injuries poisoning
Overview of Incidents Involving Mass Casualty Weapons
Initial Approach to Mass Casualty Incidents
The approach to a mass-casualty weapon (MCW) incident includes Preparedness Recognition Primary assessment and triage Secondary assessment Treatment These steps often overlap. Recognition, assessment, and treatment may take place simultaneously depending on the nature, number, and severity of the casualties. Prevention, which typically is handled by civil rather than medical agencies, eliminates the need for a medical response. But if prevention fails, preparedness efforts are crucial. Hospitals and prehospital services must have a disaster plan along with appropriate supplies and equipment to respond to an MCW incident. Disaster preparedness activities typically include a hazard vulnerability analysis and protocols to activate and deploy additional staff to specified locations and roles and to allocate resources (eg, beds, operating rooms, blood). Supplies and equipment typically include designated decontamination areas with contained drainage, floor coverings and protective gear to minimize spread of contamination, and stockpiles of antidotes or formal arrangements to obtain them from other sources. Plans typically include requirements for regular formal drills, which although only a distant approximation of an actual mass-casualty incident (MCI), help familiarize staff with the process, including the location of written procedures, supplies, and equipment (particularly those for decontamination). Recognizing MCIs involving explosives, firearms, and transportation crashes is straightforward. However, recognizing covert MCW events requires a high degree of clinical suspicion by first responders and physicians. Health care providers must first recognize that an event or cluster of illness may represent the use of an MCW. They must then determine the type of MCW and class of agent. Recognition of an MCW incident may come via intelligence or announcement by the perpetrators, environmental clues (eg, dead or dying animals, unusual odors), or environmental monitors (chemical, biological, or radiation), which may not be available at every hospital. The only clue may be observations of a large number of people presenting with unusual symptoms. However, initial reports of the identity of the agent or agents used in an MCW incident are often incomplete or in error, and a high index of clinical suspicion is invaluable. As casualties are evaluated, characteristic symptoms and signs may be recognized. Toxidromes (constellations of symptoms and signs that are typical of exposure to a class of agents) exist for several classes of chemical agents and toxins (see table Common Toxic Syndromes ) and are crucial to clinical recognition. Ultimately, laboratory analysis of clinical or environmental specimens may be required. However, diagnosis and initial treatment may need to occur without laboratory confirmation, especially for those chemical agents with short latent periods. Primary assessment and triage of casualties from an MCI differs from normal trauma assessment and triage (see table Triage Classification ). The large number of casualties in an MCI requires initial encounters and decision making to be brief, particularly when casualties involve agents with short latent periods. Triage can be particularly challenging because many patients affected by MCWs have no visible injuries and because many people at or near an MCI who were not exposed to the agent may have stress reactions (eg, hyperventilation, shaking, nausea, weakness) that mimic effects of MCW agents. In some incidents, up to 80% of patients presenting to hospitals had only a stress reaction. Differentiating purely psychologic effects from toxic, infectious, or radiological effects may be difficult. A good first step is to separate patients who are able to walk from those unable to walk; this differentiation will identify the most seriously affected. However, frequent re-triage of ambulatory patients is needed to detect those beginning to deteriorate after a latent period. Classification Explanation Expectant No pulse Not breathing Unlikely to survive given available resources Immediate Life-threatening injury or poisoning Delayed Serious injury or poisoning but not life-threatening Minimal Minor or resolving injury or poisoning Frequent re-triage of ambulatory patients following a mass-casualty incident is needed to detect those beginning to deteriorate after a latent period. Thehot zoneis the area immediately surrounding the release of the MCW agent. Risk of contamination of medical providers is greatest in the hot zone, and normally, only emergency response personnel with appropriate personal protective equipment are allowed into this zone. Such equipment typically includes toxicologic agent protective (TAP) level A gear, which affords full encapsulation with self-contained breathing apparatus. Thewarm zone(decontamination corridor) borders the hot zone. Comprehensive, whole-body decontamination (thorough decontamination) should occur in this zone. Medical personnel may need to don protective gear for primary assessment, triage, and initial treatment of casualties, especially patients exposed to chemicals. This gear typically is TAP B gear, which includes air-purifying respirators. Thecold zone(clean zone) includes hospital emergency departments. Because decontamination should have taken place in the warm zone, medical staff in the cold zone should normally be safe with standard precautions. However, hospitals still need decontamination capability because many patients who bypassed site triage and decontamination (ie, left the scene on their own and self-transported) may arrive. Inadvertent entry of contaminated patients into a hospital emergency department will change its classification to a warm or even a hot zone. Because definitive information is often lacking early in an MCI, initial assessment of the agent involved may be wrong or incomplete. Thus, it is essential to systematically reassess individual patients and the overall situation using a fast, reproducible method. Such a method should use a logical progression that addresses each of the 3 components—agent, environment, and host (patient)—of the epidemiologic triad and that considers (or reconsiders) Possible agent(s) State(s) of the agent(s) in the environment Transition of the agent to the patient (routes of entry or routes of exposure and absorption) Clinical effects of the agent, including whether the effects are local (at or near the entry site), systemic (due to distribution in the bloodstream), or both Temporal progression (duration of exposure, time of exposure, latent period, current trend of symptoms, and prognosis) Differential diagnosis and concurrent exposures or conditions Possible interactions among concurrent exposures or conditions A useful acronym to facilitate rapid secondary assessment is ASBESTOS (see table ASBESTOS*: Secondary Assessment of Mass Casualties Due to Chemical or Radiological Weapons ) ( 1.Madsen JM: Toxins as weapons of mass destruction. A comparison and contrast with biological-warfare and chemical-warfare agents.Clin Lab Med21(3):593-605, 2001. 