Anticoagulants Flashcards
What is the most common use of anti-coagulant meds?
Treat & prophylaxis of venous thromembolism (VTE)
What is the purpose of prophylaxis anti-coagulant therapy?
B/c the last thing we want is an actual clot to form & break off & travel to lungs or brain
Prophylaxis of VTE with anti-coagulants is to prevent what 2 things?
1) Pulmonary embolism (PE)
2) Deep venous thrombosis (DVT)
List 4 other indications for using anti-coagulant meds
1) Acute coronary syndromes (ACS)
2) Atrial fibrillation
3) Prosthetic heart valves
4) Post-surgical use
What is the goal of anti-coagulant therapy?
Prevent formation of a clot & progression of an already formed clot
List the 2 pathways involved in the coagulation cascade
1) Intrinsic
2) Extrinsic
What is intrinsic pathway monitored by?
aPTT
What is the extrinsic pathway monitored by?
PT/INR
Which pathway comes into play when talking about warfarin & heparin?
The extrinsic pathway
Where does the common pathway occur?
At factor Xa where both the intrinsic and extrinsic pathways converge
List the conversion of proteins that occurs during the coagulation cascade after common pathway begins
Prothrombin → thrombin → fibrinogen → fibrin → stable fibrin clot
Primary homeostasis:
If a vascular injury occurs what is the inflammatory response? Hint: 5
1) Vasoconstriction
2) Platelet activation (vWF; Fibrinogen bind)
3) Create the platelet plug
4) Leads to blood clot
5) Plasmin causes fibrinolysis & clot degradation
Secondary homeostasis:
If a vascular injury occurs how does the coagulation cascade come into play? Hint: 5
1) Platelets activate coag cascade
2) Cascade activates conversion of thrombin to fibrinogen
3) Fibrinogen converts to fibrin
4) fibrin forms the blood clot
5) Plasmin causes fibrinolysis & clot degradation
Where can we find a lot of clotting factors inside the human body?
The liver → want them activated as well!!
Is fibrinogen soluble or insoluble?
Soluble
Is fibrin soluble or insoluble?
Insoluble
What does a damaged or injured blood vessel trigger?
Release of clotting factors
Once clotting factors are released what is formed?
Platelet plug
Vasoconstriction limits BF & plts form a sticky plug
After the platelet plug is formed what happens?
Development of a clot
Fibrin strands adhere to the plug to form an insoluble clot (helps protect us)
List 3 common coagulation tests
1) Prothrombin time (PT)
2) International normalized ratio (INR)
3) Activated partial thromboplastin time (aPTT)
Prothrombin time (PT) Hint: 3
1) Measures time it takes for plasma to clot
2) Extrinsic pathway
3) Ref range: 10-13 sec
International normalized ratio (INR) Hint: 2
1) Standardizes the reporting of PT values
2) Reported for patients receiving Warfarin (Coumadin)
What two coagulation tests must always be ordered together?
PT/INR
Activated partial thromboplastin time (aPTT) Hint: 3
1) Measures time it takes for plasma (blood) to clot when exposed to a reagent
2) Intrinsic pathway
3) Ref range: 30-45 sec
Platelet functions:
What is the first step in maintaining homeostasis?
Platelet adhesion
What 2 things occur along with platelet adhesion?
1) Vasoconstriction
2) Formation of platelet plug
List 2 things platelets activate
1) Arachidonic pathway
2) Coagulation cascade
What is platelet aggregation induced by?
The release of Thromboxane A
List 2 functions of platelet aggregation
1) Stabilizes platelet plug
2) Activates Clotting cascade
Clot retraction and clot dissolution is regulated by…
Thrombin plasminogen activators
List the 3 classes of anti-coagulant medications
1) Anti-platelets
2) Anti-coagulants
3) Thrombolytic agents
Anti-platelet drugs
Small guns → very potent
Decrease aggregation & formation of platelet clot
Anti-coagulants
Medium guns → more potent than anti-plts
Interfere with clotting cascade & thrombin formation
Thrombolytic agents
Big guns
Break down the thrombus (clot) by stimulating plasmin
Anti-platelets:
When there is injury to the vessel what do the plts do?
Aggregate to the site of injury
Anti-platelets:
Once plts are at the site they release…
ADP & serotonin which help bring plts together
Anti-platelets:
ADP is a precursor to ____
Prostaglandins
What else is produced when injury occurs and what does it increase?
Thromboxane A → increases vasoconstriction & plt aggregation
What is the job of anti-platelets?
Inhibit plt adhesion & aggregation by blocking COX-1
What is average lifespan of platelets?
7-10 days
What 3 baseline lab values do we need to know before giving anti-platelets?
1) Hgb
2) Hct
3) Platelets
What plt value would require a call to the doctor before giving the med?
< 150,000 / µL
Acetylsalicyclic acid (ASA) is used to prevent
Platelet aggregation
Anti-platelet
List 5 indications for giving ASA
1) CAD/ CVA/ PAD prevention
2) Maintains AV grafts
3) Post MI
4) Post stent placement
5) Other vascular diseases
What does ASA inhibit?
