Anticoagulants and Antiplatelets Flashcards
How long do platelets survive in plasma?
7 days.
What are anti-platelet drugs?
Inhbits platelet aggregation.
How does aspirin exhibit it’s anti-platelet effect?
Inhibits platelet aggregation- alters balance between thromboxane A2 and prostacyclin.
How does clopidogrel exhibit it’s anti-platelet effect?
Inhibits ADP induced platelet aggregation.
How does dipyridamole exhibit it’s anti-platelet effect?
Inhibits platelet phosphodiesterase.
Why are anti-platelet drugs an issue in dentistry?
Prolong bleeding time following dental extractions.
- drug combination increases the risk.
What is the purpose of Antiplatelet drugs?
Reduce the risk of MI or stroke, in an at risk population.
What do anti-coagulants do?
Inhibits the clotting cascade- doesn’t affect platelets.
- reduce formation of fibrin formation, so the platelet plug will form but it will not stabilise and so, the patient will start bleeding a few hours after the extraction.
Why are anti-coagulants an issue in dentistry?
Won’t affect bleeding time but the patient will have an episode later on where they start bleeding again.
Name the three different components of haemostasis?
Vascular response
Platelet response
Plasma response (coagulation)
What occurs during the vascular response of haemostasis?
Smooth muscle within the vascular wall spasms- releases humeral factor- vasoconstriction.
What occurs during the platelet response in haemostasis?
Damage to a blood vessel during extraction causes turbulent blood flow, platelets come into contact with exposed collagen.
Platelets aggregate and release Thromboxane A2 and ADP- causes vasoconstriction and causes further aggregation of platelets.
Formation of platelet plug.
What occurs in the coagulation phase of haemostasis?
Plasma proteins and tissue components convert fibrinogen to fibrin by thrombin- forms a blood clot.
What does Factor Xa do in the clotting cascade?
Converts prothrombin to thrombin.
Factor Xa is converted from Factor X by intrinsic and extrinsic pathways- which produce phospholipids and calcium ions.
What is the process called whereby the blood clot is dissolved?
Fibrinolysis.
What processes occur during fibrinolysis?
Plasmin converts fibrin to soluble fibrin fragments.
What is Warfarin?
Coumarin base anticoagulant- inhibits synthesis of vitamin K dependent factors.
What are the vitamin K dependent factors?
2, 7, 9 and 10.
Protein C and protein S.
What occurs when the patient first takes warfarin?
Initially the patient is hyperocagulated because of the inhibition of protein C and protein S.
As vitamin K dependent factors are reduced over 2-3 days, the patient will become anti-coagulated.
As a result of the warfarin patient initially being hyper coagulated, what does the patient need to take initially until this wears off?
Heparin.
How long would it take for someone to lose the effect of warfarin?
2-3 days.
What does INR measure?
Time taken to convert prothrombin to thrombin.
What is the therapeutic range of INR?
2-4.
What drugs cannot be taken by someone on warfarin?
Statins or azoles.
NSAIDs
Alcohol
Carbamazepine, barbiturates
What drugs come under the DOACS?
Rvaroxiban
Apixaban
Dabigatran
Edoxaban
Which DOACs do you take twice a day?
Dabigatran and apixaban.
How do DOACs affect the coagulation cascade?
All are factor 10 inhibitors apart from dabigatran which is a direct thrombin inhibitor.
What does the SDCEP guidelines suggest with regards to DOACs?
Low bleeding risk- treat without interrupting medication.
Higher bleeding risks advise patient to miss/delay morning dose before treatment.
Treat early in the day, early in the week.
Limit initial treatment area.
Assess bleeding before continuing.
Stage extensive or complex procedure.
Suturing and packing.
Is there a test for DOACs?
No- bioavailability is predictable.
If someone has delayed their morning dose of DOACs, how long after extraction do they have to wait to take it again?
4 hours after haemostasis.
For Apixaban and dabigatran, what is the recommendation if a patient is undergoing high risk dental procedure?
Miss morning dose and take the evening dose at the usual time.
Why might someone be on anti-coagulation therapy?
Atrial fibrillation
Deep vein thrombosis
Heart valve disease
Mechanical heart valves
Thrombophillia
When should INR be checked before a dental extraction?
72 hours but ideally 24 hours before extraction.
What local haemostats measures should be adopted for someone on an anti-coagulant drug?
LA with adrenaline
Sutures
Pressure with gauze
Surgical
Ligation of vessels/diathermy
What changes should be done to the medication of someone taking anti-platelet drugs, prior to an extraction?
Do not interrupt medication.
Proceed with caution, local haemostatic measures and treat early in the day, early in the week.
How long should you keep a patient in the practice, post extraction, if they are on anti-coagulants?
20 minutes.
What action should be done if someone is on an anti-coagulant and anti-platelet dual therapy?
Consult with prescribing clinician regarding the patients medical condition and likelihood of bleeding.
In which cases should you never interrupt anti-coagulant or anti-platelet therapy?
Patient has had a DVT or pulmonary embolism in the last 3 months.
Patient on cardio version.
Valve replacement or coronary stents.
What pre-op instructions should be given to the patient if they are on anti-coagulants or anti-platelets?
Instructions on what to do with medication- take as usual, miss morning dose, etc.
Make sure they know when to get their INR checked.
Plan treatment for early in the day, early in the week.
What post-op instructions should be given to the patient if they are on anti-coagulants or anti-platelets?
If they start bleeding again- roll up a piece of gauze into a sausage shape, dampen it and place into socket and bite down for at leats 30 minutes.
Do this again if the bleeding still hasn’t stopped.
Emergency phone number always given to the patient incase bleeding doesn’t stop.
Plus all the usual post op advice- don’t rinse out, don’t poke the clot, no exercise that day, avoid alcohol and smoking for as long as possible. Stick to a softer diet.
Which dental procedures have a higher bleeding risk?
Biopsy
Surgical extraction
Extracting more than 3 teeth in the same area
Flap- raising procedures.
What signs would suggest that a patient’s INR is not under control?
INR fluctuates a lot.
Patient gets their INR checked every few days.
If medication is time limited and dental procedure not urgent, what is the best course of action?
Delay treatment until coagulation therapy is finished.
A patient on warfarin cannot take azole antifungals. If they presented with a fungal infection, what medication could you prescribe?
Nystatin oral suspension- 100,000 units/ml.
30ml- 1ml four times a day after food.
What are the benefits of DOACs compared to warfarin?
Predictable pharmacokinetics
Rapid onset and offset
Short half-life
Low drug-drug interactions
Wide therapeutic window
No need for blood monitoring
What is the name of the guidance for anticoagulants and antiplatelets?
SDCEP- Management of dental patients taking anticoagulant or anti-platelet medication.
What procedures are classified as high risk?
Surgical extractions requiring a flap
Surgical perio treatment
Any surgical procedure
Biopsies
Complex extractions- more than 3 extractions at once.
What procedures are classified as low risk?
Simple extractions- 1-3 teeth with restricted wound size
Incision and drainage of intra-oral swellings
Detailed six-point pocket chart
Subgingival PMPR
Restorations with subgingival margins.
Is IDB contraindicated in warfarin patients?
No but check INR to make sure it is below 4.
