Anticoags/antiplatelets/thrombolytics Flashcards
Define thrombus, thrombosis, embolus, thrombolysis, and aggregation
- thrombus - non-mobile blood clot
- thrombosis - presence of thrombus or thrombogenesis
- embolus - part of a clot that has broken off and is moving or lodged somewhere else
- thrombolysis - the breakup of a thrombus in a vein/artery
- aggregation - the clumping together of platelets to form a clot
What are the basics of the clotting cascade?
- Intrinsic pathway in the blood activated by surface contact (tissue damage), cascade of factors (12, 11, 9, 8) activate each other to form Xa
- extrinsic pathway activated by tissue damage, releases tissue factor (factor 3) to combine w/ factor 7 and form Xa
- common pathway is junction at Xa and promotes conversion of prothrombin to thrombin, fibrinogen to fibrin, and the formation of fibrin mesh & a clot
Which are the K+ dependent factors?
2, 7, 9, 10
Which labs are associated with the intrinsic and extrinsic pathways?
Intrinsic - (a)PTT
Extrinsic - PT
play table tennis inside
play tennis outside
PTT, aPTT, PT, INR values & uses
International Normalized Ratio (INR)
- PTT –> 60-70s
- aPTT –> 20-35s
- PT –> 11-13.5s
- INR –> 1.3-2s
Xa assay or UFH assay can be alternative to (a)PTT
(a)PTT for heparin, PT/INR for warfarin
Factor X assay
aka UFH
- measures activity of factor Xa in clotting cascade
- for heparin, LMWH, Xa inhibitors
Where are platelets/where do antiplatelets work?
Arterial system
Where are RBCs/where do anticoags work?
Venous system
Anticoagulants
- interfere with normal coagulation to prevent formation of new clots or prevent existing clots from growing
- does not dissolve clots
- primarily effective on venous side
- used for DVT, PE, MI, artificial valves, stroke
heparin, warfarin, enoxaparin, dabigatran
Antiplatelets
- prevent platelet aggregation for the life of the platelet (7-10 days)
- does not dissolve clots
- primarily effective on arterial side
- used for Hx of MI/CVA, TIA
aspirin, clopidogrel (plavix)
Thrombolytics
- attack & dissolve blood clots (may cause embolus)
- non-selective
- enzymes
- used for acute MI, ischemic stroke
- bind w/ fibrin to promote conversion of plasminogen to plasmin which digests clot & degrades fibrinogen, prothrombin, clotting factors
-** high alert** - best given w/in 3-4 hr of event start
- SE: anaphylaxis, dysrhythmias, hemorrhage
- antidote- aminocaproic acid
alteplase, streptokinase
Heparin
- anticoag
- binds w/ antithrombin III to inhibit thrombin action & conversion of fibrinogen to fibrin –> inhibit clot formation
- used to prevent venous thrombosis
- SubQ or IV
- Measured in units (thousands)
- frequent lab monitoring, esp if IV [PTT 1.5-2x control value, aPTT 30-85s]
- SE: bleeding, thrombocytopenia (HIT)
- antidote - protamine sulfate
not same units as insulin, use TB needle
HIT
- Heparin induced thrombocytopenia
- adverse immune reaction, ~2-3% incidence
- major, sudden drop in platelets after several days of therapy
- results in platelet aggregation & hyperthrombotic state
- stop heparin immediately
- monitor CBC
- start on anticoag w/ direct thrombin inhibitor (ie. argatroban)
also D/C warfarin if on board
Platelet value
150,000 - 450,000/µL
Low-molecular-weight heparin (LMWH)
- -parin
- inactivates factor Xa
- lower risk of bleeding
- don’t need frequent labs
- SubQ 90° w/ prefilled syringes (don’t remove air bubble)
- used to prevent DVT and actute PE after ortho/abd surgery
- don’t take aspirin or other antiplatelets concurrently
enoxaparin (Lovenox), dalteparin, tinzaparin
Direct Thrombin Inhibitors
- good if pt can’t tolerate heparin
- directly inhibits thrombin from converting fibrinogen to fibrin (step below heparin in cascade)
- DVT, PE, if pt has HIT, unstable angina, afib, stroke
- IV, SubQ
Warfarin
- oral anticoagulant
- inhibits hepatic synthesis of K+ –> affects factors 2, 7, 9, 10
- highly protein bound
- used to prevent thromboembolic conditions of thrombophlebitis, PE, & embolism formation that can cause MI/CVA
- monitor therapeutic range weekly until reached, then every 2-4 weeks
- INR 2-3s (2.5-3.5s for mechanical heart valves or recurring embolism)
- reversal agent- vitamin K
- takes 24-48 hrs to be effective
- FFP can be given for acute bleeding as a temporary fix
What drugs can displace warfarin
aspirin, NSAIDs, antiinflammatories, sulfonamides, phenytoin, cimetidine, allopurinol, oral hypoglycemics
increase free amount of warfarin –> increased dose –> increased bleeding
Complementary therapy interactions
- garlic, gingko, ginger, ginseng, feverfew, willow bark, chamomile may increase bleeding when taken with warfarin
- alfalfa may decrease effects of anticoags
- cranberry may increase INR
Xa inhibitors
- some don’t require regular labs
- given 1-2x daily
- prevents action of common pathway
rivaroxaban, apixaban (eliquis)
Clopidogrel
- antiplatelet
- adenosine diphosphate (ADP) antagonist –> decreased platelet aggregation
- used after MI & stroke to prevent recurrence
- can be givin with aspirin & may be more effective
