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IHO Week 6 > Principles of Hemostasis > Flashcards

Principles of Hemostasis Flashcards

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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
Where does tissue factor come from?
- Hidden cells exposed during injury - Microparticles floating in blood - Endothelial cells and monocytes (during inflammation)
26
Factor XII
Always hanging out. TF binds and turns to VIIa which then binds to X and makes Xa
27
What happens to the extrinsic pathway once Xa is made?
It is turned off - anything further goes through the intrinsic pathway
28
Once a small amount of thrombin is made via extrinisic...
goes up to the intrinsic pathway, activates XI to turn into XIa
29
XIa activates
IX to IXa
30
IXa activates
X to Xa
31
VIIIa
cofactor, helps with conversion IXa to Xa
32
Va
helps Xa turn protrombin into thrombin
33
What breaks up clots to FDPs
plasmin
34
plasminogen to plasma enzyme
via t-PA
35
Can give t-PA if
recent clot, speed process along (needs to be right kind of clot)
36
Protein C
Acts on cofactors VIIIa and Va.
37
If cofactors are working then...
process moves along well. If you turn off process -want cofactors to stop.
38
ATIII
Acts on both sides of cascade. | Bear hugs the activated factor and prevents from doing what supposed to do.
39
TFPI
Tissue factor pathway inhibitor - turns of extrinsic side
40
For a platelet count to account for bleeding...
would need to be extremely low (like 20,000)
41
agranular
no granules
42
Template bleeding time - why?
Evaluate platelet response to vascular injury | Some platelet disorders have a long bleeding time
43
Template bleeding time - how?
Inflate BP cuff Make incision Time how long it takes to stop bleeding
44
Template bleeding time - is it reliable?
Not really, lots of factors affect the test.
45
Closure time (CT)
Measures how quickly platelets get into and occlude small holes in a membrane.
46
Platelet aggregation tests - why?
Find platelet abnormalities
47
Platelet aggregation tests - how?
Add aggregating agents to patient's sample See if aggregate Measure DECREASE in turbidity
48
Coag lab tests
Draw blood into citrate tube Spin and decant plasma Add reagents to plasma Watch for formation of fibirn
49
Prothrombin time
plasma + thromboplastin | measures extrinsic pathway
50
Factor VII
Made by liver Need K Decreased by coumadin Short half life
51
PT increased when
Decrease in VII, X, V, II or I Coumadin Heparin DIC
52
Is PT ever decreased?
NO
53
Coumadin affects
all vitamin k dependent factors (II, VII, IX, X)
54
When should you order a PT?
Never, always an INR
55
INR
a corrected PT
56
When should you order an INR?
To assess liver function To monitor coumadin therapy Diagnose DIC assess pre-op status
57
Partial Thromboplastin Time (PTT)
plasma + phospholipid Measures intrinsic pathway APTT = same thing
58
PTT increased with
``` Hemophilia A Hemophilia B DIC Heparin Inhibitors ```
59
When should you order PTT?
``` Investigate abnormal bleeding Monitor heparin therapy Diagnose DIC Diagnose antiphospholipid antibody Assess pre-op status ```
60
thrombin time
plasma + thrombin Measures conversion of fibrinogen to fibrin Bypasses the intrinsic and extrinsic pathway
61
TT increaess
decreased fibrinogen | increased FDPs
62
When should you order a thrombin time?
When the PTT is prolonged and you want to rule out a fibrinogen problem
63
PTT mixing study
pooled plasma + patient plasma + phospholipid
64
PTT corrects
something is missing (VIII or IX usually - hemophilia)
65
PTT doesn't correct
inhibitor (anti phospholipid ab)
66
When order a mixing study?
PTT is prolonged, but TT is normal
67
Fibrin Degradation Product assay
``` measures FDP (including d dimers) VERY SENSITIVE (almost too much) ```
68
FDPS increase in
Thrombi | minor clotting
69
Factor XIII
Cross links once in clots - makes lattice shape and strengthens
70
Should order an FDP to...
Rule OUT a clot

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