Pulmonary chemical agents

Background

• Ammonia, methyl isocyanate, methyl bromide, hydrochloric acid and chlorine, phosgene
• Common toxic industrial chemicals, transported widely across country
• Can affect central or peripheral airways
  • burning and irritation to epithelial lining causing airway edema or pulmonary edema, hypoxia, and hypotension

Pathophysiology

• Choking agents combine with water in respiratory tract to form acids
• Both chlorine and phosgene react with water in respiratory tract to form hydrochloric acid

Clinical Features

Symptoms dependent on the water solubility of the chemical

• Highly water-soluble
  • Anhydrous, ammonia, Hydrogen chloride, Sulfur dioxide, Formaldehyde
  • Rapidly react with water causing damage to upper airway to vocal cords
  • Direct tissue damage causing bronchiolar/alveolar edema/airway obstruction and laryngospasm
  • Nasopharyngeal and tracheal chemical burns, upper airway obstruction
  • Laryngospasm (can occur immediately upon exposure)
  • Respiratory distress/failure, hypoxia
  • Cough
  • Chest pain
  • Arrhythmias (hydrochloric acid)
• Moderately water-soluble
  • Damage to moderate-sized airways (bronchioles)
  • Bronchospasm and wheezing
• Poorly water-soluble
  • Phosgene, Nitrogen dioxide
  • Inhaled deeply into alveoli
  • Lack of irritation of mucous membranes can cause them to go undetected
  • Respiratory distress, tachypnea, cough, pulmonary edema

Differential Diagnosis

Chemical weapons

• Blister chemical agents (Vesicants)
  • Lewisite (L)
  • Sulfur mustard (H)
  • Phosgene oxime (CX)
• Pulmonary chemical agents (Choking agents)
  • Ammonia toxicity
  • Methyl isocyanate
  • Methyl bromide
  • Hydrochloric acid
  • Chlorine gas
  • Phosgene
• Incendiary agents
  • Agent orange
  • White phosphorus
• Cyanide chemical weapon agents (Blood agents)
  • Prussic acid (AKA hydrogen cyanide, hydrocyanic acid, or formonitrile)
• Nerve Agents (organophosphates)
  • Acetylcholinesterase inhibitors
  • Household and commercial pesticides (diazinon and parathion)
  • G-series (sarin, tabun, soman)
  • V-series (VX)
• Lacrimating or riot-control agents
  • Pepper spray
  • Chloroacetophenone
  • CS

Management

• Decontaminate patient!
  • Liquid phosgene can cause off-gassing with release of toxin from clothes post-exposure
• Do not allow patient to be active as it worsens condition
• Inhaled beta agonists for bronchoconstriction
• Diuretics and corticosteroids not shown to be effective

See Also

• Chemical weapons