Strategies for medical response to mass chemical exposure handout


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Summary of preparatory reading for MUHC ED Disaster Preparedness Course for Residents

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Strategies for medical response to mass chemical exposure handout

  1. 1. Adapted from Kirk MA, and Deaton ML, Bringing Order Out of Chaos: Effective Strategies for Medical Response to Mass Chemical Exposure, Emerg Med Clin N Am 25 (2007) 527–548 Strategies for Medical Response to Mass Chemical Exposure See original article for 4 case studies. Common myths about chemical disasters  Myth 1. Hospitals will be notified in advance of arrival of chemically exposed patients.  Myth 2. The offending toxin will be rapidly identified so that on-scene and emergency department care providers will give specific and appropriate treatment.  Myth 3. Dispatchers will send emergency response units to the scene so that trained personnel will triage, treat, and decontaminate victims.  Myth 4. Casualties will be transported by ambulance and they will first transport the most serious patients already decontaminated. What really happens in a chemical event?  Reality 1. Medical personnel must often “operate in the blind” during the early stages of an event (a.k.a. the silent gap)  Reality 2. The offending chemical may not be identified for hours, or even days.  Reality 3. Emergency response personnel seldom have adequate tools or resources to effectively triage, decontaminate, and treat the large numbers of victims of a large-scale chemical exposure.  Reality 4. The first victims arriving at the hospital often arrive under their own power without direct involvement from emergency response personnel on the scene.  Reality 5. The general public can behave in ways that significantly erode the effectiveness of the emergency medical response. (e.g. mass hysteria, more patients with symptoms of fear and anxiety rather than true chemical exposure) Elements of an effective response strategy  Rapid recognition of situations or clinical presentations suggestive of hazardous chemical exposure or acts of terrorism  Closing the silent gap o Developing a community specific risk assessment to predict the most likely chemicals to be involved in an accident o Using a tiered response strategy o Creating a communications network  Prioritizing care and allocating resources effectively to do the best for the most people Recognition The best disaster plans and protocols will fail if recognition of a suspicious situation is not made early (i.e. when the first ambulatory patients arrive before any warning of the event has reached the ED). Providers can be distracted by multiple patients with traumatic injuries, sudden unconsciousness, or unexplained cardiac arrest, and by the large number of patients. Triage personnel should be trained to recognize high risk situations that could secondarily contaminate the ED by sending patients in without necessary decontamination. Farooq Khan MDCM PGY3 FRCP-EM McGill University November 14 th 2011
  2. 2. Adapted from Kirk MA, and Deaton ML, Bringing Order Out of Chaos: Effective Strategies for Medical Response to Mass Chemical Exposure, Emerg Med Clin N Am 25 (2007) 527–548 Examples:  Victims exhibiting signs and symptoms of specific toxic syndromes (see table 1)  Industrial accidents, fires, or explosions  Transportation accidents  Agricultural accidents  Clandestine drug laboratory accidents  Sudden onset of illness in large groups of people from crowed areas (especially government, political, or religious places)  Victims noticing chemical odor or vapor cloud Closing the silent gap Community-specific risk assessment Knowing the high-risk chemicals in a community can direct emergency response planning and training efforts by providing advance knowledge of their unique characteristics, clinical effects, and therapies.  Identifying agents stored, used and manufactured in the local community: o Agricultural manufacturing; petroleum refining; industrial chemical manufacturing; electric, light, and power production; and paper mills are among the most prone to hazardous chemical events through errors and accidents o Consider which chemicals are carried in mass quantities on transportation pathways by highway, rail or waterway in or close to the community  Focus on chemicals with largest potential to cause toxicity to high numbers of people, i.e. those that are: o Inherently toxic o Easily airborne o Available in large enough quantities to deliver dangerous concentrations to nearby populations Tiered Response strategy 1. Initial patient assessment: Identify the toxic syndrome(s) present in the victims (See table 1). 