LESSON 3. Chemical weapon agents

Because of the ongoing risk of chemical attack, emergency physicians must be able to care for victims of chemical weapon agents (CWAs). This article reviews the physical properties and general clinical effects of CWAs. It also describes the medical management of victims of CWAs, including the use of personal protective equipment (PPE), victim decontamination, provision of supportive care, and provision of specific antidotal therapy. To illustrate these principles with specific agents, the properties, clinical effects, and medical management of nerve agents and vesicant agents are reviewed briefly.

For excellent patient education resources, visit eMedicine's Bioterrorism and Warfare Center. Also, see eMedicine's patient education articles Chemical Warfare and Personal Protective Equipment.

Risk of exposure to chemical warfare agents

Injury from CWAs may result from industrial accident, military stockpiling, war, or terrorist attack.

Industrial accidents continue to be a significant potential source of exposure to the agents used in chemical weapons. Chemicals such as phosgene, cyanide, anhydrous ammonia, and chlorine are used widely and frequently are transported by industry. The accidental release of a methylisocyanate cloud (composed of phosgene and isocyanate) was implicated in the Bhopal disaster in 1984. These accidents continue today, with nearly 9000 occurring in the United States in 2001 alone.

CWAs first were used in 1915, when the German military released 168 tons of chlorine gas at Ypres, Belgium, killing an estimated 5000 Allied troops. Two years later, the same battlefields saw the first deployment of sulfur mustard. Sulfur mustard was the major cause of chemical casualties in World War I. CWAs have been used in at least 12 conflicts since, including the first Persian Gulf War (Iraq-Iran War). The Iraqi military also used chemical weapons against the Iraqi Kurds during the second Persian Gulf War.

Civilians have also been exposed inadvertently to chemical weapons many years after weapon deployment during war. Approximately 50,000 tons of mustard shells were disposed of in the Baltic Sea following World War I. Since then, numerous fishermen have been burned accidentally while hauling leaking shells aboard boats. Leaking mustard shells also have injured collectors of military memorabilia and children playing in old battlefields.

Although a number of international treaties have banned the development, production, and stockpiling of CWAs, these agents reportedly still are being produced or stockpiled in several countries.

Within the last decade, terrorists deployed chemical weapons against civilian populations for the first time in history. The release of sarin in Matsumoto, Japan, in June 1994 by the extremist Aum Shinrikyo cult left 7 dead and 280 injured. The following year, in March 1995, the Aum Shinrikyo cult released sarin vapor in the Tokyo subway system during morning rush hour, leaving 12 dead and sending more than 5000 casualties to local hospitals. A derivative of fentanyl was also used against terrorists holding hostages in a Moscow theater in 2002. Because of a lack of antidote available by the responders, more than 120 casualties among the hostages occurred from asphyxiation.

Several characteristics of CWAs lend themselves to terrorist use. Chemical substrates used in CWAs are widely available, and recipes for CWA production may be found on the Internet. CWAs are transported easily and may be delivered by a variety of routes. Chemical agents often are difficult to protect against and quickly incapacitate the intended targets. Most civilian medical communities are inadequately prepared to deal with a chemical terrorist attack

Types of chemical weapon agents

CWAs comprise a diverse group of hazardous substances. Major categories of CWAs include the following:

• Nerve agents (eg, sarin, soman, cyclosarin, tabun, VX)
• Vesicating or blistering agents (eg, mustards, lewisite)
• Respiratory agents (eg, chlorine, phosgene, diphosgene)
• Cyanides
• Antimuscarinic agents (eg, anticholinergic compounds)
• Opioid agents (opioid derivatives)
• Riot control agents (eg, pepper gas, cyanide, CS)
• Vomiting agents (eg, adamsite)

Date: 2015-01-12; view: 1055