Download Haemostasis

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Tests for Haemostasis
Learning objectives:
1.Know
mechanisms of haemostasis.
2.Know
disorders of haemostasis.
3.Know
how to test for haemostasis.
4.Know
abnormalities of haemostasis.
Haemostasis
Def.,
Hemostasis („hemo”=blood; sta=„remain”) is
the stoppage (arrest) of bleeding from
damaged blood vessels.
Haemostasis (cont.)
Steps: Steps:
It consists of 3 overlapping mechanisms 1. Vascular spasm 2. Platelet Plug Formation 3. Blood Clot Formation (Coagulation)
3. Blood Clot Formation (Coagulation) Haemostasis (cont.) (cont.)
Vascular Spasm It is due to local spasm of the smooth muscle
It can be maintained by platelet
vasoconstrictors e.g. serotonin
Haemostasis (cont.) (cont.)
Platelet Plug Formation • 1.
2.
3.
4.
It occurs in following steps;
Platelets adhesion
Platelet activation
Platelet aggregation
Platelet plug formation
Haemostasis (cont.) (cont.)
Blood Clot Formation Clotting Factors: ­These are plasma proteins ­Most of them are formed in the liver ­Vitamin K­dependent clotting factors are: II, VII, IX, X ­Most of them are present as proenzymes (inactive) ­Once activated, it induces a cascade reaction → to form blood clot
Haemostasis (cont.) (cont.)
Steps of Blood Clot Formation Coagulation mechanism is composed of an extrinsic
and intrinsic pathway, which eventually merge into
one
Haemostasis (cont.) (cont.)
Summary of steps of Blood Clot Formation
Summary of steps of Blood Clot Formation Haemostatic Disorders
There are 2 groups of haemostatic disorders:
1. Bleeding disorders •Haemophilia •Purpura •Vit. K deficiency
2. Intravascular clotting
Haemostatic Disorders
Purpura
Haemophilia
Def.,
It is a haemorhagic disease caused It is a congenital sex linked,
by ↓ed platelet count or function.
recessive disease carried on X
chromosome
Types and
Causes
a)Thrombocytopenic purpura→ due
to ↓ of
platelets count below
50,000/mm3
b)Non‐thrombocytopenic purpura → due to;
i) ↓of
functioning
platelets
(thromboasthenic purpura)
ii) Defect in the vessel wall as in
cases of severe vit. C deficiency or
allergy, and called vascular purpura. Include 3 types;
a) Haemophilia A:
It is the classic haemophilia.
It is caused by ↓of factor VIII
b) Haemophilia B:
It is due to ↓ of factor IX. c) Haemophilia C:
It is due to ↓of factor XI. Manifestations many subcutaneous and
submucosal hemorrhages (petichae)
Excessive bleeding after mild
trauma
Investigations • prolonged bleeding time • normal clotting time • prolonged coagulation time • normal bleeding time
Haemostatic Disorders
Haemophilia
Haemostatic Disorders
Haemophilia
Haemostatic Disorders
Haemophilia
Son of the last Tsar
of Russia – Aleksy
Romanow suffered
from Hemophilia A
Haemostatic Disorders
Purpura
Haemostatic Tests
Haemostatic Tests
Whole Blood Clotting Time
It is the time needed by blood to form clot
Procedure:
-Clean the tip of the finger with an alcohol
-Prick the finger tip with an automatic
lancet
-Note the time when blood first appears
on the skin
-Touch capillary tube to the drop of blood
-Break gently 1cm of the tube at the end
of 2 min, and every 30 sec
these after
When fibrin is formed between the two
broken pieces of tube the coagulation or
clotting time is noted
Haemostatic Tests
Whole Blood Clotting
Time
Normal Value:
4-8 min
Causes of prolonged CT:
1. Haemophilia
2. Vit K deficiency
3. Liver diseases
4. Use of oral anticoagulants
Haemostatic Tests
Bleeding Time
It is the time needed to stop bleeding
from small injury
Procedure:
-Clean the earlobe with an alcohol
-Prick the earlobe or tip of finger
with an automatic lancet
-Note the time when blood first
appears on the skin
-After half a minute (30sec) place
the edge of the filter paper on the
top of the drop of blood.
Haemostatic Tests
Bleeding Time
Normal Value:
1-5 min
Causes of prolonged BT:
1. Purpura
2. Platelets count deficiency
3. Von Willibrand disease
4. Disease of blood vessels.
S
K
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A
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Dr. Abdel Aziz Hussein, Mansoura Faculty of Medicine