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Year 3 > Patient on anti-coagulant therapy (CH) > Flashcards

Patient on anti-coagulant therapy (CH) Flashcards

1
Q

What are anticoagulants?

A

Used for treating and preventing embolic events

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2
Q

What are the most common oral anticoagulants? (2)

A
  • vitamin K antagonists e.g. warfarin
  • DOACs e.g. apixaban, rivaroxaban, dabigatran
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3
Q

What is the most common parenteral (outside of GI tract) anticoagulant?

A

Heparin

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4
Q

What is vitamin K responsible for?

A

Production of factors 2, 7, 9, 10

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5
Q

Describe the mechanism of warfarin.

A
  • block function of vitamin K epoxide reductase complex in liver –> depletion of reduced form of vitamin K = cofactor for gamma carboxylation of vitamin K dependent clotting factors
  • inhibiting factors 2,7,9,10 and protein C and S (anticoagulant proteins)
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6
Q

How does warfarin affect PT and APTT?

A
  • prolonged PT as it has the biggest effect on factor 7
  • normal APTT
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7
Q

What are the indications for warfarin?

A
  • prophylaxis of embolisation in rheumatic heart disease and AF
  • prophylaxis after insertion of prosthetic heart valve
  • 2nd line for prophylaxis and Rx of DVT and PE:
    • 6wk for distal DVT
    • 3m for provoked proximal DVT
    • 6m for unprovoked proximal DVT
    • long term if recurrent
  • TIAs
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8
Q

What anticoagulant is given with warfarin if immediate effect is required (DVT/PE)?

A

Heparin is given concurrently

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9
Q

What are some side effects of warfarin?

A
  • bleeding - advise about spontaneous bleeding, severe back pain
  • rare - alopecia, N&V
  • severe - skin necrosis or calciphylaxis
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10
Q

What is an advantage of warfarin?

A

Can be directly reversed by replacement of vitamin K

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11
Q

What are disadvantages of warfarin? (4)

A
  • long half-life
  • regular monitoring of PT and INR
  • many drug-drug interactions
  • not used in DVT and PE (2nd line)
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12
Q

What is the target INRs of patients on warfarin and what is the exception?

A
  • target INR 2.5 except metallic mitral valve replacement (2.5-3.5)
  • mitral valve replacement: 2.5-3.5
  • VTE / AF / metallic aortic valve replacement: 2.0-3.0
  • recurrent PEs: 3.5
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13
Q

What do we do if INR is raised significantly in a patient on warfarin?

A

Indicates high bleeding risk - warfarin reduced/withheld completely and vitamin K may be given and FFP

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14
Q

What do we do before emergency surgery with regards to warfarin?

A
  • if surgery can wait: give IV 5mg vitamin K 6-8h before emergency surgery
  • if surgery cannot wait: give 25-50 units/kg four-factor prothrombin complex
  • planned surgery: warfarin stopped 5 days before, INR<1.5 to proceed
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15
Q

When is warfarin contraindicated? (6)

A
  • pregnancy (risk of teratogenicity)
  • haemorrhagic stroke
  • significant bleeding
  • hepatic / renal impairment
  • within 72h of major surgery
  • within 48h postpartum
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16
Q

How long before planned surgery must warfarin be stopped?

A

5 days

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17
Q

When can surgery go ahead in a patient on warfarin?

A
  • when INR<1.5
  • if INR>1.5 give oral vitamin K a day before surgery
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18
Q

What reduces warfarin activity? (1+5)

A

P450 inducers (think induce = reduce INR) - SCARS:

  • Smoking
  • Ciroc (alcohol)
  • Anti-epileptics e.g. carbamazepine or phenytoin
  • Rifampicin
  • St John’s wart
19
Q

What increases warfarin activity (1+4)

A

P450 inhibitors (think inhibit = increase INR) - ASS ZOLES:

  • Antibiotics e.g. ciprofloxacin, isoniazid, clarithromycin, erythromycin
  • SSRIs e.g. fluoxetine, sertraline
  • Sodium valproate
  • -Zoles e.g. omepraZole, ketoconaZole, fluconaZole
20
Q

How do you manage major bleeding in an over-warfarinised patient?

A
  • stop warfarin
  • IV vitamin K 5mg (phytomenadione)
  • prothrombin complex concentrates (if not available then FFP)
21
Q

How do you manage INR>8 in an over-warfarinised patient?

