Hydrogen sulfide poisoning: symptoms, first aid

Hydrogen sulfide is a colorless gas that has a typical rotten egg odor (although the opposite is true: rotten eggs smell like hydrogen sulfide). In large quantities, this gas is poisonous, while hydrogen sulfide poisoning can occur even if it is present in the air at a concentration of 0.2-0.3 mg / l. A concentration exceeding 1 mg / l is considered fatal.

Timely action can cure hydrogen sulfide poisoning, but you need to act quickly and competently, since the gas is very toxic. [1]

Epidemiology

Hydrogen sulfide is considered a very toxic product. Its inhalation can lead to the development of a coma, convulsions, pulmonary edema, and even death. With a high content of gas in the air, death occurs immediately.

Under natural conditions, hydrogen sulfide practically does not occur: its presence is possible in transit oil gases, natural and volcanic gas, and in some water layers in dissolved form. Gas formation occurs during protein putrefaction if the sulfur-containing amino acids cysteine and/or methionine are present in the proteins. Small amounts of the substance may be present in the intestines of animals and humans, as well as in crude oil.

Hydrogen sulfide is heavier than air. For this reason, it can accumulate in mines, sewers, cesspools.

In most cases, the release of toxic substances into the atmosphere occurs during explosions or leaks at oil and gas producing wells, during earthquakes, volcanic eruptions. Fatal poisoning is often obtained by diving into sewer shafts and sewers.

Fortunately, emergencies that are accompanied by a large-scale release of hydrogen sulfide are rare. The last known major accident was in China in 2008, when a gas leak killed six people and more than twenty were seriously poisoned.

If the settlement is located in close proximity to industrial enterprises that use hydrogen sulfide in production, then the population may develop chronic poisoning.

Less than 1% of unintentional cases result in death, while the fatality rate in intentional cases exceeds 50%. [2]

Causes of the hydrogen sulfide poisoning

Most often, hydrogen sulfide poisoning occurs during leaks and accidents at work, as well as during work and visiting lowlands, wells, abandoned mines and cellars, sewers, sewers. When a liquid toxic substance is spilled, rapid evaporation occurs with transformation into a gaseous state. The presence of a gas mask does not protect the organs of vision and breathing in all cases, but only at a concentration of a toxic agent of not more than 0.5-0.6 g / cubic meter. [3], [4]

Other likely causes include:

• the release of gas into mines during the development of coal seams, in case of damage to cavities containing methane and hydrogen sulfide;
• ignoring safety precautions, non-use of gas masks and respirators in laboratories and industries that carry out work associated with the release of hydrogen sulfide gas;
• violation of the technique of physiotherapy, namely, hydrogen sulfide baths;
• living near garbage dumps and landfills, working at landfills.

Risk factors

Risk groups for hydrogen sulfide poisoning include:

• people who work for a long time in conditions of hazardous industries (from eight years or more);
• population living near chemical plants, landfills, treatment facilities;
• miners;
• employees of the system of assinization, removal and neutralization of sewage in sewerage and non-sewer facilities;
• employees of landfills, waste processing plants;
• employees of chemical laboratories;
• specialists in cleaning wells, sewers;
• diggers (diggers) - explorers of dungeons, shelters, storages, and other underground objects.

People who belong to one or another risk group should regularly receive treatment and preventive support in rehabilitation centers, sanatoriums, occupational pathology clinics.

Pathogenesis

Hydrogen sulfide is found in the composition of natural and volcanic gas, and may be present in gaseous industrial waste - in particular, in the waste material that remains after the manufacture of viscose or oil refining. The aqueous solution is represented by hydrosulfide acid.

The formation of toxic gas occurs during the decomposition of proteins, so it is usually part of gas mixtures that fill sewers and sewers, less often basements, landfills.

Laboratory hydrogen sulfide is obtained by direct synthesis and the action of acids on iron and manganese sulfide.

