VTE Flashcards
What is a DVT?
a blood clot within a deep vein
What is a PE?
a blockage caused by a blood in clot in the pulmonary arteries
What is Virchow’s triad?
3 primary factors influencing formation of a pathogenic clot
- damage to the vessel wall
- venous stasis -hypercoagulable state
What is the function of antithrombin?
inhibits thrombin (IIa), factor IXa, and factor Xa
What is the function of protein S?
cofactor for activation of protein C
What is the function of protein C?
inactivates factors Va and VIIa
What is the function of tissue factor pathway inhibitor (TFPI)?
binds to factor VIIa-tissue factor complex and inhibits activation of factor X
What is the function of plasminogen?
converted to plasmin via tissue plasminogen activator (t-PA)
What is the function of plasmin?
lyses fibrin to form fibrin degradation products
Where are the most common locations of clot formation?
- muscular veins of the calf
- valve cusp pockets of the deep calf veins
DVT once formed can:
- spontaneously lyse
- extend into more proximal veins
- embolize to the lungs causing PE
What are the clinical presentation/symptoms of DVT?
- unilateral calf or leg swelling
- calf pain or tenderness
- erythema
- warmth
- palpable cord
- Homan’s sign
What are the clinical presentation/symptoms of PE?
- dyspnea
- pleuritic chest pain
- anxiety
- tachypnea (>20 breaths/min)
- tachycardia
- cough
- hemoptysis
- diaphoresis
What is a D-dimer?
cross linked fibrin degradation fragment produced during clot dissolution that has a negative predictive value of
What are some non-invasive tests used to diagnose DVT?
- Doppler ultrasonography
- B-mode compression ultrasound
What are some invasive tests used to diagnose DVT?
Contrast venography-radiographic visualization of the involved vessels with injection of radiocontrast material
What diagnostic test is the gold standard for diagnosing DVT?
contrast venography
What is the most commonly used diagnostic test used for diagnosing a PE?
Chest CT with contrast
What diagnostic test is the gold standard for diagnosing PE?
pulmonary angiography
What is the most invasive test used to diagnose PE?
pulmonary angiography
What are ancillary tests used to diagnose PE?
- arterial blood gas
- EKG
- CXR
What is bridge therapy?
When a parenteral agent and warfarin are given together for a minimum of 5 days and until the INR is less than or equal to 2 for at least 24 hours
What are the parenteral agents?
- UFH
- LMWH
- Fondaparinux
Per CHEST guidelines, what parenteral agents are recommended over the other?
LMWH and Fondaparinux are recommended over UFH
What is the structure of UFH?
heterogenous mixture of glycosaminoglycan polysaccharide chains
What is the MOA of UFH?
binds to antithrombin via a unique pentasaccharide sequence and accelerates its interaction and inactivation of thrombin and factor Xa by 1000-fold
What other factors does UFH inhibit?
IXa, XIa, XIIa
Inhibition of thrombin requires a heparin chain that is at least _________ in length
18 saccharide units
What is the route of administration for the treatment of VTE?
continuous infusion
What is the route of administration for the prophylaxis of VTE?
subcutaneous injection, NOT intramuscular
What is intravascular binding?
creates variability and unpredictability in patient response
What do you monitor when a patient is on UFH?
- aPTT (activated partial thromboplastin time)
- platelet counts, Hgb, Hct
- signs/symptoms of bleeding
What is the dosing of UFH for VTE treatment?
IV bolus of 80 units/kg followed by 18 units/kg/hr continuous IV infusion with no renal adjustment
What is the dosing of UFH for VTE prophylaxis?
5000 units SC q8h with no renal adjustment
What are some adverse effects of UFH?
- bleeding
- Heparin-induced thrombocytopenia (HIT)
- Heparin-induced osteoporosis
How can bleeding be reversed when on UFH?
reversed with IV bolus of protamine sulfate which binds to heparin to form a table salt
What is type 1 HIT?
transient fall in platelets due to a direct effect of heparin
What is type 2 HIT?
immune-mediated reaction
What is the mechanism of type 2 HIT?
IgG antibodies directed at heparin-platelet factor 4 complexes
What is the treatment of type 2 HIT?
direct thrombin inhibitors Argatroban and Bivalirudin
What is the mechanism of heparin-induced osteoporosis?
binding of heparin to osteoblasts
What is the structure of LMWH?
heterogenous mixture of of glycosaminoglycans derived from chemical or enzymatic degradation of UFH (~1/3 of molecular weight of UFH)
What is the MOA of LMWH?
binds to antithrombin via a unique pentasaccharide sequence. Accelerates inactivation of factor Xa
What is the route of administration of LMWH?
subcutaneous injection
What is a product of LMWH?
Enoxaparin (Lovenox)
Is routine anticoagulation testing necessary in patients taking LMWH?
It is not recommended
What test could you perform to monitor patients on LMWH?
anti-factor Xa levels
When are anti-factor Xa levels drawn?
4 hours after steady state is reached (after 3rd dose)
When should anti-factor Xa levels be drawn?
- patients with a total body weight of >150 kg or BMI >50 kg/m2
- if LMWH are used in patients with renal dysfunction
What is the dosing of enoxaparin for the treatment of VTE?
1 mg/kg SC q12h or 1.5 mg/kg SC q24h
Renal adjustment: 1 mg/kg SC q24h (CrCl <30 mL/min)
What is the dosing of enoxaparin for the prophylaxis of VTE?
40 mg SC q24h
Renal adjustment: 30 mg SC q24h (CrCl <30 mL/min)
What is the preferred parenteral anticoagulant if a patient is obese and CrCl <30 mL/min?
UFH
What are some adverse effects of LMWH?
- bleeding
- heparin-induced thrombocytopenia (HIT)
- perispinal hematoma
What is the antidote used to reverse the effects of LMWH and what is its dose?
- Protamine sulfate
- LMWH administered within 8 hours: 1 mg protamine per 100 anti-factor Xa units (this is 1 mg of enoxaparin)
- a second dose of 0.5 mg protamine per 100 anti-factor Xa units if bleeding continues
What is a perispinal hematoma?
increased risk when antithrombotic medications are administered concomitantly with neuraxial blockade
What is the MOA/structure of Fondaparinux?
a synthetic analog of the pentasaccharide sequence that binds to antithrombin