Many toxic substances can affect the composition and properties of blood. Such substances include: arsenic hydrogen, cyanide compounds , copper sulfate, lead, aniline, benzene, xylene, some plant poisons, etc. However, there is a certain group of toxic substances that act selectively on the blood. Of this group of poisons, so-called hemoglobinotropic, ie, poisons that form methemoglobin, and poisons that bind blood hemoglobin are of the greatest importance for forensic medicine.
Poisoning, forming methemoglobin . These poisons include potassium chlorate (bertolet salt), sodium nitrite (nitrite), aniline, dinitrobenzene and some other substances. Poisoning by these poisons is relatively small.
Methemoglobin forming substances are quite widely used in industry (for example, potassium and sodium nitrites are used in the rubber industry, for canning meat, etc.), in medical practice (as vasodilators, etc.). Aniline is used as a raw material for the production of dyes and the production of a number of medicines, artificial resins, colored pencils and for other purposes.Go
Under the influence of these poisons, bivalent iron is oxidized, contained in oxyhemoglobin and hemoglobin, to ferric iron, with the formation of methemoglobin from hemoglobin. In this case, oxygen is combined with iron in the composition of the hydroxyl group (OH). Methemoglobin is a very resistant compound, therefore oxygen is not transported to the tissues, as a result of which acidosis occurs. Methemoglobin formation in the blood is detected by its color. The blood becomes brownish-brown, and the organs acquire the same color. Cadaverous spots - a gray-gray color, sometimes with a brownish tinge.
Signs of intoxication manifest themselves when the blood contains 30% of methemoglobin, and death occurs when it is present in the blood of 70-80%.
Depending on the dose of poison taken and the individual characteristics of the body poisoned, the severity of the poisoning may be different. In case of mild poisoning, there can be a significant latent period. In severe poisoning, the first symptoms of poisoning may be 1-2 hours after taking the poison. Poisoning is characterized by cyanosis of the mucous membranes, fingers and auricles, dizziness, headache, disorientation of orientation in space. Then join vomiting , shortness of breath, stupefaction. The skin may acquire a grayish color. Severe poisoning can develop violently and in a short time lead to death. Acute poisoning is accompanied by hemolysis of the blood. When poisoning with dinitrobenzene, the exhaled air has the smell of bitter almond, and when aniline is intoxicated, the smell of aniline. Hemoglobinuric nephrosis may develop due to hemolysis and clogged renal tubules.Go
Methemoglobin formers are temporarily deposited in the liver and fat cells. This may explain the cases of repeated methemoglobin formation with the release of poison into the blood. Most nitrites are excreted in the urine.
Diagnosis of poisoning is based on anamnesis, the results of chemical analysis of intoxicants, the clinical picture, and toxicological data. The qualitative determination of methemoglobin is performed spectroscopically by the appearance of an absorption band in the red part of the spectrum. Spectrophotometric method determines the amount of methemoglobin in the blood. In severe poisoning, methemoglobin is found in about 5-6 days.
At the autopsy of poisoned, in addition to the characteristic color of blood, organs and cadaverous spots, there is a venous plethora of all internal organs and serous membranes, minor hemorrhages in the heart, liver, spleen, kidneys, brain edema, possible necrotic changes in the upper respiratory tract and lungs with inhalation poisoning.
Poisoning with methemoglobin formers are rare, mainly in everyday life. Usually they are the result of the erroneous use of poisons inside instead of drugs or food substances.
1. Describe the mechanism of action of hemoglobinotropic poisons on the human body.
2. What is the basis for the forensic medical diagnosis of death from poisoning with poisons that form methemoglobin?
3. What is the basis of the expert's conclusion about death from carbon monoxide poisoning?
4. What is the importance of laboratory tests in the diagnosis of death from poisoning by hemoglobinotropic poisons?
5. What is the fatal concentration of carboxyhemoglobin in human blood?