Anticoagulation

Question 1

What do anticoagulants do?

Answer 1

Slow down the rate of activation of the coagulation system. Only slowing down secondary haemostasis. Antiplatelets slow primary haemostasis.

Question 2

What are anticoagulants used for?

Answer 2

1. Stroke prevention (70%)
2. VTE treatment/prophylaxis (20%)
3. Arterial thrombotic disease (10%)

Question 3

What are Dalteparin and enoxaparin examples of?

Answer 3

LMWH

Question 4

What is the mechanism of LMWH?

Answer 4

Inactivates factor Xa by stabilising antithrombin III.

Question 5

What are the side effects of LMWH and UFH?

Answer 5

1. Increased risk of bleeding.
2. Heparin induced thrombocytopenia, more clotting despite drop in platelets - less common with LMWH and UFH.
3. Osteoporosis with long term use.

Question 6

What are the contraindications for LMWH and UFH?

Answer 6

1. Bleeding disorders
2. Platelets <60
3. Previous heparin induced thrombocytopenia
4. Peptic ulcer
5. Cerebral haemorrhage
6. Severe hypertension
7. Neurosurgery

Question 7

What is the mechanism of UFH?

Answer 7

Binds to antithrombin increasing its ability to inhibit thrombin, factor Xa and factor IXa.

Question 8

How are LMWH and UFH reversed and which does it work better on?

Answer 8

1. Protamine

2. UFH fully reversed, LMWH partially reversed.

Question 9

What is the mechanism of warfarin?

Answer 9

Inhibits vitamin K dependent clotting factors (2, 7, 9, 10).

Question 10

How is warfarin reversed?

Answer 10

Vitamin K

Question 11

What should you do in each of these situations with a patient on warfarin?

1. INR 5-8, no bleed
2. INR 5-8, minor bleed (incl. epistaxis)
3. INR >8, no bleed
4. INR >8, minor bleed
5. Major bleed

Answer 11

1. Withhold 1-2 doses, restart with lower maintenance once INR <5.
2. Stop warfarin, IV vit K (slowly), restart when INR <5.
3. Stop warfarin, bleep haematology.
4. Stop warfarin, IV vit K (slowly), daily INR, repeat vit K if still high after 24h, restart at lower dose when INR <5.
5. Stop warfarin, prothrombin complex 50units/kg and 5-10mg vitamin K IV, bleep haematology.

Question 12

What should you give to someone starting warfarin and why?

Answer 12

Heparin as warfarin is initially pro-coagulative (continue until INR is in therapeutic range).

Question 13

What are the side effects of warfarin?

Answer 13

Skin necrosis (in protein C deficiency), minor and major bleeding.

Question 14

What is the target INR for these conditions and what is the normal range?

1. PE and DVT
2. AF for stroke prevention
3. Prosthetic metallic aortic valve for stroke prevention
4. Prosthetic metallic mitral valve for stroke prevention

Answer 14

NR: 0.8-1.2

1. 2-3
2. 2-3
3. 2-3
4. 2.5-3.5

Question 15

What is the mechanism of rivaroxaban/apixaban?

Answer 15

Factor Xa inhibitors

Question 16

What is the mechanism of dabigatran?

Answer 16

Direct thrombin inhibitor

Question 17

What is the major upside to DOACs compared to warfarin and what is warfarin still needed in?

Answer 17

1. Do not need such regular monitoring.

2. Metallic valves

Question 18

What are the contraindications for DOACs?

Answer 18

Severe renal/liver impairment

Question 19

What medications do DOACs interact with?

Answer 19

Heparin and clopidogrel

Question 20

What can reverse the effect of dabigatran?

Answer 20

Monoclonal antibody Idarucizumab