Methane poisoning is a pathology that occurs when the victim stays for a long time in an area with a gas concentration of more than 7 thousand mg / m3. Clinical manifestations include dizziness, a feeling of lack of air, a sharp headache, tachycardia, discoordination. Daily inhalation of a small volume of hydrocarbon leads to bradycardia, red dermagraphism, and a decrease in blood pressure. There are no severe organic changes. The disease is diagnosed on the basis of anamnesis and clinical picture. Specific treatment – evacuation from an area with a high content of methane, oxygen, symptomatic measures.
Methane poisoning is quite rare. The compound is characterized by low inertia, weakly dissolves in blood plasma, practically has no toxic effect. The symptom complex that occurs when being in an infected space is mainly due to hypoxia. In addition, the substance has extremely weak narcotic activity. Exotoxicosis associated with methane inhalation in 41.96% of cases are caused by accidents at work, in 56.25% — the result of adolescent attempts to achieve a euphoric effect. The risk group is males under 18-20 years of age, employees of mining enterprises of any age.
The number of situations where methane poisoning becomes possible is limited. Since hydrocarbon is lighter than air and quickly evaporates in an open space, this happens only in closed rooms. Inside buildings and mines, the CH4 content varies greatly depending on the height. The maximum amount of gas accumulates under the ceiling, there is practically no gas near the floor. Mine gas lesions occur in the following situations:
- The release of natural methane. The substance accumulates in the internal cavities that are present among the coal seams. When they are opened during the extraction of solid fuel, a sharp increase in the concentration of the toxicant in the air is observed. Immediately after the incident, the amount of CH4 can reach 80-100%, which leads to loss of consciousness after 5-6 breaths. Possible death of the victim.
- Industrial accidents outside the mines. Marsh gas is used in the chemical industry to produce acetylene, prussic acid, and methyl chloride. In case of accidents, the integrity of the storages is violated. If the room is poorly ventilated, there is an accumulation of hydrocarbon with a simultaneous decrease in the concentration of O2 in the surrounding space.
- Anesthesia. Poisoning is detected in adolescents who purposefully inhale gas, trying to achieve narcotic effect. Such intoxications are mild and rarely pose a danger to life. Usually, the symptoms of hypoxia that occur in the victim quickly disappear after the cessation of xenobiotic inhalation.
- Household leakage. CH4, mixed with other components, is used as fuel for gas stoves. If a person intentionally (suicide, crime) or accidentally (forgetfulness in the elderly, the extinction of the burner) leaves the gas pipeline open, the hydrocarbon accumulates inside the room. Household mixtures have a specific smell, so their presence is easily detected.
Methane itself is practically harmless. The negative phenomena that occur when it is inhaled are caused by a lack of oxygen in the surrounding air. The pathogenesis of hypoxia is based on two main links. Initially, a violation of the processes of oxidative phosphorylation develops. This leads to insufficient production of adenosine triphosphate, energy deficiency, weakening of all energy-dependent reactions. Contractures occur, protein synthesis decreases, loss of cellular resting potential.
The second link is the accumulation of lactic acid with the development of acidosis. Glycolysis is blocked, lysosomal enzymes are activated, cell autolysis occurs, and the permeability of cytoplasmic membranes increases. At the macro level, this is manifested by a disorder of the enzymatic apparatus of the body. There are violations of breathing, cardiac activity, and the work of the central nervous system. Shock is possible, which is accompanied by centralization of blood circulation, hemodynamic instability, ischemia of internal organs, brain and myocardium.
Methane poisoning is divided by reasons (industrial, domestic, for the purpose of anesthesia), course (acute and chronic), severity of the lesion (mild, moderate, severe), the presence of complications (complicated by pulmonary edema or organic brain damage, uncomplicated). Another classification option is division by type of poisoning effect:
- Hypoxia. It occurs most often. The first signs occur when the concentration of O2 decreases by 25-30%, the proportion of methane is not decisive. Experiments conducted by the St. Petersburg Academy of Sciences back in the XVIII century showed that inhaling a mixture of 80% CH4 and 20% O2 is accompanied only by a headache. Reducing the oxygen content to 10-15% without changing the proportion of marsh gas leads to the development of an oxygen starvation clinic.
- Toxic effect. It is extremely rare. Probably due to hypersensitivity to methane or the individual characteristics of the victims. There have been cases when, when inhaling air containing only 10% of hydrocarbon, signs of acute intoxication, pulmonary edema, kidney damage developed. Subsequently, patients have a long-term neurotic state.
Inhalation of a gas mixture with insufficient oxygen content leads to tachycardia, impaired coordination of movements, and an increase in breathing volume. The victims complain of headache, nausea, cardialgia, weakness. If consciousness is preserved, functional disorders of the nervous system are noted: in 80% of cases – neurasthenia, in 11% — hysteria, in 2.4% — reactive psychosis. On examination, characteristic signs of hypoxia are found: generalized cyanosis, sweating.
In severe poisoning, which is accompanied by prolonged loss of consciousness, the symptom complex expands. The patient has hemorrhages in the ocular sclera, weakening of abdominal reflexes, a change in muscle tone in the direction of its increase or decrease. Insufficient oxygenation of myocardial tissues causes hemodynamic disorders, weakening of coronary activity. Prolonged presence of a person in an area with a high content of methane provokes organic brain damage up to decortication.
