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NU 700 Pharm for Anes. > Coagulation Pharmacology > Flashcards

Coagulation Pharmacology Flashcards

1
Q

hemostasis

A

prevents blood loss, keeps blood within the vessels

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2
Q

4 steps of clot formation

A
  1. initiation
  2. amplification
  3. propagation
  4. stabilization
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3
Q

3 key players of hemostasis

A

vascular endothelium, platelets, plasma coagulation proteins

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4
Q

primary hemostasis vs secondary

A

1: when PLTs arrive to site of injury and form the initial plug
2: requires crosslinking of fibrin

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5
Q

4 events of hemostasis

A
  1. vasoconstriction
  2. formation of a temporary loose plt plug (primary…adhesion, activation, aggregation)
  3. stable fibrin clot formation (secondary)
  4. clot retraction and dissolution
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6
Q

how is plt plug formed

A

vonWillebrand factor is released and binds plts to the damaged endothelium

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7
Q

what protein binds platelets to vWF

A

glycoprotein 1B

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8
Q

how is the plt plug activated

A

Thrombin (factor 2a) binds to the plt, which causes it to change shape and release ADP & TXA2 (thromboxane A2). ADP & TX2 promote aggregation

thrombin+PLT = ADP/TXA2 release

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9
Q

4 factors that activate platelets

A

collagen, ADP, TXA2, activated neutrophils secrete plt-activating factor

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10
Q

plt aggregation…what is main factor involved

A

Fibrinogen (TXA2 and ADP uncover fibrinogen receptors on plts so fibrinogen (factor 1) can bind to plt, causing plts to link together)

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11
Q

what binds plt and fibrinogen

A

glycoprotein 2B/3A

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12
Q

what is released after endothelial injury

A

thromboplastin or tissue factor (TF or factor 3)

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13
Q

what is the first event of the extrinsic pathway of clotting cascade

A

endothelial release of thromboplastin or TF/factor 3

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14
Q

4 steps of secondary hemostasis

A
  1. generate thrombin
  2. thrombin breaks down to fibribogen (factor 1)
  3. fibrin is released
  4. fibrin stands solidify the clot (acts like a glue)
    (TFFC: thrombin, fibrinogen, fibrin, clot)
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15
Q

3 pathways of the clotting cascade and associated factors

A

intrinsic (12, 11, 9, 10)
extrinsic (3, 7, 10)
common (1, 2, 5, 10, 13)

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16
Q

steps of the extrinsic pathway (4)

A

injury to vessel releases thromboplastin (factor 3/TF) –> factor 3 forms complex w/ factor 7 on plt surface –> factor 10 –> Factor 10 is activated by Calcium to 10a

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17
Q

steps of intrinsic pathway (7)

A

exposure of blood to collagen activates factor 12 –> 12a –>11–> 11a –> 9 –> 9a complexes with factor 8a & Cal on plt surface –> this activates factor 10

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18
Q

steps of the common pathways (4)

A

factor 10a complexes w factor 5 and cal –> this converts factor 2 (prothrombin) to 2a (thrombin) –> thrombin converts fibrinogen(1) to fibrin(1a).
Factor 13 –> 13a by thrombin and calcium

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19
Q

what factor causes fibrin to crosslink and stabilize the clot

A

Factor 13a

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20
Q

all clotting factors are made in the liver except…(3)

A

vWF
TF (factor 3)
calcium (factor 4)

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21
Q

what factors are vit k dependent and require calcium for activity (board Q*)

A

2, 7, 9, 10
(2+7 is 9 not 10)

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22
Q

name for factor 1

A

fibrinogen

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23
Q

name for factor 2

A

prothrombin

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24
Q

name for factor 3

A

tissue factor (TF) or thromboplastin

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25
Q

name for factor 4

A

calcium

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26
Q

name for factor 5

A

proaccelerin or labile factor

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27
Q

name for factor 7

A

proconvertin or stable factor

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28
Q

vWF =

A

von Willebrand (doen’t have a #)

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29
Q

name for factor 13

A

fibrin stabilizing

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30
Q

5 steps to stop clotting

A
  1. liver clears activated factors
  2. AT and thrombomodulin inactivate proteases
  3. protein C inactivates fac 5 & 8
  4. thrombin inhibited (by development of fibrin)
  5. fibrinolysis via plasmin
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31
Q

what converts plasminogen to plasmin

A

tPA (tissue plasminogen activator)

