Anticoagulation Flashcards
What’s anticoagulant NOT used for?
They don’t break down existing clots (that’s done by drugs such as tissue plasminogen activator - tPA).
What’s anticoagulant used for?
To prevent blood clots from forming and to keep existing clots from becoming large or expanding
What dx states are anticoagulants used for?
Prevention and tx of DVT/PE
Prevention of stroke
Tx of acute coronary syndrome (ACS)
How many pathways are in the coagulation cascade? Name them
2 pathways
Contact activation pathway (Intrinsic pathway)
Tissue factor pathway (Extrinsic pathway)
List the factors in the intrinsic pathway
XII, XI, IX, VIII, X, V
List the factors in the extrinsic pathway
Tissue factor and VII
List the main risk factors for the development of venous thromboembolism. (U)
Surgery
Major trauma
Immobility
Cancer
Previous venous thromboembolism
Pregnancy
Estrogen-containing medications or selective estrogen receptor modulators
MOA of UFH, LMWH and fondaparinux? (U)
Bind to antithrombin (AT) -> increases AT activity 1,000 fold
Effect of antithrombin (AT)? (U)
AT Inactivates thrombin and other proteases involved in blood clotting, including factor Xa.
Which anticoagulant specifically inhibits factor Xa?
LMWHs
How does fondaparinux work?
Requires AT binding to selectively inhibit Factor Xa
What’s the brand name of fondaparinux?
Arixtra
Synthetic pentasaccharide
MOA of direct thrombin inhibitors? (U)
Blocks thrombin directly -> decreasing the amt of fibrin available for clot formation
What’s the importance of direct thrombin inhibitors and heparin-induced thrombocytopenia (HIT) antibodies? (U)
Direct thrombin inhibitors don’t cross-react with HIT antibodies
Therefore, what’s the drug of choice when HIT develops from the use of UFH (and less commonly, LMWHs)? (U)
Direct thrombin inhibitors e.g. argatroban
Does Dabigatran (Pradaxa - direct thrombin inhibitor) require blood test to monitor effectiveness? (U)
No.
Advantages of Dabigatran (pradaxa) over warfarin?
Pradaxa doesn’t require blood tests
Not subjected to food interactions
Has fewer drug interactions than warfarin
Disadvantages of Dabigatran (Pradaxa)?
Significant dyspepsia/gastritis
Increased risk of GI bleed
List agents that work by inhibiting factor Xa?(u)
Rivaroxaban (Xarelto)
Apixaban (Eliquis)
What meds should not be used in pts with prosthetic heart valves? (U)
Dabigatran (Pradaxa)
Rivaroxaban (Xarelto)
Apixaban (Eliquis)
MOA of warfarin?(u)
Vitamin K antagonist
Role of vitamin k in clotting factors? (U)
Vit k is req for the carboxylate on of clotting factors II, VII, IX, and X.
What body requires implementation of policies and protocols to properly initiate and manage anticoagulant therapy? (U)
The Joint Commission’s National Patient Safety
What’s HIT?
Immune-mediated (IgG) drug reaction -> forms antibodies against heparin when it binds to platelet factor 4 (PF 4) -> then binds to Fc receptors on platelets, -> further platelet activation
What’s the result of untreated Heparin-induced thrombocytopenia (HIT)?
Pro-thrombotic state causing many complications such as venous and arterial thrombosis (HITT)
What’s the typical onset of HIT?
5-14 days after the start of heparin
OR
Within hours if a pt has been recently exposed to heparin (within last 3 months)
Howz HIT diagnosed? (U)
Profound, unexplained drop in platelet count (> 50%) from baseline
If HIT is suspected, what should be done if pt is on UFH or LMWH?
Stop all forms of UFH and LMWH, even heparin flushes and heparin-coated catheter
If HIT is suspected, what should be done if pt is on warfarin?
Stop warfarin and start Vit K
What med is recommended in pts with HIT?
Argatroban
When should warfarin be re-started after HIT?
When platelet is at least 150,000/mm3
At what dose should warfarin be initiated and how?