A
  • stop warfarin
  • minor bleeding: IV vitamin K 1-3mg
  • no bleeding: oral vitamin K 1-5mg
  • repeat dose of vitamin K if INR still too high after 24h
  • restart warfarin when INR<5
22
Q

How do you manage INR 5-8 and minor bleeding in an over-warfarinised patient?

A
  • stop warfarin
  • give IV vitamin K 1-3mg
  • restart warfarin when INR<5
23
Q

How do you manage INR 5-8 and no bleeding in an over-warfarinised patient?

A
  • withhold 1-2 doses of warfarin
  • reduce subsequent maintenance dose
24
Q

How do you manage patient if INR<2?

A

Up warfarin dose and start LMWH

25
Q

What are some examples of DOACs?

A
  • apixaban
  • rivaroxaban
  • edoxaban
  • dabigatran
26
Q

How do DOACs work?

A
  • apiXaban and rivaroXaban = direct factor Xa inhibitor (hint X in middle of name suggests Xa inhibitor) –> prevents thrombin generation and thrombus development
  • dabigatran = direct thrombin inhibitor
27
Q

Why are DOACs preferred to warfarin?

A

Require less monitoring

28
Q

Compare apixaban vs rivaroxaban vs dabigatran in terms of mechanism, excretion and reversal.

A
  • mechanism: direct Xa inhibitor vs direct Xa inhibitor vs direct thrombin inhibitor
  • excretion: liver vs faecal vs renal
  • reversal: Andexanet alfa vs Andexanet alfa vs Idarucizumab
29
Q

What are the indications for DOACs? (5)

A
  • prevention of stroke and systemic embolism in adults with non-valvular AF and at least one risk factor
  • PE & DVT - 3m (provoked), 6m (unprovoked or active cancer), high dose for first 7d
  • prevention of VTE in adults who have undergone elective hip/knee replacement surgery
  • prophylaxis of atherothrombotic events following ACS with elevated biomarkers - in combination with aspirin +/- clopidogrel
30
Q

What are some side effects of DOACs?

A
  • bleeding - advise patients about spontaneous bleeding or severe back pain (Andexanet alfa is a specific reversal agent for FXa inhibitors when life-threatening/uncontrolled bleeding)
  • anaemia, bruising
  • angioedema
31
Q

When should DOAC dose be reduced?

A
  • two of: 80+, <60kg, serum creatinine >133umol/L
  • reduced if creatinine clearance 15-29mL/min
  • stopped if creatinine clearance <15mL/min
32
Q

What are some contraindications to DOACs? (5)

A
  • liver disease associated with coagulopathy (elevated liver enzymes)
  • prosthetic heart valve
  • antiphospholipid syndrome
  • active bleeding / high risk
  • pregnant / breastfeeding
33
Q

What drugs should you avoid if on DOAC?

A

Avoid NSAID, other anticoagulants, antiplatelets

34
Q

How do we switch from a DOAC to warfarin?

A

Do not stop apixaban immediately

35
Q

When do we stop a DOAC before surgery?

A
  • minor bleeding risk - do not stop DOAC
  • low bleeding risk - stop DOAC 24h before
  • high bleeding risk - stop DOAC 48h before
36
Q

How do we reverse apixaban/rivaroxaban (DOAC)?

A

Andexanet alfa

37
Q

How do we reverse dabigatran (DOAC)?

A

Idarucizumab

38
Q

What are the two types of heparin?

A
  • short-acting: unfractionated heparin (standard)
  • long-acting: LMWH e.g. enoxaparin, dalteparin
39
Q

How is unfractionated heparin vs LMWH administered?

A
  • unfractionated heparin: IV
  • LMWH: subcutaneous
40
Q

How is unfractionated heparin vs LMWH monitored?

A
  • unfractionated heparin: APTT
  • LMWH: via anti-factor Xa
41
Q

Which type of heparin is usually preferable and why?

A

LMWH - preferred as lower risk of heparin-induced thrombocytopenia (occurs when heparin activates antithrombin III, which forms a complex that inhibits factor Xa)

42
Q

How long before surgery must heparin be stopped?

A

May be stopped on day of surgery, since heparin has a much shorter half-life than warfarin

43
Q

What is the reversal agent for heparin?

A

Protamine sulfate

Year 3 (203 decks)

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