Coagulation Flashcards

1
Q

What are the four steps of hemostasis?

A
  1. Vascular spasm
  2. Platelet plug formation (primary homeostasis)
  3. Coagulation and fibrin formation (secondary homeostasis)
  4. Fibrinolysis
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2
Q

Where are platelets produced and by what?

A

bone marrow by megakaryocytes

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3
Q

List the three steps required to produce a platelet plug:

A
  1. adhesion
  2. activation
  3. aggregation
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4
Q

During what step does von Willebrand factor bind to the platelet?

A

step 1 - adhesion

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5
Q

During what step does von Willebrand factor bind to the platelet?

A

step 1 - adhesion

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6
Q

How does the injured blood vessel initially active the platelet plug?

A

Endothelial injury exposes collagen -> exposed collagen at site of vascular injury activates platelets.

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7
Q

Intrinsic pathway saying:

A

If you can’t buy the intrinsic pathway for $12, you might be able to for $11.98

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8
Q

Extrinsic pathway saying:

A

You can buy the extrinsic pathway for 37 cents

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9
Q

Final common pathway saying:

A

The final common pathway can be purchased at the five (5) and dime (10) for 1 or 2 dollars on the 13th of the month

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10
Q

What converts fibrinogen to fibrinogen monomer?

A

Thrombin

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11
Q

What is a normal aPTT value?

A

25-32 seconds

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12
Q

What is a normal PT value?

A

12-14 seconds

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13
Q

What is a normal INR value? What is therapeutic on warfarin?

A

~ 1
2-3 times normal

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14
Q

What is a normal ACT?

A

90-120 seconds

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15
Q

What must the ACT be before initiating CPB?

A

> 400 seconds

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16
Q

What is a normal platelet count?

A

150,000 - 300,000 mm3

17
Q

What is normal bleeding time?

A

2-10 minutes

18
Q

What is a normal D-Dimer level?

A

< 500 mg/mL

19
Q

What are differential diagnoses for elevated D-Dimer?

A

DVT
PE
DIC

20
Q

What is the mechanism of action of heparin?

A

Binds to antithrombin (a natural circulating anticoagulant) and enhances its anticoagulant ability 1,000 fold
The heparin-AT complex neutralizes thrombin and activated factors 9, 10, 11, and 12
Platelet function also inhibited

21
Q

Discuss heparin dosing and therapeutic levels:

A

cardiac surgical dose: 300-400 U/kg
VTE prophylaxis: 5,000 U SC BID or TID
Active VTE dose: 5,000 U IV, infusion ~1,250 U/hr - maintain aPTT 1.5-2.5 times normal
Unstable angina and acute MI dose: 5,000 U IV, infusion 1,000 U/hr

therapeutic aPTT: 1.5-2.5 times normal (normal 25-35 seconds)
ACT on CPB: > 400 seconds

22
Q

Where is endogenous heparin produced?

A

liver
basophils
mast cells

23
Q

How does warfarin work?

A

Inhibited Vitamin K epoxide reductase complex 1 (an enzyme).
This indirectly inhibits production of vitamin K dependent factors 2, 7, 9, 10 and Proteins C and S

24
Q
A
24
Q

What is the therapeutic level for PT/INR for warfarin therapy?

A

2-3 times normal

25
Q

What is the dose for exogenous vitamin K?

A

10-20 mg PO, IM, or IV

26
Q

List 4 classes of anti platelet drugs:

A

ADP receptor inhibitors
GIIb/IIIa receptor antagonists
COX inhibitors (non-specific)
COX 2 inhibitors

27
Q

ADP Receptor Inhibitors: examples and time to stop before procedure

A

clopidogrel - 5-7 days
ticagrelor - 5-7 days
prasugrel - 7-10 days
ticlodipine - 14 days

28
Q

GIIb/IIIa Receptor Antagonists: examples and time to stop before procedure

A

abciximab - 3 days
eptifibatide - 1 day
tirofiban - 1 day

29
Q

COX inhibitors (non-specific): examples and time to stop before procedure

A

aspirin - 7 days
NSAIDs - 1-2 days

aspirin = irreversible
NSAIDs (ibuprofen, naproxen, ketorolac) = reversible

30
Q

COX 2 inhibitors: examples and time to stop before procedure

A

celecoxib - none
rofecoxib - none

they do not affect platelet function

31
Q

List 4 examples of anticoagulants:

A

Heparins (factor 2, 10a)
thrombin inhibitors
Factor 10 inhibitors
Vitamin K antagonists (2, 7, 9, 10 and proteins c and s)

32
Q

Heparins (factor 2, 10a): examples and time to stop before procedure

A

Unfractionated - 6 hours
Low molecular weight heparins (enoxaparin, dalteparin, tinzaparin) - 1-2 days

33
Q

Thrombin inhibitors: examples and time to stop before procedure

A

argatroban - 4-6 hours
bivalarudin 2-3 hours

34
Q

Factor 10 inhibitors: examples and time to stop before procedure

A

fondaparinux - 4 days

35
Q

Vitamin K antagonists (2, 7, 9, 10, proteins c and s): examples and time to stop before procedure

A

warfarin - 2-4 days

36
Q

Fibrinolytics = Plasminogen activators: examples and time to stop before procedure

A

tPA - 1 hour
streptokinase - 3 hours

37
Q

Drugs that decrease bleeding: examples and MOA

A

aminocaproic acid - plasminogen activation inhibitor
tranexemic acid - plasminogen activation inhibitor
aprotinin - inhibits plain, kvllikrein, thrombin, and protein C
desmopressin (DDAVP) - stimulates factor 8 and vWF release
protamine - reverses effects of heparin