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32
Q

what activates protein C and what does this do

A

-thrombomodulin activates protein C
-protein C inactivates factor 5 and 8
-this inactivates thrombin

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33
Q

whats the inactive form of plasmin

A

plasminogen

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34
Q

2 substances that are incorporated in the the clot as its developing

A

plasminogen and tPA

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35
Q

what does tPA do

A

converts plasminogen to plasmin

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36
Q

what does plasmin do

A

breaks down fibrin

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37
Q

what does antithrombin (AT) do

A
  1. inhibits thrombin (2a) and 10a
  2. partially inhibits factor 9a, 11a, 12a
  3. results in anticoagulation
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38
Q

AT is a cofactor for…?

A

heparin

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39
Q

where is AT made? what happens if pt has AT deficiency?

A

-liver
-pt is unresponsive to heparin if deficient

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40
Q

prothrombin time (PT) looks at which pathways

A

extrinsic and common

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41
Q

PT is sensitive to deficiencies in…(5)

A

fibrinogen
factor 2, 5, 7, 10

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42
Q

what drugs can PT be used to monitor AC with

A

vitamin K antagonists/warfarin

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43
Q

what is INR

A

-international normalized ratio…standardized system to report PT (bc of different lab reagents)
-ratio of a pt’s PT to a normal (control) sample

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44
Q

what pathways does aptt look at

A

intrinsic and common

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45
Q

aptt is sensitive to deficiencies in factors…(2)

A

8 & 9

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46
Q

whats ACT and what pathways

A

activated clotting time
intrinsic and common

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47
Q

what prolongs ACT? what does it assess?

A

heparin
-assess adequacy of heparinization (most accurate at high conc of heparin)

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48
Q

what affects ACT results (4)

A

plt dysfunction, thrombocytopenia, hemodilution, hypothermia

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49
Q

normal PT

A

12-14s

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50
Q

normal aptt

A

25-32s

51
Q

normal ACT

A

80-150s

52
Q

normal thrombin time (common pathway)

A

8-12s

53
Q

3 classes of coag drugs

A
  1. procoagulant
  2. antithrombotics (reduce clot formation)
  3. thrombolytics (dissolve clots)
54
Q

what are procoagulants used for

A

used during sx to control bleeding and help clot formation

55
Q

examples of procoagulants (6)

A

aminocaproic acid (amicar), DDAVP, protamine, fibrinogen, activated factor 7a, topical thrombin

56
Q

2 classes of procoagulants

A

antifibrinolytics (EACA, TXA, aprotinin) and factor replacements

57
Q

Epsilon aminocaproic acid (EACA) MOA

A

competitively inhibits the binding site on plasminogen. blocking conversion to plasmin and impairing fibrinolysis

58
Q

tranexamic acid (TXA) MOA

A

-competitively inhibits the binding site on plasminogen. blocking conversion to plasmin and impairing fibrinolysis (same as EACA, but more data and better outcomes w TXA)
-TXA also directly inhibits plasmin at high doses

59
Q

What types of cases is TXA used in

A

-cardiac, ortho, trauma sx
-can also be used for neuro, hepatic, OB/gyn sx

60
Q

SE of TXA

A

seizure

61
Q

Aprotinin MOA

A

directly inhibits plasmin
(currently off market for renal/CV toxicity)

62
Q

Protamine MOA

A

-inactivates heparin via acid-base interaction
-protamine is + and hep is -…electrostatic complex is formed and inactivates hep (does NOT work on lovenox)

63
Q

protamine dosing

A

must be dosed based on how much heparin is in circulation, if too much is given you can induce coagulopathy
-1mg/100u of heparin

64
Q

protamine SE (4)

A

anaphylaxis
pulm vasoconst
R heart failure
hypotension (admin slowly to avoid)

65
Q

3 causes of protamine sensitization

A

increased risk of SE
1. NPH insulin (diabetics)
2. vasectomy (protamine made from fish sperm)
3. prior protamine exposure

66
Q

DDAVP MOA

A

stimulate release of vFW from endothelial cells and shorten bleeding time

67
Q

DDAVP dose

A

0.3mg/kg over 15-30m to avoid hypotension

68
Q

what is Fibrinogen (factor 1) affected by (3)

A

thrombin, factor 13a, plasmin

69
Q

what reduces fibrinogen levels

A
  1. hemorrhage
    2, hemodilution
70
Q

normal fibrinogen level

A

200-400mg/dl

71
Q

what level to transfuse fibrinogen? why cant you use FFP?

