Mercury poisoning is an acute or chronic intoxication with a metallic variety of this substance or its compounds (chloride, amidochloride, chlormerodrine). The main symptoms are vomiting, nausea, abdominal pain, stomatitis, proteinuria, hematuria, lethargy, drowsiness, cough. In chronic forms, encephalopathy, impaired coordination is observed. When making a diagnosis, the clinical signs of the disease and the results of atomic adsorption spectrometry are evaluated. Treatment includes antidotes, general antitoxic measures, and metabolic therapy.
T56.1 Toxic effect of mercury and its compounds
Mercury poisoning (Hg) is a relatively rare pathology, which more often occurs in a chronic variant. Regular long-term consumption of poison leads to damage to the tissues of the central nervous system, kidneys, lungs, liver, heart, oral mucosa. Acute varieties occur mainly during industrial accidents, when a large volume of toxicant is released into the environment. A dose of 2.5 g of metal vapor taken by inhalation is considered lethal. The maximum permissible concentration for the working area is 0.005 mg/m3, for residential air – 0.0003 mg/m3.
The main cause of chronic mercury intoxication is working in rooms with a high content of heavy metal vapors. Similar situations arise at the dressing processing plant, plants engaged in the production of chlorine, alkalis, metals of a high level of purification. Acute mercury poisoning is the result of oral administration of its salts. In its pure form, the metal taken by mouth is not too toxic. Other possible reasons:
- Vapor leakage during laboratory experiments. May occur during the use of equipment containing mercury. A common option is a broken thermometer. The xenobiotic contained in it is able to increase the concentration of vapors in the air to 100-150 MPC. The problem may also arise as a result of using other demonstration mercury-containing equipment.
- Insecticides. Some formulations used for the destruction of insects and pests contain mercury salts as an active component. Violation of safety regulations when using them causes acute (less often – chronic) exotoxicosis. The substance also accumulates in vegetables and fruits, which contributes to the occurrence of food poisoning.
- Medications. Outdated medical products intended for the treatment of syphilis and gonorrhea were made on the basis of liquid metal salts. In patients undergoing treatment with mercurbenzoate, the symptoms of mercurialism were determined. Today, such medicines are not used in official medicine.
- Sea fish. The tissues of marine animals living in chemically polluted areas of the world’s oceans are capable of accumulating Hg. Eating such food, a person receives a small amount of a toxic substance every day. Over time, he has signs of chronic intoxication. The food pathway of the lesion is common among the inhabitants of Japan.
- Dental fillings. The installation of seals containing amalgam was practiced until the beginning of the two thousandth years. At the moment, such technologies are no longer used on the territory of the Russian Federation, the USA, the European Union. Mercury-based fillers continue to be used in some developing countries.
- Crime and suicide. For the purpose of murder or suicide, hydrargium salts are used, the lethal dose of which does not exceed 1 gram. Similar cases were widespread in the VX-IX centuries. Today they are registered extremely rarely, as more effective, fast-acting and non-trace poisons have appeared.
Mercury, entering the body, binds to the sulfhydryl groups of blood enzymes, blocking their activity. In addition, there is a violation of the processes of biosynthesis of proteins and cellular ribonucleic acids. The target organs include the central nervous system, kidneys and liver, in which necrotic and dystrophic processes occur, functional disorders develop. The lungs, cardiovascular system, and muscles suffer somewhat less.
Mercury poisoning causes congenital deformities of the fetus. After birth, he shows symptoms of prenatal damage: functional immaturity, defects in the formation of the brain, excretion systems. Possible antenatal or early postnatal death, musculoskeletal defects, mental retardation. The teratogenic effect of the poison is more pronounced in mercurialism.
The disease is divided by severity (severe, moderate, mild), causes (domestic, criminal, professional), the type of damaging agent (metallic mercury or its salts), the presence of complications (liver, kidney failure, encephalopathy). The most common classification criterion is considered to be the nature of pathology:
- Acute mercury poisoning. It occurs due to the simultaneous intake of a large amount of a toxic substance into the body. It occurs with criminal intoxication, industrial disasters, inhalation of high-concentration vapors. A similar variety is diagnosed in 18-20% of victims.
- Mercurialism. A variant of the chronic course of the disease. The symptoms of pathology are determined in people who have been receiving small doses of Hg for a long time. It is often diagnosed in workers of industries operating liquid metal, even if the necessary precautions are observed. The share in the overall structure of the disease is 30-32%.
- Micromercurialism. Signs of exotoxicosis are detected in patients who have been in contact with mercury compounds for 5-15 years. The reason is the regular intake of microdoses of xenobiotic, leading to its accumulation. It is characterized by a less specific course. Micromercurialism accounts for about 40% of the total number of mercury exotoxicoses.
In the acute version of the course, the pathology is accompanied by the appearance of abdominalgia, vomiting, nausea, diarrhea with an admixture of blood. On the part of the nervous system, drowsiness, depression, periods of psychomotor agitation are noted. The consequences of inhaling vapors are cough, chest pain, hyperthermia. It is possible to develop pulmonary edema with the appearance of wet wheezing, foaming from the mouth, orthopnea, diffuse cyanosis, sweating.
Later, diuresis decreases, kidney failure forms. Patients complain of the appearance of a metallic taste in the mouth. Upon examination, salivation, rhinorrhea, swelling of the lymph nodes in the neck, bleeding gums are detected. A dark border is visible on the gums, which is a specific evidence of pathology. It is possible to reduce the number of red blood cells, hemodynamic instability.
With mercurialism, signs of damage to the nervous system come to the fore. The patient is determined to have neurosis, frequent mood swings, in which depression is replaced by outbursts of irritability, aggression. There are psychosomatic phenomena, arterial dystonia. Some patients complain of impaired vision caused by papillary edema or atrophy of the optic nerve. Anisocoria, swallowing disorder may be present.
