1. Hemostasis and Blood Coagulation
Prepared by
Hamad ALAssaf
2015

2. Hemostasis, Coagulation
1. Vascular Spasm
2. Platelet plug
3. Formation of clot

4. Platelets - Sequestered in spleen (30%)
- Formed in bone marrow, ,000 /µl
- Sequestered in spleen (30%)
- 2-4 m in diameter, life span 8-12 days, no nucleus

5. Platelets

6. Clot Formation

7. Formation of a Clot Intrinsic Surface Contact TF (Tissue factor)
XII-----XIIa
Extrinsic
XI-----XIa
Tissue
Damage
TF-VIIa TF
IX-----IXa
VII
X Xa X
VIII
VIIIa
XIII
Prothrombin
Thrombin
XIIIa
Stable
Fibrin
Fibrinogen
Fibrin
Common

8. Extrinsic Pathway

9. Intrinsic Pathway

10. Fibrinolytic System Plasminogen = circulating globulin
- Plasmin = proteolytic enzyme, similar to trypsin
- digest fibrin threads, fibrinogen, and other clotting factors
- Significance: removal of tiny little clots
Plasminogen activators:
- Tissue Plasminogen Activator (TPA), urokinase, streptokinase
Plasminogen inhibitors:
- plasminogen activator inhibitor (PAI-1) inhibits TPA
- Alpha2-antiplasmin blocks binding plasminogen to fibrin

11. Coagulation Defects
I. Vitamin C deficiency: lack of stable collagen (elderly, alcoholics)
collagen synthesis when dysfunctional, cause the most severe symptoms of scurvy. (Prevent healing of rupture capillaries).
II. Hepatic failure: almost all clotting factors are made in the liver
III. Vitamin K deficiency:
- required for II (prothrombin), VII, IX, and X
- fat malabsorption due to lack of bile secretion
IV. Hemophilia:
- Factor VIII (hemophilia A 1/10,000),
- Factor IX (hemophilia B 1/100,000)
- chromosome X

12. Coagulation Defects V. Thrombocytopenia:
- bleeding small capillaries and blood vessels (mucosal, skin)
- low number of platelets
- Purpura- autoimmune (common)
VI. Disseminated Intravascular Clotting:
- abnormal bleeding and clot formation
- critically ill patients
- coagulation and clot lysis in uncontrolled manner
- due to massive tissue damage
- depletion of clotting factors

13. Anti Coagulation HEPARIN ( iv or subcutaneous):
Used for Thromboembolic conditions such as :
- Venous thrombosis, pulmonary embolism
- artificial heart valves, by-pass surgery
- long-term bed immobilization
HEPARIN ( iv or subcutaneous):
immediate anticoagulation
It produces its major anticoagulant effect by inactivating thrombin and activated factor X (factor Xa) through an antithrombin (AT)-dependent mechanism.
Prolong PTT
COUMARINS (e.g. warfarin given orally ):
compete Vitamin K
2 - 4 days to act
reverse coagulation.
Prolong PT

14. Blood Coagulation Tests
Platelet count:
,000/ µl
- thrombocytopenia - aplastic anemia, autoimmune, platelet function
myeloproliferative, uremia, drugs (aspirin, antibiotics), von Willebrand Disease
Bleeding Time:
- time for skin wound to stop bleeding
- normal value < 6 minutes
- done to assess platelets function.
Clotting Time:
- the time required for blood to form a clot
- Normal value of clotting time is 2 to 6 minutes.
- used to diagnose hemophilia
Thrombin Time:
- to evaluate the level and function of fibrinogen.
- Normal values are 12 to 14 seconds.

15. Tests of Clotting Pathway
XII
Intrinsic
Extrinsic XI
Activated Partial
Thromboplastin Time
Prothrombin
Time IX
VII
aPTT
About 25 – 39 seconds
VIII PT
About 12 seconds
The PTT is used to evaluate the coagulation
factors XII, XI, IX, VIII, X, V, II (prothrombin) and I (fibrinogen). X
PT test evaluates the coagulation factors
VII, X, V, II, and I (fibrinogen). V
Prothrombin (II)
Thrombin

16. Common condition present
PT result
PTT result
Common condition present
Prolonged
Normal
Liver disease, decreased vitamin K, decreased or defective factor VII.
Hemophilia A or B (decreased or defective factor VIII or IX) or factor XI deficiency, von Willebrand disease, factor XII deficiency, or lupus anticoagulant present.
Decreased or defective factor I (fibrinogen), II (prothrombin), V or X, severe liver disease, disseminated intravascular coagulation (DIC).
indicate normal hemostasis.
Partial Thromboplastin Time (PTT) is a performance indicator of the efficacy of both the "intrinsic" and the common coagulation pathways.
Prothrombin Time (PT) and its derived measures of prothrombin ratio (PR)
and international normalized ratio (INR) are measures of the extrinsic pathway.