Anticoagulants: coag cascade and heparins Flashcards Preview

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Flashcards in Anticoagulants: coag cascade and heparins Deck (58):
1

What are coagulation factors?

Enzymes

2

What happens as the steps of coagulation go on?

The initial signal is amplified

3

Where is the coagulation cascade made?

In the liver

4

What does the final pathway of the coagulation cascade result in?

Conversion of prothrombin (II) to thrombin

5

What does the conversion of prothrombin to thrombin catalyze

Conversion of fibrinogen to fibrin

6

What does fibrin activate?

Plasmin and tissue plasminogen activator (t-PA)

7

What balance maintains homeostasis

The balance of procoagulants (coag factors) and endogenous anticoagulants

8

Give some examples of endogenous anticoagulants

Proteins C and S
Antithrombin III

9

What are proteins C and S important for

Warfarin dosing

10

What is antithrombin III important for?

Heparin dosing

11

What does the fibrinolytic system do?

Degrades fibrin

12

What does the degradation of fibrin result in?

Fibrin split products (FSP)
Fibrin Dimers (d-dimer)

13

What are fibrin split products also known as

Fibrin degradation products (FDPs)

14

What do increased levels of FSP, FDPs, and d-dimers suggest?

Presence of thrombi
(think DVT)

15

What are some examples of venous thrombi?

DVT
"Red thrombus"
Venous stasis thrombi

16

What is a complication of venous thrombi?

Pulmonary embolus

17

What are some examples of arterial thrombi?

Platelet driven
"White thrombus"

18

What are some complications of arterial thrombi?

Stroke
MI

19

Recall virchow's triad

Hypercoaguable state
Endothelial injury
Circulatory stasis

20

List some risks for thrombosis

Surgery
Cancer
Immobility
Varicose veins
Pregnancy

21

What is a potential complication of anticoagulation agents?

Bleeding

22

Is bleeding from an anticoagulant an allergy?

No!
Just an extension of their MOA

23

What is the MOA of heparin

It binds to antithrombin III
(AT III)

24

What is required for heparin binding

A specific pentasaccharide sequence

25

Heparin limitations

look at slides 20 and 21

26

What is unfractionated heparin (UFH)

A heterogeneous mix of sulfated glycosaminoglycans

27

What portion of UFH have the pentasaccharide?

1/3

28

How much more anticoagulant does UFH antithrombin complexes have than just antithrombin alone?

100-1000x more

29

What is UFH effective on?

Soluble fibrin -> not clot bound

30

What does UFH do to the thrombus?

Prevents growth/propagation

31

What does UFH allow the pt's system to do?

Allows pt's fibrinolytic system to degrade the clot

32

How do we measure UFH

By the activated Partial Thromboplastin Time (aPTT)

33

What kind of heparin is used as DVT prophylaxis

subq UFH

34

How much subq UFH is used as DVT prophylaxis

5000 units q12 or q8

35

What is the risk of heparin induced thrombocytopenia (HIT) with SubQ UFH for DVT prophylaxis?

It is that of IV UFH
*increased risk

36

List some advantages of UFH

Immediate anticoagulants
Measured by aPTT
Has a reversing agent (Protamine)

37

List some disadvantages of UFH

Non-linear kinetics
Frequent lab testing needed
Increased risk of bleeding

38

What is Protamine sulfate used for

Reverse UFH

39

What is the MOA of Protamine

combines w/ strongly acidic heparin

40

Is HIT I immune or non-immune

Non-immune

41

HIT I prevalence

10% of pts

42

HIT I description

Ok -> not very concerning
Transient due to clumping of platelets -> usually an artifact

43

How quickly does HIT I happen?

Immediately

44

Is HIT II immune or non-immune

Immune
Mediated by anti-platelet factor 4

45

Prevalence of HIT II

<3%

46

HIT II description

Happens 5-10 days after heparin
Platelet count falls by >50% from baseline

47

If pt has HIT II what do you test for?

PF4

48

How do you reduce the risk of HIT w/ a pt with low molecular weight heparin?

When this is the first heparin started in the pt

49

How is low molecular weight heparin (LMWH) dosed?

Weight based linear dosing

50

How do you administer LMWH?

SubQ

51

What is an available LMWH agent?

Enoxaparin

52

When are LMWH agents indicated?

ACS tx
DVT
PE
VTE prophylaxis in high risk populations

53

List some advantages of LMWH

More favorable benefit/risk ratio
More predictable dose response ratio
No IV access required
No routine testing

54

List some disadvantages of LMWH

SubQ administration causes pain
Testing requires anti-Xa -> not readily available
Possible upper weight max
No protamine reversal

55

Enoxaparin dosing for acute DVT w/ or w/o PE in an inpatient setting

1 mg/kg/dose (rounded) SubQ q12 hours
1.5 mg/kg (rounded) SubQ once daily

56

Enoxaparin dosing for acute DVT w/ or w/o PE in an outpatient setting

1 mg/kg/dose (rounded) SubQ q12

57

Is LMWH more or less costly than UFH?

Less

58

Is the risk of HIT higher or lower with LMWH than UFH?

Lower risk of HIT