Anticoagulants and Antiplatelets Flashcards
(31 cards)
What is hemostasis?
Process that stops bleeding
- Formation of a platelet plug
- Production of fibrin
What does the clotting cascade create? What are the 2 pathways?
Results in fibrin - a clot forming substance
Coagulation cascade is divided into intrinsic and extrinsic pathways
When should anticoagulants be used? How do they function?
Used prophylactically to prevent clot formation (thrombus) or an embolus (dislodged clot). Works on different points of cascade depending on drug
Does not impact existing blood clots
Should be used in cases of:
- MI
- Unstable angina
- Atrial fibrillation
- DVT eg. major orthopedic surgery
- Indwelling devices (mechanical heart valves)
- Pulmonary embolism
What 4 drugs prevent clot formation?
- Heparin
- Low-molecular-weight heparins (LMWH)
- Warfarin - oral
- Direct Factor X and Thrombin inhibitors
When should anticoagulants not be used?
- Drug allergy
- Acute bleeding process
- Thrombocytopenia
Which anticoagulant drug is contraindicated in pregnancy?
Warfarin
What are the adverse effects (5) of anticoagulants?
Bleeding risk increases with increased dosages
- Gums bleed
- Nosebleeds
- Unusual bruising
- Anemia/low Hct (hematocrit)
- Tarry stool
How does Heparin impact the clotting cascade?
Indirectly affects Thrombin II, Factor Xa, and other factors in the *intrinsic pathway
What is a common issue with Heparin dosing?
It’s very unpredictable (due to varying lengths of molecules)
- It’s monitored by activated partial thromboplastin times (aPTT)
- Measures the intrinsic pathways
- aPTTs need to be 1.5-2.5 greater than control
How is Heparin given, and what are some of its characteristics?
Given IV or SC
Effective within minutes
Short half life (1-2 hours)
When should Heparin use be stopped? What’s the antidote?
When Heparin-induced thrombocytopenia (HIT) occurs
- 1-5% of population
- Stop heparin administration and use alternatives
Hypersensitivity reactions
- Urticaria, fever, chills
Protamine sulfate - antidote
What is an example of LMWH and how is it different from Heparin?
*Enoxaparin
More predictable anticoagulant response Does not require frequent laboratory monitoring - Often given at home Given SC - Indirectly inhibits Factor X only - Less thrombocytopenia than heparin - Protamine sulphate - same antidotes
What are 2 alternatives to Heparin
- Danaparoid
- SC or IV
- Structurally distinct from heparin - Fondaparinux
- Synthetic
- SC or IV
What are some client implications for Heparin and LMWHs?
Heparin:
Double check dosages with another RN
SC doses must be SC not IM
Preferred site is abdomen
LMWH:
SC in abdomen only
Rotate sites around lower abdomen below umbilicus
How does Warfarin work?
- Very similar to coumarin.
- Vitamin K antagonist.
- Vitamin K is essential for production of several clotting factors (VII, IX, X, prothrombin)
- Max effect may take 3-5 days
How is Warfarin monitored?
Through a clotting lab test (prothrombin time (PT))
- Needs to be 1.3-1.5 times the normal level to be therapeutic
INR (international normalization reference ratio)
- Corrects for lab-to-lab variability in testing
- Normal target INR range needs to be 2-3 x control
- The highest therapeutic range needs to be at 2.5-3.0. Normal is 0.8-1.2
These both measure activity of extrinsic pathway
What happens to warfarin effectiveness when too much or too little vitamin K in diet?
Vitamin K decreases the effect of warfarin because it’s a key part in the clotting cascade.
Too much vitamin K = lowered effect of Warfarin
Too little vitamin K = increased effect of Warfarin
Patient teaching on Warfarin
Keep intake of vitamin K constant (tomatoes, dark leafy green vegetables)
Be careful in taking other meds or natural products (drug-drug interactions
What are 2 examples of Direct-Acting Oral Anticoagulants (DOACs), and what’re the advantages?
Dabigatran Direct thrombin inhibitor - Rapid onset - Fixed doses - No blood test - Few drug-drug interactions - No dietary concerns - Lower risk of bleeds
Rivaroxaban
Direct Factor Xa Inhibitor
Similar advantages as dabigatran
What’re the adverse effects for all anticoagulants?
Increased bleeding (mild-life threatening)
Patient education on all anticoagulants?
Importance of regular lab testing, signs of abnormal bleeding (bleeding gums, unexplained nosebleeds, bruising, heavier menstrual bleeding, bloody or tarry stools, vomiting blood, bloody urine or sputum, abdominal pain)
What is the function of Antiplatelet agents, and what are 2 examples?
To prevent platelet activation by inhibiting cyclooxyrgenase pathway
Acetylsalicylic acid causes the irreversible inhibition of COX in platelets
Clopidogrel (Plavix) is a irreversible ADP receptor blocker
When should you use antiplatelet agents?
To prevent clots and reduce risk of fatal and nonfatal strokes
What are the benefits and consequences of combining ASA and clopidogrel?
Produces additive antiplatelet activity, but increases bleeding potential
