3. Vascular Injury
Exposure of collagen and vWF Tissue factor exposure
Platelet adhesion and release Activation of coagulation
Platelet recruitment and activation Thrombin generation
Fibrin formationPlatelet aggregation
Platelet – fibrin thrombus
4. • Drugs used in thrombosis
• Anticoagulants: drugs which prevent clotting by inhibiting clotting factors
(coagulation process) (used in prevention and treatment of thrombosis).
• Antiplatelets: drugs which prevent and inhibit platelet activation and
aggression (used as prophylactic therapy in high risk patients).
• Thrombolytics or Fibrinolytics: act by dissolving existing or already formed
thrombi or emboli and used in the acute treatment of thrombosis.
•
14. Antiplatelet Agents
• Clopidogrel
• Irreversibly inhibit ADP receptor subtype P2Y12 receptor,
required for platelet activation
• Half life 8 hrs
• 5 days for platelet recovery
15. Antiplatelet Agents
• Mixing of Aspirin treated platelets ex-vivo, with 30-50 %
untreated donor platelets, restored abnormal platelets
aggregation response. So, infusion of 2-3 adult dose of donor
platelets are effective in emergency reversal of aspirin in
adults.
Vilahur et al 2007
Li et al 2012
British journal of Haematology 2012, 160, 35-46
16. Antiplatelet Agents
• Reversal
Elective surgery wait for 5-7 days
For emergency surgery, replacement with platelet transfusion
should be consider
For conservative management, platelet transfusion is not
recommended (risk/benefit ratio)
Desmopressin (0.4 micrg/kg) can be consider spcifically in patient
with Uremia
No role of FFP and Protamine
Dastur CK, Stroke and Vascular Neurology 2017
22. UFH
• Acts on intrinsic pathway
• Inactivates IX, X, XI and XII and thrombin and inhibit conversion of
fibrinogen to fibrin
• Metabolized in liver and reticulo endothelial system
• No Renal adjustment
• Dose : 60-80 Unit/kg bolus f/b 12-18 Unit/kg/hr
Px - 5000 Unit Bd / Tid
• Monitoring by aPTT level
• Does not affect Prothrombin Time
23. UFH
• Shorter half life 30-90 minutes
• Reversal
If stopped before 4 hours, no need of any reversal
If infusion is going on, calculate last 2-2.5 hours of heparin and give
protamine sulphate 1 mg/100 unit of heparin (maximum 50 mg)
If dose unknown, give 50 mg of protamine
100 % reversal effect
Mesure aPTT before OT
No role of FFP or Vitamin K
24. LMWH
• Enoxaparin and Dalteparin
• Inhibit factor X>II
• Does not affect aPTT and PT level
• Renal clearance, so dose adjustment in renal failure
• Dose: Therapeutic - I mg/kg bid or 1.5 mg/kg od
(1 mg/kg od in renal failure)
Prophylactic – 40 mg sc od
• No need of monitoring (factor Anti Xa level can be monitored
in special case)
25. LMWH
• Reversal
For elective surgery, stop before 24 hours
For immediate reversal,
- last dose < 8 hours – 1 mg protamine / 1 mg enoxaparin
(additional 0.5 mg protamine / 1 mg enoxaparin can be used)
- last dose 8-12 hours – 0.5 mg protamine / 1 mg enoxaparin
60 % reversal
No use of FFP or Vitamin K
26. Fondaparinux
• Indirect Factor Xa inhibitor
• Does not affect aPTT and PT
• No need of monitoring
• Renal clearance (C/I if CrCl < 30 ml/min)
• Dose : Prophylactic : 2.5 mg sc od
Therapeutic : < 50 kg 5 mg sc od
50-100 kg 7.5 mg sc od
> 100 kg 10 mg sc od
28. Warfarin
• Inhibit Vitamin K dependent factor II, VII, IX and X
• Mesure PT for dose adjustment
• Half life 36 hrs.