The gas is heavier than air, therefore, during the ejection, it tends not to rise up, but to spread along the surface. May form explosive mixtures. [5], [6]

At the production level, hydrogen sulfide is used to produce sulfur, sulfuric acid, metal sulfides and organic sulfur compounds, mercaptans, thiophene. In the medical field, a gaseous substance is used for physiotherapy in the form of hydrogen sulfide baths: micromolar concentrations help protect cells from necrotic processes and cell death, stimulate antioxidant protection and have an anti-inflammatory effect. Higher concentrations become toxic to cells.

In case of poisoning, local and general toxic effects of hydrogen sulfide are detected. In victims, irritation and swelling of the upper respiratory tract is noted, necrotic-altered areas are formed. When highly concentrated hydrogen sulfide is inhaled, cytochrome C-oxygenase is inhibited, and the processes of oxidative phosphorylation are disrupted. The content of cellular ATP decreases, pronounced lactic acidosis increases. The predominant lesion affects the brain structures, the cardiovascular system, nerve fibers, and skeletal muscles. 

The respiratory center is depressed when the density of the poisonous substance is more than 500 ppm, which is associated with a failure of neurotransmitter production in the corresponding parts of the central nervous system. With the onset of hypoxia, respiratory paralysis develops, which leads to the death of the victim due to acute respiratory failure.

When exposed to low concentrations of hydrogen sulfide less than 30 ppm, the toxic effect is lost and neutralized due to mitochondral oxidation of the substance. [7]

Symptoms of the hydrogen sulfide poisoning

The clinical picture of poisoning largely depends on the stage of intoxication, on the duration and magnitude of contact with hydrogen sulfide.

The first stage is characterized by headaches, dizziness, general weakness and irritability, decreased pain sensitivity. Photophobia, spasm of accommodation, lacrimation, pain in the eyes, conjunctival edema and hyperemia are noted. The heartbeat becomes more frequent, the blood pressure indicators are unstable. The upper respiratory tract suffers: dryness of the nasal mucosa and pharynx appears, the voice becomes hoarse. Local pruritus is possible.

The second stage is characterized by the development of toxic neurasthenia, which is manifested by severe exhaustion and emotional instability. The victim complains of severe pain in the head, neuro-emotional problems. Characterized by a feeling of aching in the eyeballs (neuroretinitis), increased heart rate, dullness of smell, cough with difficulty breathing, chest pain. On the part of the digestive system, heartburn, a feeling of heaviness in the stomach, and diarrhea are noted. Possible signs of dermatitis.

With the development of the third stage of hydrogen sulfide poisoning, the victim develops signs of encephalomyelopathy: impaired memory and attention, dizziness, sudden apathy, hallucinations (sometimes nightmares), sense of smell is lost. Characterized by tactile hallucinations, severe tremor of the upper limbs. There is a syndrome of polyneuropathy with profound sensory disturbances (up to complete anesthesia), pain in the arms and legs, along the nerve trunks during palpation. Distal weakness and diffuse amyotrophy predominate among motility disorders. Autonomic disorders are represented by increased sweating, blue hands and feet, diffuse hyperemic demographism. Peripheral vision decreases, visual illusions (figures or dots) appear, visual fields narrow, scotomas and signs of cataracts are noted. The heartbeat slows down, there are pains in the liver, dyspepsia. Dermatitis becomes similar to eczema. [8]

First signs

Initial manifestations may vary slightly, depending on the volume and concentration of the inhaled gas. [9]

In general, with hydrogen sulfide poisoning, at first a person feels a strong weakness in the legs and arms, apathy appears, and appetite is lost.

There may be pain in the eyes, increased tearing, blurred vision, photophobia, liquid discharge from the nose, swelling on the face.

With prolonged inhalation of hydrogen sulfide, pulmonary edema may develop, breathing becomes difficult, pain behind the sternum and in the throat appears. Many are concerned about coughing, dizziness, impaired consciousness.

Dyspeptic disorders are manifested more often in the form of nausea and vomiting.

The heartbeat becomes more frequent, tremors appear in the fingers, cramps in the arms and legs.

Mental manifestations are expressed in irritability, neurasthenia, increased fatigue, decreased concentration.

