Hydrogen sulfide poisoning: symptoms, first aid

Hydrogen sulfide is a colorless gas that has a typical rotten egg smell (although, in fact, it is the opposite: rotten eggs smell of hydrogen sulfide). In large quantities, this gas is poisonous, and hydrogen sulfide poisoning can occur even when 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.

Taking timely measures allows you to 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 highly toxic product. Inhaling it can lead to coma, convulsions, pulmonary edema, and even death. With high levels of gas in the air, death occurs immediately.

Hydrogen sulfide is practically not found in natural conditions: its presence is possible in transit petroleum gases, natural and volcanic gas, in some water layers in dissolved form. The gas is formed during protein decay if the proteins contain sulfur-containing amino acids cysteine and/or methionine. 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, and cesspools.

In most cases, toxic substances are released into the atmosphere during explosions or leaks at oil and gas production wells, earthquakes, and volcanic eruptions. Fatal poisoning is often caused by diving into sewer shafts and collectors.

Fortunately, accidents involving large-scale releases of hydrogen sulfide are rare. The last known major accident was in China in 2008, when a gas leak killed six people and left more than twenty seriously poisoned.

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

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

Causes hydrogen sulfide poisoning

Most often, hydrogen sulfide poisoning occurs during leaks and accidents at work, as well as during work and visits to lowlands, wells, abandoned mines and cellars, collectors, sewers. When a liquid toxic substance is spilled, it quickly evaporates and transforms into a gaseous state. The presence of a gas mask does not protect the organs of vision and respiration in all cases, but only when the concentration of the toxic agent is no more than 0.5-0.6 g / cubic meter. [ 3 ], [ 4 ]

Other possible causes include:

• gas leakage into mines during the development of coal seams, when cavities containing methane and hydrogen sulfide are damaged;
• ignoring safety precautions, failure to use gas masks and respirators in laboratories and in production facilities that carry out work associated with the release of hydrogen sulfide gas;
• violation of the technique of physiotherapy, namely hydrogen sulphide baths;
• living near garbage dumps and landfills, working in landfills.

Risk factors

The risk groups for hydrogen sulfide poisoning include:

• people who have worked in hazardous production conditions for a long time (eight years or more);
• population living near chemical plants, landfills, and treatment facilities;
• miners;
• workers in the sewage treatment, removal and neutralization system in sewerage and non-sewage facilities;
• workers at landfills and waste processing plants;
• chemical laboratory staff;
• specialists in cleaning wells and sewers;
• diggers – explorers of dungeons, shelters, storage facilities, and other underground objects.

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

Pathogenesis

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

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

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

The gas is heavier than air, so when emitted it tends not to rise upwards, but to spread along the surface. It can form explosive mixtures. [ 5 ], [ 6 ]

At the industrial level, hydrogen sulfide is used to obtain sulfur, sulfuric acid, metal sulfides and sulfur-organic compounds, mercaptans, and thiophene. In the medical field, the 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. The victims experience irritation and swelling of the upper respiratory tract, necrotic areas are formed. When inhaling highly concentrated hydrogen sulfide, inhibition of cytochrome C-oxygenase occurs, oxidative phosphorylation processes are disrupted. The content of cellular ATP decreases, and pronounced lactic acidosis increases. The predominant damage affects brain structures, the cardiovascular system, nerve fibers, and skeletal muscles.

The respiratory center is depressed at a toxic substance density of over 500 ppm, which is associated with a failure of neurotransmitter production in the corresponding areas 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 mitochondrial oxidation of the substance. [ 7 ]

Symptoms hydrogen sulfide poisoning

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

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

The second stage is characterized by the development of toxic neurasthenia, which manifests itself in severe exhaustion and emotional instability. The victim complains of severe headaches, neuro-emotional problems. A feeling of aching in the eyeballs (neuroretinitis), increased heart rate, dullness of smell, cough with difficulty breathing, chest pain are characteristic. From the digestive system, heartburn, a feeling of heaviness in the stomach, diarrhea are noted. Signs of dermatitis are possible.