A

-100mg/dL
-FFP may not correct the underlying issue

72
Q

what can you use instead of fibrinogen

A

cryoprecipitate

73
Q

recombinant activated factor 7a MOA/use

A

-used off label for pro-hemostatic effects for lifethreatening hemorrhage
-increases thrombin, complexes w TF at injury site, amplifies hemostatic activation

74
Q

FDA MedWatch for recomb factor 7a

A

risk of thromboembolic events PE/DVT if use off label

75
Q

major downside to recomb factor 7a

A

can normalize elevated INR and PT lab values without actually correcting the coag defect internally

76
Q

Prothrombin Complex Concentrates (PCCs)
ex: KCENTRA has what factors

A

2, 7, 9, 10

77
Q

Prothrombin Complex Concentrates (PCCs) use/MOA

A

vitamin K antagonist/warfarin reversal (PCC used more worldwide, FFP in the US)

78
Q

when to use PCC

A

lifethreatening bleeding, increased INR requiring urgent reversal
–acts quickly and readily available (no cross-matching)

79
Q

2 classes of antithrombotic drugs and purpose

A

Purpose: reduce formation of clots
Classes: anticoagulants (AC) and antiplatelets

80
Q

AC uses (3)

A

CV procedures, thromboprophylaxis, CV diease/afib

81
Q

heparin MOA

A

bind to AT and inhibit factor 2a, 10a, 9a, 11a, 12a

82
Q

when AT and heparin bind, it forms a complex that…

A

increases the rate of the thrombin-antithrombin reaction by 1000-10,000 times

83
Q

heparin use (3)

A
  1. VTE prophylaxis
  2. ACS
  3. periop AC (ecmo, HD circuits)
84
Q

heparin onset IV and SQ

A

IV: immediate
SQ: 1-2h

85
Q

heparin dose for cardiac surgery

A

300-400 u/kg IV bolus

86
Q

aptt goal with heparin

A

1.5-2.5x normal…typically 30-35sec

87
Q

ACT monitoring for heparin

A

-use for high heparin doses
-looks at intrinsic pathway (factor 12a initiates clot cascade)
-detects onset of clot formation

88
Q

what influences ACT during CT surgery (4)

A

hypothermia, low plt, presence of aprotinin, preexisting coag deficiencies (fibrinogen, factor 12, 7)

89
Q

how often to monitor ACT/heparin during CT surgery and goal ACT

A

before IV heparin given, 3-5 min after hep, 30min intervals
-goal >350/400 (site specific goal)

90
Q

what is HIT

A

heparin induced thrombocytopenia
-begins w/in hours of exposure
-drop in plt count (50% in severe cases)
-caused by heparin-dependent antibodies

91
Q

heparin reversal agent?
and consideration?

A

-protamine (1mg for every 100u of circulating heparin)
-protamine clearance is more rapid than heparin –> risk for heparin rebound

92
Q

vit k antagonists use (3)
(warfarin)

A

prevent VTE, prevent stroke w/ prosthetic valves and afib, tx for thrombophilia

93
Q

warfarin MOA

A

-inhibit vit k eroxide reductase whih converts vitK dependent facctors to their active forms
-factors 2, 7, 9, 10

94
Q

target INR w warfarin

A

2-3 (2.5-3.5 w mech valves)

95
Q

5 things that can change INR (not meds)

A
  1. diet
  2. undisclosed drug use
  3. poor compliance
  4. “surreptitious self-medication”
  5. alcohol
96
Q

what class is xarelto (rivaroxaban)

A

direct factor 10a inhibitor

97
Q

xarelto use (7)