In more complex cases, fainting episodes are noted, and when large doses of toxic gas are inhaled, a coma and death occur due to paralysis of the respiratory tract and cardiac arrest. [10]

Forms

Hydrogen sulfide poisoning is divided into different categories and stages - in particular, depending on the causes of intoxication (professional, catastrophic, domestic), on the course of the pathological process (acute or chronic), on the presence of complications (uncomplicated or complicated). The pathogenetic feature of poisoning is also important:

• with dominant damage to the respiratory system;
• with damage to the central nervous system;
• with damage to the cardiovascular system.

Depending on the severity of intoxication, there are:

• Mild hydrogen sulfide poisoning can be obtained if relatively small amounts of hydrogen sulfide are inhaled for a long time. Such a toxic degree often develops among those who live in unfavorable areas, among workers in the chemical industry. Poisoning is characterized by visual impairment, disorders of the upper respiratory tract. Systemic signs are usually subtle or absent.
• Moderate poisoning is possible in laboratory workers in the event of a release of toxic gas, as well as in workers in mines and industrial oil production. The defeat is characterized by a sudden deterioration in well-being, followed by the development of a complete picture of intoxication.
• A severe degree occurs with an intensive release of hydrogen sulfide from storage facilities, when immersed in mines and sewer systems. There is a strong depression of the respiratory system, death occurs quickly. Timely evacuation of the victims is often not possible.

Hydrogen sulfide gas belongs to the third hazard class. The average daily maximum allowable content of it on the ground is 0.008 mg per cubic meter, and indoors - 0.01 mg per cubic meter. The first signs of intoxication occur when a concentration of 0.006 mg/liter is inhaled for more than four hours.

Acute hydrogen sulfide poisoning occurs when its content in the air is 0.2-0.3 mg/liter. The presence in an amount of more than 1 mg / liter is fatal, with a fatal outcome occurring immediately after inhalation. The explosive content of gas in the air is from 4.5 to 45%.

Chronic poisoning with hydrogen sulfide is a toxic process that occurs as a result of prolonged exposure to elevated gas concentrations (in excess of the maximum allowable concentrations). Pathology is characterized by symptoms of damage to the upper respiratory tract, cardiovascular system, digestive system, hematopoietic organs, eyes and skin.

Complications and consequences

Moderate, severe and chronic hydrogen sulfide poisoning can lead to mental impairment in more than half of the victims. This complication is associated with a prolonged state of hypoxia and intoxication, which negatively affects the brain tissue. The scale of damage depends on the degree of poisoning, on the general health of the victim, on the presence of concomitant pathologies.

Approximately 6-7% of patients who have been exposed to the toxic effects of gas develop psychoses and neuroses, and 1.5% of people become disabled due to the appearance of numbness or paralysis of the limbs.

The formation of pathologies of the digestive and cardiovascular systems is not excluded. Relatively often, doctors register myocardial dystrophic processes with the further development of cardiac insufficiency.

With a mild degree of intoxication (pain in the head, dizziness), medical assistance may not be required, the patient's condition returns to normal within 24 hours (in the absence of repeated inhalation of hydrogen sulfide). If the victim is a child or a pregnant woman, then a doctor's consultation is required.

After curing a patient who has undergone an acute form of poisoning, a vegetative-asthenic syndrome (chronic fatigue syndrome) can become a distant consequence. There is also a weakening of memory, polyneuritis, disorders of the extrapyramidal system responsible for the vestibular apparatus. [11]

Diagnostics of the hydrogen sulfide poisoning

Diagnosis is carried out on the basis of information received from the victim himself or from eyewitnesses of the incident. Clarification of the current situation also plays a role: the doctor must examine the place where the patient was found (especially if he was admitted unconscious). Hydrogen sulfide poisoning can be suspected if the victim was removed from a well, cellar, mine, collector. The diagnosis must be confirmed by a specialist toxicologist.

With severe intoxication of the body, a specific hydrogen sulfide odor can also come from the patient during exhalation. There are also symptoms typical of poisoning.

