The causes of methaemoglobin and symptomatic methemoglobinemia, predictions

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2017.08.29
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Hemoglobin

An abnormal form of hemoglobin, in which bivalent iron atoms are oxidized to trivalent under the influence of toxic substances, oxygen-containing drugs or due to hereditary disorders of hemoglobin molecules is called methemoglobin.

Reincarnation of natural hemoglobin into metaemoglobin occurs by its oxidation, as a result of which the iron formula of Fe2 + passes into the trivalent state - Fe3 +.

Molecule of methemoglobin

Content

  • Features
  • Methemoglobin: the norm in the blood, the concept and varieties
  • Diagnosis and treatment of methemoglobinemia in adults and children
  • Toxic substances that synthesize methaemoglobin
  • Methods to prevent the oxidation of iron hemoglobin

Features

The main distinguishing feature of methemoglobin is that it is not able to bind to molecules oxygen and transfer it to human organs and tissues, which results in oxygen starvation organism.

In the blood of a healthy person, methemoglobin is present in small amounts. The norm of methemoglobin in the blood is approximately 1% (with an error of up to 3%). If his presence exceeds the specified rate, the disease comes - methemoglobinemia.

Formation of anomalous form

Methemoglobin: the norm in the blood, the concept and varieties

Methemoglobinemia is a disease in which a significant part of hemoglobin in erythrocytes contains oxidized ferric iron. Hemoglobin, as the most important element, is responsible for the transportation of oxygen through the body. Oxidizing to methemoglobin, it loses this property, which leads to hypoxia of organs and tissues.

There are three forms of methemoglobinemia:

  • Congenital. Very rare form of the disease. Does not affect the duration and quality of life.
  • Genetic. With this form of the disease, the cause of the increase in the proportion of methemoglobin becomes a genetic predisposition. In this case, a congenital metabolic error occurs that leads the body to the state of methemoglobinemia. The consequences of this form of the disease are very serious: mental retardation, microcephaly. Life expectancy is short, as a rule, people die at a young age.
Genetic form
  • Acquired. This form is more common. It arises because of the effects on the body of substances that cause methemoglobinemia. Occurs as a result of taking a number of drugs or under the influence of toxic substances.

Diagnosis and treatment of methemoglobinemia in adults and children

Symptomatic signs and consequences of methemoglobinemia depend on the form and level of methemoglobin:

  • Level 3-15% - there is a characteristic pale, gray or cyanotic skin tone, thickening of the nail plates.
  • The level of 15-20% - appears cyanosis.
  • Level 25-50% - physiological consequences are noted: migraine, general weakness, shortness of breath, chest pain, confusion.
  • Level 50-70% - syncope, mental disorders, convulsions, coma.
  • The level of more than 70% is lethal.

The disease of methemoglobinemia affects both adults and children, including newborns.

Levels of danger
A characteristic feature for all forms of methemoglobinemia is the chocolate-brown tinge of blood, when taking analyzes it does not change its color.

To diagnose the disease in an adult patient, the doctor evaluates the symptoms, assigns laboratory tests. When diagnosing, it is very important to identify the cause of hypoxia. If this condition is caused by poisoning, it is necessary to exclude the possibility of carbon monoxide entering the bloodstream. When this substance gets into the blood, a strong compound, carboxyhemoglobin, is formed. Like methemoglobin, it is not able to transport oxygen to cells and tissues. A distinctive sign of poisoning with carboxyhemoglobin is the bright red color of the blood.

Excessive amount of methemoglobin in the blood can be observed in both women and men. However, men are susceptible to this disease 66.59% less than a woman. Cases of death in men with methemoglobinemia are not fixed.

To diagnose methaemoglobinemia in newborn children, the doctor performs special tests and studies to measure the level of methhemoglobin in the blood.

In particular, such studies include:

  • The color of blood. With the disease, it acquires a rich brown color.
  • Biochemistry of blood. Elevated bilirubin in biochemical analysis may indicate methaemoglobinaemia.
  • Analysis of the concentration of methemoglobin in the blood of the child.
  • General blood analysis. If the child is sick, the level of ESR decreases, and hemoglobin and red blood cells increase.

In children with hereditary disease, the following external signs of the disease are often observed:

  • A pronounced cyanosis on the skin and mucous membranes.
  • Deformity of the shape of the skull.
  • Lag in psychomotor development.

Methemoglobinemia affects children, both male and female. However, newborns risk acquiring a hereditary or congenital disease more often than boys.

Toxic substances that synthesize methaemoglobin

The main reason for the concentration in the blood of methemoglobin is the ingress of pathogenic chemicals into the body as a result of an overdose of drugs based on aniline and its derivatives. A substance that is capable of converting hemoglobin to methemoglobin is called a methemoglobin-forming agent.

The main methaemoglobin-forming agents:

  • local anesthetics;
  • nitrates and nitrites;
  • Nitric oxide;
  • Primarch;
  • naphthalene;
  • hydrazine derivatives;
  • sulfonamides.
It is necessary to treat with special care the medicinal preparations made on the basis of methemoglobin-forming agents. Before using the medication, you should read the instructions for use and dosage.
Cyanosis - one of the signs of pathology

Methods to prevent the oxidation of iron hemoglobin

To maintain health, it is worth knowing how to prevent the formation of excess methaemoglobin in the blood. For this purpose, there are two ways.

  1. Prevent the pathogenic effect of penetrating the red blood cells of the oxidants of iron before they damage the molecules of hemoglobin. To do this, the enzyme glutathione peroxidase is injected into the blood. In this case, the reduced glutathione acts on pathogenic oxidants in the blood, neutralizes them and prevents the synthesis of methemoglobin. This method will help prevent the further development of methemoglobinemia, but can lead to the formation in the blood of substances obtained as a result of denaturation of hemoglobin - Geyntts bodies.
  2. Recover damaged by oxidized iron molecules of hemoglobin. This method is used with the help of two enzymatic systems: NAND-dependent and NANDP-dependent methaemoglobin reductase. In the first system, the products of the anaerobic stage of glucose processing (NAND), the second - hexose monophosphate transformation (NANDF), act as agents that repair damaged hemoglobin substances. As a result of hexose monophosphate transformation under the influence of hexose-6-phosphate dehydrogenase (G-6f-DG), the reducing agent - nitinamide - adenine dinucleotide phosphate (NANDPH) is synthesized. He takes part in the transformation of methemoglobin into hemoglobin in the presence of NADPH-methemoglobin reductase, and also as a result of the reduction of oxidized ferric iron with the participation of the NANDP-dependent glutathione reductase.

Methemoglobin is a hazardous substance. Synthesis of hemoglobin into methemoglobin leads to serious disorders in the composition and quality of the blood. To avoid concentration in the body, it is necessary to systematically carry out preventive procedures and monitor the dosage of the drugs used.

The influence of nitrates on the human body is told in the video:

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