Mechanism of hemostasis copy

dr Bipul Borthakur

1. Mechanism of hemostasis Fibrinolysis Control of hemorrhage DR BIPUL BORTHAKUR PROF OF ORTHOPAEDICS,SILCHAR,ASSAM,INDIA

2. Hemostasis T erm ‘ Hemostasis ’ means prevention of blood loss. Arrest of blood flow and control of hemorrhage from an injured blood vessel. Process by which bleeding at any site is arrested by formation of hemostatic plug. Maintainance of normal blood flow within the circulatory system.

3. Function of hemostasis Maintain blood in fluid state. Arrest bleeding followed by trauma. Removes platelet plug when healing is complete.

4. Events Vascular constriction Platelet plug formation Blood clot formation Fibrous tissue growth into clot

5. Vascular constriction Localised myogenic spasm Local autacoid factors Nervous reflexes platelets release thromboxane A2 which is responsible for vasoconstriction of smaller vessels

6. Platelet plug formation Platelet adhesion Platelet activation Platelet aggregation Temporary hemostatic plug formation

7. Platelet adhesion Done by von willebrand factor Fibronectin and other components of extra-cellular matrix helps Degranulation occurs Ca2+ is essential

8. Platelet aggregation Follows adhesion and granule release Thromboxane A2 amplifies aggregation Forms primary hemostatic plug Aggregation is reversible This is followed by secondary hemostasis .

9. Blood clot formation The clot is a meshwork Fibrin fibers also adhere to damaged surfaces of blood vessels Contraction causes expression of fluid from clot serum

10. Initiation of coagulation Formation of prothrombin activator It starts by trauma to the vascular wall and the adjacent tissues Contact of blood with damaged endothelial cells

11. Prothrombin activator is formed by EXTRINSIC PATHWAY INTRINSIC PATHWAY

12. CLOTTING FACTORS FACTOR 1- FIBRINOGEN FACTOR 2-PROTHROMBIN FACTOR 3-THROMBOPLASTIN TISSUE EXTRACT FACTOR 4-CALCIUM FACTOR 5-LABILE FACTOR/PROACCELERIN FACTOR 7-STABLE FACTOR FACTOR 8-ANTIHEMOPHILIN FACTOR 9-CHRISTMAS FACTOR FACTOR 10-STUART PROWER FACTOR FACTOR 11-PLASMA THROMBOPLASTIN ANTECEDANT FACTOR 12-HAGEMAN/CONTACT FACTOR FACTOR13-FIBRIN STABILIZING FACTOR

13. ROLE OF CALCIUM Except first two steps in intrinsic pathway calcium ions are required for all clotting steps Calcium seldom falls low in our body as significant as to affect clotting.

14. F ibrinolysis It is a process by which blood clot is prevented from growing & becoming pathologic. It is physiological process It can be dangerous if it were to expand beyond boundary It prevents clot formation but doesnot destroys the clot.

15. The clot stimulates tissue plasmin activator TPA converts plasminogen to plasmin Plasminogen is found in blood Plasmin further cleaves fibrin to degrade thrombi Clot removal happens at a slow pace to enable endothelial breach to heal.

16. Control of hemorrhage Initially one should classify hemorrage in order to control it Source :- External & internal Nature:- Arterial (bright red,jet flow) Venous(dark red) Capillary

17. Time:- Primary (at time of trauma) Reactionary(within 24 hours of trauma/surgery) Secondary (7-14 days of trauma/surgery) Volume:- Mild (<500ml) Moderate (500-1000ml) Severe (<1 litre)

18. Surgical hemostasis Mechanical methods Thermal methods Chemical and biological methods Radiological/interventional methods Adequate blood/blood products transfusion

19. Mechanical Direct digital pressure Tourniquet Ligation Suturing Clips Bone wax

20. Direct pressure will be suited for only bleeding from capillary and vennules Limb elevation Tourniquet application at specific pressure points for arteries. Splintage is used for long bone fractures as bony fragments may lacerate vessels and medullary bleeding.

21. Ligature of large vessels with reef knot Main artery of limb is exposed by dissection at the most accessible point. Thermal methods like cryosurgery Electrocautery Monopolar /bipolar diathermy Harmonic devices Laser surgery

22. Chemical and biological methods Tranexamic acid ( antifibrinolytic ) Epinephrine and oxytocin causes vasoconstriction Microfibrillar collagen & thrombin causes coagulation Absorbable collagen,gelatin,cellulose,quikclot causes hemostasis by their hygroscopic effect.

23. Interventional radiology is used for controlling internal hemorrhage Especially in PPH

24. Supportive measures with IVF,blood transfusion should be done Analgesics Antiinflamatory drugs Early operative intervention.

25. अन्तवन्त इमे देहा नित्यस्योक्ता: शरीरिण: | अनाशिनोऽप्रमेयस्य तस्माद्युध्यस्व भारत || 18|| antavanta ime dehā nityasyoktāḥ śharīriṇaḥ anāśhino ’ prameyasya tasmād yudhyasva bhārata Meaning- Only the material body is perishable; the embodied soul within is indestructible, immeasurable, and eternal. Therefore, fight, O descendent of Bharat.