The analyzes are presented by a general blood test (hypochromic anemia, lymphocytosis with leukopenia, anisocytosis, accelerated ESR, basophilic erythrocyte granularity) and a biochemical blood test (increased levels of liver enzymes ALT, AST and alkaline phosphatase, as well as an increased level of bilirubin).

Instrumental diagnostics for hydrogen sulfide poisoning includes the following studies:

• electroencephalography (symptoms of dysfunction of the midbrain structures, imbalance of rhythmic brain activity);
• spirography (decreased vital capacity, forced exit volume (1) and Tiffno index);
• measurement of acid-base balance (decrease in pO2 and increase in pCO2);
• bronchoscopy (catarrhal signs on both sides, atrophic or subatrophic form of endobronchitis);
• overview x-ray of the lungs (phenomena of pneumosclerosis, emphysema, sometimes - the formation of bronchiectasis);
• fibrogastroduodenoscopy (erosive lesion of the digestive tract);
• electrocardiography (signs of myocardial dystrophy);
• echocardiography (signs of myocardial hypokinesia);
• ultrasound examination of the liver (diffuse changes in the hepatic parenchyma);
• computed tomography (phenomena of cerebral atrophy, enlarged ventricular system of the brain, small hypodense foci);
• examination of the fundus (hyperemia of the retinal vessels, pallor of the nipples with transformation into atrophy);
• electromyography, electroneuromyography (reduced excitability and nerve conduction).

Instrumental and laboratory diagnostics can be adjusted by the doctor depending on the indications, on the stage of poisoning and the presence of additional diseases and conditions. [12]

Differential diagnosis

Hydrogen sulfide poisoning should be distinguished from alcohol intoxication, chronic oil poisoning, acute cerebrovascular accident, drug overdose, hypertensive encephalopathy, and epilepsy.

Infection with other gaseous substances should be excluded by analysis of the detected clinical symptoms.

Alcohol intoxication is characterized by an indication of the abuse of alcoholic beverages. During the diagnosis, toxic alcoholic hepatitis, withdrawal symptoms, and hepatic encephalopathy are detected. Gastritis and ulcers of the stomach and duodenum are characteristic.

In case of hypertensive encephalopathy, there is a history of arterial hypertension and lack of contact with toxic gases. The defeat of the digestive system is not typical.

To exclude the narcotic state, the patient performs a toxic-chemical blood test.

When evaluating a patient with hydrogen sulfide poisoning, the following differences should be considered.

• Hydrocarbons commonly cause shortness of breath and cough, and may also cause respiratory distress. Infiltrates can be seen on a chest x-ray. CNS depression and myocardial dysfunction may also occur. [13]
• Cyanide has the same mechanism of action as hydrogen sulfide, and some symptoms may also overlap in patients, including convulsions, tachypnea, and coma. Cyanide, however, is also more commonly associated with headache, nausea, vomiting, arrhythmias, cyanosis, and renal and hepatic failure. Cyanide usually smells like almonds, not rotten eggs. [14]
• Patients with carbon monoxide poisoning and methemoglobinemia may also have headache, shortness of breath, and confusion, but are also more likely to have symptoms of chest pain, nausea, and vomiting. [15], [16]

Treatment of the hydrogen sulfide poisoning

Treatment of patients with hydrogen sulfide poisoning is prescribed both drug and non-drug.

Non-drug measures include:

• appointment of bed or semi-bed rest (depending on the severity of hydrogen sulfide poisoning);
• diet food according to tables No. 5 or No. 15;
• performing breathing exercises to eliminate bronchial stagnation;
• chest massage to optimize regional circulation and improve bronchial function;
• electrophoresis in the form of a galvanic collar according to Shcherbak No. 10 to improve blood circulation and trophism of the brain, reduce the excitability of the cerebral cortex.