With the development of the third stage of hydrogen sulfide poisoning, the victim develops signs of encephalomyelopathy: memory and attention disorders, dizziness, sudden apathy, hallucinations (sometimes nightmares), and loss of smell. Tactile hallucinations and severe tremors of the upper extremities are characteristic. There is a polyneuropathy syndrome with profound sensitivity disorders (up to complete anesthesia), pain in the arms and legs, and along the nerve trunks when palpated. Distal weakness and diffuse amyotrophy predominate among motor disorders. Vegetative disorders are represented by increased sweating, cyanosis of the arms and legs, and diffuse hyperemic demography. Peripheral vision decreases, visual illusions (figures or dots) occur, the visual field narrows, scotomas and signs of cataracts are noted. The heartbeat slows down, pain in the liver area and dyspepsia appear. Dermatitis becomes similar to eczema. [ 8 ]

First signs

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

In general, when poisoned with hydrogen sulfide, a person initially feels severe weakness in the legs and arms, apathy appears, and appetite is lost.

Possible symptoms include eye irritation, increased lacrimation, deterioration of vision, photophobia, runny nose, and swelling of the face.

With prolonged inhalation of hydrogen sulfide, pulmonary edema may develop, breathing becomes difficult, pain appears behind the breastbone and in the throat. Many people are bothered by coughing, dizziness, and loss of consciousness.

Dyspeptic disorders most often manifest themselves in the form of nausea and vomiting.

The heartbeat quickens, the fingers start to tremble, and the arms and legs start to cramp.

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

In more severe cases, fainting episodes are observed, and when inhaling large doses of toxic gas, a comatose state 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), the course of the pathological process (acute or chronic), 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, the following are distinguished:

• Mild hydrogen sulfide poisoning can occur if you inhale hydrogen sulfide in relatively small quantities over a long period of time. This toxic level often develops in those who live in unfavorable areas and in chemical industry workers. Poisoning is characterized by deterioration of vision and upper respiratory tract disorders. Systemic symptoms are usually barely noticeable or absent altogether.
• Moderate poisoning is possible in laboratory workers in the event of a toxic gas release, as well as in workers in mines and industrial oil production. The defeat is characterized by a sudden deterioration in health followed by the development of a full picture of intoxication.
• A severe degree occurs with intensive release of hydrogen sulfide from storage facilities, when diving into mines and sewer systems. Strong depression of the respiratory system is noted, death occurs quickly. It is often impossible to evacuate victims in a timely manner.

Hydrogen sulphide gas is classified as a third hazard class. The average daily maximum permissible content of it in the area is 0.008 mg per cubic meter, and indoors - 0.01 mg per cubic meter. The first signs of intoxication occur when inhaling a concentration of 0.006 mg/liter for more than four hours.

Acute hydrogen sulfide poisoning occurs when its content in the air is 0.2-0.3 mg/liter. Its presence in quantities greater than 1 mg/liter is fatal, and death occurs immediately after inhalation. Explosive gas content in the air is from 4.5 to 45%.

Chronic hydrogen sulfide poisoning is a toxic process that occurs as a result of prolonged exposure to elevated gas concentrations (exceeding maximum permissible concentrations). The 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 deterioration of mental abilities in more than half of the victims. This complication is associated with a prolonged state of hypoxia and intoxication, which negatively affects brain tissue. The extent of damage depends on the degree of poisoning, the general health of the victim, and the presence of concomitant pathologies.

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

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

In case of mild intoxication (headache, dizziness), medical assistance may not be required; the patient's condition will return 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 mandatory.

After recovery of a patient who has suffered from acute poisoning, a long-term consequence may be vegetative-asthenic syndrome (chronic fatigue syndrome). Memory loss, polyneuritis, and disorders of the extrapyramidal system responsible for the vestibular apparatus are also noted. [ 11 ]

Diagnostics hydrogen sulfide poisoning

The diagnosis is made based on information received from the victim 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 pulled out of a well, cellar, shaft, or collector. The diagnosis must be confirmed by a toxicologist.

In case of severe intoxication of the body, a specific hydrogen sulphide smell may also come from the patient during exhalation. Symptoms typical of poisoning are also present.

The tests include a complete blood count (hypochromic anemia, lymphocytosis with leukopenia, anisocytosis, accelerated ESR, basophilic granularity of erythrocytes) and a biochemical blood test (elevated levels of liver enzymes ALT, AST and alkaline phosphatase, as well as elevated bilirubin levels).

