Anticoagulants Flashcards
how does heparin work?
binds AT III
Enhances its activity 1000 fold
Which factors does AT III inhibit?
9-12
What kind of chemical compound is heparin?
Sulfated glycosaminoglycan
Can be either bovine or porcine derived
What is a unit of heparin?
Volume of heparin-containing solution that will prevent 1 ml of citrated sheep blood form clotting for 1 hour after the addition of 0.2 ml of 1:100 CaCl
Because of its large size, heparin does not cross the placenta. T/F
T
Pts taking anticoagulants may be changed heparin once they become pregnant
Heparin is well abosorbed and may be taken PO. T/F
F
Heparin has poor lipid solubility
Why isnt heparin given IM?
Risk of hematoma
Heparin is ________ protein bound.
highly
What determines the half life of heparin?
dose dependent
What is normal aPTT and ACT?
aPTT 30 sec
ACT: 90-120s
What ACT would you want to see in vascular surgery?
250 s
What are some clinical uses of heparin?
Venous Thrombosis/ Pulmonary Embolism Post MI thrombosis Unstable angina Post thrombolysis Extra-corporeal circulation DIC Pregnancy uses Bridge therapy with longer acting drugs
Define:
Thrombus
Embolus
Thrombus- Formation of a clot
Embolus- When a clot moves and lodges somewhere else
What is the dose of heparin for vascular surgery pts? CPB pts?
Vascular 100 units/kg
CPB 300-400 units/kg
Flor vascular surgery, you should ask the surgeon if they would like to redose heparin after __________ _________.
about 45 minutes. at vascular dose half life is about 1 hour
How much circulation time should you give after giving heparin and before cross clamping?
3 min
What are the contraindications for heparin?
Ocular surgery
Intracranial surgery
Spinal/ Epidural
Peripheral nerve blocks
What is mild thrombocytopenia?
Most common
205 days post exposure
Platelet count < 100K cells/mm3 blood
Reversible
What is considered severe thrombocytopenia?
More than 5 days out Platelet count < 50K cells/mm3 blood Heparin resistance HITT Thrombosis is 20%. Mortality is 40%
What is HITT?
How common is it?
Heparin-Induced Thrombocytopenia and Thrombosis
5-28% patients develop HIT
Seen as fall in platelet count after heparin exposure
Heparin therapy must be discontinued
What is protamine made from? What’s the mechanism for inactivating heparin?
made from salmon sperm
protamine is + charged, while heparin is -, so they bind together
What is the dose of protamine?
text says 1mg/100 u heparin
Why should protamine be given on a pump or in a minidrip setup?
Causes hypotension with rapid administration
What happens if too much protamine is given?
the protamine prolongs anticoagulation and becomes an anticoagulant itself
what are side effects of protamine?
hypotension
pulmonary hypertension
allergic reaction
Which patients are likely to have a protamine alllergy?
NPH insulin
Vasectomy/Infertility
Fish allergy
What are two alternatives to protamine?
Platelet factor 4 (PF4)
- Platelet concentrates
- Heparin-binding protein
- Reverses actions of heparin
Heparinase-I
-Heparin-degrading enzyme
OR you could just wait it out
What is enoxaparin?
Lovenox--low molecular weight heparin given as subq shots DVT prophylaxis ( total hip or knee)--not given in or
What size is lovenox?
400-500 daltons
How often is lovenox taken?
once daily
Coumarin derivatives may cross the placental barrier and cause fetal abnormalities. T/F
T
Coumarin derivatives cause defective protein formation of which coag factors?
2,7,9,10
Jen’s mnemonic: 2+7=9 and then 10…
Anticoagulation with coumarin derivatives is rapid. T/F
F, because it takes time for new, defective proteins to form, these have delayed onset
What 2 labs should be monitored with coumarin?
PT
INR-therapeutic between 2-3
What are the clinical uses of coumarin derivatives?
Prevent venous thromboembolism Prevent systemic embolism -A-fib -Mechanical heart valves Stroke prevention
How long should coumadin be discontinued before surgery?
5 days
What can be given as a bridge for coumadin? how long should they be discontinued before
surgery?
Heparin (last dose 4 hours preop)
LMWH (last dose 24 hours preop)
What do you do if a pt on coumadin comes to the OR emergently?
