Lewisite

In pure form lewisite is a colorless and odorless liquid, but it usually contains small amounts of impurities that give it a brownish color and an odor resembling geranium oil. It is heavier than mustard, poorly soluble in water but soluble in organic solvents. Lewisite is a vesicant (blister agent). It also acts as a systemic poison, causing pulmonary edema, diarrhea, restlessness, weakness, subnormal temperature, and low blood pressure.

In order of severity and appearance of symptoms, it is:

• A blister agent
• A toxic lung irritant, absorbed in tissues, and a systemic poison
• When inhaled in high concentrations, may be fatal in as little as 10 minutes
• On contact, pain and twitching occur instantly.
• Edema of the conjunctiva and lids follow rapidly and close the eye within an hour. Inflammation of the iris usually is evident by this time. After a few hours, the edema of the lids begins to subside, while haziness of the cornea develops.

WARNING! Liquid arsenical vesicants cause severe damage to the eye.

Liquid arsenical vesicants produce more severe lesions of the skin than liquid mustard.

• Stinging pain is felt usually in 10-20 seconds after contact with liquid arsenical vesicants. The pain increases in severity with penetration and in a few minutes becomes a deep, aching pain.
• Contamination of the skin is followed shortly by reddening of the skin, then by blistering, which tends to cover the entire affected area.
• There is deeper injury to the connective tissue and muscle, greater vascular damage, and more severe inflammatory reaction than is exhibited in mustard burns. In large, deep, arsenical vesicant burns, there may be considerable necrosis of tissue, gangrene and sloug

The vapors of arsenical vesicants are so irritating to the respiratory tract that conscious casualties will immediately try to flee the area to avoid the vapor. Severe respiratory injuries are likely and produces a burning sensation followed by profuse nasal secretion and violent sneezing. Exposure causes coughing and production of large quantities of froth mucus.

Injury to respiratory tracts, due to vapor exposure is similar to mustard's, however, edema of the lung is more marked and frequently accompanied by pleural fluid.

An antidote for lewisite is Dimercaprol. This ointment may be applied to skin exposed to lewisite before actual blistering has begun. Some blistering is inevitable in most arsenical vesicant cases.

The treatment of the reddened, blisters and denuded areas is identical with that for similar mustard lesions. Burns severe enough to cause shock and systemic poisoning are life-threatening. Even if the casualty survives the acute effects, the prognosis must be guarded for several weeks.