Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Practicals Latest Physiology Hb Estimation
INDICATIONS FOR HEMOGLOBIN
ESTIMATION
1. To determine presence and severity of anemia: Anemia refers to low hemoglobin
concentration
or oxygen-carrying capacity of blood.
Clinical signs of anemia (pallor of skin, conjunctival vessels, or
mucous membranes are unreliable for diagnosis of anemia.
2. Screening for polycythemia: Polycythemia refers to
increased hemoglobin level above the normal range.
It may be primary, secondary, or relative .
3. To assess response to specific therapy in anemia.
4. Estimation of red cell indices (along with packed cell
volume and red cell count) i.e. mean cell hemoglobin and mean cell hemoglobin
concentration.
5. Selection of blood donors.
Sahli's Acid Hematin Method :
Principle: Blood is mixed with an acid solution so that
hemoglobin is converted to brown-colored acid hematin.
This is then diluted with water till the brown color
matches that of the brown glass standard. The
hemoglobin value is read directly from the scale.
Equipment :
1. Sahli's hemoglobinometer: This consists of Sahli's graduated
hemoglobin tube (marked in grams and percent) and a
comparator with a brown glass standard.
2. 2. Sahli's pipette or hemoglobin pipette (marked at 20 l or
0.02 ml).
3. Smal glass rod (stirrer).
4. Dropping pipette.
Reagents :
1.N/10 hydrochloric acid
2. Distilled water
Specimen: EDTA-anticoagulated venous blood or blood
obtained by skin puncture.
Method :
1.Place N/10 hydrochloric acid into Sahli's graduated
hemoglobin tube up to the mark of 2 grams.
2.Take blood sample in Sahli's pipette exactly up to 20 l mark.
Blood adhering to the exterior of the pipette is wiped away
using absorbent paper or gauze.
3.Add blood sample to the acid solution, mix with a glass stirrer,
and allow to stand for 10 minutes.
4. Add distilled water drop by drop till the color of the solution
matches that of the glass standard.
5.Take the reading of the lower meniscus from the graduated
tube in grams
Disadvantages :
? About 95% color of acid hematin is attained at the end of 10 minutes.For
maximum
color development, much longer time (1 hour) is required.
? Perfect matching with the brown glass standard is not possible.
? Carboxyhemoglobin, methemoglobin, and sulfhemoglobin are not converted to
acid hematin. HbF is also not converted to acid hematin and therefore this
method
is not suitable in small infants.
? Development of color is slow and acid hematin solution is not stable.
? Source of light (daylight or artificial) will influence
the visual comparison of colors.
? Personal error in matching brown glass standard with test solution is 10%.
? Color of brown glass standard fades with time.
REFERENCE RANGES (WORLD HEALTH ORGANIZATION):
? Adult males: 13.0 - 17.0gm/dl.
? Adult females (non-pregnant): 12.0 ? 15.0gm/dl.
? Adult females (pregnant): 11.0 - 14.0 gm/dl.
? Children, 6-12 years: 11.5 - 15.5 gm/dl.
? Children, 6 months to 6 years: 11.0 ? 14.0 gm/dl.
? Children, 2 ? 6 months: 9.5 ? 14.0 gm/dl.
? At birth (full term): 13.6 ? 19.6gm/dl.
CRITICAL VALUES :
? < 7 gm/dl (severe anemia)
? > 20 gm/dl (hyperviscosity)
Other methods :
1. Colorimetric methods: In these methods, color comparison is made between the
standard and the test sample, either visually or by colorimetric methods.
? Visual methods: Tallqvist chart, Sahli's acid hematin method, and
WHO hemoglobin color scale.
? Photoelectric methods: Cyanmethemoglobin (hemiglobincyanide)
method, oxyhemoglobin method, and alkaline hematin method.
2.Gasometric method .
3.Chemical method.
4.Specific gravity method .
This post was last modified on 30 November 2021