Anticoags Flashcards
Knee surgery, SOB, heart palpitations. What would a diagnosis be?
PE
What is the best diagnostic tool for a PE?
CTA
Well’s criteria
Clinical si/sx of DVT, HR>100, immobilization atleast 3 days or surgery previous 4 weeks, previous PE or DVT, hemoptysis, malignancy with recent or palliative treatment
What are some considerations regarding anticoags for PE treatment?
Risk of bleeding, which drug is most appropriate, what’s the best dose, how should it be monitored, what complications can happen, how long should pt be treated
What are some risk factors for bleeding complaints with anticoags?
> 65, previous episodes of significant bleeding, thrombocytopenia, concurrent antiplatelet therapy, issues with admin or monitoring, recent surgery, frequent falls, liver failure
What would be the most appropriate initial treatment for someone with PE?
Parenteral anticoags or oral factor Xa inhibitors
What are the factor Xa inhibitors?
Rivaroxaban (Xarelto) and Apixaban (Eliquis)
What are the advantages of factors Xa inhibitors?
Avoid injections such as with LMWH, avoid frequent lab draws for monitoring like Warfarin
Direct factor Xa inhibitors
No risk of HIT, only oral, expensive, no antidote if bleeding
What is Rivaroxaban (Xarelto) used to treat?
DVT, PE, AFib
What does Apixaban (Eliquis) treat?
DVT, PE, AFib
How should Rivaroxaban (Xarelto) be dosed for VTE?
15mg PO BID x 21 days, followed by 20mg PO Daily
What are the 3 functions of thrombin in coagulation?
- Converts fibrinogen to loose fibrin
- Converts factor 13 to 13a which converts loose fibrin to stable fibrin
- Activates many proteins and platelets in a + feedback loop within clotting cascade
What are the 2 clotting pathways?
Intrinsic and extrinsic
What is the intrinsic pathway?
Everything necessary for it is in the blood
What is the extrinsic pathway?
Requires cellular elements outside the blood
How does the intrinsic pathway work?
Exposed collagen-> 12 to 12a, 11 to 11a, 9 to 9a, 10 to 10a, prothrombin to thrombin, fibrinogen to fibrin
How does the extrinsic pathway work?
Subendothelial tissue is exposed to blood-> tissue factor binds factor 7, 9 to 9a, 10 to 10a, prothrombin to thrombin, fibrinogen to fibrin
What is antithrombin 3?
Naturally occurring anticoagulant that inactivates thrombin and several other clotting factors (including factor 10a)
What must be bound to heparin in order for activation?
Antithrombin 3
Heparin is naturally occurring and present on what?
Endothelial cells
What are some advantages of LMWH over UFH?
Greater bioavailability when given SUBQ, duration of effect is greater with less frequent injections, response is correlated with body weight (can use fixed dose), no monitoring, low risk HIT, less bleeding, less recurrent VTE events
Fondaparinux (Arixtra)
Similar to LMWH in structure and function, similar safety and efficacy as it, no difference in mortality, VTE disease or major bleeding
Binds to antithrombin and catalyzes reaction of factor Xa inactivation
Fondaparinux (Arixtra)
Synthetic pentasaccharide
Fondaparinux (Arixtra)
Used for DVT PPX for patients with a history of HIT
Fondaparinux (Arixtra)
What are the types of LMWH?
- Enoxaparin sodium (Lovenox)
- Dalteparin sodium (Fragmin)
- Tinzaparin sodium (Innohep)
- Nadroparin
What type of LMWH is most commonly used?
Enoxparin
Which type of LMWH can cause renal failure?
Tinzaparin Sodium (Innohep)
Which drug is preferred in patient who cannot take oral meds?
LMWH
LMWH is also preferred in who?
Patients if Factor Xa inhibitors are unavailable or unaffordable
What is the appropriate dose of Enoxaparin to treat PE in a patient with normal renal function?
1mg/kg q12hr
OR
1.5mg/kg q24hr
What are the indications for IV UFH in an acute PE?
Persistent hypotension (massive PE), increased risk of bleeding, concern about SUBQ absorption (morbid obesity), CrCl<30mL/min, anticipate imminent surgical procedure
What is the most appropriate diagnosis chest to order for DVT?
LE venous Doppler ultrasound (NIVS)
What is the Well’s criteria for DVT?
Active cancer, bedridden, unilateral calf swelling >3cm, entire leg swollen, localized tenderness, pitting edema, recent lower extremity immobilization, alternative diagnosis at least as likely
Your patient with acute DVT has CrCl 25mL/min, what is the best initial treatment?
Unfractionated heparin (gtt)
Anticoagulation in severe renal failure (CrCl <30)
Lovenox -> dont use
Rivaroxaban -> dont use
Eliquis -> was not studied
UFH -> safe
What is the dose of Enoxparin used for DVT PPX in a hospitalized patient?
40mg SC Daily
What is the dose of Enoxparain used to prevent DVT in a hospitalized pt with CrCl <30mL/min?
30mg SC daily
What is the loading dose of heparin for acute PE?
80 units/kg
What rate do you order the heparin drip to run?
18 units/kg/hr
How do yo monitor the effect of a heparin drip?
Check interval PTT levels, check interval Factor Xa activity
After being on heparin gtt x 5 days, there is a significant drop in PLT level. What condition should you be most concerned for?
HIT (heparin induced thrombocytopenia)
What is type 1 HIT?
Within first 2 days of exposure and platelet count normalized with continued heparin therapy
What is type 1 HIT a result of?
Form direct effect of heparin on the platelet activation
What is type 2 HIT?
Occurs 4-10 days after exposure and has life and limb threatening thrombotic complications
How is type 2 HIT mediated?
Autoimmune mediated
When should you suspect HIT if the pt has had no previous heparin exposure?
Decreased in platelets by >50%, 5-10 days after initiation of heparin, evidence of thrombosis
When should you suspect HIT for someone with a previous heparin exposure?
Decrease in platelets >50%, 1-10 days after re-exposure to heparin, evidence of thrombosis
What is the best next step for someone who develops HIT?
D/C heparin, start a direct thrombin inhibitor
What is the MOA of direct thrombin inhibitors?
Bind to thrombin directly and inhibit its activity
DTIs
No risk of HIT, used for treatment of HIT
What are the parenteral DTIs?
Bivalirudin (IV)
Argatroban (IV)
Desirudin (SC)
What is an oral DTI?
Dabigatran (Pradaxa) used to treat VTE and AFib
What is used to treat HIT?
DTIs, direct thrombin inhibitors
How long should someone with antiphospholipid ab syndrome remain on anticoagulation?
Indefinitely
Provoked VTE therapy duration
3 months
Unprovoked VTE duration of therapy
Atleast 3 months, after 3 months assess the risks/benefits of continued therapy
If low-mod bleeding risk -> indefinite
If high-> stop at 3 months
What is the INR goal?
2-3
How many days after starting Warfarin is it reasonable to adjust the dose based on the INR?
3 days
What dose of Warfarin is most commonly used to start?
5mg
Initial therapy for VTE is typically what?
LMWH, UFG, or DOA
HIT is a potential complication of what?
UFH
Txt of PE for a pt with HIT usually involves what?
DTIs
Warfarin is commonly prescribed as the long term agent for what?
VTE, 3 months indefinite, INR 2-3
Bridge the heparin product with warfarin due to what?
Delayed Warfarin activity
Cancer patients do better on what?
Long term LMWH or VTE