2. Bleeding disorders are a group of conditions that result
when the blood cannot clot properly.
When blood vessel is punctured, cut, or otherwise
damaged the following mechanism are activated to
arrest the bleeding (hemostasis).
- Hemostasis involves the following 4 interrelated steps:
1. Vasoconstriction (contraction of injured blood vessels).
2. Platelet plug formation.
3. Formation of a blood clot (blood coagulation) through
both intrinsic and extrinsic pathways.
4. Fibrinolysis (dissolution of the clot).
3. - Excessive and prolonged bleeding (spontaneous
bleeding) may result from defects of:
1. Platelets
2. Blood vessel walls
3. Coagulation of blood
4. A patient with bleeding disorders requires the
following investigation:
I. Capillary resistance test (Hess test)
II. Bleeding time
- Duke method
- Ivy method
III. Clotting time (coagulation time)
- Capillary tube method
- Test tube method
IV. Platelet count
V. Prothrombin time
VI. Thrombin time and other tests
5. I. Capillary resistance test (Hess test):
Aim: to assess the mechanical fragility of the capillaries (and
formation of a platelet plug) by raising the pressure within them.
Principle: Consists of inflating a sphygmomanometer cuff placed
around the arm and inspecting the petechiae appearance.
Procedure:
1. Mark a 6 cm diameter circle on the front of the forearm, in
antecubital fossa.
2. Apply a blood pressure cuff on the upper arm, 1-2 cm above the
circle.
3. Raise the pressure to 60 mm Hg, and maintain the pressure for 5-15
minutes.
4. Appearance of more than 10 new petechiae (pink or red spots in the
skin) is a positive test.
5. Release the cuff and after few minutes count the fresh petechiae
within the circle.
6. Clinical significance of Hess test:
A positive test is observed when:
- The capillaries are weaken by a disease
- In cases of thrombocytopenia.
8. II. Bleeding Time (BT):
BT is the time interval between the skin puncture and spontaneous,
unassisted (i.e., without pressure) stoppage of bleeding. The BT test
is an in vivo test of platelet function. There are two methods for
measuring bleeding time:
1. Dukes method
2. Ivy method
1. Dukes method:
Procedure:
1. Get a deep (3-4 mm) finger-prick under aseptic conditions to get free
flow of blood.
2. Absorb/remove the blood drops every 30 second by touching the
puncture site with a clean filter paper, without pressing or squeezing
the wound.
3. Note the time when bleeding stops, i.e., when there is no trace of
blood spot on the filter paper.
4. Count the number of blood spots and express the result in minute
- Normal bleeding time = 1-5 minutes.
9. 2. Ivy method:
- This methods is more reliable than the Duke method.
Procedure:
1. Clean the skin over the front of the forearm with 70% alcohol.
2. Apply a blood pressure cuff on the upper arm, raise the pressure
to 40 mm Hg and maintain it there till the end of the
experiment.
3. Clean the skin area once again, make a 1-3 mm deep skin
puncture, about 5-6 cm below the antecubital fossa (Avoid the
area of large vessels).
4. Note the time.
5. Remove the blood every 30 seconds by absorbing it along the
edges of a clean filter paper by gentle touching the wound
with it, till the bleeding stops
-Normal BT with this method is between 2-6 minutes
11. Clinical significance of BT:
1. Bleeding time is not a reliable test because; it depends
on the site and depth of puncture, and also it depend
on the weather (cold or warm), the cold weather
promote vasoconstriction of the capillaries in the skin
and thus shorten BT and the reverse is happening in
the hot weather.
2. Bleeding time is increased in purpura (deficiency of
platelets or vessel wall defects) while it is usually
normal in hemophilia.