Max. of 5mg
Overlap with non-heparin anticoagulant for a minimum of 5 days until INR is within target for 24 hrs
What’s preferred anticoagulant in pts that req urgent cardiac surgery or PCI?
Bivalirudin
MOA of UFH?
Binds to antithrombin (AT)
Inactivates thrombin (Factor IIa) & factor Xa (as well as factors IXa, XIa, XIIa and Plasmin)
Prevents the conversion of fibrinogen to fibrin
What’s the usual infusion rate of UFH for tx? Concentration?
25,000 units in 250ml in D5W (or 1/2 NS or NS)
100units/ml
What’s tne strength of UFH used in line flush (HepFlush)?
10 units/mL, 100units/mL
Uses of heparin “lock-flushes” (Hep-Flush)
Used to keep IV lines open
Note: there’s been fatal errors from choosing incorrect heparin strength
What’s the dose of UFH for prophylaxis of VTE?
5,000 units SC Q8-12H
What’s used when using UFH for tx of ACS/STEMI, adjusted body weight or actual body weight?
Actual body weight
What’s the antidote of UFH? Dosing? Max dose?
Protamine
1mg of protamine per 100 units of UFH
Max dose - 50mg
Which UFH pdts contain black box warnings? Why?
Some heparin pdts contain benzyl alcohol.
Theses pdts are contraindicated in neonates and infants
SE of UFH?
Bleeding (epistaxis, ecchymosis, gingival, GI etc)
Thrombocytopenia
Heparin induced thrombocytopenia (HIT)
Hyperkalemia
Osteoporosis (with long- pterm use)
What SE of UFH is associated with long-term use of UFH?
Osteoporosis
Howz UFH monitored?
aPTT
OR
anti-Xa level: 0.3-0.7 units/mL
How often is aPPT monitored when pt is on UFH?
6hrs after initiation and Q 6hrs until the therapeutic range of 1.5-2.5 x control
What’s the therapeutic range of aPTT?
1.5-2.5 x control (pts baseline)
What other parameters are monitored when a pt is on UFH? How often?
Platelet count
Hgb
Hct
These are monitored at BASELINE and DAILY to monitor for thrombocytopenia and bleeding
Why does UFH have an unpredictable anticoagulant response?
UFH has variable and extensive binding to plasma proteins and cells
List the agents that may increase clotting risk. What should be done when starting UFH?
Estrogen and SERMS and other anticoagulants
They should be discontinued if UFH is required
MOA of LMWHs?
Work similar to heparin except that the inhibition is much greater for Factor Xa than Factor IIa
List agents that are LMWHs.
Enoxaparin (Lovenox)
Dalteparin (Fragmin)
What’s the brand name of Enoxaparin?
Lovenox
What’s the dose of Enoxaparin (Lovenox) for prophylaxis of VTE?
30mg SC Q12H or 40mg SC daily
What’s the dose of Enoxaparin (Lovenox) for prophylaxis of VTE if CrCl < 30mL/min?
30mg SC daily
What’s the dose of Enoxaparin (Lovenox) for tx of VTE and UA/NSTEMI?
1mg/kg SC Q12H or 1.5mg/kg SC daily
What’s the dose of Enoxaparin (Lovenox) for tx of VTE and UA/NSTEMI if CrCl < 30mL/min?
1 mg/kg SC daily
What’s the dose of Enoxaparin (Lovenox) for tx of STEMI? In < 75yrs? Max dose?
< 75 yrs = 30mg IV bolus + 1 mg/kg SC dose followed by 1mg/kg SC Q12H
Max dose: 100mg for the 1st 2 doses ONLY
What’s the dose of Enoxaparin (Lovenox) for tx of STEMI? In > 75yrs? Max dose?
0.7mg/kg SC Q12H (no bolus)
Max 75mg for the 1st 2 doses ONLY
What’s the dose of Enoxaparin (Lovenox) for tx of STEMI in CrCl < 30mL/min?
1 mg/kg SC daily