A
  1. reduce stroke risk w afib
  2. DVT prophylaxis
  3. DVT treatment
  4. tx of PE
  5. reduce risk of recerrent DVT/PE
  6. w/ ASA to reduce risk of CV events in CAD/PAD pts
  7. can be used w HIT
98
Q

anesthetic concern w/ xarelto

A

-neuraxial anesthesia
-can remove epidural cath 18h AFTER last dose given
-must wait 6h to give next dose after d/c epidural

99
Q

Direct Thrombin Inhibitor drugs

A

bivalirudin, argatroban, lepirudin, desirudin

100
Q

Bivalent direct thrombin inhibitors/MOA

A

-bivalirudin, lepirudin, desirudin
-bond to thrombin in a bivalent manner at the catalytic site and fibrinogen-binding site

101
Q

argatroban use

A

prophylaxis or treatment of thrombosis in pts with HIT or high risk of HIT needing PCI

102
Q

argatroban aptt goal and elimination

A

-1.5-3x baseline
-liver (not renal dosing needed)

103
Q

Dabigatran Etexilate (Pradaxa) anesthetic concern

A

-direct thrombin inhibitor
-neuraxial anesthesia…first dose can be given 2h after catheter removal
-observe for s/s of neuro dysfunction
-adjust dose for renal dysfunction

104
Q

antiplatelet moa

A

inhibit thrombus formation by inhibiting plt aggregation and inhibiting adhesion to clot (reversibly or irreversibly)

105
Q

altiplt agents

A

-COX inhibitors, P2Y12 receptor antagonists, Plt GP 2b/3a antagonists

106
Q

cox inhibitors
-2 types
-MOA

A

NSAIDs/ASA
-acts on arachidonic acid cascade, COX normally converts AA to prostacyclin and thromboxane A2 which gets blocked

107
Q

ASA MOA

A

-non-selective and irreversible COX inhibitor
-COX1 is more sensitive to ASA
-prevents formation of thromboxane A2 to prevent plt aggregation

108
Q

COX 1

A

maintain integrity of gastric lining and renal BF
initiate the formation of thromboxane A2*

109
Q

COX 2

A

synthesized PG mediators in pain and inflammation

110
Q

when to stop ASA before sx?

A

-7-10 days bc ASA effect on plt is irreversible and lasts for the life of the plt (low risk)
-continue ASA for pts at mod-high risk for CV events getting non-cardiac sx

111
Q

when to resume ASA post-op?

A

~24h

112
Q

how to reverse ASA

A

plt transfusion

113
Q

NSAID MOA

A

reversible, nonsel COX inhibitor
-antipyretic, antiinflamm, antiplt effects

114
Q

P2Y12 antagonists: thienopyridines MOA

A

irreversibly inactivate ADP-binding site of P2Y12 receptor

115
Q

P2Y12 antagonists: thienopyridines drug examples

A

ticlopidine, clopiddogrel (Plavix), prasugrel (Effient), ticagrelor

116
Q

when to dc thienopyridines before sx

A

5-7d before elective sx and avoid regional anes until effects of drug have dissipated

117
Q

what is dual antiplt therapy

A

Dual antiplatelet therapy = a thienopyridine (ADP
P2Y12 receptor antagonist) coadministered with
aspirin

118
Q

when to stop vit k antagonists before sx? when to resume?

A

-5 days before if low risk for VTE
-12-24h post op if adequate hemostasis
-if high risk for VTE use hep or lovenox to bridge after dc

119
Q

when to stop heparin drip before sx? resume?

A

-stop 4-6h preop
-resume >12h post op
-if high risk of bleeding, wait 48-72h post op to resume

120
Q

when to give last dose of lovenox before sx? resume?

A

-last dose 24h prior to sx
-resume 24h post-op (low risk)
-48-72h post-op if high risk

121
Q

risks w/ ASA in periop setting

A

MI/CV events > bleeding

122
Q

how long to delay sx after bare metal stent placement

A

6 weeks

123
Q

how long to delay sx after drug eluding stent

A

6 months

124
Q

what if pt needs surgery after stent placement before the 6week or 6 month goal is met?

A

If surgery is required before this time has passed, dual anti-platelet therapy should be continued
unless the risk of bleeding is thought to outweigh the risk of stent thrombosis

NU 700 Pharm for Anes. (6 decks)

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