Instrumental diagnostics for hydrogen sulfide poisoning includes the following studies:

• electroencephalography (symptoms of dysfunction of the midbrain structures, imbalance of rhythmic brain activity);
• spirography (reduced vital capacity, forced expiratory volume (1) and Tiffeneau 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);
• general x-ray of the lungs (signs 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 liver parenchyma);
• computed tomography (cerebral atrophy, enlarged ventricular system, small hypodense foci);
• examination of the fundus (hyperemia of the retinal vessels, pallor of the nipples with transformation into atrophy);
• electromyography, electroneuromyography (decreased excitability and nerve conduction).

Instrumental and laboratory diagnostics can be adjusted by the doctor depending on the indications, 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 poisoning with petroleum products, acute cerebrovascular accident, drug overdose, hypertensive encephalopathy, and epilepsy.

Inhalation by other gaseous substances should be excluded by analyzing the clinical symptoms detected.

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

In hypertensive encephalopathy, the anamnesis indicates arterial hypertension and the absence of contact with toxic gases. Damage to the digestive system is not typical.

To exclude a drug-induced state, the patient undergoes a toxic-chemical blood test.

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

• Hydrocarbons commonly cause dyspnea and cough and may cause respiratory distress. Infiltrates may be seen on chest radiograph. CNS depression and myocardial dysfunction may also occur.[ 13 ]
• Cyanide has the same mechanism of action as hydrogen sulfide, and patients may also share some of the same symptoms, including seizures, tachypnea, and coma. Cyanide, however, also more commonly presents with headache, nausea, vomiting, arrhythmia, cyanosis, and renal and hepatic failure. Cyanide typically has an almond-like odor rather than a rotten egg odor.[ 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 hydrogen sulfide poisoning

Treatment for patients with hydrogen sulfide poisoning is prescribed both medicinal and non-medicinal.

Non-drug measures include:

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

Drug therapy includes the following stages:

• 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, and eliminate borderline disorders;
• taking bronchodilators – to eliminate bronchial spasms and improve respiratory function;
• taking mucolytics – to optimize the rheological properties of sputum secretions and improve drainage function;
• taking medications that support and improve the function of the hepatobiliary system - to relieve the symptoms of toxic hepatitis;
• taking proton pump inhibitors and H2 _- antihistamines – if ulcerative-erosive pathological processes are detected in the digestive tract;
• anti-inflammatory therapy – to eliminate polyneuritic symptoms;
• taking systemic antihistamines – to treat dermatological signs of hydrogen sulfide poisoning;
• Iron-containing drugs – to correct hypochromic anemia.

A victim of hydrogen sulfide poisoning is registered with a dispensary with mandatory observation by a neurologist, therapist, and ophthalmologist. Rehabilitation measures are carried out twice a year and include spa treatment, moderate physical activity, physiotherapy, massage, reflexology, and 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.
• They call an ambulance.
• If the organs of vision are affected, the person is taken to a darkened room, and compresses soaked in a solution of baking soda or a 5% solution of boric acid are applied to the eyes. A mixture of "adrenaline-novocaine" can be dripped into each eye.
• If the victim has lost consciousness, it is not recommended to use ammonia solution: chlorine is allowed. It is necessary to monitor the frequency and depth of breathing and heartbeat. If indicated, indirect cardiac massage should be performed.
• The victim should drink plenty of clean water (mineral water is possible) or milk.

First aid for hydrogen sulfide poisoning

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

The antidote to hydrogen sulfide is methemoglobin, so the victim is given a 1% solution of methylene blue in glucose, which promotes 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. Methemoglobin levels should be checked within 30 to 60 minutes after treatment with sodium nitrite. If methemoglobin levels become dangerous, methylene blue may be given. In addition to administering sodium nitrite to treat hydrogen sulfide, there is some evidence that hyperbaric oxygen may 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 of 100% oxygen under a pressure of 1 atm.
2. Intravenous administration of a 1% solution of methylene blue in 25% glucose (Chromosmon).
3. Inhalation administration of amyl nitrite.
4. Further symptomatic treatment with appropriate medications.