Prostaglandin production
What does ASA bind to?
Highly bound to plasma proteins
How long does ASA inhibit plt aggregation for?
A single dose (325 mg) can inhibit plt aggregation for the life of the plt (7-10 days)
How long prior to surgery should ASA be stopped?
At least 1 week prior
What is important to keep in mind if ASA is being used for pain relief?
It could cause some bleeding as it is still an anti-platelet
Who should take baby ASA (81 mg; low dose)?
Patients who have had heart attacks are usually on low dose
List 2 side effects of ASA
1) Bleeding
2) GI side effects
What type of ASA can help decrease GI side effects?
Baby ASA → enteric-coated
What types of patients should ASA be used cautiously in?
Those w/ hepatic/ renal impairment
List 3 things caused by ASA toxicity
1) Tinnitus
2) Hyperventilation
3) Metabolic acidosis
What age group should NOT receive ASA?
Children < 18 yrs → can cause Reye syndrome
What is Reye syndrome?
Rare but serious condition that can lead to brain as well as liver damage (in some cases can be lethal)
Drug interactions of ASA:
List 5 drugs that can increase risk of toxicity if taken with ASA
1) Oral anti-coagulants
2) Heparin
3) Methotrexate
4) Oral DM meds
5) Insulin
Drug interactions of ASA:
What kind of meds may decrease ASA effects & cause ulcers?
Steroids
List 3 other drug interactions of ASA
1) ACE inhibitors
2) Beta blockers
3) NSAIDs
Why are NSAIDs contraindicated if taking ASA?
Counteract & compete with COX-1 site that we want on the plts
Patient teaching for ASA:
How to prevent bleeding Hint: 2
1) Soft bristle toothbrush
2) Electric razor (both males & females)
Patient teaching for ASA:
List 2 teaching points
1) Do NOT stop taking on own
2) Call MD for any signs of bleeding
→ Nosebleed > 5 min
→ Black tarry stools
→ Heavy menstrual cycle
→ Excessive bruising (that gets bigger)
Patient teaching for ASA:
Preventing risk of GI bleeding Hint: 4
1) Always take with food
2) Watch alcohol (ETOH) intake
3) Limit caffeine intake
4) Do NOT chew enteric-coated tabs
What could happen to a patient who is on ASA after a heart attack (MI) if they stop taking it?
Increases risk of another HA
What other anti-platelet is often used in combination with ASA?
Clopidogrel (plavix)
How does Clopidogrel (plavix) work?
Inhibits ADP receptors through P2Y12 inhibitors
→ Precursor to prostaglandins
→ Inhibits plt aggregation
List 2 indications for giving Clopidogrel (Plavix)
1) Post stent
2) Post MI
How long after taking Clopidogrel (plavix) will it start to take effect?
Starts to work in 24-48 hrs but not see full effects for 4-6 days
How should Clopidogrel (plavix) be taken?
With or without food
When should Clopidogrel be stopped prior to surgery?
4-10 days prior
Clopidogrel is generally well tolerated but may cause what 2 Sx?
1) Rash
2) Diarrhea
What lab test should we get prior to starting someone on Clopidogrel? & what levels should we monitor?
Get a CBC and monitor P2Y12 levels to see what’s going on
List 4 other Anti-platelet drugs that are P2Y12 inhibitors
1) Ticagrelor (Brilinta)
2) Prasurgrel (Effient)
3) Ticlopidine (Ticlid)
4) Cangrelor (Kengreal)
List 2 pros and 1 con of the other P2Y12 inhibitor drugs (besides Plavix)
Pros:
1) May be more effective in ↓ plt aggregation than plavix
2) Quicker onset
Cons:
1) Now have generic, but still expensive
List 6 reasons P2Y12 inhibitors should not be given
1) Known bleeding disorders
2) Active bleeding
3) Closed head injuries
4) CVA until we can prove theres no bleed (hemorrhagic stroke = NO)
5) Pregnancy
6) Lactation
List 4 adverse effects of P2Y12 inhibitors
1) Bleeding
2) H/A
3) GI effects (N/V)
4) Skin rashes
What should patients look out for when on P2Y12 inhibitors to determine if they’re bleeding? Hint: 4
1) Increased bruising
2) Bleeding gums
3) Shaving/ small cuts
4) Severe bleeding w trauma/ falls
Why is it important to know what herbal supplements a patient is taking if prescribed an anti-platelet?
