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Flashcards in Coagluation Deck (23)
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1
Q

What is the mechanism of action of heparin?

A

activating antithrombin III (ATIII)
accelerating the rate at which antithrombin inhibits thrombin (factor IIa) and factor Xa

1g protamine reverses 100U of heparin
Monitor aPTT

2
Q

What is the mechanism of HIT type II?

A

immune-mediated
antibodies (IgG) against complex of platelet factor 4 (PF4) and heparin
5–14 days

3
Q

What is the mechanism of action of LMWH (eg.enoxaparin, dalteparin) ?

A

activating AT III –> inhibiting factor Xa
little effect on thrombin inhibition

Protamine incompletely reverses

4
Q

Is the risk of HIT higher or lower with LMWH compared to heparin?

A

fivefold lower with LMWH than with heparin due to its lower affinity for PF4

LMWH should NOT be used to anti-coagulate HIT patients because most HIT antibodies exhibit cross-reactivity with LMWH

5
Q

What is the mechanism of action of fondaparinux?

A

factor Xa inhibition

cleared unchanged in the kidneys, it is contraindicated in patients with renal insufficiency

6
Q

What is the mechanism of argatroban?

A

synthetic direct thrombin inhibitor

7
Q

List the direct thrombin inhibitors and how do you monitor their effects?

A

argatroban
dagibitran
lepirudin
bivalrudin

Monitor = aPTT

8
Q

What is the mechanism of action of warfarin?

A

interferes with the synthesis of the vitamin K–dependent clotting proteins, which include factors II, VII, IX, and X and protein C and S

9
Q

How is warfarin’s anticoagulant effect monitored?

A

prothrombin time (PT) or INR

10
Q

What is the mechanism of action of dabigatran?

A

oral direct thrombin inhibitor

11
Q

Is there an antidote for the oral factor Xa inhibitors?

A

No

12
Q

What is the mechanism of action and side effects of aspirin?

A

irreversible inhibition of cyclooxygenase 1 and 2 (COX-1 and COX-2)

antithrombotic effect = primarily inhibition of COX-1 on platelets

SE = dyspepsia, peptic ulcers with bleeding and perforation

13
Q

What is the mechanism of action of dipyridamole?

A

inhibiting phosphodiesterase –> blocks breakdown of cyclic adenosine monophosphate (cAMP) –> Increased levels of cAMP reduce intracellular calcium and inhibit platelet activation

14
Q

Name 3 platelet ADP receptor antagonists.

A

ticlopidine
clopidogrel
prasugrel
ticagrelor

15
Q

Name 3 platelet Gp IIb/IIIa receptor inhibitors.

A

abciximab - long half-life
eptifibatide
tirofiban

16
Q

List some drugs that decease warfarin’s effects

A
barbiturates
carbamazepine
cholestyramine
nafcillin
phenobarbital
phenytoin
rifampin
17
Q

List some drugs that increase warfarin’s effects

A

Levofloxacin
omeprazole
amiodarone

18
Q

What are the mechanisms of action for oral anti-platelet agents?

A

ASA - COX2 inhibitor
Dipyrimadole - PDE inhibitor
ADP inhibitors - block P2Y12 receptor on platelets

19
Q

What drugs can be used w/ a history of HIT type-II?

A

fondaparinux
argatroban
bilavrudin

20
Q

Explain the mechanism of action of un-fractioned Heparin.

A

binding to Antithrombin III (ATIII) and accelerating its activity by 100-1000 times

The ATIII-heparin complex primarily inhibits thrombin (Factor IIa) and factor Xa

21
Q

What are the 3 types of protamine reactions?

A

Systemic hypotension from histamine release

Anaphylactic reaction (IgE Mediated)

Severe pulmonary hypertension and right ventricular failure - IgG mediated immune reaction - more common in patients with fish allergy, previous vasectomy, or prior exposure to protamine or NPH insulin.

22
Q

Describe an advantage and a disadvantage of bivalirudin and argatroban to heparin.

A

Unlike heparin, bivalirudin and argatroban can be used in HIT patients, but they have no antidote to reverse their effects.

23
Q

Compare the mechanism of action of Rivaroxaban (Xarelto) and Dabigatran (Pradaxa)?

A

Rivaroxaban (Xarelto) is a direct factor Xa inhibitor

Dabigatran (Pradaxa) is a direct thrombin inhibitor