ABNORMAL HEMOGLOBIN DERIVATIVES
‘Hemoglobin derivatives’ refer to a blood test to detect and measure the percentage of abnormal hemoglobin derivatives. Hemoglobin is the only carrier for transport of oxygen, without which tissue death occurs within few minutes. When hemoglobin is altered, its oxygen carrying capacity is decreased resulting in lack of oxygen. So, it is important to know about the causes and the effects of abnormal hemoglobin derivatives. Abnormal hemoglobin derivatives are formed by carbon monoxide (CO) poisoning or due to some drugs like nitrites, nitrates and sulphanamides.
Abnormal hemoglobin derivatives are:
1. Carboxyhemoglobin
2. Methemoglobin
3. Sulfhemoglobin.
Normal percentage of hemoglobin
derivatives in total hemoglobin:
Carboxyhemoglobin : 3% to 5 %
Methemoglobin : less than 3%
Sulfhemoglobin : trace (undetectable).
Abnormally high levels of hemoglobin
derivates
in blood produce serious effects.
These derivatives
prevent the transport of oxygen
resulting in oxygen lack
in tissues, which may be fatal.
CARBOXYHEMOGLOBIN
Carboxyhemoglobin or carbon
monoxyhemoglobin is the abnormal hemoglobin derivative formed by the
combination of carbon monoxide with
hemoglobin. Carbon monoxide is a colorless and odorless gas. Since hemoglobin
has 200 times more affinity for carbon monoxide than oxygen, it hinders the
transport of oxygen resulting in tissue hypoxia. Normally, 1% to 3% of
hemoglobin is in the form of
carboxyhemoglobin.
Sources of Carbon Monoxide
1. Charcoal burning
2. Coal mines
3. Deep wells
4. Underground drainage system
5. Exhaust of gasoline engines
6. Gases from guns and other weapons
7. Heating system with poor or
improper ventilation
8. Smoke from fire
9. Tobacco smoking.
Signs and Symptoms of
Carbon Monoxide Poisoning
1. While breathing air with less than
1% of CO, the Hb saturation is 15% to 20% and mild symptoms like
headache and nausea appear
2. While breathing air with more than
1% CO, the Hb saturation is 30% to 40%. It causes severe
symptoms like:
i. Convulsions
ii. Cardiorespiratory arrest
iii. Unconsciousness and coma.
3. When Hb saturation increases above
50%, death occurs.
METHEMOGLOBIN
Methemoglobin is the abnormal
hemoglobin derivative formed when iron molecule of hemoglobin is oxidized from
normal ferrous state to ferric state. Methemoglobin is also called ferrihemoglobin.
Normal methemoglobin level is 0.6% to
2.5% of total hemoglobin. Under normal circumstances also, body faces the threat
of continuous production of methemoglobin. But it is counteracted by erythrocyte
protective system called nicotinamide adenine dinucleotide (NADH) system, which
operates through two enzymes:
1. Diaphorase I (nicotinamide adenine
dinucleotide phosphate [NADPH]dependent
reductase): Respon sible for 95% of
the action.
2. Diaphorase II (NADPHdependent methemoglobin
reductase): Responsible for 5% of the action.These two enzymes prevent the
oxidation of ferrous iron into ferric iron.
Methemoglobinemia
Methemoglobinemia is the disorder
characterized by high level of methemoglobin in blood. It leads to tissue hypoxia,
which causes cyanosis and other symptoms. Causes of methemoglobinemia
Methemoglobinemia is caused by variety
of factors:
1. Common factors of daily life:
i. Well water contaminated with
nitrates and nitrites
ii. Fires
iii. Laundry ink
iv. Match sticks and explosives
v. Meat preservatives (which contain
nitrates and nitrites)
vi. Mothballs (naphthalene balls)
vii. Room deodorizer propellants.
2. Exposure to industrial chemicals
such as:
i. Aromatic amines
ii. Fluorides
iii. Irritant gases like nitrous oxide
and nitrobenzene
iv. Propylene glycol dinitrate.
3. Drugs:
i. Antibacterial drugs like
sulfonamides
ii. Antimalarial drugs like
chloroquine
iii. Antiseptics
iv. Inhalant in cyanide antidote kit
v. Local anesthetics like benzocaine.
4. Hereditary trait:
Due to deficiency of
NADH-dependant reductase or presence of abnormal hemoglobin M. Hemoglobin M is common in babies
affected by blue baby syndrome (a pathological
condition in infants, characterized by bluish skin discoloration
(cyanosis), caused by congenital heart defect).
SULFHEMOGLOBIN
Sulfhemoglobin is the abnormal
hemoglobin derivative, formed by the combination of hemoglobin with hydrogen sulfide.
It is caused by drugs such as phenacetin or sulfonamides.
Normal sulfhemoglobin level is less
than 1% of total hemoglobin.
Sulfhemoglobin cannot be converted
back into hemoglobin. Only way to get rid of this from the body is
to wait until the affected RBCs with
sulfhemoglobin are destroyed after their lifespan.
Blood Level of
Sulfhemoglobin
Normally, very negligible amount of
sulfhemoglobin is present in blood which is nondetectable. But when itslevel
rises above 10 gm/dL, cyanosis occur. Usually, serious toxic effects are not
noticed.
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