Bleeding Disorders

Question 1

What is the appropriate coagulation model?

Answer 1

Cell-based model: explains deficiencies in traditional clotting cascade model and why the absence of some factors is greater than the absence of others

Question 2

What does prothrombin time measure? What is a normal prothrombin time? Do we use prothrombin time?

Answer 2

Extrinsic pathway (tissue factor pathway) and common pathway - assess deficiency in PT, liver disease, antiplatelet drugs, warfarin

11-14 seconds

Prothrombin time (PT) = test used to help detect and diagnose a bleeding disorder or excessive clotting disorde

International normalized ratio (INR) = calculated from a PT result and is used to monitor how well the blood-thinning medication (anticoagulant) warfarin (Coumadin®) is working to prevent blood clots.

Question 3

What is an INR?

Answer 3

International normalized ratio (standardized PT value)

measures coagulation function of extrinsic (tissue factor) pathway. Normal value = 1

Used to monitor warfarin

ideal for low intensity warfarin therapy = INR of 2-3

ideal for high intensity warfarin therapy (like mechanical heart valve) = INR of 2.5-3.5

Question 4

what does aPTT measure? what is normal? what can it detect?

Answer 4

activated partial thromboplastin time measures the intrinsic pathway

normal = 25-35 seconds, assess intrinsic pathway problems such as heparin, von Willebrand dz, hemophilia

Question 5

what is a normal platelet count?

Answer 5

150-450k per mL

Question 6

what is von willebrands disease?

Answer 6

most common inherited bleeding disorder = 1% of population

vWF binds factor VIII in circulating blood, unbound factor VIII is destroyed

Question 7

What is the MOA of warfarin?

Answer 7

inhibits the synthesis of vit-K dependent coagulation proteins (2, 7, 9, 10) and proteins C, S, and Z

Question 8

How should you treat a patient that is on warfarin who needs dental surgery?

Answer 8

Med consult
Get INR within 24 hrs of surgery
Have to discontinue warfarin for several days due to long half life

JADA 2009 - suggest INR of up to 4 is acceptable for most dental procedures

Morimoti - perio surgery can be performed with INR less than 3 using local hemostatic measures

Question 9

why are people on direct anticoagulants?

Answer 9

medication fo choice for patients w/ Afibb, hx of venous thromboembolism (PE)

do not require lab monitoring, have rapid and short onset (differs from warfarin)

Question 10

MOA of Pradaxa

Answer 10

Factor 2a (thrombin) reversible inhibitor
DIRECT THROMBIN INHIBITOR

12-15 hr half life (needs to be discontinued at least 24 hrs pre-op). Cannot be measured with PT, INR, or PTT

Question 11

MOA of Xarelto/Eliquis

Answer 11

Direct factor Xa inhibitors (thus inhibit the formation of the fibrin clot)

Have a half life of 6-12 hrs
Metabolized by liver CYP3A4 enzyme thus has dietary and drug interactions (grapefruit juice)

No defined therapeutic range . Cannot be measured with PT, INR, or PTT

Question 12

What happens if patient who is taking Xa inhibitor has a bleeding emergency?

Answer 12

Reversal agent - Xa protein that acts as a decoy for the ZA inhibitor, must be given via IV infusion

Question 13

why are people on antiplatelet drugs?

Answer 13

Prevention of recurrent MI, stroke, TIA, coronary thrombosis, and within 1 year of cardiac stent placement

Question 14

what are examples of antiplatelet drugs?

Answer 14

aspirin, clopidogrel (plavix)

Question 15

what is the MOA of aspirin?

Answer 15

Irreversibly inhibits platelet cyclo-oxygenase and impairs platelet aggregation

Question 16

What is the MOA of Plavix?

Answer 16

Plavix (clopidogrel) -inhibits the fibrinogen receptor on the platelet

Use of these drugs prolongs bleeding time

Question 17

What are examples of higher-risk dental procedures for bleeding?

Answer 17

3 or more extractions
GBR

definitely consult with general physician

Question 18

What are examples of low risk dental procedures that do not require interruption of anticoagulation therapy?

Answer 18

Implant placement
Soft tissue biopsy
Dental extractions of less than 3 teeth that are not surgically complex

Question 19

What are common drug interactions with warfarin?

Answer 19

Amoxicillin, Augmentin, Metronidazole, Clinda, NSAIDs,

Question 20

what are common drug interactions with direct oral anticoagulatants?

Answer 20

NSAIDs, azole antifungals, clarithromycin, erythromycin

Question 21

What are local hemostatic agents that you would be prepared to use in a bleeding emergency?

Answer 21

Collaplug - physical effect to stabilize clot (bovine collagen dressing)

Gelfoam - absorbable gelatin sponge - physical stabilization of clot

Surgicel/Actcel - cellulose. physical stabilization

CANNOT USE SURGICEL & TOPICAL THROMBIN TOGETHER. SURGICAL INACTIVATES TOPICAL THROMBIN

Topical thrombin - directly converts fibrinogen to fibrin

Tranexamic acid - competitive inhibitor of plasminogen activation

Question 22

Explain the intrinsic pathway

Answer 22

Intrinsic pathway = PTT pathway

Injury to blood vessels leads to:
-activation of 12 > 12a
12a activates 11 > 11a
11a activates 9 > 9a
2a activates 8 > 8a

8,9, and Calcium activate
10 to become 10a

THIS CARD NEEDS WORK