2. Staff protection: based on the toxic syndrome(s) identified, medical personnel refer to ‘‘just in time’’ training to guide efforts at personal protection and decontamination of staff and victims. 3. Empiric treatment and antidote administration: the knowledge of the toxic syndrome immediately identifies the most appropriate treatment options including time urgent and life-saving antidotes (e.g. Mark-1 kits, cyanide antidotes). 4. Confirmation of causative chemicals: the toxic syndrome narrows down the list of potential causative chemicals allowing selective and efficient confirmatory lab testing to identify specific agents while waiting for scene analyses and factual details of the incident to corroborate. 5. Chemical-specific therapies: once specific causative agents are identified, administer any chemical-specific therapies that might be needed and make more informed decisions about patient disposition. Communications network  Police, fire departments, self-defense forces, poison information centers, and hospitals need to form an information network.  The regional poison centers’ abilities to acquire and disseminate information in a crisis makes it a critical information resource in the communications network,  Responders and health care providers at all levels must be able to readily exchange information. This requires a common language with which to describe events as they unfold
  3. 3. Adapted from Kirk MA, and Deaton ML, Bringing Order Out of Chaos: Effective Strategies for Medical Response to Mass Chemical Exposure, Emerg Med Clin N Am 25 (2007) 527–548 Prioritizing care and resource allocation – “Doing the best for the most” 1. Decontamination  Prevent further harm to the patient o Decrease contact time and concentration of agent o Rapidly remove clothing and copiously irrigate contaminated skin and eyes  Minimize secondary contamination of personnel and existing patients 2. Immediate life-saving care  Focus on critically ill poisoned patients in whom supportive care measures alone will improve the outcome of acute reversible conditions, e.g. o Maintaining a patent airway o Preventing hypoxia o Treating shock 3. Urgent antidote or specialized therapy  Antidotes exist for few chemicals and are often in short supply during mass exposure events, e.g. nerve agents and cyanide  Using toxic syndrome guided decision making, antidotes can be targeted to those critically ill patients that need it most in a time-dependent manner and avoided in patients without clear indications. 4. Psychological needs of patients, families, care providers, media, and the community  The greatest diagnostic challenge for evaluating a patient who has potential poisoning is determining if the patient’s problem is due to direct toxic effects of chemicals.  Several patients will be asymptomatic but fearful of being poisoned and will seek medical care for reassurance. The greatest number of patients seeking care is often asymptomatic, or symptomatic and perceiving poisoning but not experiencing obvious signs or symptoms of poisoning.  Low-level exposure to highly toxic substances can cause nonspecific symptoms similar to those reported for perceived poisoning. During a mass chemical exposure, the diagnosis of fear and anxiety is by exclusion only.  Spread of mass hysteria can be prevented by: o Separating patients into small groups o Removing patients from “line of sight” activities such as the presence of ambulances, fire trucks, television cameras, and workers in protective clothing. These sights and sounds signal that the situation is dangerous and enhance anxiety. o Delivering information and reassurance. o Recognizing and responding to the emotional response (outrage) to risk mostly by listening to patients’ concerns. People need a sense of control, and providing specific actions will give patients some sense of control Toxicology principles applied in clinical decision making during mass chemical exposures 1. Identifying toxic syndrome Can be easily accomplished looking at:  Vital signs  Mental status  Pupil size  Mucous membrane irritation
  4. 4. Adapted from Kirk MA, and Deaton ML, Bringing Order Out of Chaos: Effective Strategies for Medical Response to Mass Chemical Exposure, Emerg Med Clin N Am 25 (2007) 527–548  Lung exam for wheezes or rales  Skin for burns, moisture, and color 2. Route of exposure Inhaled/aerosolized vs absorbed through skin can predict toxicity 3. Dose High concentrations and long duration of exposure lead to worse toxicity, therefore time in toxic environment and distance from areas of highest concentration can aid in triaging patients