Hemostasis is the process by which bleeding is stopped. It occurs through four main mechanisms: vascular constriction, formation of a platelet plug, formation of a blood clot through coagulation, and growth of fibrous tissue into the blood clot. Platelets play a key role by adhering to exposed collagen in injured vessels to form the initial platelet plug. The coagulation cascade then forms a fibrin clot through the extrinsic and intrinsic pathways. Anticoagulants such as heparin and warfarin prevent clotting through different mechanisms. Tests such as prothrombin time and bleeding time are used to assess coagulation function.

1. Hemostais

2. Hemostasis
Hemostasis : stoppage of bleeding
Hemostasis is achieved by several mechanisms:
• (1) vascular constriction,
• (2) formation of a platelet plug,
• (3) formation of a blood clot as a result of blood coagulation, and
• (4) eventual growth of fibrous tissue into the blood clot to close the
hole in the vessel permanently

3. Vascular Constriction
• Local myogenic spasm
• Local factors
• Nervous reflexes
- Smaller vessels – Platelets – Thromboxane A2

4. Platelet Plug formation
Platelets
1. Actin and Myosin
2. Calcium stores
3. ATP and ADP
4. Fibrin stabilising factor
5. Growth factors

5. Platelet Plug formation
• Platelet - glycoprotein coating
• Von Wilebrand factor
• ADP
• Thromboxane A2

6. Blood Coagulation
CLOTTING FACTORS ----

- 15 to 30 secs
- 3 – 6 mins
- 20 mins to one hour
FATE
- Fibroblast invasion or
- Clot dissolution

7. Blood Coagulation
Prothrombin -----Liver
Vit K -------Prothrombin
Fibrinogen -----Liver

8. Clot retraction
Role of Platelets
Role of Thrombin
Role of calcium

9. Extrinsic Pathway

10. Intrinsic Pathway

11. Interaction between the pathways
• Extrinsic – fast – 15 secs
• Intrinsic – slow – 1 to 6 mins

12. Anti Coagulants and
Coagulation tests
Dr Pranith

13. Anticoagulants
• Intravascular
• Outside the body

14. Intravascular anticoagulants
• Smooth endothelial surface
• Fibrin and Anti thrombin III
• Heparin – antithrombin complex
• Plasmin –tPA

15. Anticoagulants outside the body
• Heparin
• Warfarin
• Calcium removal

16. Endothelial surface factors
• Smooth endothelium – contact factor – 13
• Glycocalyx
• Thrombomodulin –
• 1. clears thrombin
• 2. activates Protein C

17. Protein C role in fibrinolysis – anti coagulant

18. Fibrin and anti thrombin 3
- 80 to 90% thrombin absorbed by fibrin
Anti-thrombin 3 –Heparin cofactor
- Removes thrombin
- Removes activated clotting factors
- Heparin increases activity of anti thrombin by 100 times
- Mast cells – situated in ? How it helps
- Basophils

19. Plasmin
• Plasminogen –tPA
• Plasmin ----breaks down fibrin .
-Factors - 5 , 8 ,12
• tPA injections
• Streptokinase and Urokinase

20. Streptokinase

21. Vit K
• Liver carboxylase
• Factors 2,7,9,10
• Intestinal bacteria
• New Born
• GI disease – Bile duct obstruction

22. Thrombocytopenia
• Small vessels
• 50,000
• ITP
• Rx
-Splenectomy
-fresh whole blood

23. Anticoagulants outside the body
• Heparin
- Instantaneously
- Lasts up-to 4 hrs
• Warfarin
- not immediate 50% in 12 hrs
- vKORc1
- Factors 2,7,9,10
• Calcium removal
-Oxalate
-Citrate

24. Hemophilia
• A and B
• X linked recessive
• 85% and 15%
• Symptoms
• Treatment

25. Scurvy
• Vit C
• Vessel Wall

26. Bleeding time
• Duke s method
• IVY method

27. Dukes Method

28. Ivy method

29. Clotting time
• Capillary glass tube method
• Lee and white method

30. Capillary glass tube method

31. Lee and white method

32. Prothrombin time (PT)
• Blood + oxalate
• Oxalated blood + Calcium +
tissue factor
• Normal Prothrombin time 12
secs

33. International normalised ratio
• Normal is 0.9 to 1.3
• High INR
• Low INR
• On Warfarin

34. THANK YOU