Organophosphate poisoning is an acute intoxication that occurs during inhalation, transdermal or oral ingestion of certain insecticides (carbophos, chlorophos, thiophos) or chemical warfare agents (sarin, soman, VI-gases). Main signs: miosis, pain in the eye area, vomiting, increased sweating, abdominal pain and chest soreness, bradycardia, ataxia, respiratory paralysis, convulsions. Pathology is diagnosed on the basis of anamnesis, clinical picture and information obtained during laboratory examination. Treatment includes cholinolytics, cholinesterase reactivators, symptomatic therapy.
T60.0 Organophosphate and carbamate insecticides
Organophosphate (OP) — fluoroanhydrides of phosphoric or methylphosphonic acid. Poisoning by them accounts for 1-2% of the total number of acute exotoxicoses. The poison is able to penetrate through the skin without damaging it. At high concentrations of xenobiotics, pathological symptoms occur within a few minutes. Organophosphorus compounds sprayed in the air form a persistent cloud located near the surface of the earth, which persists for 4-6 hours. Military toxic substances are capable of holding a toxic concentration for several days. Lethal doses vary greatly depending on the properties of a particular compound.
The absolute majority of cases are associated with violation of safety regulations when processing fields or premises from insects. Organophosphate poisoning occurs when the use of a gas mask is refused, protective suits are insufficiently tight, and the spray is directed at people. Such intoxications are usually mild or moderate, since the dose of the drug obtained is relatively small. Other possible reasons:
- Substance abuse. The peak of occurrence was in the 80-90s of the XX century. Today there is a steady downward trend in the number of such cases. Phosphoric acid derivatives can cause hallucinations and an altered state of consciousness, which up to a certain point makes them in demand among drug addicts.
- Military actions. During military campaigns and terrorist acts, chemical warfare agents can be used: soman, sarin. Poisoning is severe, since persistent forms of OP are used, capable of long-term maintenance of a high concentration. The half—year dose of sarin is 1.7 g, soman is 60 mg.
- Suicide. Attempts to commit suicide with organophosphate compounds are relatively rare, their frequency does not exceed 3-4% of the total number of suicides. As a rule, common insecticides with medium or low toxicity are used: carbophos, chlorophos, bromophos and demufos, so the effectiveness of the method is not too high.
The main pathogenetic mechanism of action of OP is the suppression of cholinesterase activity by 30-80%, disruption of the synthesis and hydrolysis of acetylcholine. Poisoning with organophosphate substances of an extremely severe degree leads to 100% inhibition of the enzyme. There is an accumulation of ACH in synapses, which is accompanied by their overexcitation, disruption of the brain, heart, smooth and striated muscles. Full recovery of the central nervous system occurs after 147 days, the blood system — after 48 days.
The toxicant also has a direct stimulating effect on cholinergic structures, so the severity of intoxication does not always correspond to the amount of blocked cholinesterase. OP also sensitizes the body’s cholinergic receptors to its own HE, which leads to a relapse of symptoms after complete purification from the toxic substance. The latter mechanism involves accelerated release of accumulated acetylcholine, which provokes its excessive accumulation on presynaptic membranes.
Organophosphate poisoning can be subdivided by the name of the toxicant (sarin, carbophos, soman); the ways of poison intake (inhalation, transdermal, oral); the mechanism of occurrence (unintentional defeat, suicide, military actions); the period of intoxication (latent, acute, complications and consequences). In clinical practice , classification by severity is common:
- Easy. No more than 20-30% of cholinesterase is blocked. The leading syndromes are the following: neurotic, myotonic, cardiac, gastrointestinal, respiratory disorders. Occurs during a short stay in an infected area, more often with careless use of household insecticides.
- Medium. The volume of the blocked enzyme varies from 30 to 80%. The main syndromes: psychoneurotic, bronchospastic. There may be signs corresponding to mild intoxication. It occurs during suicide attempts with the use of low-toxic substances or during prolonged stay in an area treated with insecticides.
- Severe and lethal. The basis of the clinical picture is a convulsive-paralytic syndrome. There is a pronounced violation of breathing, hemodynamics. Develops when entering the zone of action of combat gases, oral or inhalation intake of highly toxic OP. It is accompanied by early and late complications.
Organophosphate poisoning is manifested by symptoms of damage to several organs and systems. On the part of the respiratory apparatus, bronchospasm, expiratory dyspnea, cough with the separation of a large amount of sputum, dyspnea, pulmonary edema are noted. Disruption of the gastrointestinal tract leads to vomiting, nausea, cramping abdominal pain, involuntary defecation. Sweat and salivary glands react by increasing secretion – there is salivation, increased sweating.
The defeat of the cardiovascular system is accompanied by bradycardia, weakening of hemodynamics, a transient increase in blood pressure with its subsequent fall. The reaction of the organs of vision consists in the appearance of myosis, anisocoria, spasm of accommodation (the victim loses the ability to see at a great distance). With severe intoxication, sharp weakness, involuntary twitching of isolated muscle groups, paralysis and paresis are determined. Convulsions, depression of consciousness up to coma, signs of suppression of the activity of the respiratory and vasomotor centers are possible.