Vit K ( usually given enterally)
FFP
recombinant factor VII
What are the side effects of coumadin?
Hemorrhage
Skin necrosis
Fetal changes
- CNS damge
- hemorrhage
Can a breast feeding mother take coumadin?
yes-doesn’t affect breast milk
What is the goal of giving thrombolytics?
REstore circulation to a previously occluded vessel
What is the mechanism of thrombolytics?
activate plasminogen to plasmin-the key to starting clot breakdown
Name 4 thrombolytics
Streptokinase
Urokinase
Alteplase-TPA
Anistreplase
Which drugs are considered antithrombotic?
Hirudin
Aspirin
Clopidogril
What’s another name for Hirudin?
How does it work and what are ists clinical uses?
Argatroban Supresses platelet function Clincally- -Prevention of DVTs in hip replacement -Alternative to heparin in HITT
Aspirin blocks production of _________
Thromboxane
Clopidogrel is is prodrug with slow onset. T/F
T
How long should clopidigrel be stopped before surgery?
7 days
what is doese of clopidegrel?
75mg/day
What are the indications for clopidogrel?
Reduce rate of stroke, MI and death after MI
Peripheral artery disease
Acute coronary syndrome
What are the platelet glycoprotein IIb/IIIa antagonists?
HOw do they work?
Abciximab, Eptifibatide, Tirofibran
Block frbrinogen form binding to receptors in the final common pathway of platelet aggregation
What are the uses of glycoprotein IIB/IIIa antagonists?
INterventional cardiology procedures
acute coronary syndrome
How do you monitor glycoprotein IIb/IIIa antagonists?
ACT and platelet count
Name 2 antifibrinolytics. How do they work? What is their use?
Lysine analogs and Aprotinin -Amicar and transexamic acid Inhibit proteolytic activity of plasmin Used for cardiopulmonary bypass -Since during CPB the fibrinolytic pathway gets upregulated
What are guidelines for surgery after balloon angioplasty?
If less than 14 days delay elective surgery
After 14 days proceed to OR on aspirin
What are guidelines for Bare metal stent?
If less than 30-45 (4-6 weeks) days delay elective surgery
After 30-45 days proceed to OR on aspirin
What are guidelines for drug eluting stent?
If less than 365 days delay elective surgery
After 365 days proceed to OR on aspirin
What is periop managemet of pts at high risk for cardiac events?
Continue aspirin through periop period
Stop plavix at least 5days (prefer 10d)
Resume plavix 24 hours post op
What is periop mangaement for pts at low risk for cardiac events?
Discontinue antiplatelet therapy 7-10d efore surgery
Resume antiplatelet therapy 24 hours postop
What is timeline for heparin surrounding neuraxial anesthesia?
Needle placement ok 1 hour before heparin
D/C heparin 2-4 hours before catheter removal
LMWH for bridge therapy—needle placement 24 hours after last dose
Sub Q heparin is a contraindication for Neuraxial anesthesthesia. T/F
F
HOw long is surgery delayed after a bloody tap?
24 hours
What should be checked on pts receiving heparin for > 4 days before neuraxial anesthesia?
Platelet count
What are guidelines for neuraxial anesthesia for pts with oral anticoagulants?
40% of each factor for normal coagulation
INR < 1.5 associated with normal hemostasis
D/C coumadin 4-5 days
INR MUST be normalized
Avoid other anti-clotting drugs
Catherter removal with INR < 1.5
What should INR be before catheter is removed on a pt receiving neuraxial anesthesia on coumadin
<1.5
How long should plavix be D/Ced befor neuraxial anesthesia?
7 days
NSAIDS aside from asprin have short term effects on platelets that return to normal in ____ days with no increase in risk of spinal hematoma
3
HOw long should epidural be avoided when abciximab?
until platelet function has recovered-24 hours
Which neuraxial technique is best with direct thrombin inhibitors?
NONE
Which class of drugs is an absolute contraindication for neuraxial anesthesia?
thrombolytics
What is the pradaxa?
Direct thrombin inhibitor similar to coumadin. Doesn’t require monitoring like coumadin
What is the drawback to pradaxa?What is therapy?
no reversal
The therapy is : time, activated charcoal, dialysis
