CHEMICAL AGENTS
CLINICAL PEARLS AND PITFALLS
Chemical agents may secondarily affect first responders or medical
providers.
Providers must address airway, breathing, and circulation while
decontaminating the patient.
Removal of clothing is a simple and effective first step to
decontamination.
Nerve-agent poisoning can resemble cyanide poisoning in certain
ways, but nerve agents may have cholinergic symptoms.

Current Evidence
Mass casualties can result from the accidental or intentional release of either
traditional chemical warfare agents (CWAs) or toxic industrial chemicals. During
World War I, chemical agents such as chlorine, phosgene, and sulfur mustard
were used on an unprecedented scale. These agents are sometimes referred to as
first-generation chemical warfare agents. The second-generation chemical agents
are the G-series nerve agents, so called because Germany developed them before
and during World War II. After that war, structurally different kinds of nerve
agents were developed and were designated V-series nerve agents; these are thirdgeneration chemical agents. The G- and V-series nerve agents are also called
traditional nerve agents. Nerve agents, along with sulfur mustard, were used by
Iraq against Iran and against Kurdish villages in Iraq during the Iran–Iraq War of
the 1980s. In 1995, religious terrorists released sarin in the Tokyo subway system
and flooded the local medical system with casualties. Tragically, sarin was also
used in the Damascus suburb of Ghouta during the Syrian civil war in 2013,
killing more than 1,400 civilians, and weaponized chlorine has been used in the
same conflict as recently as 2018. Fourth-generation agents (FGAs) are one
category of so-called “nontraditional agents (NTAs)” investigated by certain
countries after the development of VX. Much information about the FGAs (and
other NTAs) remains classified. The FGAs include the A-series agents, or
Novichok compounds, which are low-volatility nerve agents even more persistent

than VX. One of the A agents was used in the 2018 assassination attempt on
Sergei Skripal in Salisbury, UK.


The physical forms of CWAs are dictated by their chemical structures and by
properties such as volatility (speed of evaporation), which is inversely related to
environmental persistence. Nonpersistent agents are gases (such as chlorine and
phosgene) or volatile liquids (such as cyanide and the G-series nerve agents) at
ambient temperatures. Persistent agents, which can be either solids or lowvolatility liquids, include sulfur mustard and the V- and A-series nerve agents and
can pose a high risk of secondary contamination from the environment or from
contaminated casualties. Routes of exposure to CWAs are primarily inhalational
and dermal; ocular, enteral, and parenteral (from contamination of wounds) are
less common. Inhalation is the typical route of exposure for volatile,
nonpersistent agents, although aerosolized liquids and solids, even those of low
volatility, can also be inhaled. Effects following exposure may be local (at or near
the sites of exposure), systemic (at body sites remote from the sites of exposure),
or both. Although CWAs may begin damaging tissue immediately upon exposure,
with inhaled phosgene or dermal exposure to sulfur mustard, VX, or the A-series
NTAs the onset of signs and symptoms may be delayed for several hours or even
longer.
This section of the chapter focuses on the extremely potent nerve agents but
will also detail other categories of toxic CWAs and several industrial chemicals.
General principles of supportive care for poisoned patients are detailed in Chapter
102 Toxicologic Emergencies ; these principles also apply largely to the general
support of CWA victims.

Goals of Treatment
The goals of emergency therapy are prompt recognition of chemical casualties,
immediate decontamination, acute supportive care, and administration of specific
antidotes and other medical countermeasures, as applicable, while protecting

medical providers and hospital infrastructure from secondary contamination.