In the described cases of the direct toxic effect of hydrocarbon in patients, a sharp increase in body temperature, a pronounced weakening of the heart function was determined. Moist pulmonary wheezing was heard, a cough with foamy sputum was detected. There was oliguria or complete absence of urine associated with the development of renal failure. The other symptoms did not differ from acute hypoxia. Pathological changes were relatively easily stopped. The victims had minor mental abnormalities for 2 months.
Methane poisoning and associated hypoxia lead to organic brain damage. This happens with prolonged oxygen starvation. Cerebral tissues undergo irreversible changes, which affects the subsequent work of the body. Residual phenomena may affect the motor or psychological sphere. Some patients after the restoration of consciousness have paresis and paralysis of the limbs, epileptomorphic syndrome, impaired vision, sense of smell and tactile sensitivity.
Psychological transformations manifest themselves in the form of emotional and volitional impoverishment, mood swings, mental instability, and a decrease in mental abilities. In severe cases, memory loss occurs, the skill of orientation in the environment is lost. Over time, the symptoms of damage to the central nervous system may weaken, but their complete disappearance almost never occurs. The most unfavorable variant of the course of posthypoxic encephalopathy is brain death — irreversible cessation of the activity of the cerebral cortex.
Diagnosis of methane poisoning is carried out by ambulance crews who arrived at the scene. Confirmation of the diagnosis is the task of a toxicologist or resuscitator. Mild lesions do not require hospitalization, the patient is examined and observed by a therapist. If there are persistent symptoms, you may need to consult a cardiologist, neurologist, psychiatrist. The following survey methods are used:
- Physical. The characteristic clinical signs of hypoxia are determined. The pulse is above 90 beats / minute, blood pressure is reduced by 10-20 units from the norm. With severe oxygen starvation, bradycardia may occur, and a drop in blood pressure to critical indicators. Auscultation of the lungs in rare cases allows you to detect wet wheezing, while listening to the heart — deafness of tones. Saturation level is ≤90-93%.
- Hardware. The ECG determines the reduction of RR intervals of less than 1 second. It is possible to develop blockades with the occurrence of arrhythmia. Electroencephalography in comatose patients shows a decrease in intracerebral conduction of the nerve impulse. There is no evidence of cerebral activity during decortication.
- Laboratory. A decrease in the partial pressure of oxygen, an increase in the concentration of carbon dioxide in the blood is revealed. The pH shifts to the acidic side. There is an increase in potassium content, a decrease in sodium ions, and other electrolyte disturbances. There may be an increased accumulation of lactate. Hematocrit >40-48%.
Treatment can be carried out on an outpatient basis or on the basis of a hospital. The choice of method depends on the severity of the lesion. People in an unconscious state or with severe mental disorders need hospitalization. Exotoxification of a mild degree allows you to refuse to place the patient in a medical facility. Only first aid is required.
At the scene of the accident
The victim should be taken out into the fresh air, laid down, a roller or a stand should be placed under his feet so that they are raised by 30-40 °. This will ensure maximum blood flow to vital organs. Embarrassing clothes are unbuttoned. The arrived ambulance team conducts oxygen inhalation through nasal cannulas. In the presence of pulmonary edema, ethyl alcohol is used as a defoamer. Narcotic analgesics are contraindicated. Further therapy is carried out according to indications. It may require the introduction of sedatives, cardiac agents, infusion solutions.
In the hospital
The patient is placed under observation. To eliminate the effects of hypoxia, nootropic drugs are prescribed. If technically possible, 5-7 sessions of hyperbaric oxygenation are performed. Neurotic states are indications for the use of sedatives and hypnotics. In order to correct electrolyte disorders, saline solutions are infused. With severe acidosis, buffers (4% sodium bicarbonate) are used. Peace, fresh air, and proper nutrition are shown.
In intensive care
Resuscitation allowance is required for patients with severe poisoning. In case of respiratory disorders, the patient is intubated and transferred to artificial respiratory support. Edema of the lungs or brain is a reason for the use of loop diuretics, restrictions of the injected fluid. In case of kidney damage, strict control of the water balance, hemodialysis is indicated. Circulatory insufficiency is corrected with the help of cardiotonics, vasopressors. Shock conditions require special anti-shock therapy. Round-the-clock monitoring with the help of an anesthesiological monitor is necessary.
Rehabilitation is recommended after severe and moderate exotoxicosis, if the victim retains certain residual phenomena. With neurasthenia, the patient is prescribed sedative medications for up to six months. It requires taking medications that improve cerebral circulation, the duration of the course can reach 12 months. Neurological phenomena are an indication for sanatorium-resort rehabilitation measures. The patient should be monitored by a neurologist.
Prognosis and prevention
The prognosis of methane poisoning is usually favorable. After evacuation to a zone with a normal oxygen content, consciousness is restored. The risk of developing irreversible consequences increases with prolonged stay indoors with a high concentration of methane. A sharply unfavorable prognosis is noted in patients who have been unconscious for a long time, with diagnosed brain death. In the latter case, the restoration of reason is impossible, the patient is on artificial life support until the exhaustion of internal reserves and death.
To prevent methane poisoning during work in coal mines, insulating and auxiliary respirators, self-rescuers are used. The gas concentration in the working area is checked with the help of special devices. In everyday conditions, it is necessary to monitor the condition of the equipment, the presence of a specific aroma. In order to prevent attempts to drug adolescents with household gas, it is necessary to carry out educational activities, monitor their social circle and interests. If you are prone to the use of psychoactive substances, you may need the help of a child psychologist, a narcologist.