anticoagulants/anemia/urology Flashcards
phases of hemostasis
vascular platelet coagulation common insoluble
Generally only for arterial or intracardiac thrombosis as these thrombi are rich in platelets
antiplatelits
fibrinolytic
when the clot is already made and targeted on it’s own
used for acute treatment
anticoagulants can be used to affect platelet aggregation on the venus or arterial side?
both
hit’s the factors
thrombi/emboli in the venous sysplatelettem have relatively low count of ____compared to ti arterial thrombosis
thrombi/emboli in the venous sysplatelettem have relatively low count of platelets
Dissolve existing thrombus and are for the acute treatment of thrombosis (MI, ischemic stroke, massive PE)
fibrinolytic
Anticoagulants inhibit the formation of ______
Anticoagulants inhibit the formation of fibrin clots
Three major types of anticoagulants are available
heparin and related products, which must be used parenterally; direct thrombin and factor X inhibitors, which are used parenterally or orally; and the orally active coumarin derivatives (eg, warfarin).
heparin MOA
Heparin binds to antithrombin via its pentasaccharide sequence. This induces a conformational change in the reactive center loop of antithrombin that accelerates its interaction with factor Xa.
lower molecular weight heparin
still big
but only deactivates facot Xa
can not deactivate thrombin
what is necessary in order to induce thrombin inhibition with heparin
To potentiate thrombin inhibition, heparin must simultaneously bind to antithrombin and thrombin. Only heparin chains composed of at least 18 saccharide units (MW ~5,400 Da) are of sufficient length to perform this bridging function.
indications of heparin
” Prophylaxis & tx of venous thrombosis (DVT/PE) & peripheral arterial embolism
“ Early tx unstable angina (UA) or acute MI, AF w/ embolization
“ Disseminated intravascular coagulation
“ Prevents coagulation as blood passes through extracorporeal circuit in dialysis & arterial/cardiac surgery, coronary angioplasty, coronary stents, lab specimen, catheters
“ Consumptive coagulopathies
“ Prevention of thrombosis in pts with heart valve
factors that heparin affects
” Affects primarily factor IIa & Xa (also IXa, Xia, XIIa)
MOA of heparin UFH
” Prevents fibrin formation from fibrinogen during active thrombosis
“ Inhibits prothrombin conversion to thrombin
“ Induces secretion of tissue factor pathway inhibitor
dosing of heparin
only IV/SQ
clearance of heparin
- Plasma T½: 1-2 hrs í dose dependent
- T½ prolonged in anepheric pts, severe renal impairment, cirrhosis í no dose adj in RF
- NO dose adjustment not necessary in RF (renal failure) or HD pts (hemodialysis
dosing of heparin
is weight based
monitor therapy with heparin (goal)
blood draw every 30 (measures activity of thrombin, Xa, IXa) o Goal: 1.5-2.5 x control (sec) or hep level 0.3 - 0.7 by antifactor Xa heparin levels o Goal for DVT/PE: 60-100 secs í risk of bleeding @ 100 secs o Goal for AMI: 60-80 secs
what are we worried about
heparin induced thrombocytopenia
looks for platelet drop of below 50,000 or >50% decline form baseline
can lead to gangrene
main adverse reaction of heparin
bleeding and bruising
antidote for heparin
Protamine for unfractionated heparin; protamine reversal of LMW heparins is incomplete
antidote for warfarin
Vitamin K1, plasma, prothrombin complex concentrates
LMWH indications
” Prevention of venous thrombus (general/orthopedic surgery)
“ Tx of DVT w/ or w/o PE
“ Bridging anticoagulation: continue 24-48hrs after INR therapeutic
“ Need to cover before at full effect
Monitor (less = easier outpt tx):
“ SCr, CBC
“ No need to monitor APTT
advantages of heparin
” Increased plasma ½ life
“ Lower incidence of HIT
“ Less risk of osteoporosis
“ No need to monitor APTT - still need CBC, SCr
“ More predictable dose-response relationship
“ Less monitoring “ easy outpt tx option
pregnancy category for heparin
b
Protamine
UFH Reversal Agent
administration of protamine
” Administer SLOWLY í IV injection over 1-3 mins, NTE 50mg in 10 min
Fondaparinux (Arixtra) MOA
Synthetic Factor Xa inhibitor
monitoring for LMWH
” SCr, CBC
“ No need to monitor APTT
ADE of Fondaparinux (Arixtra)
- Hemorrhage
- Anemia, (elderly, poor renal fxn, < 50kg higher risk)
- Fever
- Nausea
found a pair of neux
half life of heparin
LMW
fondaparinux
1-2 h=hep
3-7 h= LMWH
15 h= fonda
clotting factors inhibited by warfarin
II
VII
IX
X
2+7=9
missin 1!