Drug therapy includes the following steps:

• detoxification - to protect cells from the negative effects of free radicals and neutralize exogenous toxic substances;
• antioxidant treatment - to stabilize the immune defense and non-specific response of the body;
• anxiolytic treatment - to relieve anxiety, improve sleep quality, eliminate borderline disorders;
• taking bronchodilators - to eliminate bronchospasm, improve respiratory function;
• taking mucolytics - to optimize the rheological properties of sputum, improve drainage function;
• taking drugs that support and improve the function of the hepatobiliary system - to relieve signs of toxic hepatitis;
• taking proton pump inhibitors and H ₂ -antihistamines - if ulcerative-erosive pathological processes are detected in the digestive tract;
• anti-inflammatory therapy - to eliminate polyneuritic symptoms;
• taking systemic antihistamines - for the treatment of dermatological signs of hydrogen sulfide poisoning;
• iron-containing preparations - for the correction of hypochromic anemia.

A victim of hydrogen sulfide poisoning is registered at the dispensary with obligatory supervision by a neuropathologist, therapist, ophthalmologist. Rehabilitation activities are held twice a year and include spa treatment, moderate physical activity, physiotherapy, massage, reflexology, exercise therapy.

First aid for hydrogen sulfide poisoning

• The victim is provided with access to fresh air, the collar and belt are loosened, and if necessary, artificial respiration is performed.
• An ambulance is called.
• If the organs of vision are affected, then the person is taken to a darkened room, lotions soaked in a solution of baking soda or in a 5% solution of boric acid are applied to the eyes. You can drip a mixture of "adrenaline-novocaine" into each eye.
• If the victim has lost consciousness, then it is not recommended to use an ammonia solution: it is allowed to use chlorine. It is necessary to control the frequency and depth of breathing and heartbeat. According to the indications, an indirect heart massage should be performed.
• The victim should drink plenty of pure water (mineral water is possible) or milk.

First aid for hydrogen sulfide poisoning

Treating hydrogen sulfide poisoning at home is not recommended and should be done by a medical professional. Treatment is usually complex and rather complicated, drugs are prescribed depending on the symptoms and severity of intoxication.

Hydrogen sulfide antidote is methemoglobin, so the victim is injected with a 1% solution of methylene blue in glucose, which contributes to the formation of methemoglobin and the subsequent binding of hydrogen sulfide.

Sodium nitrite promotes the conversion of sulfide to sulfmethemoglobin, which is less toxic than sulfide. This drug is most effective if given within minutes of hydrogen sulfide poisoning. After treatment with sodium nitrite, the level of methemoglobin should be checked within 30-60 minutes. If the methemoglobin level becomes dangerous, methylene blue may be given. In addition to administering sodium nitrite to treat hydrogen sulfide, there is some evidence that hyperbaric oxygen can help improve oxygen delivery to organs. Another drug, cobinamide, has shown promise in animal models. [17].  [18]. [19]

In general, first aid is carried out in stages:

1. Inhalation administration of 100% oxygen at a pressure of 1 atm.
2. Intravenous administration of a 1% solution of methylene blue in 25% glucose (Chromosmon drug).
3. Inhalation administration of amyl nitrite.
4. Further symptomatic treatment with appropriate drugs.

Medications

Detoxifiers:

• Dextrose - 500.0 intravenous drip for 10 days. With caution, infusions are carried out with impaired renal function.
• Isotonic sodium chloride solution - 150.0 intravenous drip, a course of 10 days.

Vascular means:

• Pentoxifylline - intravenous drip 5.0 per 150 ml of isotonic sodium chloride solution for 10 days. In some patients, side effects of the drug in the form of tremor, paresthesia, allergic skin reactions, flushing to the skin of the face, and tachycardia are possible.

Antioxidant Therapy:

• Tocopherol acetate - in capsules of 200 mg orally, 1 piece twice a day, for 10 days. Treatment is recommended to be repeated after 2-3 months.

Secretolytic, stimulating airway therapy:

• Ambroxol - in tablets of 30 mg, 1 piece three times a day, for 10 days. The drug is not prescribed for violation of bronchial motility and increased secretion of mucus, with severe renal / hepatic insufficiency, with gastric ulcer and duodenal ulcer.

Bronchodilators:

• Fenoterol hydrobromide or ipratropium bromide 1-2 inhalations three times a day for 10 days. Contraindications: hypertrophic obstructive cardiomyopathy, tachyarrhythmia.
• Theophylline - in tablets of 200 mg, 1 piece twice a day, for 10 days. The drug is not used if the patient has a tendency to develop seizures (an exception is when anticonvulsant treatment is carried out). Theophylline can provoke or aggravate cardiac arrhythmia, which requires additional monitoring by a doctor.

