IQ 200 Walden University Quantum Hematology Exam Practice

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 (22, the major adult Hb), HbF (22, the major

fetal Hb), and HbA2, a minor adult Hb

TABLE 1: THE HUMAN HEMOGLOBINS

Hemoglobin

Composition

Representation

A

22

95-98% of adult Hb

A2

22

1.5-3.5% of adult Hb

F

22

Fetal Hb, 0.5-1%

Gower 1

22

Embryonic hemoglobin

Gower 2

22

Embryonic hemoglobin

Portland

22

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.