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

General Principles of Hemostasis Flashcards

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
Q

What does Xa do to TF,VIIa complex

A

Turn it off - then more fibrin needs to be made via intrinsic pathway

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26
Q

How to activate XI

A

thrombin

XI –> XIa

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27
Q

How to activate IX

A

XIa

IX –> IXa

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28
Q

What factors/cofactors help speed up process

A

VIII (complex with IXa)

V (helps Xa do its job)

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29
Q

How to activate X

A

TF, VIIIa (extrinsic) - once
IXa (intrinsic)
X –> Xa
complex with Va to be more efficient

30
Q

which pathway works first

A

Extrinsic, once get Xa then turn off

31
Q

TF

VII

A

Extrinsic (sextrinsic)

32
Q

Complicated side

A

Intrinsic (sintrinsic)

33
Q

Clot lysis pathway

A

Plasminogen activated → Plasmin by t-PA –> break up clot into FDPs

34
Q

Cascade inhibition

A

Protein C
TFPI
ATIII

35
Q

Protein C

A

inhibit cofactors VIIIa, Va

36
Q

ATIII

A

inhibit activated factors (XIa, IXa, Xa, TF/VIIa, Xa, thrombin)

37
Q

TFPI

A

inhibit TF/VIIIa

38
Q

How do platelet count

A

done by particle counter

39
Q

normal platelet number

A

150-450 x10^9/L

40
Q

morphology of platelet normally have

A

granulomeres

hyalomeres

41
Q

template bleeding time evaluates

A

platelet response to vascular injury

Some platelet disorders have a long bleeding time

42
Q

How template bleeding time

A

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

43
Q

limitation template bleeding time

A

Lots of factors affect the test!

Some consider the test unreliable.

44
Q

closure time (CT)

A

alternative to bleeding time

how quickly platelets occlude small holes in a membrane

45
Q

platelet aggregation finds

A

platelet function abnormalities

46
Q

How does platelet aggregation work

A

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

47
Q

limitation/caveat with platelet aggregation test

A

always repeat abnormal test

48
Q

Coagulation lab tests

A

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

49
Q

Factor VII

A

Made by liver
Needs K
Dec. by Coumadin
Short half-life (so really the one you want to watch, goes down faster)

50
Q

Prothrombin Time

A

Plasma + thromboplastin

Measures extrinsic pathway (factor VII)

51
Q

Things that increase prothrombin time

A

Dec. VII, X, V, II, I
Coumadin
Heparin
DIC

52
Q

When should you order a PT

A

Never - order an INR instead

53
Q

Coumadin affects what factors

A

II, VII, IX, X

54
Q

What is an INR

A

corrected PT

55
Q

When shoudl you order an INR

A

To assess liver function
To monitor Coumadin therapy
To diagnose DIC*
To assess pre-op status

56
Q

Partial thromboplastin time

A

Plasma + phospholipid
Measures intrinsic pathway
APTT = same thing

57
Q

PTT increased when

A

Hemophilia A, B
DIC
Heparin
Inhibitors

58
Q

When should you order a PTT

A

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
Q

Thrombin time

A

Plasma + Thrombin
Measures coversion of fibrinogen to fibrin
Bypasses intrinsic and extrinsic pathways

60
Q

TT increased when

A

Dec. fibrinogen (ie trauma)

Inc. FDPs

61
Q

PTT Mixing Study

A

Pooled plasma + patient plasma + phospholipid
If PTT corrects: something missing
If PTT doesn’t correct: inhibitor

62
Q

When should you order a mixing study

A

When PTT is prolonged, but TT is normal
If PTT corrects = factor deficiency
If PTT doesn’t correct = inhibitor present

63
Q

how to measure extrinsic side

A

PT, INR

64
Q

how to measure intrinsic side

A

PTT

65
Q

how to measure fibrinogen to fibrin

A

TT

66
Q

Fibrin Degradation Product Assay

A 
measures FDPs (including D-dimers)
Very sensitive (almost too sensitive to dx a bad clot)
67
Q

D-dimers

A

breakdown products of cross-linked fibrin

68
Q

what cross links fibrin

A

Factor XIII

69
Q

When are FDPs increased?

A

Thrombi

Minor clotting

70
Q

When to order an FDP assay?

A

Rule out a clot - not rule in

IHO Week 6 (EH) (9 decks)

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