ANTI PLATELETS & ANTI COAG

Question 1

what classes of drugs affect bleeding?

Answer 1

can be divided into
- antiplatelets
- anticoagulation
- drugs affecting fibrinolysis

Question 2

Give an overview of the drugs affecting coagulation…

Answer 2

Heparins
- naturally occuring
- unfractionated
- LMWH

Warfarin

DOACs

Question 3

what are the use of antiplatelets vs anticoagulants

Answer 3

antiplatelets mostly for arterial clots

anticoagulants have little effect on these and mostly used for veins

Question 4

Indications for aspirin use?

Answer 4

inflammation, pain

MI primary prevention
Q RISK > 20% , HTN >50yrs = 75mg

MI secondary prevention = 75mg OD

dual antiplatelet therapy post MI/Stent - asprin and clopidogrel/ ticagrelor 1 yr and then aspirin alone.

Question 5

what is coronary angioplasty? what is coronary stenting?

Answer 5

angioplasty - dilation of balloon in narrowed coronary artery

stenting - wire mesh tube to hold open coronary vessel - can be bare metal stent or drug eluting stents (coating in drug preventing inflammation and clot formation)

Question 6

what are the complications of a stent insertion?

Answer 6

thrombosis and ischaemia

restenosis - proliferation and migration of the endothelium through the stent into the lumen = forms neointima

both have increased risk in bare metal stents

Question 7

how is thrombosis and restenosis of stents prevented?

Answer 7

drug eluting stents

Dual antiplatelet therapy = aspirin + P2Y12 inhibitor (clopidogrel, ticagrelor)

1 month of dual for bare metal stents (once vessel wall has formed after 1 month risk of thrombosis drops)

12 months for drug eluting stents (these take longer to form vessel wall but overall less risk anyway)

monotherapy with aspirin for life.

Question 8

how do you manage a patient post stent insertion that requires surgery?

Answer 8

they will require dual antiplatelet therapy

options:
- use bare metal stent + dual therapy 1 month and therefore delay surgery by 1 month
- if surgery cant be delayed or drug eluting stent was used and need anti platelet therapy for 6 months then decide if antiplatelet therapy can be stopped or not - depends on risk of bleeding in surgery and location of surgery e.g. neurosurgery
- low risk bleeding - continue dual
- high risk - continue aspirin, stop others
- emergency - platelet transfusion and TXA
- may also need to stop aspirin for neurosurgery , cardiac

restart 24 hrs after if bleeding managed.

Question 9

how long prior to surgery do the common antiplatelets need to be stopped?

Answer 9

clopidogrel = 7 days
prasugrel = 7 days
ticagrelor = 5 days

Question 10

should aspirin for primary prevention be stopped for surgery ?

Answer 10

yes can be safely stopped
7-10 days before

Question 11

How are antiplatelets managed for neuroaxial blockade?

Answer 11

aspirin / NSAIDs - continue

clopidogrel / prasugrel = stop 7 days before. can restart 6 hrs post catheter removal

Ticagrelor = 5 days before. 6hrs after catheter removed

GPIIb/IIIa (tirofiban) = 8 hours before, 6 hours post
GPIIb/IIIa (acixamab) = 48 hrs before

dipyrimadole = dont need to stop but wait 6 hrs after catheter removed before giving next dose.

Cangrelor - stop 90mins before

Question 12

how are anti-coagulants managed pre neuroaxial blockade?

Answer 12

warfarin - stop 3 to 5 days before and await for INR <1.4

Dabigatran = 48-96 hrs before (depends on renal function)
rivaroxaban and apixaban = 48hrs

heparins
unfractionated = stop 4 hours before (can start 1 hr after)
prophylactic LMWH = stop 12 hours before, start 2 hours after
treatment LMWH = stop 24 hrs before, start 2 hours after

Question 13

what are the contraindications to anticoagulation?

Answer 13

bleeding - actively , recent haemorrhagic stroke, haemorrhagic disorders, GI ulcer

surgery - neuro/opthalmic in last 12 weeks, GI in last 6 weeks

reactions - history of anaphylaxis , HIT

other
- acute bacterial endocarditis
- severe uncontrolled HTN
- severe renal impairment (only for LMWH)