Medicines

Detoxification agents:

• Dextrose - 500.0 intravenously by drip, for 10 days. Infusions are carried out with caution in case of impaired renal function.
• Isotonic sodium chloride solution – 150.0 intravenously by drip, for a 10-day course.

Vascular agents:

• Pentoxifylline - intravenous drip 5.0 per 150 ml of isotonic sodium chloride solution, for 10 days. Some patients may experience side effects of the drug in the form of tremors, paresthesia, allergic skin reactions, flushing of the face, tachycardia.

Antioxidant therapy:

• Tocopherol acetate - in capsules of 200 mg orally, 1 piece twice a day, for 10 days. It is recommended to repeat the treatment after 2-3 months.

Secretolytic, stimulating therapy of the respiratory tract:

• Ambroxol - in tablets of 30 mg, 1 piece three times a day, for 10 days. The drug is not prescribed for bronchial motility disorders and increased mucus secretion, severe renal/hepatic insufficiency, 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 tablet twice a day, for 10 days. The drug is not used if the patient has a tendency to develop seizures (except for cases when anticonvulsant treatment is carried out). Theophylline can provoke or worsen 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 course of treatment, the patient may experience drowsiness, dizziness, headache.

Nonsteroidal anti-inflammatory drugs:

• Meloxicam - intramuscularly 15 mg/1.5 ml daily for 10 days. The drug is not prescribed in case of hypersensitivity to it. In case of gastric ulcer, gastritis, renal failure, Meloxicam is prescribed with great caution.

Anxiolytic drugs:

• Tofisopam - in tablets of 50 mg, one tablet twice a day, for 10 days. Prescribed with caution in decompensated chronic respiratory distress, acute respiratory failure, epilepsy, closed-angle 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 1.0 daily for a week.
• Pyridoxine hydrochloride – intramuscularly 1.0 daily for a week.

Proton pump inhibitors:

• Omeprazole - one tablet twice a day for 10 days. The drug can cause minor hypomagnesemia, which manifests itself as increased neuromuscular excitability, tachycardia, increased blood pressure, and arrhythmia.

Prevention

To prevent hydrogen sulfide poisoning during accidents and mass gas emissions, it is recommended to wear a cotton-gauze bandage consisting of ordinary gauze, which is folded in four layers, with cotton wool placed between the layers. There should not be a lot of cotton wool, otherwise it will be difficult to breathe. The bandage is moistened in a 2% soda solution and applied to the face area so that it fits tightly and covers the mouth-nasal area well. The ties should be fixed.

In general, prevention consists of observing safety regulations during work in laboratories, enterprises, and mining mines. Workers in the relevant laboratories and enterprises must always have direct access to respirators, gas masks, and other protective equipment.

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, and seal the window frames with tape;
• Move along the street only across the direction of the wind and, if possible, use transport to leave the polluted area as quickly as possible.

If signs of poisoning are detected, you should see a doctor and not try to treat yourself.

Forecast

Hydrogen sulfide is a very toxic substance that affects the central nervous system. This gas is classified as class three on the scale of potential danger. This information should always be remembered when there is a distinct smell of hydrogen sulfide. However, the most unfavorable aspect is that hydrogen sulfide inhibits the reaction of the olfactory nerve, so a person very quickly stops feeling the unpleasant aroma, although the intoxication process continues and increases.

The lethal air concentration of the substance is 0.1%: with such a 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 noticeable, but severe poisoning manifests itself violently: pulmonary edema, nervous paralysis, convulsions followed by a comatose state are noted. With a low air concentration of hydrogen sulfide, intoxication is not so dangerous, but very uncomfortable: the victim experiences dizziness, headache, nausea. Long-term exposure to small doses of toxic gas leads to chronic headaches, cachexia, periodic fainting, deterioration of vision, photophobia.

Moderate exposure to hydrogen sulfide has a favorable prognosis. Exposure at high doses can result in serious complications and death. There is some evidence that long-term exposure can result in chronic neurocognitive deficits, probably secondary to oxygen deprivation following 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 drug support for the cardiac and respiratory systems, administer vitamin and mineral preparations, and glucose.