Anticoagulation Flashcards
(43 cards)
1
Q
Warfarin vs. Xa inhibitors vs. direct thrombin inhibitors vs. fibrinolytics
what treats what in the coagulation cascade
A
- warfarin blocks factors early in the cascade (II, VII, IX, X - same factors targeted by KCentra)
- oral Xa inhibitors have “xa” in the name
- fondaparinux is an indirect Xa inhibitor
- direct thrombin (factor IIa) inhibitors include dabigatran and argatroban
- heparin products target Xa and thrombin (think apixaban + dabigatran coverage) by activating/increasing antithrombin activity
Xa: prothrombin into thrombin
thrombin: fibrinogen into fibrin
- all the above ultimately prevents fibrin (holds clots together) from forming
- fibrinolytics break up a clot that’s already been formed
2
Q
what does VitK do?
A
- VitK activates factors II, VII, IX and X
- warfarin prevents it from doing that
3
Q
lab monitoring for heparin vs. lovenox
A
- heparin and lovenox inhibit Xa and are indirect thrombin inhibitors through their activation of antithrombin
- therefore in theory, anti-Xa levels and aPTT should estimate their activity, however, lovenox has more Xa activity and Xa is the best option for lovenox while heparin can go either way
although you don’t really need to monitor for lovenox
4
Q
why no DOAC for ACS?
A
ACS is acute, main target of drug therapy is platelet aggregation
5
Q
why no antiplatelet for DVT?
A
not sufficient
6
Q
heparin “therapeutic” dosing
A
- VTE: 80 U/kg bolus followed by 18 U/kg/hr infusion
- UA/NSTEMI/STEMI: 60 U/kg bolus followed by 12 U/kg/hr infusion
7
Q
what’s a heparin flush
A
no therapeutic purpose, purpose is to prevent clots from forming in IV lines
8
Q
heparin monitoring - how often do you check and what are your goals
A
- check an anti-Xa or aPTT every 6 hrs with first level being checked 6 hrs after initiation
- aPTT goal: 1.5-2.5x control
- antiXa goal: between 0.3 and 0.7 U/mL
9
Q
lovenox “therapeutic dosing”
A
- VTE: 1mg/kg BID or 1.5mg/kg QD (if CrCl < 30, 1mg/kg QD)
- UA/NSTEMI: 1mg/kg BID (if CrCl < 30, 1mg/kg QD)
- STEMI in pt <75: 30mg IV bolus + 1mg/kg SQ loading dose followed by 1mg/kg BID (if CrCl <30, change subsequent doses from BID to QD)
- STEMI in pt >75: no bolus start at 0.75mg/kg BID (if CrCl < 30, 1mg/kg QD)
VTE dose can include 30mg SQ BID
10
Q
what patients might benefit from lovenox monitoring and when would you obtain your labs?
A
- recommended in preggers
- may consider monitoring in renal insufficiency, obesity, low weight, peds, elderly
- obtain level 4 hrs after dose
11
Q
what happens in HIT
A
- Ab forms and attacks the heparin-platelet factor 4 (PF4) complex (no, this is not a coagulation cascade factor, this is a different factor
- Ab-heparin-PF4 complex binds to platelets and activates them -> pro thrombic state
so why do platelets go down? you’re using them, you’re not bleeding
12
Q
what are the 4Ts and what lab tests are there for dx/confirming HIT?
A
- Thrombocytopenia: >50% plt drop
- Thrombosis: new clot or skin lesions (necrotizing or non-necrotizing)
- Timing: 5-10 days after first exposure to heparin, within hours if heparin exposure in past 3 months
- Other: inability to identify other causes
- if with 4Ts, HIT is reasonably suspected, can send for an ELISA test and, if desired, confirm with functional assay
13
Q
what to do when patient has HIT
and is there a specific patient population that may have a few extra steps (hint, hint: yes)
A
- stop all heparin products including lovenox
- if patient is on warfarin: stop and admin VitK - why? because warfarin usage in pts with low plt count is correlated with warfarin-induced limb gangrene and necrosis (yikes)
- but isn’t HIT a prothrombotic state? yes - so prevent those clots with argatroban, but be careful if pt has to restart warfarin, because argatroban artificially raises INR
- if urgent surgery or PCI is required, we prefer bivalirudin
- fondiparinux also has an off-label use for HIT
14
Q
when do we dose reduce apixaban for a.fib?