• 5 days for INR to become normal
• Target INR 2-3
29. Warfarin
• For immediate reversal of INR
• Inj vit K 10 mg iv with PCC or FFP
• PCC – 4 factor or 3 factor PCC 1500-2000 IU
Cost and availability
Rapid and specific reversal
• FFP – 15 – 20 ml/kg (6-8 units of FFP)
Shorter duration of action
large volume infusion and more complication
Slow reversal than PCC
Target INR <1.5
31. Warfarin
• Supratherapeutic INR without bleeding
• INR 5-9 – omit 1-2 dose+- 1.25 -5 mg PO vitamin K
• INR >9 ( no bleed )- omit 1-2 dose +/- 2.5 - 5 mg PO vitamin K
• Surgery Reversal
INR > 1.5-2.5 hrs.
• Sx <24 hrs – 0.5 -1 mg IV vit.K x1 +/- 5-8 ml/kg FFP
• Sx 24-96 hrs- 0.5 -1 mg PO vitamin K
INR > 2.5 – 5
• Sx <24 hrs – 1-2.5 IV Vitamin K +/- 5-8ml /kg FFP
• Sx 24-96 hrs – 1-2.5 mg PO vitamin K
32. Warfarin
• For elective surgery
• Stop warfarin before 5 days
• Switch over to UFH / LMWH
• Stop UFH / LMWH before surgery
33. Dabigatran
• NOAC
• Direct thrombin inhibitor (Argatroban, bivalirudin)
• Dose : 150 mg PO bd
if CrCl 15-30 ml/min – 75 mg PO bd
• No need of monitoring for therapeutic effect but Thrombin
time will be elevated
• No use of FFP or Protamine
• Indication : Stroke prevention in non valvular AF
34. Dabigatran
• Reversal
• For elective surgery, stop before 24 hours
• For emergency reversal, Idarucizumab (Praxbind®)
Infuse two 2.5 gram/50 mL vials undiluted over 5-10 minutes each
- Second vial should be infused within 15 minutes of first vial
• Activated Charcoal – within 1 hr. of Dabigatran
• Dialysis – Last resort, removes 60% of dabigatran(mainly in renal failure)
• 4 factor PCC (50 unit/kg) if Praxibind is not available
• Factor VIIa can be tried
• A normal aPTT and TT rules out clinically relavent Dabigatran effect.
35. Factor Xa inhibitors
• Rivaroxaban, Apixaban, Edoxaban
• Elective surgery – stop before 24 hours
• Emergency reversal
• If presenting within 2 hours of intake – activated charcoal
• 4 factor PCC – 50 units / kg
• Laboratory testing not helpful
• Not dialysable
37. Thrombolytic agents
• Cryoprecipitate 10 units
• If fibrinogen <150 mg/dl post cryoprecipitate, consider
additional cryoprecipitate
• 6-8 unit of platelet concentrate
• If cryoprecipitate not available, FFP can be given
• If not available, than tranexamic acid 15-20 ml/kg
38. Protamine Sulphate
• Protamine is basic in nature and combine with acidic heparin
• Calculate dose
• Maximum dose 50 mg (1 ampoule)
• Severe Allergic reaction
• Administration
Dilute in 5 ml of sterile water
Inject over 10 minutes
39. TAKE HOME MESSAGE
DRUG Elective Emergency Not indicated Monitoring
Aspirin
Clopidogrel
Stop before 5-7 days Platelet concentrate
Desmopressin
(Uremia)
FFP
Vitamin K
Protamine
None
UFH Stop before 4-6
hours
Protamine Sulphate
(100%)
FFP
Vitamin K
aPTT
LMWH Stop before 24 hours Protamine Sulphate
(60 %)
FFP
Vitamin K
Anti Xa level
Fondaperinux Stop before 24 hours FVIIa FFP
Vitamin K
Protamine
Anti Xa level
Warfarin Stop before 5-7 days Vitamin K
4 PCC 50 Unit/kg
FFP 15-20 ml/kg
Protamine PT
40. Drug Elective Emergency Not indicated Monitoring
Dabigatran Stop before 24 hours Activated Charcoal
Praxbind 5 gm
4 factor PCC
Dialysis
FFP
Vitamin K
Protamine
TT
aPTT
Rivaroxaban Stop before 24 hours Activated Charcoal
4 factor PCC
FFP
Vitamin K
Protamine
Dialysis
None
Thrombolytics --- 10 Cryoprecipitate
6-8 RDP
FFP
---- Fibrinogen