Lewisite 2chlorovinyldichloroarsine Vesicants

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Lewisite (2-chlorovinyl-dichloroarsine) Vesicants
A case of dermatitis in loco minoris resistensia
(dermatitis in an area of decreased local
resistance due to previous injury to the skin).
Original chemical believed to be Lewisite agent.
National Institute for Occupational Safety and
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Vesicants / Blistering Agents

• Lewisite

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Overview Lewisite

• Lewisite (2-chlorovinyl-dichloroarsine)
• Colorless, odorless, oily liquid
• Impurities give it a brown to blue-black color
  and the odor of geraniums
• Hydrolyzes rapidly
• Maintaining biologically active concentrations in
  high humidity is difficult

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Overview Toxicity

• Less likely than mustard to be used by terrorists
• Acute toxicity levels not well defined
• Dermal exposure
• 0.05 - 0.1 mg/cm2 produces erythema
• 0.2 mg/cm2 produces vesication
• 30 drops (2.6 mg) can kill an average man
  through systemic toxicity

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Overview Toxicity

• Ocular exposure
• 15-minute exposure to a vapor concentration of 10
  mg/m3 produces conjunctivitis
• Inhalation exposure
• LCt50 is estimated to be about 1500 mg min/m3

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Protective Equipment

• Ordinary clothing and surgical gear offer little
  or no protection
• Respirator, impermeable protective clothing,
  gloves and over-boots are required

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Detection

• Cannot be detected by automated chemical agent
  detectors
• Arsenic forms colored products with reagents
• Draeger tubes available that react with organic
  arsenicals
• Gas-chromatographic techniques can be used for
  identification

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Decontamination

• Efficient and quick -- serious damage occurs
  within minutes
• Skin
• Absorbing powders Fullers earth, talcum powder
• Chemical inactivation
• Efficacy of water is unclear and may spread the
  agent

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Decontamination

• Mucous Membranes and Eyes
• Flush affected mucous membranes immediately with
  water
• Flush eyes with water, saline or isotonic sodium
  bicarbonate

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Signs and Symptoms

• Dependent upon affected areas
• Unlike the mustards, lewisite has no latency
  period and causes immediate pain
• Less severe injuries than those from mustards

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Signs and Symptoms

• Eyes
• Animal tests edema of the lids, conjunctivae,
  and cornea, early meiosis
• Severe exposures
• Involvement of iris and ciliary body
• Depigmentation, atrophy of iris stroma
• Immediate blepharospasm and edema helps prevent
  prolonged exposure

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Signs and Symptoms

• Eyes
• Serious injuries
• Pannus formation, massive necrosis, and blindness
• A 0.001 ml droplet can perforate and destroy the
  eye

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Signs and Symptoms

• Dermal
• Liquid or vapor form burns upon contact
• Erythema within 15-30 minutes
• Painful vesication within a few hours
• Blisters start small and expand to cover entire
  erythematous area
• Taking up to 4 days to occur
• Blister roof contains entire epidermal layer

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Signs and Symptoms

• Dermal
• Liquid exposure
• Pigment changes do not occur and minor lesions
  heal
• Coagulative necrotic lesions
• Large, deep lewisite burns may show necrosis,
  gangrene and slough

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Signs and Symptoms

• Respiratory Tract
• Immediate irritation and congestion from the
  nasal cavity to the lower airways
• Symptoms start with rhinorrhea
• Obstruction caused by airway secretions and
  fragments of necrotic epithelium

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Signs and Symptoms

• Respiratory Tract
• Severe cases
• Pseudomembrane formation and pulmonary edema
• Avoid bronchopneumonia
• Inhaled dose
• Victim dies in a few days
• Pulmonary edema
• Mechanical asphyxia due to obstruction
• Sepsis

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Signs and Symptoms

• Systemic Action
• Liver toxicity and systemic arsenic toxicity
• Lewisite shock
• Result of protein and plasma leakage from the
  capillaries

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Signs and Symptoms

• Systemic Action
• Subnormal body temperature, restlessness,
  hypotension, and T-wave elevations
• Generalized weakness, muscle cramping, and red or
  green colored urine
• Gastrointestinal symptoms

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Treatment

• No specific treatment available
• Arsenic toxicity must be addressed
• Aim of therapy is to relieve symptoms, prevent
  infection, promote healing

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Treatment

• Indications for systemic treatment
• Cough with dyspnea or sign of pulmonary edema
• Skin burn the size of the palm of the hand or
  larger
• Skin contamination covering 5 or more of the
  body surface,
• Immediate damage or where erythema develops over
  the area within 30 minutes

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Treatment

• Dimercaprol is used to chelate arsenic
• Deep, intramuscular injection
• Standard dose 3-5 mg/kg IM every 4 hours for
  four doses
• Reserved for severe exposure exhibiting pulmonary
  edema or shock

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Treatment

• Caveats
• Eyes
• Do not use topical anesthetics or bandages
• Use systemic, narcotic analgesics
• Skin
• Hospitalization for presence of deep, severe
  burns
• Ingestion
• Do not induce vomiting
• Activated charcoal is of no use
• Milk will help hydrolyze the agent

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Long Term Medical Sequelae

• Lacking data from which to predict
• Chronic pulmonary disease and persistence of
  acute, severe injuries to the eye
• Does not appear to be mutagenic, teratogenic, or
  carcinogenic

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Environmental Sequelae

• 7 times less persistent than the mustard agents
  in the environment
• Hydrolyzes rapidly
• Not found in soil
• Lewisite oxide
• Found in the soil demonstrates legacy
  contamination

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Summary

• Less likely than mustards to be used by
  terrorists
• Only military-grade protective gear can prevent
  exposure
• Immediate decontamination is critical
• Signs and symptoms are dependent upon affected
  areas

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Summary

• Pain and physical signs are immediate
• No specific antidote or treatment
• Aim of therapy is to relieve symptoms, prevent
  infection, and promote healing
• Systemic arsenic treated with dimercaprol (BAL)
  chelation