[Popular Science China]-Acute phosgene poisoning

Acute phosgene poisoning is a systemic disease caused by inhaling a large amount of phosgene in a short period of time, with acute respiratory damage as the main feature. Pulmonary edema is very likely to occur. Phosgene (COCL2) is chemically called carbonyl chloride, which is made by mixing carbon monoxide and chlorine through activated carbon. It is a colorless gas with the smell of moldy hay and rotten apples at room temperature. Its toxicity is 10 times greater than that of chlorine, making it a highly toxic substance.

Causes Phosgene, as an important chemical raw material, is widely used in industries such as fuel manufacturing, metal smelting, pesticides and pharmaceuticals, and fire-fighting equipment. There are opportunities for exposure to phosgene during the production, storage and transportation of phosgene, leakage of phosgene, violation of safety operating procedures by staff, too fast addition of materials, or valve failure causing phosgene to escape, incomplete cleaning of equipment during maintenance, or failure to completely replace it with nitrogen, which can cause phosgene poisoning accidents. In addition, phosgene can be produced when aliphatic chlorocarbons such as carbon tetrachloride, chloroform, and trichloroethylene are burned.

Clinical manifestations Phosgene poisoning incubation period is generally 6 to 15 hours, but can be as short as 2 hours or even shorter. The impact of phosgene on the human body is mainly manifested as acute poisoning, and the clinical manifestations are divided into four stages.

1. Stimulation period

In the early stages of inhaling phosgene, symptoms of eye and upper respiratory tract irritation may appear, such as tearing, itchy throat, coughing, chest tightness, shortness of breath, etc., and may also cause dizziness, headache, nausea, etc.

2. Symptom remission period

After inhaling phosgene, there is generally a symptom relief period of 3 to 24 hours, during which time the symptoms of the irritation period may be alleviated or disappear, but lung lesions are still developing.

3. Pulmonary edema stage

Lung lesions gradually develop into pulmonary edema, which may cause fever, dizziness, irritability, chest tightness, shortness of breath, difficulty breathing, cyanosis, cough, coughing up pink foamy sputum, and even shock and death.

4. Recovery period

After active treatment, pulmonary edema is gradually absorbed and basically recovered after 3 to 4 days. Autonomic dysfunction may occur during the recovery period. Generally, there are no sequelae.

examine

1. Chest X-ray

It is a necessary means to diagnose pulmonary edema in acute phosgene poisoning. Pulmonary edema changes to interstitial pulmonary edema in the early stage, which often appears in the latent period without obvious symptoms. Chest X-rays can show increased lung texture, widened hilar shadows, unclear boundaries, and scattered small dot-like shadows and reticular shadows in both lungs. Different degrees of poisoning will result in different X-ray signs.

2. Arterial blood gas analysis

Decreased arterial oxygen tension with acid-base imbalance.

3. Lung function

There may be obstructive ventilation dysfunction and CO diffusion dysfunction.

4. Electrocardiogram

Severely ill patients may have symptoms of myocardial damage, such as ST segment depression and flat T waves.

5. Peripheral blood and biochemical tests

White blood cells, neutrophils, red blood cells, hemoglobin, etc. can all be elevated.

The diagnosis is based on a clear history of short-term exposure to phosgene, clinical symptoms and signs of acute respiratory damage, chest X-ray manifestations, combined with other examinations such as blood gas analysis, and comprehensive analysis of on-site hygiene survey data. The diagnosis can be made by excluding similar manifestations caused by other respiratory diseases.

Grading Standard:

1. Mild poisoning

Cough, shortness of breath, chest tightness or chest pain, scattered dry or wet rales in the lungs. X-ray chest films show enhanced lung texture or blurred edges. The above manifestations are consistent with bronchitis or peribronchitis.

2. Moderate poisoning

Anyone who has any of the following conditions:

(1) Chest tightness, shortness of breath, cough, sputum, etc., with blood in the sputum, often accompanied by mild cyanosis, dry and wet rales in both lungs, and chest X-rays showing dot-like or small patchy shadows in the middle and lower lung fields. The above symptoms are consistent with acute bronchopneumonia;

(2) Chest tightness, shortness of breath, cough, and sputum are more severe, breath sounds in both lungs are reduced, and there may be no obvious rales. Chest X-ray shows increased lung texture, widened hilar shadows, unclear boundaries, scattered small dot-like shadows and reticular shadows in both lungs, decreased transparency of the lung field, thickening of horizontal fissures, and sometimes bronchial cuff signs or Kirschner B lines. The above manifestations are consistent with acute interstitial pulmonary edema.

Blood gas analysis often shows mild or moderate hypoxemia.

3. Severe poisoning

Anyone who has any of the following conditions:

(1) Obvious dyspnea, cyanosis, frequent coughing, coughing up white or pink foamy sputum, extensive moist rales in both lungs, chest X-ray shows small flakes, cloud-like or cotton-like shadows of varying sizes with blurred edges in both lung fields, which sometimes merge into large flakes or are distributed in a butterfly shape, and blood gas analysis shows PaO2/FiO2≤40kPa (300mmHg). The above manifestations are consistent with diffuse alveolar pulmonary edema or central alveolar pulmonary edema;

(2) The above conditions are more serious, with respiratory rate (>28 times/min) or (and) respiratory distress, chest X-ray shows large fused shadows in both lungs, and blood gas analysis shows PaO2/FiO226.7kPa (200mmHg). The above manifestations are consistent with acute respiratory distress syndrome;

(3) Asphyxiation;

(4) concurrent pneumothorax and mediastinal emphysema;

(5) Severe myocardial damage;

(6) Shock;

(7) Coma.

treat

1. General treatment

Anyone who inhales phosgene should leave the scene quickly to a place with fresh air, take off contaminated clothing immediately, stay quiet, stay in bed and keep warm. They should be closely observed for at least 48 hours, paying attention to changes in pulse, breathing, lung auscultation and other conditions.

2. Oxygen therapy

Early and reasonable oxygen therapy can be used, such as nasal cannula, high-frequency ventilation or hyperbaric oxygen, to correct hypoxemia in a timely manner.

3. Prevent and treat pulmonary edema

Glucocorticoids should be used early, in sufficient doses, and for a short period of time. For patients with severe conditions, shock therapy can be given and fluid infusion can be controlled. Defoaming agents such as dimethyl silicone oil aerosol can be used for inhalation, and attention should be paid to keeping the airway open.

4. Symptomatic treatment

Prevention and treatment of complications: maintain stable blood pressure, adequate fluid replacement, diuresis, correction of acid-base and electrolyte disorders, rational selection of antimicrobial drugs to prevent and treat infection, and immediate mechanical ventilation support treatment when acute respiratory distress syndrome occurs.

prevention

1. The production equipment is sealed and the synthesis device is equipped with an automatic control system to reduce the chance of workers' contact.

2. Strengthen tail gas treatment, reduce waste gas discharged during phosgene production, and prevent environmental pollution.

3. Strictly follow safety operating procedures, take personal protection measures, and equip personal protective equipment.

4. Personnel engaged in phosgene operations should undergo regular health examinations.