Many herbal supplements can inhibit plt aggregation as well
List 3 things to remember for ALL anti-platelet drugs
1) Only prescribing doc can stop the med
2) Must take every day, unless instructed otherwise
3) Medication should be stopped min of 2-5 days (~ 1 wk) prior to surgery or elective procedure
List 2 functions of anti-coagulants
1) prevent new clots from forming
2) Prevent growth of existing clots (i.e. MI)
List 2 things anti-coagulants do NOT do that ppl believe they do
1) Thin blood
2) Dissolve a clot
List 2 indications for prescribing anti-coagulants
1) DVT
2) Clot from A-fib
List 3 conditions that increase coagulation activity
1) Stasis of blood flow
2) Increase production of pro-coagulation factors
3) Decrease in anticoagulant factors
Coagulation activity:
Stasis of BF Hint: 3
1) Immobility, sedentary or post-op pts
2) HF
3) A-fib
Coagulation activity:
Increase production of pro-coag factors Hint: 3
1) Cancer
2) Pregnancy & PP period
3) Oral contraceptives
Coagulation activity:
Decrease in anticoagulant factors Hint: 2
1) Cirrhosis (chronic liver failure)
2) Vit K deficiency
List 6 drugs considered anti-coagulants
1) Heparin
2) Warfarin (Coumadin)
3) Apixaban (Eliquis)
4) Dabigatran (Pradaxa)
5) Enoxaparin (Lovenox)
6) Rivaroxaban (Xarelto)
How does heparin work?
Anti-thrombin inhibitor
→ interferes w/ conversion of prothrombin to thrombin
List 2 routes of admin for heparin
1) SubQ
2) IV
When would heparin be the drug of choice?
Acute patients due to its fast onset of action
List the 2 types of heparin
1) Unfractionated
2) Low molecular weight heparin (LMWH)
What is the antidote for heparin?
Protamine Sulfate
When would you use the antidote: Protamine Sulfate?
If a person’s platelets are really being impacted by anticoagulant properties of heparin
List 2 examples of patients coming into the hospital who should NOT receive heparin
1) Patient w an open fracture
2) Hypotension secondary to bleeding
How is heparin initially administered?
As an IV bolus or loading dose, followed by continuous drip
How many units of heparin is usually given in a bolus?
5000 Units
What is the usual heparin drip rate?
1000-1300 Units/ hr
How many units of heparin are given if basing off weight?
80 Units/ kg (can be less) as bolus & then 18 units/ kg/ hr
List 1 thing to monitor when giving a heparin drip
1) aPTT usually 1.5-2.5 times baseline control
→ Nomogram/ protocol usually used
→ PTT should normalize ~ 2-6 hrs after heparin stops
When should PTT be checked after starting heparin?
6 hrs later → then determine if dose should ↑, ↓, or stay the same
What would happen to the patient if their PTT is too high?
They will bleed
What would happen to the patient if their PTT is too low?
Clots will grow
What must ALWAYS be checked when giving heparin?
Dose with another RN → b/c it’s a high risk drug
Calculating a heparin drip:
Patient: weight 185 lbs. (84 kg). Heparin 25,000U/250 ml D5W. Order reads: Heparin 1350 units/hour. aPTT comes back at 80 seconds .
Following the protocol, what adjustments are indicated?
**Units per hour to decrease drip ________
**New units per hour_______
**ml/hr_______
1) Decrease infusion rate by 2 units/kg/hr → 2 x 84 kg = 1680U
2) New units per hr = 1184 U/hr → 1350 - 168 = 1184
3) mL/hr = 11.84 → 250 mL/ 25000U x 1184U / 1 hr
How does unfractionated heparin work?
Inhibits thrombus & clot formation by blocking factor Xa
What are the 2 routes unfractionated heparin can be administered?
1) IV
2)SubQ
List 2 things to note ab unfractionated heparin
1) Should not be mixed (multiple drug interactions)
2) Safe in pregnancy, but considered 2nd line therapy
List 3 adverse effects of unfractionated heparin
1) Bleeding
2) Heparin-induced thrombocytopenia
3) Hypersensitivity
Therapeutic range for unfractionated heparin
Narrow therapeutic range
Requires lab monitoring
What should PTT be if pt is on unfractionated heparin?
In therapeutic range = 46-70
Call physician if > 70
What is low molecular weight heparin (LMWH) used for?
Commonly used for DVT prophylaxis, MIs
Drug of choice if they do NOT have clot already
List 2 drugs considered LMWH
1) Enoxaparin (Lovenox)
2) Dalteparin (Fragmin)
How should LMWH be administered?
SubQ only
→ Admin 2 in away from umbilicus; no rubbing/ no aspiration
Is LMWH safe during pregnancy?
YES → considered 1st line
Does LMWH require lab monitoring?
NO
What type of heparin could a pt be discharged home on?
LMWH
What is another reason to be extremely careful with heparin dosing?
There is a lot of dose variability (from 1,000 to 50,000 units) → could impact pts risk of bleeding
How does heparin-induced thrombocytopenia occur?
Caused by Ab directed against complexes formed by a plt protein, plt factor 4, & heparin
Usually takes ~ 1-4 days after initial intro to heparin
Heparin- induced thrombocytopenia important points Hint: 2
1) Potentially life-threatening immune complication
2) Plt count drops by half within 24 hrs of admin
List 5 management options for heparin-induced thrombocytopenia
1) Stop the heparin
2) Alternative anticoagulant, if needed
3) Antidote: Argatroban → direct thrombin inhibitor
4) Lepirudin (Refluden → another antidote not as used)
5) Monitor for bleeding
