anti-platelete and anti-coagulant therapy Flashcards
what is the mechanism of heparin ?
heparin stimulates antithrombin 3 which in turn inactivates factor Xa and factor IIa
how is heparin monitored ?
1- unfractionated heparin - aPTT
2- anti-Xa assay for low molecular weight heparin
when a patient iis not taking heparin it should be zero
what is the normal PT ?
10-13 seconds
what is the normal PTT ?
25 to 35 seconds
what is the advantage of LMWH overr unfracctionated?
longer half life
less cchane of bleeding
dosing is simple
no need to monitor
what are the indications of unfractionated heparin ?
1- if the risk of bleeding is high
2- in situations where rapid reversal of anticoagulation is necessary is required
3- in massive PE following thrombolysis
4- in cases of proximal LL oedema where LMWH is not working
is unfractionated heparin or LMWH easier to reverse ?
unfractionated heparin
both reversed by protamine sulphate
what is the treatment of overdose of heparin ?
in unfractionated heparin , stop the infusion which is usually sufficient if not then give protamine sulphate
why is warfarin bridged by heparin ?
because warfarin reaches its maximum effect after 3-5 days
also warfarin inhibits protein C and S at the beginning ( inhibits anticoagulation)
which anticoagulant is safe for pregnancy ?
heparin not warfarin
what is the mechanism of action of warfarin ?
inhibits vitamin k which in turn inhibits the activation of the coagulation factors
which pathway does warfarin inhibit ?
extrinsic pathway
what is the clinical use of warfarin ?
for purposes of chronic anticoagulation
how is warfarin monitored ?
using INR ( prolongs PT )
what is the target INR for patients on warfarin ?
for DVT or PE target is 2.5 (between 2-3)
patients with recurrent VTE the target is 3.5 ( 3-4)
what are the complications of warfarin ?
bleeding
fatal bleeding
purple toes syndrome
what are the drugs that interact with warfarin ?
antifungals
amiodarone
aspirin containing products
when do we consider that the patient is in warfarin toxicity ?
INR above 5
what is the treatment of warfarin overdose ?
1- INR 6-8 but no bleeding , or minor bleeding - stop the warfarin for 24-48 hours , reccheck INR and then re introduce the drug art a lower dose in 2-7 days
2- INR more than 8 with no bleeding or minimal bleeding , then stop the warfarin for 48 hours , consider oral vitamin K or slow infusion of vitamin K
3- life threatening or sight threatening
stop warfarin
administer prothrombin complex concentrate
also give vitamin K to maintain reversal
why is fresh frozen plasma not recommended for warfarin toxicity ?
not fast enough
what are the absloute contraindications to anticoagulants ?
haemorrhagic diathesis
severe hypertension
previous cerebral hge
CNS trauma
GI bleeding
history of heparin sens or HIT
what are the relative contraindications to anticoagulants ?
uremia
liver disease
chronic alcoholism
subacute bacterial endocarditis
when is thrombolysis used ?
Massive PE
phlegmasia cerulea dolens
when is an IVC filter used instead of anticoag in PE ?
1- when anticoagulants are absolutely contraindicated
2- recurrent VTE despite therapy
3- serious complications due to anticoag
4- free floating thrombus
5- patients with limited pulmonary reserve won’t survive another PE
what are the new oral anticoagulants ?
direct thrombin inhibitors
factor Xa inhibitors
what are examples of anti platelets ?
aspirin , clopidogrel
when can dabigatran be used ( direct thrombin inhibitor ) ?
1- primary prevention of VTE in patients undergoing total hip replacement
2- prevention of stroke and systemic embolism in patients with nonvalvular Afib
3- treatment and prevention of DVT and PE in adults
what are the uses of rivaroxaban ( factor Xa inhibitors ) ?
1- prevention of VTE in adult patients undergoing hip or knee replacement
2- prevention of stroke and systemic embolism in non valvular afib
3- treatment of DVT and prevention of recurrent DVT and PE in adults
what is the first line treatment for ACS ?
percutaneous coronary intervention
aspirin
if not aspirin then clopidogrel
if the problem is central or peripheral ?
clopidogrel
