Nerve Agents
INTRODUCTION
Chemical warfare and chemical terrorism both employ certain classes of chemical compounds as weapons of mass destruction to achieve military or political ends. Military medical officers and enlisted medical personnel need to become familiar with the chemistry and toxicology of these compounds to be able to recognize and manage casualties produced by these agents. The growing recognition of the very real battlefield and terrorist threat of the use of chemical-warfare agents has fueled the interest in this subject among both military and civilian health care providers Characteristics of Nerve Agents
Characteristics
Remains in a liquid state
Unless exposed to extreme cold or heat. Extreme heat will cause the liquid to become a vapor
Ranges from very volatile, to little volatility (remains in a liquid or oily state)
Colorless to light brown and odorless
Inhibits the body's enzyme acetylcholinesterase which allows the neurotransmitter acetylcholine, to accumulate at the nerve endings where it causes excessive stimulation of the "target" muscle, gland or organ
Anticholinesterase inhibit the cholinesterase enzymes
Tabun (GA
Sarin (GB)
Soman (GD)
GF
V-agent (VX)
(1) Eyes - primarily G agents
(2) Inhalation - primarily G agents
(3) Skin absorption - primarily V agents
(4) Ingestion - primarily V and thickened G agents
(5) Systemic - combination of two or more routes
(6) Signs and symptoms will depend on the severity of exposure and the route of entry into the body
(a) Significant absorption through the skin requires a period of minutes
(b) The effects may be reduced by quickly removing contaminated clothing and neutralizing liquid nerve agent on the skin
Mild
Exposure to small amounts of vapor usually causes effects in the eyes, nose, and lungs
(1) Difficulty in seeing (dimness of vision due to miosis)
(2) Unexplained frontal headache
(3) Unexplained rhinorrhea (worse than a cold or hay fever)
(4) Tightness in the chest or difficulty in breathing
(5) Excessive flow of saliva (drooling)
(6) Localized sweating at the exposure site
(7) Muscular twitching at exposure site
Severe
All the signs and symptoms of mild exposure as well as
(1) Nausea and vomiting
(2) Confused behavior
(3) Severe muscular twitching and general weakness
(4) Convulsions
(5) Loss of bowel and bladder control
(6) Loss of consciousness
(7) Respiratory failure
(8) Death - usually the result of complete respiratory system failure
(1) Put on your protective mask
(2) Give the alarm
(3) Perform a hasty self-evaluation for signs or symptoms of nerve agent poisoning
(4) Administer antidote if signs and/or symptoms are noted. Use one MARK I Nerve Agent Antidote Kit (NAAK) auto-injector set. Each set includes
(a) Atropine-2 mg (drug of choice)
(b) Pralidoxime Chloride (2-PAMCL) 600 mg; 2 ml
(5) Decontaminate your skin if necessary. Use the M291 decon kit
(6) Put on remaining protective clothing (MOPP level 4)
(7) Seek buddy-aid or medical care
Buddy-aid - Casualty is unable to care for himself
(1) Take immediate steps to protect yourself
(2) Mask the casualty, and if possible have him clear the mask
(3) Place the casualty on his side or in prone position to allow for drainage
(4) Administer 3 MARK I NAAKs
(5) Administer 1 Convulsant Antidote for Nerve Agent (CANA) injector immediately after the third MARK I NAAK. The CANA injector is not part of the MARK I, but is part of the treatment for severe nerve agent poisoning
(6) Secure the used injectors on the casualty's upper left pocket flap of the battle dress overgarment (BDO)
(7) Decontaminate casualty's exposed skin
(8) Evacuate and provide assisted ventilations if necessary
CAUTION: Only medical personnel are allowed to give more than 3 MARK I's.
(9) Additional atropine can be given at 3-5 minutes intervals, until signs of atropinization appear: Heart rate above 90 bpm, diminished bronchial secretions
SUMMARY
The effects of nerve agent poisoning may be prolonged several days to weeks. If treatment is delayed too long, death will occur in most cases. This simply re-emphases the important of both prompt identification of signs and symptoms as well as treatment.