Sahli and pcv

1. DETERMINATION OF HB CONCENTRATION
AND HEMATOCRITE VALUE
Edited by
Dr. Dina hamdy merzeban
Physiology Lecturer at Fayoum university

2. DETERMINATION OF HB
CONCENTRATION
Definition:-
Hb in gm/100 ml blood or % to normal,
% reading of Hb is normally 100%.
Clinical significance:
1. To diagnose anemia, polycythemia.
2. It estimates oxy & reduced Hb (not
met & carboxy Hb).
3. To determine type of anemia,
calculate MCH (blood indices).

4. PRINCIPAL
■ Adding HCl to the blood causes :-
1. Hemolysis of RBCs
2. Formation of acid hematin
HCl + Hb → acid hematin (brown in color)
■ The intensity of color is proportional to
hemoglobin content in blood .

5. THE ROLE OF HCL IN DETERMINATION OF HB
CONTENT
 As it is hypotonic results in
the hemolysis of RBCs.
 Convert the hemoglobin to
a brownish acid hematin .

6. APPARATUS
■ Sahli apparatus
(haemoglobinometer
or haemometer) which
is composed of :-
1. Sahli tube
2. Pippette
3. Colour comparator

7. Micro tube
of sahli
pipette
Colour Comparator
tube
Sahli Tube for
blood

8. STEPS
1. Put 0.1 HCl till the mark 10%
2. Add 0.02 ml blood (using the micro tube of the
pipette)
3. Shake for 15 minutes
4. HCl + Hb → acid hematin (brown in color)
5. Add distilled water to the acid hematin drop by
drop
6. Match colors at full arm length and against
light.

9. PRECAUTIONS
1. Be sure that there is no air bubbles
in the blood column.
2. Clean the tip of pippette from any
blood to avoid false high results.
3. Withdraw the blood horizontally
from the finger
 Ensure alcohol is completely dried
 Avoid compression of the finger .

10. DEFINITION:
% Ratio of RBCs volume to total blood volume.
PRINCIPLE:
Specific gravity of RBCs :1090,
WBCs & platelets 1060
plasma 1030,
Haematocrite value
(packed cell volume)

11. APPARATUS
Heparinized capillary tube
(red mark)

12. STEPS
1. Pinprick the thumb
2. Withdraw blood into the heparinized cappilary
tube till ¾ th of its length
3. Close the end of the tube with paste
4. Place the tube in the centrifuge for 5 minutes
5. Read the percentage of RBC to blood volume

14. WHAT ELEMENTS FORM THE BUFFY
COLORED LAYER ON THE TOP OF PACKED
CELLS?
 Specific gravity of WBCs = 1060 [form a thin
layer (buffy coat) above RBCs].
What is normal range of PCV ?
 Male 46± 6%
 Female 42± 6%

15. CLINICAL SIGNIFICANCE
• Diagnosis of anemia, polycythemia.
• To determine type of anemia calculate MCV & other
blood indices.

16. DESCRIBE THE ABNORMALITIES OF PCV?
A) The conditions in which PCV is increased:
• Polycythemia: physiological (high altitudes
or newly born) or pathological.
• Dehydration (vomiting, diarrhea, profuse
sweating, Burns , loss of water ,
Hemoconcentration
B) The conditions in which PCV is decreased:
• Anemia, female sex, overhydration &
pregnancy (hemodilution)

17. HAEMATOCRITE VALUE IS HIGHER
IN VENOUS BLOOD WHY?
• Due to Cl- shift phenomena
HH2O + CO2 H2CO3
HCO3
H+
CL-
Carbonic anhydrase enzyme