2. THE HEMATOCRIT VALUE (H.V)
•
It is the ratio of the volume of red cells to the
volume of whole blood.
•
It is also called the packed cell volume (PCV).
3. Method of determination of H.V
•
A blood sample from the subject is placed in a
special tube called Wintrobe tube (hematocrit
tube) that contains an anticoagulant and is then
centrifuged in microhematocrit centrifuge.
•
H.V is calculated by dividing the blood cell
column by the total blood column and multiplying
by 100.
4.
5. •
Normal range of H.V :
•
45 % in adults (40- 47 % in males and 36- 42
% in females)
•
52 % in newly born infants
6. Factors affecting H.V
•
H.V is affected by changes in the red cell
volume relative to the plasma volume.
Decreased H.V
1- Overhydration.
2- Anemia
7. Increased H .V
Physiological as in newborn babies.
Pathological as in
1-Polycythaemia
2- Dehydration as in vomiting and diarrhea.
9. •
ESR is the height of the clear column of
plasma that is left at the top of a vertically
suspended non-coagulated blood sample.
•
After the 1st hour it is 5-7 mm in males
and 8-10 mm in females.
10. Mechanism
•
With any tissue damage there will be excess
production of the gamma globulins and
fibrinogen.
•
They form an insulator around RBCs decreasing
the repellence forces between the individual
RBCs, allowing more of them to be displaced
down-words by the effect of gravity; rouleaux
formation.
11. Causes that increase the ESR
Any tissue damage as in:
1. Menstruation in females.
2. Trauma
3. Bacterial infection
4. Parasitic infestation
5. Autoimmune diseases
6. Tumors.
Polycythaemia decreases the ESR.