Systemic antihistamines:

• Cetirizine - in tablets of 10 mg, 1 tablet daily for 10 days. During the reception, the patient may experience drowsiness, dizziness, pain in the head.

Non-steroidal anti-inflammatory drugs:

• Meloxicam - intramuscularly at 15 mg / 1.5 ml daily for 10 days. The drug is not prescribed for hypersensitivity to it. With gastric ulcer, gastritis, renal failure, Meloxicam is prescribed with great care.

Anxiolytics:

• Tofisopam - in tablets of 50 mg, one piece twice a day, for 10 days. Prescribed with caution in decompensated chronic respiratory distress, acute respiratory failure, epilepsy, angle-closure glaucoma.

Hepatoprotective agents:

• Ursodeoxycholic acid - 250 mg three times a day for 10 days. At the beginning of treatment, diarrhea may occur, less often - skin itching.

Metabolic agents:

• Thiamine chloride - intramuscularly at 1.0 daily for a week.
• Pyridoxine hydrochloride - intramuscularly at 1.0 daily for a week.

Proton Pump Inhibitors:

• Omeprazole - one tablet twice a day for 10 days. The drug can cause slight hypomagnesemia, which is manifested by an increase in neuromuscular excitability, tachycardia, increased blood pressure, arrhythmia.

Prevention

To prevent hydrogen sulfide poisoning in case of accidents and massive gas emissions, it is recommended to wear a cotton-gauze bandage consisting of ordinary gauze, which is folded into four layers, and cotton wool is placed between the layers. There should not be too much cotton, otherwise it will be difficult to breathe. The bandage is moistened in a 2% soda solution and applied to the face so that it fits snugly and covers the oral-nasal area well. Ties should be fixed.

In general, prevention consists in observing safety regulations during work in laboratories, enterprises, and mining mines. Respirators, gas masks, and other protective equipment should always be readily available to workers in relevant laboratories and facilities.

To reduce the harmful effects of toxic hydrogen sulfide gas on the body in emergency situations:

• close the entrance doors and windows, block the ventilation outlets, hang wet sheets or blankets on the doors, glue the window frames with adhesive tape;
• move along the street only across the direction of the wind and as soon as possible, if possible, use transport to leave the polluted area.

If signs of poisoning are still found, then you need to go to the doctor and not try to be treated on your own.

Forecast

Hydrogen sulfide is a highly toxic substance that affects the central nervous system. This gas belongs to the third class on the scale of potential danger. This information should be remembered whenever there is a feeling of a clear hydrogen sulfide smell. However, the most unfavorable point is that hydrogen sulfide inhibits the reaction of the olfactory nerve, so very quickly a person ceases to feel an unpleasant odor, although the process of intoxication continues and grows.

The lethal air concentration of the substance is 0.1%: with this gas content, death occurs within 10 minutes. Higher concentrations of hydrogen sulfide lead to death almost instantly, it is enough to inhale the toxic substance only once.

Mild intoxication may not be immediately noticed, but severe poisoning manifests itself rapidly: pulmonary edema, nervous paralysis, convulsions, followed by a coma. With a low air concentration of hydrogen sulfide, intoxication is not so dangerous, but very uncomfortable: the victim develops dizziness, headache, and nausea. Prolonged exposure to small doses of toxic gas leads to chronic headaches, cachexia, periodic fainting, visual impairment, and photophobia.

Moderate exposure to hydrogen sulfide has a favorable prognosis. Exposure at high doses can lead to serious complications and death. There is some evidence that long-term exposure can lead to chronic neurocognitive deficits, probably secondary to oxygen deprivation after loss of consciousness. 

Hydrogen sulfide poisoning can be neutralized if timely measures are taken: provide access to fresh air, saturate the respiratory tract with oxygen, provide medical support for the cardiac and respiratory systems, introduce vitamin and mineral preparations, glucose.