VTE Flashcards
Blood stasis
Favors clotting through concentrating the elements for blood clot formation
Vascular injury
Injury disrupts the protective barrier initiating blood clot formation
Hypercoagulability
- Can be inherited or acquired
- Linked to certain medications
- Typically results from a combination of inherited and acquired thrombotic risk factors
Pathophysiology
- Hemostasis is the process responsible for maintaining circulatory system integrity
- Clotting Process
- —-Begins with vasoconstriction of the injured vessels followed by
- —Formation of a platelet plug
- —-Two-part process of platelet activation and platelet aggregation
- Activation of the clotting cascade
Clinical presentation
- DVT: leg pain/swelling, can be unilateral or bilateral; warmth
- Pulmonary Emboli: dyspnea, tachypnea, tachycardia, anxiety, “feeling of impending doom”
- -Diagnosis: can be assessed with Wells Score and confirmed with diagnostic testing
- Labs: D Dimer (>500mcg/L)
- Ultrasound is the gold standard for DVT
- Chest CT (angiogram) gold standard for PE
- If have contrast allergy; may do an MR angiogram
- Altered renal function, consider a VQ scan
DOAC
- Rivaroxaban
- Apixaban
- Edoxaban
- Dabigatran
- Do not require routine monitoring
- Rivaroxaban and dabigatran are not recommended for -CrCl <25-30mL/min
- Accumulating evidence in the use for cancer associated VTE
- HOLD 2-3 days prior to procedures
DOAC drug class info
- Rivaroxaban, apixaban, edoxaban, and betrixaban directly inhibit factor Xa
- Most have good bioavailability
- All reach plasma concentration within four hours
- Renally eliminated to variable extent
- Rivaroxaban, apixaban, edoxaban have a half life of 9-12 hours
- Dabigatran half life is 14-17 hours
- Rivaroxaban and apixaban are metabolized via the CYP3A4 pathway
- Bleeding is the most common adverse effect
- Adding ASA with DOAC can increase bleeding risk
LMWH
-Chemical or enzymatic derivative of UFH with approx. 1/3 of the size
Smaller size allows for less binding to the cells and proteins
-Inhibits Factor Xa over thrombin; cannot monitor by aPTT levels but by heparin Xa levels
-Peak effect is 3-5 hours; half life is 3-6 hours
-Bleeding is the most common side effect
-Reversal agents include Andexanet and ciraparantag
-Cannot be used in patients with an adverse reaction to UFH, including HIT
LMWH & Fondaparinux
- Both are SQ and weight based
- LMWH is preferred for patients with cancer associated VTE
- –LMWH is used prior to starting edoxaban and dabigatran
- —LMWH or UFH are used as a bridge when initiating warfarin therapy
- Fondaparinux is used when a patient has a heparin allergy
- Contraindicated with CrCl <30mL/min
- LMWH preferred during pregnancy
Fondaparinux
- Inhibits only Factor Xa
- Rapidly and completely absorbed following SQ administration; peak plasma levels in 2-3 hours
- Half life is 17-21 hours
- Comparable to LMWH when used for VTE treatment
- Adverse effect is bleeding
- No specific antidote
Unfractionated Heparin
-Rapid on/rapid off;” preferred prior to procedures
-Quick onset of 1-2 hours; peaks at 3 hours
Half life: 30 minutes
-Dose is weight based; although typically a loading dose to start with IV infusion
-Dose is adjusted based on coagulation test results including an aPTT or antifactory Xa
-Can be used safely in patients with a CrCl <30mL/min
-Can be used during pregnancy
UFH dosing
-Prophylaxis for DVT/PE
5,000 units two to three times daily
-Treatment dose for DVT/PE
Weight based infusion protocol per institution protocol
-Monitor aPTT or Heparin Xa and platelets
-Goal aPTT: 1.5 to 2.5 times normal lab values
-Heparin Factor Xa
-Goal range 0.3-0.7units/mL
-Check six hours after starting -of infusion and with each dose change
Warfarin
- Blocks the conversion of inactive Vitamin K to the active form in the liver
- Reduced vitamin K is required for the synthesis of Factors II, VII, IX, and X in the liver which results in non-functional clotting factors.
Warfarin info
- Has no direct effect on previously circulating clotting factors or previously formed thrombus; active clotting factors must be depleted before effect
- -To see full effect can take up to 5-6 days
- –Rapidly absorbed in the GI tract
- Has many food and drug interactions
- Drugs or herbs that inhibit CYP enzymes can increase effect
- Food rich in Vitamin K may reduce the effect
Warfarin monitoring
- Maintenance dose adjustments are based on weekly dose requirements
- Usually reduced or increased by 5-25%
- Effect on dose changes may not be evident for 5-7 days
- Those with stable INR are usually checked every 4-6 weeks; at times can go ever 8-12 weeks
