IQ 200 Walden University Quantum Hematology Exam Practice
IQ 200 Walden University Quantum Hematology Exam Practice
Hemoglobin Synthesis
It occurs in the RBC precursors from the globin polypeptide chain and heme. This
synthesis stops in the mature RBCs.
Hb is a tetramer, formed of 4 polypeptide chains with a heme group attached to
each chain. These polypeptides are of different chemical types. Each chain is
controlled by a different gene, which is activated and inactivated in a special
sequence.
Alpha chain is controlled by two sets of gene (i.e. 4 genes), which are present on
chromosome No. 6. Beta, Gamma and Delta chains are controlled by one set of
genes (i.e 2 genes) for each chain, which are present on chromosome No. 11.
The most common Hbs are HbA (22, the major adult Hb), HbF (22, the major
fetal Hb), and HbA2, a minor adult Hb
TABLE 1: THE HUMAN HEMOGLOBINS
Hemoglobin
Composition
Representation
A
22
95-98% of adult Hb
A2
22
1.5-3.5% of adult Hb
F
22
Fetal Hb, 0.5-1%
Gower 1
22
Embryonic hemoglobin
Gower 2
22
Embryonic hemoglobin
Portland
22
Embryonic hemoglobin
At birth, Hbf forms about 70% of the total Hb, while Hb-A forms the rest.
By 6 months of age, only trace amounts of gamma chain are synthesised and very
little amounts of residual Hb-F are present. At 6-12 months age, Hb-F forms 2% of
the total Hb, while Hb-A forms the rest. Hb-A2 forms about 3% of the total Hb.
The release of oxygen from red cells into tissue is strictly regulated. Under normal
condition, arterial blood enterstissues with an oxygen tension of 90 mmHg and
hemoglobin saturation close to 97%. Venous blood returning from tissues is
deoxygenated. The oxygen tension is about 40 mmHg; the oxyhemoglobin
dissociation curve describes the relation between the oxygen tensions at
equilibrium. The affinity of hemoglobin for oxygen and the deoxygenation in tissues
is influences by temperature, by CO2 concentration, and by the level of 2,3-
diphosphoglycerate in the red cells. In the case of tissue or systemic acidosis, the
oxygen dissociationcurve shifted to the right and more oxygen is released. The
same effect results from the uptake of carbon dioxide,which raises the oxygen
tension of carbon dioxide.
The oxygen supply to peripheral tissues is influenced by three mechanisms:
1. The blood flow, which controlled by the heart beat volume and the
constriction or dilatation of peripheral vessels.
2. The oxygen transport capacity, which depends on the number of red blood
cells and the hemoglobin concentration.
3. The oxygen affinity of hemoglobin
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Clinical Significance
Hemoglobin concentrations below 12 gm/dl in men and 10.2gm/dl women indicate
an anemic condition and produce symptoms progressing from weakness,
tachycardia, and dizziness to dyspnea at rest, cardiac failure, and coma. Symptoms
of anemia range from mild to severe and depend on the degree of Hemoglobin
deficit, the extent of physiologic adaptation, and the intensity of physical exertion.
Thus a moderately severe anemia of acute onset (hemorrhage) may produce
severe symptoms, whereas the same degree of anemia developing very gradually
can be asymptomatic due to compensatory changes.
Hemoglobin values may also be affected by other disease states as well as
nonpathologic conditions such as age, sex, altitude, and the degree of fluid
retention or dehydration. New-born infants normally exhibit hemoglobin
concentrations higher than adults that sustainthem during early life before active
erythropoiesis begins. After puberty, male and female hemoglobin values differ due
to the greater body mass and higher oxygen requirements of men.
Normal Values
Age
RBC/ million
Hb gm/dl
Hematocrit
Cord blood
5+-1
16.5 +- 3
55+-10
3 months
4+- 0,8
11.5 +- 2
36+-6
6 months
4.8 +-0,7
7 Y-12Years
4.7 +-0.7
13+- 1
38+-4
Adult M
5.5+- 1
15.5 +- 2.5
47+-7
Adult –Female
4.8+-1
14+- 2.5
45+-5
Variations
Elevated hemoglobin may occur with the following:
Dehydration as a result of prolonged vomiting or severe diarrhea
Hemoconcentration such as in shock or immediately after hemorrhage
High altitude
Polycythemia or erythrocytosis
Severe burns
Decreased hemoglobin may occur with the following
Anemia resulting from increased blood destruction or decreased blood
production
Cirrhosis
Hemorrhage as a result of trauma or childbirth
Hyderemia of pregnancy or fluid retention
Hypothyroidism
Idiopathic steatorrhea
Intravenous overload
Leukemia
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Determining the Concentration of Hemoglobin
The cyanmethemoglobin (hemiglobincyanide; HiCN) method has the advantage of
convenience and a readily available, stable standard solution.
Hemiglobincyanide (HiCN) Method
Principle
Blood is diluted in a solution of potassium ferricyanide and potassium cyanide. The
potassium ferricyanide oxidizes hemoglobins to hemiglobin(Hi; methemoglobin),
and potassium cyanide provides cyanide ions (CN-) to form HiCN, which has a
broad absorption maximum, at a wavelength of 540 nm and compared with that of
a standard HiCN solution.
Reagent
The diluent is detergent-modified Drabkin reagent
Potassium ferricyanide (K3Fe(CN6) 0.20 g
Potassium cyanide (KCN) 0.05 g
Dihydrgen potassium phosphate 0.14 g
(anhydrous (KH2PO4)
Non-ionic detergent-e.g, Sterox S.E. 0.5 ml
(Harleco) or Triton X-100 (Rohm and Haas) 1.0 ml
Distilled water to 1000 ml
The solution should be clear and pale yellow, have a pH of 7.0 to 7.4, and give a
reading of zero when measured in the photometer at 540 nm against water blank.
Substituting dihydrogen potassium phosphate, KHP2PO4, in this reagent for
sodiumbicarbonate, NaHCO3, in the original Drabkin reagent shortens the time
needed for complete conversion of Hb to HiCN from 10 minutes to 3 minutes. The
detergent enhances lysis of erythrocytes and decreases turbidity from protein
precipitation.
Care must be taken with KCN in the preparation of the Drabkin solution, as salt or
solutions of cyanide are poisonous. The diluent itself contains only 50 mg KCN per
liter, less than the lethal dose for a 70-kg person. However, because HCN is
released by acidification, exposure of the diluent to acid must be avoided. Disposal
of reagents and samples in running water in the sink is advised. The diluent keeps
well in a dark bottle at room temperature, but should be prepared fresh once a
month.