All complications are divided into early and late. Early ones occur on 1-2 days from the moment of intoxication. Late ones can be diagnosed from 3 to 150-200 days. The first include central respiratory paralysis caused by damage to the corresponding center of the brain, recurrent bronchospasm, acute pneumonia, myocardiodystrophy, intoxication psychosis, nephropathy and hepatopathy with the development of multiple organ failure. The incidence of early complications is about 5-7%.
In the later stages, peripheral paralysis of the respiratory muscles, toxic encephalopathy, polyneuritis, asthenovegetative syndrome may form. In some patients, persistent paresis and hemiparesis of the extremities, nerve damage accompanied by impaired function of internal organs, fecal incontinence, urine are determined. A relapse of the clinical picture of intoxication is also possible. Organophosphate poisoning is complicated by late pathological phenomena in 3-4% of cases.
The basis of diagnosis is the clinical picture and anamnesis of the patient. The diagnosis is made by an ambulance doctor or a toxicologist of a specialized center (with the independent treatment of the victim). Consultations of a gastroenterologist, neurologist and other specialists are required. Pathology is differentiated with drug poisoning, neurotoxic poisons, substances capable of affecting the activity of cholinesterase (ovulation inhibitors, muscle relaxants, arsenic, glucocorticosteroids). Survey methods:
- Physical. There is confusion, lethargy, coma. On examination — cyanosis or pallor of the skin, spontaneous twitching of individual muscle groups or clonic-tonic convulsions. Blood pressure is higher or lower than normal, breathing is difficult, pulse is reduced. With auscultation of the lungs, wet wheezing can be heard, there is a productive cough.
- Laboratory. The color change of the indicator during a laboratory test is 22-40 minutes. There is a shift in the pH of the blood to the acidic side, a violation of the electrolyte balance. The partial pressure of oxygen is reduced, the carbon dioxide content increases. With kidney damage, urea and creatinine accumulate. Against the background of hepatic pathology, there is an increase in AST, ALT.
- Hardware. They are used mainly for the diagnosis of complications. Pulmonary edema is manifested by flying shadows on the X-ray, with bronchospasm, the volume of forced exhalation is sharply reduced. ECG shows atrial fibrillation, tachycardia caused by direct myocardial damage or hypotension.
Before the arrival of medics, the victim should be evacuated from the chemical contamination zone, laid down, and provided with fresh air. If the toxicant gets on unprotected skin, this area must be wiped with a 10% ammonia solution. Cases of eye damage require washing with 2% sodium bicarbonate followed by instillation of atropine. The consequences of oral use of the poison can be reduced if, immediately after contact with it, the stomach is washed with a probe-free method and activated charcoal is given. The sorbent dose is calculated according to the formula 1 tablet per 10 kg of weight.
First aid is provided by the ambulance brigades. The main measure is the introduction of atropine, which neutralizes the effect of organophosphorus compounds. The drug is administered intravenously, with severe tachycardia – intramuscularly 1 ml of 0.1% solution every 15 minutes. In case of oral intoxication, probe gastric lavage, administration of enterosorbents, infusion of saline agents is carried out. Symptomatic therapy includes anticonvulsants, pressor amines, bronchodilators, diuretics. In case of impaired consciousness and breathing, tracheal intubation is performed, followed by a transfer to a ventilator.
The basis of the therapeutic scheme are cholinesterase reactivators and cholinolytics. Among the latter is atropine. Patients receive it at intervals of 15 minutes. The evaluation criterion for a sufficient amount of antidote therapy is the occurrence of atropine delirium, this may require 20-30 ml of the drug. HE reactivators (isonitrosine, dipiroxime) are used at all stages of poisoning. The scheme is selected individually, depending on the severity of the pathology and the category of the patient (children, adults, old people).
To combat the emerging disorders, the patient receives symptomatic treatment. Succinic acid preparations, respiratory stimulants, antidepressants, neuroleptics, antioxidants, anticonvulsant medications, calcium channel blockers are prescribed. For accelerated removal of xenobiotics, the method of forced diuresis and intestinal stimulation (saline laxatives) is used. If necessary, resuscitation is provided (intubation, ventilator, hemodialysis, titrated dopamine administration, monitoring).
After discharge, the patient is prescribed outpatient follow-up treatment. He should carefully monitor his condition, regularly visit a general practitioner or therapist. Medical support includes the use of nootropics, antipsychotic and cardiac drugs. It is recommended to visit health resorts located in coniferous forests. In the presence of paresis, observation of a neurologist, taking medications that improve neuromuscular conduction, physical therapy is required.
Prognosis and prevention
Full recovery takes about two hundred days. During this period, delayed complications may occur. The time of hospitalization of patients with mild and moderate lesions usually does not exceed 10-15 days. The duration of inpatient treatment of severe victims depends on the course of the somatic stage of exotoxicosis and the regenerative capabilities of the body. The mortality rate is 12.9%. The main cause of deaths is paralysis of the respiratory center, untimely medical care.
To prevent organophosphate poisoning, it is necessary to strictly comply with safety requirements. When working with pesticides and herbicides, insulating gas masks are used, clothing that does not allow the toxicant to get on the skin. Soldiers taking part in combat operations must be trained in chemical hazard recognition skills and provided with protective equipment. At home, OP should be stored in closed rooms, where children and people with unstable mentality do not have access.