Wk 14 Anti-Coagulants and Anti-Platelets Flashcards
- What are the two stages of hemostasis?
Formation of platelet plug, reinforcement of platelet plug with fibrin (Coagulation)
- How does heparin work as an anticoagulant?
Assists antithrombin in inactivating thrombin & factor Xa
- How does warfarin work as an anticoagulant?
Decreases synthesis of clotting factors dependent on vitamin K
- How do thrombolytic drugs work?
Promote conversion of plasminogen to plasmin
- Arterial thrombi cause what kind of injury?
Local injury
- Venous thrombi cause what type of injury
Distal injury
- Name the three categories of drugs for thromboembolic disorders? Where in the vascular system do they work?
Anticoagulants - veins
Antiplatelet agents - arteries
Thrombolytics – veins or arteries
- What factors does heparin deactivate? What does this prevent?
Assists antithrombin in deactivating thrombin & factor Xa to prevent more venous thrombi.
- What factor do low molecular weight anticoagulants deactivate?
Factor Xa
- Which anticoagulant can be given during pregnancy?
Heparin
- What is the antidote for heparin?
Protamine sulfate
- Which lab is used to monitor heparin? What is the recommended range?
aPTT 1.5-2X the control
- What potentially-fatal disorder occurs with heparin?
Heparin induced thrombocytopenia (HIT)
- List contraindications to heparin.
Thrombocytopenia; uncontrollable bleeding; surgery of eye, brain, or spinal cord; lumbar puncture or regional anesthesia
- List signs and symptoms indicative of bleeding?
Decreased BP, increased HR, bruises, petechiae, hematomas, red or black/tarry stools, discolored/cloudy urine, pelvic pain from ovaries, headache or faintness, lumbar pain from adrenal gland
- Discuss the proper administration of heparin SubQ.
Lower abdomen, rotate sites; no rubbing; no aspiration; 2” from umbilicus; 25-26 gauges, ½ to 5/8 needle; gentle, firm pressure for 1-2 min after.
- List drugs which may increase bleeding with heparin.
ASA, antiplatelet drugs, NSAIDS, glucocorticoids
- What is the antidote for low molecular weight anticoagulants?
Protamine sulfate
- How does warfarin work?
Interferes with synthesis of Vitamin K-dependent clotting factors
- Where in the vascular system does warfarin work?
Veins
- How is warfarin distributed? Can it enter the placenta or breast milk?
Highly-protein bound, crosses placenta and enters breast milk
- What lab is used to monitor warfarin therapy? What is the suggested range?
PT & INR; INR 2-3 (3-4.5 if mechanical heart valve or recurrent systemic embolism)
- Which anticoagulant is Pregnancy Category X?
Warfarin (Coumadin)
- What is the antidote for warfarin?
Vitamin K (phytonadione)
- List contraindications to warfarin.
Active bleeding; severe thrombocytopenia; decreased synthesis of vitamin K (alcoholism, Vitamin K deficiency, liver disease); surgery of eye, brain, & spinal cord; lumbar puncture or regional anesthesia; pregnancy & lactation
- What would you tell a patient on warfarin who wants to take Tylenol?
Need to monitor INR - 4 tablets a day for one week can increase risk of elevated INR by 10X (May need to lower warfarin dose)
- What two drugs increase the synthesis of Vitamin K dependent clotting factors?
Vitamin K, oral contraceptives
- What foods are high in vitamin K?
Spinach, kale, lettuce, turnips, greens, cabbage, watercress, peas, asparagus, broccoli, oats, whole wheat, green tea, mayonnaise, canola oil, soybean oil.
- How does dabigatran (Pradaxa) work?
Directly binds thrombin, which prevents fibrin formation and activation of factor VIII.
- What are the advantages of dabigatran (Pradaxa) over warfarin? Disadvantages?
Less bleeding, faster onset, no blood work, fewer food interactions, dosing not based on lab or weight. GI distress, no antidote, less experience, BID dosing.
- How does rivaroxaban (Xarelto) work?
Directly inhibits Factor Xa, which prevents fibrin formation.
- In what part of the vascular system do antiplatelet agents work?
Arteries
- List three classes of antiplatelet agents.
ASA, P2Y12ADP receptor antagonists, glycoprotein IIb/IIIa receptor antagonists
- How does aspirin work? How long are platelets affected?
Inhibits COX-1, decreasing platelet aggregation and vasoconstriction. 7-10 days
- How do ADP receptor antagonists work? How long are platelets affected?
Block ADP receptors and prevents platelet aggregation (clopidogrel- Plavix). 5 days.
- What is a significant adverse blood dyscrasia that may be caused by the ADP receptor antagonist, clopidogrel (Plavix)? What drugs may prevent its action?
Thrombotic thrombocytopenia purpura (TTP). Proton inhibitors may inhibit CYP2C19, which activates Plavix.
- How do GP IIb/IIIa receptor antagonists work? Size of effect?
Blocks GP IIb/IIIa receptors & prevents fibrinogen bridges. Large effect, because final step in platelet aggregation.
- What is the major adverse effect of thrombolytic therapy?
Serious bleeding
