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 http://chemm.nlm.nih.gov/chemmist.htm ), 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 ... 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