Thallium poisoning is a symptom complex that occurs as a result of ingestion of heavy metal salts into the body. In the early period of intoxication, dyspeptic syndrome, respiratory and cardiovascular disorders develop. Then neurological symptoms are added: paresthesia in the extremities, myalgia, convulsions, hallucinations. A characteristic sign of thallium intoxication is diffuse alopecia. The diagnosis is confirmed after determining the concentration of thallium in blood plasma, urine, and hair. Medical care includes intestinal lavage, forced diuresis, antidote therapy, if necessary – hemodialysis, hemosorption.
ICD 10
T56.8 Toxic effect of other metals (thallium)
General information
Thallium intoxication is acute, subacute or chronic poisoning accompanied by enterotoxic, cardiotoxic, neurotoxic, nephrotoxic and other effects. Despite the low specific weight in the structure of heavy metal intoxication, thallium poisoning occupies a special place among them due to the high toxicity of compounds, difficulties in diagnosis, treatment, and high risks of death.
Causes
Poisoning with thallium salts can be household or industrial, accidental, suicidal or criminal in nature. Toxic compounds can enter the body enterally (with food, water), inhaled (with inhaled vapors and dust), percutaneously (through intact skin). Thallium poisoning is possible in the following cases:
- Contact with toxic chemicals. Thallium salts are found in insecticides used in agriculture to control pests. Also, thallium sulfates are part of rodenticides (rat poison), so poisoning can occur during the processing of cultivated plants, deratization of premises without protective equipment.
- Industrial contact with metal. Workers engaged in the production of electrical equipment, pyrotechnics, fluorescent paint, thermometers, optical lenses, jewelry and other products have an increased risk of poisoning in production.
- The use of contaminated water and food. Cases of group and mass poisoning are described with the use of grain, plant food, drinking water containing thallium salts. These poisonings can be either unintentional or intentional (for the purpose of killing one or a group of persons, chemical terrorism). Vegetarians and smokers suffer more from the increased intake of thallium into the body.
- Use for therapeutic and diagnostic purposes. In the recent past, thallium salts have been used to treat ringworm, remove unwanted hair as part of depilatory creams. Currently, the use of thallium in medicine is limited by its presence in radioactive isotopes (199Tl, 201Tl, 204Tl) used for scintigraphy and myocardial SPECT. Theoretically, intoxication can develop if too high a dose of the drug is administered.
Pathogenesis
Thallium (Tl) is included in the group of highly toxic heavy metals of the 1st hazard class, has a pronounced damaging effect on the digestive tract, respiratory, circulatory, nervous system, kidneys. The toxic concentration of Tl is 0.1-0.5 mcg/ml in blood plasma and more than 0.2 mcg/ml in urine. The lethal dose when taking the toxicant inside is 14-20 mg / kg.
The maximum concentration in the blood is reached within 2-3 hours after poisoning. In the body, thallium accumulates unevenly in various organs: kidneys, gonads, spleen, brain, bone marrow, hair. The half-life of Tl can take from 3-5 to 30 days. Thallium is excreted from the body mainly through the urinary organs and intestines, to a lesser extent with bile, sweat, saliva, sebum.
The main toxic effects are associated with the ability of Tl+ ions to replace K+ ions in sodium-potassium adenosine triphosphatase, which leads to the displacement of intracellular potassium. By disrupting the functioning of various enzymes, thallium inhibits the synthesis of many proteins. The toxic element forms insoluble complexes with vitamin B2, thereby causing a disorder of riboflavin metabolism, its insufficiency, a violation of energy metabolism in cells. Thallium intoxication leads to increased lipid peroxidation processes, membrane damage and cell death.
Accumulating in the hair follicles, thallium inhibits the synthesis of keratin, causing atrophy of hair follicles and hair loss. To date, the enterotoxic, neurotoxic, cardiotoxic, nephrotoxic, mutagenic effect of the metal has also been proven. Thallium can overcome the placental barrier, causing congenital alopecia and nail dystrophy in the fetus.
Symptoms
The clinical picture of thallium intoxication depends on a number of factors: the dose, the way the toxicant enters the body, the duration of contact. The first signs of acute poisoning appear within a few hours to 1-2 days. First of all, toxic gastroenteritis occurs, accompanied by vomiting, epigastric pain, diarrhea (sometimes bloody) or constipation. One of the characteristic early signs of thallium poisoning is the staining of urine in green.
Symptoms of gastrointestinal tract damage persist for several days, then respiratory and cardiovascular disorders join them: shortness of breath, cough, tachycardia, arrhythmia, increased blood pressure (less often arterial hypotension), chest pain.