Clinical Considerations
Clinical Recognition
Chemical attacks can generate large numbers of casualties with a common
exposure history, but the recognition of even isolated cases is important. Perhaps
the most critical emergent decision for ED staff is to distinguish cyanide from
nerve-agent poisoning because the immediate antidotal therapies are quite
different. In both cases victims may present with sudden collapse, coma, and
seizures, with many deaths occurring rapidly. However, nerve-agent casualties
will more likely exhibit miosis, cyanosis, copious oral and nasal secretions,


bronchorrhea, and bronchospasm. In individual cases, clinical differentiation may
be difficult. Further, features of poisoning may be partially obscured by trauma
when chemicals are disseminated explosively; significant numbers of atraumatic
casualties will be more easily recognized as chemical in nature.
Toxidromes—constellations of signs and symptoms suggestive of a specific
class of poison—can be very useful in narrowing differential diagnoses, although
patients may exhibit incomplete or atypical signs and symptoms such as with the
cholinergic toxidrome (for nerve agents). Just as with biologic agents, it is
convenient to categorize chemical weapons exposures as causing predominantly
neurologic, respiratory, or dermatologic syndromes that can help the practitioner
in identifying an offending agent ( Fig. 132.3 ). There are several resources that
will be helpful to ED physicians, including internet-accessible and downloadable
algorithms and related tools (e.g., the CHEMM Intelligent Syndromes Tool, or
CHEMM-IST, at ), local medical
toxicologists, regional poison control centers (1-800-222-1222), and public health
authorities.
Triage Considerations: General Management, Decontamination, and

Personal Protection
Ideally, the general management of chemically contaminated victims begins with
prehospital providers at the scene (“hot zone”), garbed in appropriate personal
protective equipment (PPE), providing extrication, triage, medical stabilization,
and immediate or spot decontamination such as the prompt removal of any
suspicious liquid from a casualty. Patients are then transferred to the “warm
zone,” a receiving area for chemical casualties ( Fig. 132.4 ). The Occupational
Safety & Health Administration (OSHA) designates sites such as a hospital
corridor as the “warm zone.” The warm zone may also be located outside as with
a tent on hospital grounds ( Fig. 132.5 ). The warm zone is separated from the
“cold zone” (beginning no later than the entrance to the ED) by a “hot line,” or
liquid-control zone, beyond which no liquid contamination is permitted to pass.
That is, patients should be thoroughly decontaminated before entering the cold
zone.
Many patients, especially those who are self-referred, may arrive for ED care
having not been decontaminated at the scene. Unstable and contaminated patients
present a particular challenge. For such patients, it is useful to conceptualize the
phases of emergent resuscitation in the warm zone as the ABCDDs: airway,
breathing, circulation, immediate or spot decontamination, and drugs (including
anticonvulsants and antidotes). It is often mistakenly assumed that


decontamination and medical treatment are two separate and sequential
operations. In reality, many chemical casualties will require emergent medical
resuscitation and stabilization before undergoing thorough patient
decontamination, and immediate decontamination is a component of emergent
resuscitation.
A fundamental way in which resuscitation of a chemically contaminated victim
may differ from a victim of a non-HAZMAT scenario is that personnel garbed in
PPE functioning in the warm zone outside of the ED will be challenged to

intervene with advanced life support measures. Here, ABC support will more
likely take the form of airway maneuvers, suctioning, bag-valve-mask (BVM)
ventilation, and chest compressions rather than endotracheal intubation or
establishment of an IV line. These decisions will be influenced by the ability to
ventilate a patient with BVM as well as the specific level of training of the first
receiver. As the ABCs are being attended to in the warm zone, immediate
decontamination in the form of patient disrobing should begin. Simple disrobing
may remove as much as 90% of the contamination hazard to healthcare personnel
but does not obviate the need for more thorough decontamination. Finally, in the
warm zone prior to thorough washing/showering, patients believed to be victims
of severe nerve-agent toxicity may be treated with autoinjector-delivered IM
antidotes. Once stabilization and spot decontamination have been performed,
patients with possible liquid decontamination should undergo thorough
decontamination before entering the cold zone to receive definitive care in a clean
environment. As soon as possible, the treating clinician should conduct a
secondary assessment of the patient.