Coagulopathy

Question 1

What stages are involved in blood clot formation?

Answer 1

vasoconstriction
platelet plug formation
fibrinogen to fibrin by thrombin

Question 2

Aspirin and Clopidogrel are often used in conjunction. Why? What stages do they interfere with?

Answer 2

aspirin = prevents formation of a platelet plug, inhibits platelet aggregation by altering balance between thromboxane A2 and prostacyclin
clopidogrel = inhibits ADP induced platelet aggregation
They work as effective anti-platelets and reduce blood clot formation - work more effectively when used together

Question 3

Give an example of an anticoagulant and describe how it works.

Answer 3

warfarin = inhibits the vitamin K dependent reactions of the coagulation cascade
heparin = indirect thrombin inhibitor; binds to antithrombin III and enhances the natural anticoagulatory effect
rivaroxaban = factor Xa inhibitor
dabigatran = direct thrombin inhibitor

Question 4

What is the pattern of getting haemophilia?

Answer 4

autosomal recessive

males are affected, females can be carriers or affected

Question 5

What is the pattern of getting Von Willebrands disease?

Answer 5

autosomal dominant gene - both sexes equally affected

Question 6

How does Von Willebrands disease affect haemorrhage?

Answer 6

deficiency in von willebrands factor and reduction in factor VIII levels; vWF binds to factor VIII in normal circulation and releases it by the action of thrombin to help with platelet adhesion
It therefore causes reduced platelet aggregation and less blood clot formation

Question 7

What is thrombophilia? How may it be caused (inherited or acquired)?

Answer 7

Thrombophilia is increased tendency towards clot formation
Inherited causes: protein S deficiency and protein C deficiency - inhibitors of clotting cascade, factor V Leiden - genetic mutation of Factor V clotting factor, causes increased clotting
Acquired causes: pregnancy, immobilisation, antiphospholipid syndrome, oral contraceptive pill, surgery, trauma

Question 8

What is disseminated intravascular coagulation (DIC)?

Answer 8

widespread activation of coagulation cascade causing formation of small clots throughout body - impacts multiple organs

Question 9

What is anticoagulation? How may it be caused (inherited or acquired)?

Answer 9

Anticoagulation is decreased ability for clot formation
Inherited causes: Von Willebrands disease, Haemophilia A (factor VIII deficiency), Haemophilia B (factor IX deficiency)
Acquired causes: drugs (antiplatelets, anticoagulants), secondary - liver disease (caused by alcohol, hepatitis, drug induced)

Question 10

What are the treatment options for Von Willebrands disease, Haemophilia A and Haemophilia B?

Answer 10

Von Willebrands and Haemphilia A = tranexamic acid (antifibrinolytic), DDAVP (aka desmopressin), recombinant factor VIII
Haemophilia B = tranexamic acid, recombinant factor IX

Question 11

What are the measurements for bleeding and clotting? What are normal values for these?

Answer 11

bleeding = platelets (150-400 x 10^9/L), FBC, bleeding time
clotting = INR - international normalised ratio, PTT - prothrombin time (13-18secs), APTT - activated partial thromboplastin time (33-48secs)
Thrombin time? (9-12secs)

Question 12

What are the dental implications for patients with haemophilia?

Answer 12

Need to liaise with haematologist before dental procedure likely to cause bleeding
Avoidance of block anaesthesia (infiltration ok)

Question 13

What are the dental implications for the anticoagulated patient?

Answer 13

Management of warfarin during dental care - INR must be checked 24hrs prior to treatment, anything above 4 is too dangerous
Common drug interactions - eg antibiotics