Phosgene

Not to be confused with phosgene oxime (CX)

Background

• Phosgene (carbonyl chloride), chemical formula COCl2, is a colorless gas (at low temperatures, can also exist as a liquid)
• Classically described as having odor of freshly cut hay
• Used as a chemical weapon, and accounted for 80% of deaths from poison gas in WWI
• Currently most frequently used in the industrial setting
  • Used in the manufacture of plastics, dyes, pharmaceuticals and pesticides
• Heavier than air → stays close to ground

Pathophysiology

• Hydrolysis = phosgene reacts with water in the lungs to form hydrochloric acid
  • Likely not clinically significant
• Acylation = causes oxidative damage and depletes glutathione
  • Damages alveolar membrane, increases vascular permeability
  • Leads to noncardiogenic pulmonary edema

Clinical Features

• Due to lower water solubility than other irritant gases (e.g. Chlorine gas), phosgene causes less immediate irritation of the mucous membranes and therefore is able to penetrate to and damage the lower respiratory tract
• Immediate effects (depends on concentration) - mucous membrane irritation, tachypnea, shallow breathing
  • At low concentrations, no immediate symptoms may be noted
• Latent phase length is inversely proportional to inhaled dose
• Delayed effects (depends on total inhaled dose) - respiratory distress, cough, and finally pulmonary edema
  • May take hours to develop

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

Evaluation

• No specific test for exposure - workup should be based on history and sypmtoms. Consider:
  • Laboratory studies (e.g. CBC, CMP, lactate)
  • Chest X-ray
  • ABG

Management

• Supportive care is the mainstay of treatment (no specific antidote exists)
• Use supplemental oxygen only as needed, and then at low concentrations to avoid reactive oxygen species formation
• If intubation required, use ARDS lung-protective strategies

Specific treatment options

Note: Evidence is lacking, and generally based on case reports and expert opinion - consultation with local poison control is recommended

• Corticosteroids
• N-acetylcysteine (IV or nebulized)
• NSAIDS (e.g. Ibuprofen, Colchicine)
• Terbutaline
• Nebulized albuterol

Disposition

• Admit

See Also

• Pulmonary chemical agents