It's a beautiful summer afternoon in the city. The streets are bustling with window shoppers,
and diners grab an early bite on the restaurant patios. Families enjoy an outdoor music festival
in the park, while children fly kites nearby. Few observe as a drone appears overhead and descends
towards the unsuspecting crowd. Flying just above their heads, the drone sprays a steady stream of
mist as it quickly passes back and forth. After several minutes of confusion, the drone then
disappears as quickly as it came, and multiple individuals begin to stagger and collapse on the
grass, losing consciousness, while the rest of the crowd runs screaming from the park leaving
behind a few stragglers who stumble and fall to their knees. EMTs and fire fighters soon arrive,
but see no obvious injuries, as from gunshots or an explosion. What's happening? Terrorist
attacks are growing in frequency and complexity worldwide and are a global cause for concern.
In addition to myriad conventional weapons, chemical-warfare agents developed for the
battlefield are increasingly being used against civilians in community settings as well as in
conflict zones. Responders need to understand that these attacks entail unique issues in on-the-scene
safety and require a rapid medical response. Known and suspected chemical-warfare agents
have properties such as high volatility and the rapid onset of incapacitating or lethal effects,
making them particularly attractive weapons for acts of terrorism. The constellations of signs and
symptoms — characteristic of an agent's class — are called toxidromes. Nerve agents, asphyxiants,
and opioids are the three classes of chemical- warfare agents that require urgent identification
in order to administer appropriate antidotes in addition to decontamination and supportive care,
as well as to aid in determining the correct personal protective equipment.
All other known agents are incapacitating and potentially lethal but have no specific
lifesaving antidote, and therefore require urgent decontamination and supportive care.
Understanding of the toxidromes that characterize the various classes of chemical agents,
as well as a familiarity with the patterns of injuries caused by conventional weapons
that might be employed in a multimodal attack, are required for a quick assessment of victims,
and to help provide an efficient and safe response.
Returning to our initial scenario, we demonstrate how first responders use knowledge of toxidromes,
as well as associated training in proper mitigation techniques, to deal with this
chaotic situation. The first responders quickly assess the scene for signs of chemical agents:
this might include more victims than would be expected from a blast or gunfire; multiple victims
with no obvious signs of trauma; or clusters of victims collapsing with similar symptoms.
Since a chemical agent is suspected, the responders initially remain at a safe
distance to thoroughly analyze the scene both upwind, and uphill, as many chemical weapons
are heavier than air and will sink to low-lying areas. Does the agent appear to be in a gas or a
liquid state? Is the threat neutralized, or is the scene still active? Are there other safety
issues such as fire, building collapse, or active combatants? After donning protective gear and
ensuring the scene is secure, the responders quickly establish hot, warm, and cold zones:
the hot zone is the contaminated area, the cold zone is the uncontaminated area,
and the warm zone — between the hot and cold zones — is where decontamination units may be staged.
The responders are then free to assess the victims. The responders find that
the victims all have similar symptoms of decreased mental status and confusion.
Some exhibit a reduced breathing rate, or have stopped breathing altogether, and most present
with pinpoint pupils, all signs of an opioid agent such as the fentanyl derivative carfentanil,
a potentially deadly synthetic opioid 10,000 times the potency of morphine. The responders administer
naloxone and provide emergency care, then move the victims from the park to the warm zone,
where they decontaminate, provide supportive care, and then transport the victims to the hospital.
Knowledge of toxidromes is an essential area of training for all first responders.
Bystanders, including physicians who are not part of the response team,
are advised to stay clear of any active scene involving a chemical
attack so as to avoid both confusion and the danger of becoming victims themselves.
Appropriate training, equipment, and coordination are necessary to protect the health and safety of
both victims and emergency personnel when responding to a toxidrome.