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IHO Week 6 (EH) > General Principles of Hemostasis > Flashcards

General Principles of Hemostasis Flashcards

(70 cards)

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1
Q

Hemostasis is a balancing act between

A

pro-clotting and anti-clotting

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2
Q

pro-clotting

A

plugs up holes in blood vessels

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3
Q

anti-clotting

A

keep clotting under control

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4
Q

3 steps in pro-clotting

A

blood vessel constricts
Platelets form a plug
Fibrin seals up plug

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5
Q

blood vessel constriction –>

A

blood loss dec.

Platelets and factors meet

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6
Q

primary hemostasis

A 
Platelets form a plug.
  Proteins are exposed
  Platelets adhese
  Granules release contents
  Platelets aggregate
  Phospholipids are exposed
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7
Q

secondary hemostasis

A 
Fibrin seals up plug.
  Tissue factor is exposed
  Cascade begins
  Cascade makes fibrin
  Fibrin solidifies plug
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8
Q

Platelet adhesion vs. aggregation

A

cover initial hole vs. cover other prior platelets

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9
Q

anticlotting methods

A

Cascade inhibition

Clot lysis

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10
Q

Cascade inhibition players

A

TFPI
ATIII
Proteins C, S

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11
Q

Clot lysis players

A

t-PA

plasmin

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12
Q

Platelet granules

A

α (fibrinogen, vWF)

δ (serotonin, ADP, Ca2+)

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13
Q

Membranes of platelets

A 
Phospholipids (activate coag factors)
GP = glycoprotein
GP Ia (binds collagen)
GP Ib (binds vWF) 
GP IIb-IIIa (binds fibrinogen)
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14
Q

GP1a

A

binds collagen - mediates first platelet adhesion

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15
Q

GP1b

A

binds vWF = vonWillebron Factor to help platelets bind to each other

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16
Q

GP IIb-IIIa

A

binds fibrinogen

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17
Q

a granules

A

fibrinogen, vWF

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18
Q

d granules

A

serotonin, ADP, ca2+

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19
Q

Bottom line of cascade pathway

A

fibrinogen –> fibrin

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20
Q

How to make fibrin

A 
fibrinogen --> fibrin
Need thrombin (activated prothrombin)
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21
Q

How to activate prothrombin

A

–> thrombin

Need Xa

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22
Q

Activated X is important why

A

X –> Xa
central part of whole process - where extrinsic and intrinsic pathways meet
Necessary for prothrombin –> thrombin

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23
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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24
Q

What does TF do in cascade?

A

Join up with VII (already activated in blood) –> TF, VIIa –> go to activate X –> Xa

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25
What does Xa do to TF,VIIa complex
Turn it off - then more fibrin needs to be made via intrinsic pathway
26
How to activate XI
thrombin | XI --> XIa
27
How to activate IX
XIa | IX --> IXa
28
What factors/cofactors help speed up process
VIII (complex with IXa) | V (helps Xa do its job)
29
How to activate X
TF, VIIIa (extrinsic) - once IXa (intrinsic) X --> Xa complex with Va to be more efficient
30
which pathway works first
Extrinsic, once get Xa then turn off
31
TF | VII
Extrinsic (sextrinsic)
32
Complicated side
Intrinsic (sintrinsic)
33
Clot lysis pathway
Plasminogen activated → Plasmin by t-PA --> break up clot into FDPs
34
Cascade inhibition
Protein C TFPI ATIII
35
Protein C
inhibit cofactors VIIIa, Va
36
ATIII
inhibit activated factors (XIa, IXa, Xa, TF/VIIa, Xa, thrombin)
37
TFPI
inhibit TF/VIIIa
38
How do platelet count
done by particle counter
39
normal platelet number
150-450 x10^9/L
40
morphology of platelet normally have
granulomeres | hyalomeres
41
template bleeding time evaluates
platelet response to vascular injury | Some platelet disorders have a long bleeding time
42
How template bleeding time
Inflate blood pressure cuff Make incision Time how long it takes to stop bleeding
43
limitation template bleeding time
Lots of factors affect the test! | Some consider the test unreliable.
44
closure time (CT)
alternative to bleeding time | how quickly platelets occlude small holes in a membrane
45
platelet aggregation finds
platelet function abnormalities
46
How does platelet aggregation work
Add aggregating agents to patient’s sample See if platelets aggregate Measure decrease in sample turbidity
47
limitation/caveat with platelet aggregation test
always repeat abnormal test
48
Coagulation lab tests
Draw blood into citrate tube Spin tube, decant plasma Add reagents to plasma Watch for formation of fibrin
49
Factor VII
Made by liver Needs K Dec. by Coumadin Short half-life (so really the one you want to watch, goes down faster)
50
Prothrombin Time
Plasma + thromboplastin | Measures extrinsic pathway (factor VII)
51
Things that increase prothrombin time
Dec. VII, X, V, II, I Coumadin Heparin DIC
52
When should you order a PT
Never - order an INR instead
53
Coumadin affects what factors
II, VII, IX, X
54
What is an INR
corrected PT
55
When shoudl you order an INR
To assess liver function To monitor Coumadin therapy To diagnose DIC* To assess pre-op status
56
Partial thromboplastin time
Plasma + phospholipid Measures intrinsic pathway APTT = same thing
57
PTT increased when
Hemophilia A, B DIC Heparin Inhibitors
58
When should you order a PTT
To investigate a history of abnormal bleeding To monitor heparin therapy To diagnose DIC To diagnose an antiphospholipid antibody (ie. SLE, syphilis) To assess pre-op status
59
Thrombin time
Plasma + Thrombin Measures coversion of fibrinogen to fibrin Bypasses intrinsic and extrinsic pathways
60
TT increased when
Dec. fibrinogen (ie trauma) | Inc. FDPs
61
PTT Mixing Study
Pooled plasma + patient plasma + phospholipid If PTT corrects: something missing If PTT doesn’t correct: inhibitor
62
When should you order a mixing study
When PTT is prolonged, but TT is normal If PTT corrects = factor deficiency If PTT doesn’t correct = inhibitor present
63
how to measure extrinsic side
PT, INR
64
how to measure intrinsic side
PTT
65
how to measure fibrinogen to fibrin
TT
66
Fibrin Degradation Product Assay
``` measures FDPs (including D-dimers) Very sensitive (almost too sensitive to dx a bad clot) ```
67
D-dimers
breakdown products of cross-linked fibrin
68
what cross links fibrin
Factor XIII
69
When are FDPs increased?
Thrombi | Minor clotting
70
When to order an FDP assay?
Rule out a clot - not rule in

IHO Week 6 (EH) (9 decks)

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