Methaemoglobinemia - it increased the amount of hemoglobin that contains oxidized iron in the blood cells of the erythrocyte.Methemoglobin is one of the derivatives of hemoglobin, which is on a par with carboxyhemoglobin and sulfgemoglobinom contained in red blood cells in a small concentration.
methemoglobin formation takes place on a regular basis as a result of intracellular metabolic processes, but as a result of increase of its content, is suffering severe oxygen conveying function of red blood cells.
Under normal physiological conditions, the endogenous regulation mechanisms allow to keep the concentration of methemoglobin within 1.5% in total hemoglobin.In the process of oxidation iron and excessive formation of ferric iron, which is part of methemoglobin can have a stimulating effect of both internal and exogenous factors.
emergence of symptoms of methemoglobinemia may be caused by different etiopathogenetic factors, such as congeni
For methemoglobinemia in infants in the neonatal period often develops as a result of conditions accompanied by severe metabolic acidosis, a decrease in physiological activity metgemoglobinreduktazy, goiter with concomitant intestinal colonization by bacteria with increased nitroobrazuyuschey function.With the introduction of the products constituting the first lures children in breast period, there may be a transient methemoglobinemia caused by the high content of nitrates in drinking water and food.Moreover type fetal hemoglobin, which is observed in the neonatal period is more prone to oxidation processes than adult hemoglobin.
Disorders stool as diarrhea propensity almost 50% of cases accompanied by an increase in blood methemoglobin concentrations, and in the present state of play the role of two basic mechanisms: the progression of metabolic acidosis and increased formation of nitrite from nitrate, as a result of exposure to gram-negative pathogenic bacteria.
should separately consider the pathogenesis of methemoglobinemia appearance depending on the state of functioning metgemoglobinreduktazy.Under normal conditions, its function is to restore the oxidized iron and normalization of pathological methemoglobin.The period from birth and until they reach the age of four months is critical, and even full-term baby is at risk of symptoms of methemoglobinemia due to reduced physiological activity metgemoglobinreduktazy.In this regard, special consideration in regard to the study blood tests should be given to patients in this age period.
In adults, more common types of acquired methemoglobinemia associated with poisoning metgemoglobinoobrazovatelyami, that is the chemical nature of substances capable of converting hemoglobin to methemoglobin and pathological contribute to its concentration in the blood.These substances should include aniline dyes, nitrate, higher doses of nitroglycerin.
small category of patients infants, are persons with congenital or hereditary predisposition to the accumulation of methemoglobin.In this case, the mechanism of the development of methemoglobinemia is a complete absence of activity of enzymes involved in the reduction of methemoglobin, and in the presence of a particular form of hemoglobinopathies.
toxic methemoglobinemia type arise with prolonged duration of enterocolitis of different origin, associated with impaired absorption and synthesis of nitrates.
When assigning patients to drugs and quinine sulfonamides group should take into account that the active ingredients of these drugs have oxidizing properties and even their admission for a single patient may experience symptoms of methemoglobinemia.
emergence and extent of progression of clinical symptoms in patients with methaemoglobinaemia depends on many factors: age of the patient, presence or absence of concomitant cardiac and vascular disease, the level of concentration of methemoglobin in the blood and etiopathogenetic mechanism of its occurrence.
There is evidence that under the situation where the concentration of methemoglobin in the hemoglobin composition generally does not exceed the 20% limit, the patient did not notice any changes in the functioning of the whole organism.However, the measurement of the concentration of methemoglobin by spectrophotometry absorption type measured by the co-oximeter allows a closer look at the appearance of certain clinical symptoms in patients, depending on the degree of progression of the accumulation of methemoglobin in the blood.
Thus, the rate of less than 3 nm is observed in the rate of any human being, and thus he does not note any changes in health.At a concentration of 3-15 nm in the framework of the patient visually there is some gray color of the skin diffuse nature.The concentration of methemoglobin level of 15-30 nm is accompanied by the emergence of pronounced cyanosis of the skin and the dark staining of blood.Indicators on co-oximeter 30-50 nm are always accompanied by severe respiratory and vascular disorders in the form of the appearance of dyspnea, dizziness, severe weakness or even a short-term loss of consciousness.At a concentration of 50-70 nm in clinical symptoms in the foreground neurological disorders caused by prolonged hypoxia of the brain, in the form of a deep degree of disturbance of consciousness, increased convulsive readiness.In addition, patients have abnormalities in cardiohemodynamic a rhythm disturbance of the heart.In a situation where the concentration of methemoglobin-over 70 nm, there comes death.
specific clinical symptoms accompanied by a water-nitrate methemoglobinemia, resulting from acute toxic effects metgemoglobinoobrazovateley synthetic origin.In this situation, it marked the debut of acute clinical manifestations, and rapid progression of the clinical picture.In a situation where there is a slight degree of saturation of the blood methemoglobin observed transient cyanosis of the skin, headache, and disorientation.When properly conducted detoxification therapy, all of the above symptoms disappear, and there is a full recovery efficiency.
In the absence of pharmacological activities such as detoxification marked increase in severe neurological symptoms and hemodynamic disorders, the development of enhanced hemolysis in the lumen of vessels and related hemoglobinuria.
metgemoglobinoobrazovateley Prolonged exposure can induce methemoglobinemia chronic course with a tendency to relapse intoxication syndrome.
The basis of all methods of treatment of methemoglobinemia put pathogenetic principle, based on the reduction of ferric to ferrous.Basic pathogenetic reasonable medication in this situation is the parenteral administration of methylene blue in a therapeutic dose of 1 mg per 1 kg of patient weight.It is recommended to use this drug only at concentrations greater than 30% of methemoglobin, and in many cases in a few hours after injection indicated complete leveling of clinical manifestations.Much attention should be paid to the definition of an individual dose of methylene blue as an overdose of the drug can induce hemolytic anemia.
In a situation where methemoglobinemia is accompanied by deficiency of glucose-6-phosphate dehydrogenase, it is expedient to hold an exchange transfusion in the amount of at least 4 liters and of antioxidant therapy (ascorbic acid in a daily dose of 2 g).
in infancy in children with symptoms of methemoglobinemia caused fermentopathy, sound is the appointment of ascorbic acid at a dose of 0.1 g three times a day orally and riboflavin in a daily dose of 0.02
Mild methemoglobin concentration recorded duringco-oximetry, it does not require the use of antidote therapy and should be accompanied by a follow-up of the patient.
In a situation where the patient suffers from acute methaemoglobinaemia toxic genesis need to perform urgent activities consists in treating the affected skin with running water and eliminate the impact of emissions.Pathogenetically substantiated treatment for severe intoxication severity of methemoglobinemia is conducting passive oxygen therapy.
as a symptomatic therapy that promotes stimulation demetglobinezatsii is intravenous infusion of 40% glucose in a volume of 50 ml, intramuscular administration of 600 mcg of Vitamin B12, intravenously drip-sodium thiosulfate.