40. Anticoagulants Flashcards
mechanisms involved in hemostasis
- vasoconstriction
- formation of platelet plug
- sequential activation of clotting factors
- reparation of the opening in the damaged vessel by growth of fibrous tissue
How does the coagulation cascade lead to formation of fibrin clot
- injured cells release prothrombin activator
- prothrombin activator changes prothrombin to thrombin
- thrombin changes fibrinogen to fibrin
- fibrin forms insoluble web over injured area to stop blood flow
atherosclerosis often involves arteries supplying what areas of the body
- heart -> MI
- brain -> stroke
- legs -> DVT
3 types of antithrombotic medications
- anticoagulants (prevents new clot formation -> does not dissolve formed clots)
- antiplatelets (prevent arterial thrombosis)
- thrombolytics (dissolve thrombi and limit tissue damage)
indication for use of anticoagulants
- thrombophlebitis
- DVT
- PE
- ACS -> PCI or STEMI
MOA of heparin
- varies according to dosage
- low dose: inactivates factor Xa and inhibits conversion of prothrombin to thrombin
- high dose: inactivates IX, X, XI, XII, and thrombin and inhibiting conversion of fibrinogen to fibrin
side effects/adverse effects of heparin
- HIT
- ecchymosis
- bleeding risk
- hypersensitivity
- N/V
How do you evaluate effectiveness of heparin
PTT in therapeutic range (based on institution); around 60-90
contraindications of heparin
severe thrombocytopenia
patient teaching for heparin
- rotate injection sites (to be given SQ)
- increased bleeding risk (hold pressure to wounds and report severe sxs)
What type of medicine is enoxaparin
LMWH
MOA of enoxaparin
inactivates coagulation factor Xa and produces anticoagulation
uses of enoxaparin
- DVT prophylaxis
- ACS
- unstable angina
- acute DVT
administration of enoxaparin
- peaks 3-5 hours and lasts 12 hours
- subcutaneous injection
- air bubble needed to follow the injection
- don’t rub site after injection
adverse effects of enoxapain
- injection site hematoma
- nausea
- peripheral edema
- bleeding
safety info for enoxaparin
- lower bleeding risk than heparin
- more stable response
- no PTT monitoring
antidote to heparin and enoxaparin
protamine sulfate
antibodies develop to platelet factor 4 complexed w/ heparin; may also develop w/ LMWH but less common
heparin induced thrombocytopenia (HIT
sxs of HIT
- thrombocytopenia
- thrombosis by peripheral platelet consumption and platelet activation
- platelets decrease by 30-50% of baseline
MOA of warfarin
interferes w/ hepatic synthesis of vitamin K dependent clotting factors
uses of warfarin
- prevention of venous thromboembolism
- atrial fibrillation
- embolization
- coronary thrombosis
- pulmonary embolism
- inherited clotting disorders
adverse effects of warfarin
- bleeding/hemorrhage
- anemia
- headache
- fever
- dizziness
- lethargy
- fetal malformations
- abnormal bone development
contraindications for warfarin
- pregnancy
- bleeding or hemorrhaging tendancies
How do you evaluate effectiveness of warfarin
PT/INR testing; should be in therapeutic range (typically 2-3)
antidote to warfarin
vitamin K
MOA of apixaban
factor Xa inhibitor
uses for apixaban
- nonvalvular afib
- DVT
- PE
- venous thromboembolism prophylaxis (THA, TKA)
side effects/adverse effects of apixaban
- hemorrhage
- thrombosis w/ premature discontinuation
contraindications for apixaban
hypersensitivity
- active bleeding
antidote for apixaban
andexanet alfa
What type of drug is argatroban?
direct thrombin inhibitor (DTI)
MOA of argatroban
directly inhibits thrombin from converting fibrinogen to fibrin
uses of argatroban
- HIT
- PCI for adults who have risk of developing HIT
- treatment for DVT or PE
how is argatroban administered
IV only
adverse reactions of argatroban
- bleeding
- hypotension
- chest pain
- cardiac arrest
- injection site reaction
- N/V and GI upset
- anemia
- hematoma
What is the antidote for argatroban
there isn’t one
antiplatelets are used as prophylaxis for what?
- prevention of MI or stroke for pts w/ FHx
- prevent repeat MI or stroke
- prevention stroke for pts having TIAs
What is the recommended dose of ASA for pts w/ FHx of stroke or MI
- 50-325mg/day for stroke
- 75-162 mg/day for MI
When a pt is going in for surgery, when must antiplatelets be discontinued
7 days before surgery
What type of medication is clopidogrel?
antiplatelet
MOA of clopidogrel
inhibits platelet aggregation and prevents adenosine diphosphate (ADP) from binding to ADP platelet receptor
use of clopidogrel
prevent thrombosis associated w/ unstable angina, acute MI, stroke, and TIA
adverse effects of clopidogrel
- hypotension
- hypertension
- bronchospams
- elevated hepatic enyzmes
- peptic ulcer
pt teaching for clopidogrel
- may increase bleeding
- may increase bleeding when taking certain supplements (ginger, garlic, and green tea)
- effects decreased w/ grapefruit juice
when are labs for heparin dosing drawn
1 hour before dosing
when are labs drawn for warfarin
- daily until therapeutic
- drawn every 2-4 weeks for duration of therapy unless the dose is adjusted
What is the goal of thrombolytic agents
reestablish blood flow ASAP to prevent/limit tissue damage
What type of medicine is alteplase (Activase)
thrombolytic
MOA of alteplase
- converts plasminogen to plasmin -> digests fibrin and dissolves clot
- also initiates fibrinolysis
uses of alteplase
- dissolve existing clots
- acute MI
- DVT
- CVA
- PE
- arterial thrombosis
- clear IV catheters
adverse effects of alteplase
- abnormal bleeding
- stroke (LT)
- dysrhythmias (LT)
- pulmonary edema (LT)
contraindications for alteplase or any thrombolytic therapy
- uncontrolled severe HTN
- aneurysm
- AV malformation
- known coagulopathy or internal bleeding
- intracranial/intraspinal surgery or trauma in past 3 months
- intracranial mass
- recent major surgery
- current use of oral anticoagulants
when must alteplase be given
- within 12 hours of sxs of MI
- within 3 hours of CVA
what is the antidote to alteplase
aminocaproic acid
