The normal values for hemoglobin determinations
are as follows:
Methods for hemoglobin determination are many
and varied. The most widely used automated method is
the cyanmethemoglobin method. To perform this
method, blood is mixed with Drabkins solution, a
solution that contains ferricyanide and cyanide. The
ferricyanide oxidizes the iron in the hemoglobin,
thereby changing hemoglobin to methemoglobin.
Methemoglobin then unites with the cyanide to form
cyanmethemoglobin. Cyanmethemoglobin produces a
color which is measured in a colorimeter,
spectrophotometer, or automated instrument. The color
relates to the concentration of hemoglobin in the blood.
Manual methods for determining blood hemoglobin
include the Haden-Hausse and Sahli-Hellige methods.
In both methods, blood is mixed with dilute hydrochloric
acid. This process hemolyzes the red cells, disrupting the
integrity of the red cells membrane and causing the
release of hemoglobin, which, in turn, is converted to a
brownish-colored solution of acid hematin. The acid
hematin solution is then compared with a color standard.
HEMATOCRIT (PACKED CELL VOLUME)
The hematocrit or packed cell volume (PCV)
determines the percentage of red blood cells (RBCs) in
The normal hematocrit value for men is 42% to
52%; for women, 37% to 47%; and for newborns, 53%
to 65%. When hematocrit determinations are below
normal, medical conditions such as anemia and
leukemia may be present. Above-normal hematocrit
determinations indicate medical conditions like
dehydration, such as occur in severe burn cases.
Currently, automated hematology analyzers
supply most hematocrits. However, when hematology
analyzers are not available, hematocrit determinations
can be manually performed by the microhematocrit
method or macrohematocrit method. Both methods
call for the blood to be centrifuged, and the percentage
of packed red cells is found by calculation.
The microhematocrit method is the most accurate
manual method of determining blood volume and
should be used whenever feasible.
requirements and the step-by-step procedures for
performing the microhematocrit method will be
covered in the following sections.
Materials Required for Microhematocrit
To perform a hematocrit using the micro-
hematocrit method, the following materials are
· Capillary tubes, plain or heparinized
· Modeling clay sealant
· Microhematocrit centrifuge
· Microhematocrit reader
To perform the microhematocrit method, you
should follow the steps listed below:
1. Fill the capillary tube two-thirds to
three-quarters full with well-mixed, oxalated
venous blood or fingertip blood. (For fingertip
blood use heparinized tubes, and invert several
times to mix.)
2. Seal one end of the tube with clay.
3. Place the filled tube in the microhematocrit
centrifuge, with the plugged end away from the
center of the centrifuge.
4. Centrifuge at a preset speed of 10,000 to 12,000
rpm for 5 minutes. If the hematocrit exceeds 50
percent, centrifuge for an additional 3 minutes.
5. Place the tube in the microhematocrit reader.
Read the hematocrit by following the
microhematocrit reading device.
TOTAL WHITE BLOOD CELL COUNT
The total white cell (leukocyte) count determines
the number of white cells per cubic millimeter of
blood. A great deal of information can be derived from
white cell studies. The white blood cell count (WBC)
and the differential count are common laboratory tests,
and they are almost a necessity in determining the
nature and severity of systemic infections. Normal
WBC values in adults range from 4,500 to 11,000 cells
per cubic millimeter; in children the range is from
5,000 to 15,000 cells per cubic millimeter; and in
100 ml blood
Woman............................12.5 to 15.................83 to 110
Men....................................14 to 17..................97 to 124
Newborn infants................17 to 23..................97 to 138