As a result of thallium poisoning, the central nervous system suffers significantly. Neurological disorders are represented by insomnia, postural tremor, muscle pain, ataxia, epileptiform seizures. Painful paresthesia in the extremities is typical, followed by the formation of sluggish paralysis, para- or tetraparesis. Damage to the optic nerve is manifested by double vision, ptosis, decreased vision, strabismus. Possible mental disorders in the form of disorientation, inappropriate behavior, hallucinations.
10-14 days after contact with thallium, hair loss begins, which is diffuse in nature. Skin changes appear (peeling, cracks, plantar and palmar hyperkeratosis, hyperpigmentation) and nail plates (fragility, transverse white lines). With a favorable outcome, neurological disorders persist for a long time, hair loss stops after 1-2 months.
Complications
According to its toxigenic effects, thallium poisoning is comparable to arsenic and lead poisoning. With thallium intoxication, several systems are affected simultaneously, toxic encephalopathy develops, toxic myocardiodystrophy, respiratory and renal insufficiency.
With severe acute intoxication, a comatose state quickly occurs, within 3-10 days the victim may die from paralysis of the respiratory muscles, acute heart failure, brain edema. A dangerous, potentially fatal complication is intestinal bleeding.
Nonfatal complications of thallium intoxication include retinal atrophy, impotence in men and infertility in women, depression, irreversible cognitive decline.
Diagnostics
Diagnosis of thallium poisoning is very difficult due to the lack of clear anamnestic data, the variety and non-specificity of symptoms. Victims need to be examined by a toxicologist, neurologist, gastroenterologist, ophthalmologist, psychiatrist, dermatologist. The following methods are used for lifetime etiological diagnosis:
- Analysis for heavy metals. The thallium content is determined in urine, blood serum by mass spectrometry. Intoxication is diagnosed when the reference values are exceeded: >0.72 mcg / l in blood, > 1 mcg / l in urine. At a later date, hair and nails can be used for chemical and toxicological analysis.
- EFI. To study the state of neuromuscular transmission, electroneuromyography is performed, with increased convulsive activity, an EEG may be required. Cardiovascular disorders are recorded using electrocardiography.
- Ophthalmological examination. With the development of optical neuropathy, visometry, ophthalmoscopy, fundus biomicroscopy, electroretinography are performed.
Differential diagnosis
In the course of differential diagnosis , the problem of excluding the following pathologies is solved:
- poisoning with other chemical compounds (lead, mercury, selenium, arsenic);
- polio;
- Guillain-Barre syndrome;
- alimentary polyneuritis (hypovitaminosis B1);
- botulism;
- acute porphyria;
- drug intoxication (isoniazid, phenytoin, etc.).
Treatment
Patients with thallium intoxication are hospitalized in the department of toxicology or ICU. The main stages of treatment include stopping the intake of the toxicant, its excretion from the body, correction of functional disorders. For these purposes , the:
- Detoxification. To remove the poison in the first hours after the diagnosis of poisoning, gastric lavage, intestinal lavage with saline solutions, and laxatives are given. Activated charcoal is prescribed, which adsorbs thallium well. To enhance renal excretion, forced diuresis is performed. In severe poisoning, extracorporeal detoxification methods are used: hemodialysis, hemodiafiltration, hemosorption, plasmapheresis.
- Antidote therapy. Potassium-iron hexacyanoferrate, unithiol, solutions of potassium iodide or sodium are used as an antidote for thallium poisoning. These drugs form poorly soluble compounds with thallium, do not allow it to be absorbed in the intestine and accelerate excretion from the body.
- Support for vital functions. If necessary, correction of cardiovascular and respiratory disorders is carried out. Infusion volemic and inotropic support is carried out, cardiotropic agents, hepatoprotectors are administered. In case of respiratory insufficiency, oxygen therapy is carried out, according to indications – a ventilator.
- Neurotropic therapy. In order to relieve neurological symptoms, B vitamins, a-lipoic acid, microcirculation correctors, anticholinesterase drugs are prescribed. If necessary, analgesics and sedatives are added.
Prognosis and prevention
Severe poisoning with thallium compounds is accompanied by a critical disorder of vital functions (blood circulation, respiration, nervous regulation), often ends fatally and is diagnosed posthumously. The outcome of the event directly depends on the accuracy and speed of diagnosis, the timing of the start of intensive therapy. Mononeuropathies, tremors, asthenia, emotional and cognitive disorders persist in recovered patients for a long time. The victims require long-term neurological treatment and psychological rehabilitation. Prevention of thallium poisoning consists of ensuring industrial safety, combating soil and water pollution, and preventing criminal incidents.