ABNORMAL HEMOGLOBIN DERIVATIVES

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.