10
s
c
all of these are synthesized by the liver
MOA of warfarin
Vit K is co-factor for post-translational carboxylation of glutamate residues to -carboxyglutamates on Vit K-dependent proteins
Factors II, VII, IX, X require -carboxylation for biologic activity
two flavors of warfarin
I and S
DDI w/ warfarin
Inhibitors: Bactrim, Flagyl, barbiturates, CBZ, PHT, Cholestyramine, Sucralfate, Vit K, RIF, SJ Wort, Ginseng - doses
Potentiating: INH, -azoles, EtOH (liver dz), APAP, NSAID, Statins, amiodarone, TMX-SMX, garlic tabs, gingko biloba, other anticoags í doses
two isomers in warfarin
S isomer: 5 x more potent
and associated with CYP2C9
R CYP3A4
cyp1a2
enzyme inhibited by warfarin
vitamin k oxide reductase needed for activation and conversion
only anticoagulant we can use in pt w/ prosthetic heart valve
warfarin
dietary restrictions with warfarifn
Vit K intake; TPN —> BEWARE of OTC supplements (MVI, Teas, etc)
- intake: Abx, fat malabsorption
INR
international normalized ratio
Sweet spot between thrombotic and hemorrhage
between 2.0-3.0
how frequently do you check INR
Daily while inpatient -> twice weekly outpatient, until INR stable -> weekly -> bi-weekly -> monthly
why don’t we front load warfarin anymore
if you give big dose you see a big change in factor 7
but you’re also knocking out coagulation and can make them procoagulated ???
48 mins
caution with warfarin should be taken wiht
Hepatic Dysfxn - impaired synthesis of factors ( decrease initial dose; increase INR & albumin)
- Hyper-metabolic states
(hyperthyroid, fever) –> increase warfarin sensitivity by increasing catabolism of Vit K-dependent factors
- CHF - sensitivity
CHF caution
exacerbation with different doses
(hyperthyroid, fever . considerations
increase warfarin sensitivity by increasing catabolism of Vit K-dependent factors
DDI with warfarin
DDI:
Inhibitors: Bactrim, Flagyl, barbiturates, CBZ, PHT, Cholestyramine, Sucralfate, increase Vit K, RIF, SJ Wort, Ginseng - decrease doses
Potentiating: INH, -azoles, EtOH (liver dz), APAP, NSAID, Statins, amiodarone, TMX-SMX, garlic tabs, gingko biloba, other anticoags –> increase doses
INR for mechanical prosthetic valves
- INR 2.5-3.5:
INR bioprosthetic valves
- INR 2-3:
Metabolic Variability seen with heparin
Hereditary resistance (occurs in rats & humans); Requires 5-20x more vs. average dose d/t ltered affinity of receptor for warfarin
Phytonadione
reversal for warfarin
INR of 3.5-5 what do you do
lower dose resume at decreased level
INR of 5-9 w/out bleeding what do you do
omit 1 or 2 doses then resume at decreased
over 9 no sig bleeding
hold war
give vit k 3-5mg
exepect reduce in 24-48 hours
INR over 20
hold warfarin
vitamin k 10 mg
slow IV or SQ