A
if 2 of the three are met:
- > 80 years old
- SCr >1.5
- weight < 60kg
15
Q
edoxaban dosing
A
- start with: in afib patients - kidney function must be not good but also not bad - CrCl must be between 15 and 95
- if CrCl > 50 do 60mg QD; if < 50 do 30mg QD
for VTE 60mg daily with a 5-10 day bridge in
- qualify for 30mg if CrCl 30-50, < 60kg or DDI
16
Q
rivaroxaban dosing: counseling points
missed dose, administration
A
- doses 15mg+ must be taken with evening meal, if less, take whenever doesn’t matter
- once daily doses: if missed dose, take ASAP but if close to next dose, don’t take and don’t double up
- twice daily dose of 15mg: can double up (whoaaaaa)
17
Q
Rivaroxaban dosing
A
- afib: CrCl >50 do 20mg, if <50 do 15mg (with limited data on efficacy if CrCl < 15)
- VTE: initial phase of 15mg BID followed by 20mg QD - if giving indefinitely, can switch to 15mg after 6 months of the 20mg (use with caution if CrCl <50 and avoid if <15)
- post-surg DVT ppx: 10mg (duration depends on surgery)
- CAD/PAD: 2.5mg BID in combo with baby asa
18
Q
peri-operative DOAC suspension
A
- rivaroxaban and edoxaban: 24 hrs
- apixaban: 24hrs if low bleed risk surg, 48 if mod-high bleed risk
- dabigatran: 1-2 days if CrCL 50+, 3-5 if CrCl <50
19
Q
can you crush DOACs?
A
- can crush Xa inhibitors (rivaroxaban, eliquis, edoxaban)
- canNOT crush dabigatran
20
Q
warfarin to DOAC conversion
A
Stop warfarin, and start DOAC based on INR:
- Rivaroxaban INR < 3
- Edoxaban INR < or equal to 2.5
- Apixaban INR <2
- Dabigatrain INR < 2
21
Q
DOAC to warfarin conversion
A
- apixaban and rivaroxaban: stop and then start warfarin at next scheduled dose
- edoxaban: follow package insert
- dabigatran: start warfarin 1-3 days prior to stopping dabigatran (day depends on renal fxn)
22
Q
quick and dirty/lazy DOAC DDI
A
- apixaban: avoid with strong dual CYP3A4 and PGP inducers
- rivaroxaban: || AND inhibitors, as well as cobicistat (so probs just don’t jump to this one if HIV pt)
- edoxaban: PGP substrate
- dabigatran: PGP substrate - avoid with rifampin; if CrCl <50 dose reduce to 75mg BID if concurent dronaderone or systemic ketoconazole; DDI with cobicistat - pt specific recs based on risk, renal fxn and indication
23
Q
dabigatran dosing
A
- afib: 150mg BID; 75mg BID if CrCl <30 (but greater than 15)
- VTE: 150mg BID after 5-10 day bridge; do NOT use if CrCl <30
- ppx following hip surgery: 110mg on day 1 then 220mg QD; do NOT use if CrCl < 30
24
Q
do DOACs affect your aPTT or INR?
A
- only dabigatran affects aPTT and INR - it can raise them
edoxaban can raise LFTs though
25
warfarin dosing
- **healthy patients**: start at **< 10mg for 2 days, then adjust** dose per INR
- **dose reduced** (**< 5mg**) patients include: elderly, malnourished, liver disease, DDI that increase warfarin levels, HF, and high risk of bleed
## Footnote
adjust dose based on INR:
- goal INR 2-3 for most patients
- goal 2.5-3.5 for high risk indications: mechnaical mitral valve, 2 mechanical heart valves, or mechanical aortic valve with an additional risk factor for clot
26
Anticoagulation in pregnant patients
- Lovenox preferred for prevention *and treatment of VTE*
- warfarin: do NOT use unless mechanical heart valves and at high risk for thromboembolism
- DOACs have not been studied adequately, therefore use not recommended
27
what genetic mutations do you need to consider for warfarin pts?
