Haemostasis

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Haemostasis
Dr. Venkatesh M. Shashidhar. Senior Lecturer in
Pathology Fiji School of Medicine
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Hemostasis
BV Injury
Tissue Factor
Neural
Coagulation Activation
Platelet Activation
Blood Vessel Constriction
Primary hemostatic plug
Plt-Fusion
Reduced Blood flow
Thromibn, Fibrin
Stable Hemostatic Plug
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Coagulation
Intrinsic 12,11,9,8 (aPTT-)
Extrinsic-7 (PT)
Common Path (TT) FX ? FXa
Prothrombin? Thrombin
Fibrinogen ? Fibrin
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Clot formation retraction
Fibrinogen
Thrombin F-XIIIa
Fibrin Mononer
Fibrin Polymer
Cross Linked Fibrin
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Coagulation

• Biological amplification system. 1? 2x108
• Surface activation Collagen, tissue, Plt.
• Proteolysis cascade - precursors to enzymes
• Two pathways FX Common pathway
• Final Thrombin Fibrin mesh - stable clot
• Factor XIII not serene protease clot retr.
• Clot lysis immediate in circulation.

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Limitations of Coagulation

• Plasma Inhibitors of activated factors.
• Antithrombin-III, Heparin, ?2 Antiplasmin.
• Protein C F 85 and fibrinolysis.
• Blood flow dilution clearing.
• Plasminogen ?Plasmin (Fibrin, 58)
• FDP Inhibit thrombin

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Platelets

• Bone marrow Megakaryocytes 10d, 4000
• Life span 7-10d, N.count 150-400x109/l
• 36 hours in spleen - 1/3 of plt in spleen
• Functions
• Hemostatic plug formation
• Coagulation factors - release, synthesis
• Surface binding sites for fibrinogen, VWF
• Surface platelet antigens, HPA1

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Tests of Hemostasis

• Screening tests
• Bleeding.T - To test Platelet BV function
• Prothrombin.T Extrinsic, aPTT Instrinsic
• Thrombin.T Both paths. (DIC)
• Specific tests
• Factor assays
• Tests of thrombosis TT, FDP, DDA,
• Platelet function studies
• Adhesion, Aggregation, Release PG pathway
  tests.
• Bone Marrow study

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Summary

• Complex system to keep blood fluid
• To block leakage on injury.
• BV, PLT Coagulation
• Complex inhibitory mechanisms
• Complex thrombolysis mechanisms.
• Screening tests BT, CT (PT, aPTT)
• Special tests Factor assay, PLT function etc.

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Disorders of Hemostasis

• Vascular disorders
• Scurvy, easy bruising, Henoch-Schonlein purpura.
• Platelet disorders
• Quantitative - Thrombocytopenia
• Qualitative - Platelet function disorders
  Glanzmans
• Coagulation disorders
• Congenital - Haemophilia (A, B), Von-Willebrands
• Acquired - Vitamin-K deficiency, Liver disease
• Mixed/Consumption DIC