How do platelets work?
Tissue injury occurs and arachnodinic acid is released causing platelet recruitment and aggregation (TxA2 and ADP). This forms a weak clot. The coagulation cascade is triggered and that creates fibrin that wraps around the clot to make it strong.
What dose of aspirin is needed for anti-platelet effects?
Baby aspirin (81mg)
What does aspirin prevent?
MI and stroke
What is the MOA of aspirin?
Blocks COX1
COX1 converts arachidonic acid to TxA2. When we take aspirin, we block that action, so TxA2 is not created–so no platelet recruitment and aggregation and no coagulation so no fibrin clot–all leads to making you bleed
What are the adverse effects of aspirin?
GI problems (dyspepsia, ulcers, bleeding) Tinnitus (dose dependent)
What kind of antagonist is clopidogrel?
ADP P2Y12
What are the indications for taking clopidogrel?
MI and ischemic stroke
What is the MOA of clopidogrel?
Blocking the production of ADP
ADP is not created, so we don’t get platelet recruitment and aggregation..so no coagulation cascade…so no fibrin clot formed..so you bleed
Clopidogrel is ineffective for __% of people due to _____.
40% of people due to genetic variations
Clopidogrel has many _____ interactions.
CYP
What do we teach our patient to look for to know they are having a GI bleed?
Black, tarry stool (melena)
Coffee ground emesis
What happens if a patient abruptly stops taking clopidogrel?
Can cause clotting to occur too fast–thrombotic event
What is the clotting cascade?
An injury occurs and stuff happens that activates factor X, which activates factor II (thrombin). That works together with fibrinogen to form a fibrin clot
Who gets blood thinners?
DVT and PE (prevention and treatment)
A-fib
MI
Mechanical heart valve
Is warfarin highly variable or highly predictable?
Highly variable
Does warfarin have a low or high therapeutic index?
LOW
What can affect warfarin levels?
Diet (vitamin K) and genetics
What is the MOA of warfarin?
The liver makes clotting factors X and II by using VITAMIN K. After it makes them, vitamin K is deactivated until they are needed to be made again. Warfarin blocks that reactivation of vitamin K. Eventually there is no more clotting factors.
How long does it typically take for there to be no more clotting factors in the body after warfarin deactivates vitamin K?
5 days
If a patient eats a lot of vitamin K, do they need a low or high dose of warfarin to be an effective blood thinner?
High dose
What lab tests do we look at for warfarin?
PT and INR
What does PT tell us?
Nothing; it just gives us the number we need to get the INR
What does INR correct?
The PT level
What is a normal INR?
1
What is the INR for most clients?
2-3
What is the INR for a patient with mechanical heart valves?
2.5-3.5 (needs thinner blood)
What do we teach our client who is taking warfarin?
- Consistency in VITAMIN K foods
- Interactions
- S&S of bleeding (melena, bloody urine, coffee ground emesis)
What pregnancy category is warfarin?
X
Can we give warfarin to a patient with impaired renal function?
Yes; warfarin is eliminated by the liver, so you don’t need good renal function to take warfarin
Is heparin rapid acting or slow acting?
Rapid
Does heparin have a long or short half life?
Short (1.5 hours)
Is heparin lipid soluble or polar?
Highly polar
Since heparin is highly polar, how can we administer it?
IV and SQ only
Is heparin highly variable or highly predictable?
Highly variable–must get lab work!!
How do we monitor heparin?
Look at the PTT levels
What does the PTT levels tell us?
How long it takes blood to clot
How long does it take blood to clot in a normal person?
40 seconds
How long does it take blood to clot if you are on anti-coagulant therapy?
60-80 seconds
What are some of the safety issues with heparin? (4)
- Bleeding risks
- Heparin-induced-thrombocytopenia
- Don’t take with anti-platelet meds
- Heparin dose vs. heparin lock
What is the antidote for heparin toxicity?
Protamine sulfate
What is the MOA of enoxaprin?
Inhibits factor X
Is enoxaparin polor or lipid soluble?
Polar
How do we administer enoxaparin?
Sub Q ONLY
Is enoxaparin variable or predictable?
Predictable
How enoxaparin have a long or short half life?
Long
What is special about administering enoxaparin?
Enoxaparin comes in a prefilled syringe that has a bubble in it. You get the bubble to the top of the syringe so that it is the last part to be injected in. The purpose of the bubble is to help seal off the injection site to prevent bruising
What blood count needs to be watched with enoxaparin? What other level needs to be watched?
Platelets; anti-Xa levels
How is enoxaparin excreted? What does this mean?
Excreted renally; monitor renal function