- CYP2C9 * 2 or * 3 alleles
- polymorphism of VKORC1 gene
## Footnote
presence of one or both of the following can lead to inccreased bleed - testing for these isn't necessarily recommended, but it is underlined in the NAPLEX book, so know for test question
28
warfarin DDI
- **S-enantiomer**: more active, is primarily metabolized by CYP **2C9**
- **R-enantiomer**: less active, primarily metabolized by **CYP3A4** (these interaction are less important than 2C9)
## Footnote
CYP 2C9 inducers decrease INR, inhibitors increase INR
- amiodarone: decrease warfarin dose 30-50%
- tamoxifen: avoid concurrent use
29
warfarin tablet colors
**P**lease **L**et **G**reg **B**rown **B**ring **P**eaches **T**o **Y**our **W**edding
## Footnote
- pink 1mg
- lavender 2mg
- green 2.5mg
- brown 3mg
- blue 4mg
- peach 5mg
- teal 6mg
- yellow 7.5mg
- white 10mg
30
what food things/herbals can increase bleed risk in warfarin patients
- chondroitin
- dong quai
- high doses of fish oil
- 5 Gs: garlic, ginger, ginkgo, ginseng, glucosamine
- Vit E
- willow bark
31
how do you bridge warfarin
continue warfarin and therapeutic parenteral AC until for at least 5 days AND INR >2 for at least 24 hrs
32
protamine use and dosing
protamine 'reversal' for heparin products
## Footnote
- **IV heparin**: 1mg of protamine per 100 U of heparin administered in the last 2.5 hrs (max dose of 50mg)
- **enoxaparin given <8 hrs ago:** 1mg per 1 mg (only neutralizes about 60% of antiXa activity)
- **enoxaparin given >8 hrs ago**: 0.5mg per 1mg
33
praxbind dosing
idarucizumab
## Footnote
2.5 g IV twice, with second dose being <15 minute safter first (total 5 g)
34
how often should you check an INR in a warfarin patient on a stable dose
up to every 12 weeks if *consistently* stable
## Footnote
if a previously stable patient has a single INR <0.5 out of range, can maintain current dose and recheck in 1-2 weeks
35
vitamin K considerations
## Footnote
boxed warning, ROA, storage
- ADR: hypersensitivity rxn/anaphylaxis - lower risk with slower infusion
- ROA: IV or PO (SQ has variable absorption and IM has high risk of hematoma)
- needs to be protected from light, even during admin
36
Contraindications to four factor prothrombin
- hx of HIT (it contains heparin)
-
## Footnote
- can't use KCentra in DIC (disseminated itravascualr coaguation)
- can't use Balfaxar in IgA deficiency with Ab to IgA
37
4 factor prothrombin vs. 3 factor, what factor is missing
four factor has factor VII
## Footnote
therefore, 3 factor must additionally be given with fresh frozen plasma or factor VII (novoseven)
38
when to give what when reversing warfarin
- **INR <4.5 without bleeding**: reduce or skip warfarin dose and monitor INR
- **INR 4.5-10 without bleeding**: hold 1-2 doses of warfarin and monitor INR
- **INR > 10 without bleeding**: PO Vit K 2.5-5mg, monitor INR and resume warfarin when INR therapeutic
- **major bleeding**: slow IV injection of Vit K 5-10mg alongisde 4F PCC
39
perioperative management of warfarin
- stop warfarin 5 days prior and bridge with heparin - if pt at low risk for thromboembolism, don't have to bridge
- resume 12-24 hours after surgery if pt had no major blood loss
## Footnote
- if pt INR is elevated 1-2 days before surgery can give low dose VitK (1-2mg)
40
anticoag recs for afib patients who will undergo cardioversion
- afib episode lasting >48 hours or unknown: anticoag for at least 3 weeks prior and 4 weeks after cardioversion
- afib lasting < 48 hours undergoing elective cardioversion: start therapeutic AC at presentatoin, perform cardioversion, and continue for at least 4 weeks
41
CHADSVASc - and when to anticoagulate
| you tell me where the 2s go ;)
- CHF: 1
- HTN: 1
- Age >75: 2
- Diabetes: 1
- Stroke/hx of: 2
- Vascular disease (MI, PAD): 1
- Age 65-74: 1
- Sex: 1 for female
## Footnote
- if non-sex score = 1, may consider AC
- if non-sex scpre = 2+, AC recommended
42
HAS-BLED
- HTN: SBP >160
- Abnormal kidney or liver fxn
- Stroke hx
- Bleed tendency
- Labile INR
- Elderly (65+)
- Drugs with bleed risk or excess EtOH use
| determines bleed risk with higher score = higher risk
43
lovenox administration counseling points
- inject in the stomach, at least 2 inches from belly butto
- do NOT get rid of air bubble
- hold syringe like a pencil and insert at 90 degree angle
- depress plunger until syringe fully emptied
- take syringe out and push against to plunger to activate safety shield before disposing in a sharps container
- do NOT rub injection site - may cause bruising