Mercury poisoning, provoked by taking its chemically related forms, is accompanied by limb ischemia. Patients note the appearance of dark pink spots on the tips of their toes and hands. Nails, hair, teeth begin to fall out, skin itching occurs. Additional symptoms are a violation of coordination, tremor, a drop in muscle tone. During specialized tests, a decrease in skin sensitivity is detected.
It manifests itself as a set of non-specific phenomena that are rarely associated with mercury consumption at the stage of primary diagnosis. There are signs of inflammatory diseases of the respiratory tract, a small tremor of the fingers on the hands, a decrease in working capacity. Irritability, intolerance to interfering factors is determined. The clinical picture is poorly expressed, but progresses over time.
Possible complications include multiple organ failure, which is diagnosed in 37% of patients with an acute form of pathology. In 48% of patients, it develops after 10-20 years of regular intake of metal or its salts into the tissues. Another common consequence of mercurialism is neurological changes, which often invalidate a person. About 38% of the victims have similar signs.
Inhalation of mercury vapor is accompanied by the development of pneumonia in 15-17% of patients, manifestations of toxic pulmonary edema are found in 20%. Approximately 10% of patients complain of problems with vision, hearing, tactile sensitivity. Almost all people who have suffered mercury poisoning note their own short temper, frequent conflicts with others, partial desocialization. This leads to difficulties in communicating with family and friends, management at work.
Simultaneous mercury poisoning is diagnosed by an ambulance paramedic. The diagnosis is confirmed in the hospital, where the patient is assigned a number of laboratory and instrumental examinations. Consultations of a neurologist, gastroenterologist, therapist are required. Mercurialism is detected during the patient’s treatment at a polyclinic or a toxicology center. The following diagnostic methods are used:
- Physical. The skin is of normal color or pale, there are periods of increase and decrease in blood pressure. Muscle tone is insufficient. The tones of the heart are deaf, wheezing can be heard in the lungs. Tachycardia is possible. There are dark spots on the distal phalanges of the fingers, sometimes trophic ulcers form. There is a border on the oral mucosa, areas of bleeding.
- Laboratory. The mercury content in the blood exceeds 5.8 micrograms/l. This indicator is determined using adsorption atomic spectrometry. Indirect evidence of mercurialism is eosinophilia, leukopenia, anemia, agranulocytosis. An increase in the activity of liver enzymes, creatinine, and urea is possible.
- Hardware. When using metallic Hg inside, it can be seen on radiographic images of the intestine, with intravenous administration – in the vessels of the lungs. Computer and magnetic resonance imaging can detect changes in the parenchyma of the kidneys, liver, and cerebral tissues. There is evidence of rhythm disturbance on the ECG.
Primary measures are standard for most poisonings. The victim should be removed from the zone of chemical contamination, provide fresh air, unbutton the restraining clothes. If the toxicant has been ingested, it is necessary to induce vomiting, rinse the stomach in a non-probe way. The exception is the defeat of mercury nitrate, which causes chemical burns. Chronic varieties do not require emergency pre-medical measures.
It is carried out only in acute conditions. Symptomatic therapy aimed at correcting existing disorders is indicated. Pulmonary edema requires infusion of loop diuretics, airway sanitation, and intubation of the victim. Seizures are eliminated with the help of benzodiazepines, anticonvulsants. Pronounced psychomotor agitation is eliminated by the introduction of antipsychotic medications. Unithiol is used as an antidote.
Gastric lavage is performed with the introduction of a probe. The working solution is pure water with the addition of crushed activated carbon. After the end of the procedure, the victim is given to swallow adsorbent tablets, the amount of which should correspond to the body weight. It is permissible to use weak solutions of food acids or table salt to clean the stomach. This increases the efficiency of manipulation.
The main method of therapy is demercurialization using unithiol. The drug forms low-toxic soluble compounds with Hg, which are excreted in the urine. The remedy is prescribed in courses, the duration is 3-4 days, the interval is 1-4 months. The duration of treatment can reach 1 year. Patients also receive cacarboxylase, multivitamins, nootropic drugs, glucocorticoids, folic acid, d-penicillamine as an additional antidote.
Post-syndrome therapy is indicated. Muscle relaxants are recommended for patients with central hypertension and a tendency to seizures, and anabolic steroids are recommended for children with a lack of muscle mass. For the purpose of sedation, sedative medications are given, including herbal ones. ATP is used to maintain the work of the heart, hepatoprotectors are used in the liver. Renal insufficiency is an indication for hemodialysis.
It can flow for several years. The convalescent is recommended to follow a diet with a restriction of spicy, salty, fatty, high-protein dishes. Table salt should be excluded in order to avoid the development of edema. Diuresis is subject to careful monitoring. With a decrease in the daily volume of urine, the amount of fluid consumed is limited, diuretics are used as prescribed by a doctor. Any contact with the toxicant is excluded.
Prognosis and prevention
The prognosis for life is favorable. About 95% of people suffering from moderate or mild mercurialism overcome the 20-year survival threshold. In acute intoxication, the mortality rate is 13-18%. Some residual symptoms persist throughout life in 67% of patients, some of them become disabled. The severity of the consequences is directly proportional to the amount of metal taken and the time of contact with it.
To prevent mercury poisoning, sanitary and hygienic standards should be strictly observed. In areas where work is carried out that requires the use of liquid metal, it is necessary to make regular measurements. If the MPC is exceeded, people should be evacuated, the infection zone is subject to chemical demercurialization with 20% ferric chloride. Broken thermometers and other mercury-containing products must be handed over to special services.