Anticoagulants

Question 1

What are two indications for anticoagulant therapy?

Answer 1

Venous thrombosis

Atrial fibrillation - stroke prevention

Question 2

What does heparin do?

Answer 2

increase the effect of antithrombin, has an immediate effect

Question 3

How is heparin administered?

Answer 3

IV or SC

Question 4

What are the 2 forms of heparin?

Answer 4

unfractioned

LMWH

Question 5

What does anti-thrombin act on?

Answer 5

thrombin, factor Xa, factor VII, Factor VIII

Question 6

Which factor leads to thrombin formation?

Answer 6

factor Xa

Question 7

What does heparin act on?

Answer 7

thrombin (helps out antithrombin here)

Question 8

How is unfractionated heparin monitored?

Answer 8

Activated partial thromboplastin time (APTT)

Question 9

How is LMWH heparin monitored?

Answer 9

Anti-Xa assay, BUT monitoring not normally necessary

Question 10

Give 3 complications of heparin.

Answer 10

Bleeding
Heparin induced thrombocytopenia with thrombosis(HITT) - monitor FBC in patients on heparin
Osteoporosis with long term use

Question 11

What may be needed in severe bleeding as a complication of heparin? What does this do for both unfractionated and LMWH?

Answer 11

Protamine sulphate (reverses antithrombin effect)
This provides a complete reversal for unfractionated
Partial reversal for LMWH

Question 12

How does warfarin work?

Answer 12

inhibits action of vitamin K

Question 13

Where is vit K absorbed?

Answer 13

upper intestine

Question 14

What does vit K need for absorption?

Answer 14

bile salts

Question 15

Vit K adds a carboxyl group to 4 clotting factors - what are these?

Answer 15

2,7,9,10, as well as protein c and s

Question 16

What is factor II?

Answer 16

prothrombin

Question 17

Where are 2,7,9 and 10 synthesized?

Answer 17

liver

Question 18

Is Vit K’s carboxylation essential for the clotting factors to work?

Answer 18

yes

Question 19

When do protein c and s become active?

Answer 19

When vit K adds a carboxyl group to them

Question 20

Carboxylation of the clotting factors by vitamin K means that the factors can bind to what?

Answer 20

phospholipid

Question 21

What does warfarin do to Vit K?

Answer 21

antagonizes - stops it being able to add a carboxyl group to the clotting factors, therefore reducing/preventing their coagulant activity

Question 22

Does warfarin have a narrow or wide therapeutic window?

Answer 22

narrow

Question 23

What mathematical “correction” (of the PT ratio) for differences in the sensitivity of thromboplastin reagents
allows for comparison of results between labs and standardizes reporting of the prothrombin time?

Answer 23

INR: International Normalized Ratio

Question 24

What is INR: International Normalized Ratio used for?

Answer 24

monitors warfarin

Question 25

What bleeding complications may occur with warfarin therapy (mild and severe)?

Answer 25

Mild: skin bruising, epistaxis and haematuria
Severe: GI, intracerebral, significant drop in Hb

Question 26

How should warfarin therapy be reversed?

Answer 26

Administer oral Vitamin K
Administer clotting factors (FFP or factor concentrates)
Clinical and laboratory
assessment of response

Question 27

Speed of action of types of warfarin therapy reversal?

Answer 27

Vitamin K - 6 hours

Clotting factors - immediate