP Ib (vWF)
GP IIb-IIIa (fibrinogen)

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17
Q

GP Ia

A

Binds collagen

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18
Q

GP Ib

A

Binds vWF

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19
Q

GP IIb-IIIa

A

binds fibrinogen

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20
Q

vWF

A

helps platelets stick together

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21
Q

fibrinogen to fibrin mediated by what enzyme?

A

Thrombin (IIa)

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22
Q

Prothrombin to thrombin mediated by?

A

Xa

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23
Q

What activates X to Xa in extrinsic pathway?

A

TF and VIIa

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24
Q

What activates VII in Extrinsic pathway?

A

exposed TF

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25
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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26
Q

Factor XII

A

Always hanging out. TF binds and turns to VIIa which then binds to X and makes Xa

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27
Q

What happens to the extrinsic pathway once Xa is made?

A

It is turned off - anything further goes through the intrinsic pathway

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28
Q

Once a small amount of thrombin is made via extrinisic…

A

goes up to the intrinsic pathway, activates XI to turn into XIa

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29
Q

XIa activates

A

IX to IXa

30
Q

IXa activates

A

X to Xa

31
Q

VIIIa

A

cofactor, helps with conversion IXa to Xa

32
Q

Va

A

helps Xa turn protrombin into thrombin

33
Q

What breaks up clots to FDPs

A

plasmin

34
Q

plasminogen to plasma enzyme

A

via t-PA

35
Q

Can give t-PA if

A

recent clot, speed process along (needs to be right kind of clot)

36
Q

Protein C

A

Acts on cofactors VIIIa and Va.

37
Q

If cofactors are working then…

A

process moves along well. If you turn off process -want cofactors to stop.

38
Q

ATIII

A

Acts on both sides of cascade.

Bear hugs the activated factor and prevents from doing what supposed to do.

39
Q

TFPI

A

Tissue factor pathway inhibitor - turns of extrinsic side

40
Q

For a platelet count to account for bleeding…

A

would need to be extremely low (like 20,000)

41
Q

agranular

A

no granules

42
Q

Template bleeding time - why?

A

Evaluate platelet response to vascular injury

Some platelet disorders have a long bleeding time

43
Q

Template bleeding time - how?

A

Inflate BP cuff
Make incision
Time how long it takes to stop bleeding

44
Q

Template bleeding time - is it reliable?

A

Not really, lots of factors affect the test.

45
Q

Closure time (CT)

A

Measures how quickly platelets get into and occlude small holes in a membrane.

46
Q

Platelet aggregation tests - why?

A

Find platelet abnormalities

47
Q

Platelet aggregation tests - how?

A

Add aggregating agents to patient’s sample
See if aggregate
Measure DECREASE in turbidity

48
Q

Coag lab tests

A

Draw blood into citrate tube
Spin and decant plasma
Add reagents to plasma
Watch for formation of fibirn

49
Q

Prothrombin time

A

plasma + thromboplastin

measures extrinsic pathway

50
Q

Factor VII

A

Made by liver
Need K
Decreased by coumadin
Short half life

51
Q

PT increased when

A

Decrease in VII, X, V, II or I
Coumadin
Heparin
DIC

52
Q

Is PT ever decreased?

A

NO

53
Q

Coumadin affects

A

all vitamin k dependent factors (II, VII, IX, X)

54
Q

When should you order a PT?

A

Never, always an INR

55
Q

INR

A

a corrected PT

56
Q

When should you order an INR?

A

To assess liver function
To monitor coumadin therapy
Diagnose DIC
assess pre-op status

57
Q

Partial Thromboplastin Time (PTT)

A

plasma + phospholipid
Measures intrinsic pathway
APTT = same thing

58
Q

PTT increased with

A 
Hemophilia A
Hemophilia B
DIC
Heparin
Inhibitors
59
Q

When should you order PTT?

A 
Investigate abnormal bleeding
Monitor heparin therapy
Diagnose DIC
Diagnose antiphospholipid antibody
Assess pre-op status
60
Q

thrombin time

A

plasma + thrombin
Measures conversion of fibrinogen to fibrin
Bypasses the intrinsic and extrinsic pathway

61
Q

TT increaess

A

decreased fibrinogen

increased FDPs

62
Q

When should you order a thrombin time?

A

When the PTT is prolonged and you want to rule out a fibrinogen problem

63
Q

PTT mixing study

A

pooled plasma + patient plasma + phospholipid

64
Q

PTT corrects

A

something is missing (VIII or IX usually - hemophilia)

65
Q

PTT doesn’t correct

A

inhibitor (anti phospholipid ab)

66
Q

When order a mixing study?

A

PTT is prolonged, but TT is normal

67
Q

Fibrin Degradation Product assay

A 
measures FDP (including d dimers)
VERY SENSITIVE (almost too much)
68
Q

FDPS increase in

A

Thrombi

minor clotting

69
Q

Factor XIII

A

Cross links once in clots - makes lattice shape and strengthens

70
Q

Should order an FDP to…

A

Rule OUT a clot

IHO Week 6 (7 decks)

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