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EMS Mass Casualty Management

Editor: Chadi I. Kahwaji Updated: 10/10/2022 8:02:53 PM


A mass casualty incident (MCI) is defined as “an event that overwhelms the local healthcare system, where the number of casualties vastly exceeds the local resources and capabilities in a short time.” Any MCI can rapidly exhaust available resources for not only the MCI but also the normal day-to-day tasks of the hospital. Each hospital should institute a surge plan in preparation for anticipated, progressive, insidious ("notice" events), and sudden-onset ("no-notice" events) disasters occurring within the community.[1][2][3][4][5] First and foremost, in responding to an MCI, the type of MCI present must be identified. Categories include:

  • Planned (sporting event)
  • Conventional, which usually have some level of recurring frequency (transportation incidents, burn, and severe weather events)
  • Chemical, biological, radiological
  • Nuclear agents from an unintentional or accidental release or act of terrorism
  • Catastrophic health events (nuclear detonation, major explosion, a major hurricane, pandemic influenza, or others).

The keys to successfully managing the chaos of a fast-paced, moving MCI can be delineated with the organization of the 5 “S's”: “scene safety assessment, scene size-up, send information, scene set-up, and START (Simple Triage and Rapid Treatment).”

Clinical Significance

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Clinical Significance

Activation of an MCI

Those deemed capable of declaring an MCI activation may differ amongst different county and state protocols within the United States. However, it is fairly universal that Incident Command and local hospitals have the authority to declare an MCI. Most regions are flexible in this regard, allowing public safety agencies with the jurisdiction of overseeing incident scene management, emergency management services (EMS) personnel who arrive first on the scene, Central Medical Emergency Dispatch, hospitals, and regional council staff to declare MCI to engage immediate, early action.[6][2][7][8][9]

Communications and Incident Management

Flexible, integrated communication and information systems are key to successfully allocating resources and organizing an effective response to an MCI. A command center should be organized and equipped with multiple radios tuned into separate frequencies that are “uninterrupted by a priority scan frequency lock-out,” which is effective. Each scene commander should have headsets, microphones, clipboards, and checklists to provide continuous scene dynamics feedback.

On Scene Control

The extent of an MCI is not solely dependent on the total number of created potential patients but is exacerbated by other complicating factors coined “MCI Multipliers.” MCI Multipliers can range from limited scene accessibility, biohazard contamination, self-deploying responders not equipped or experienced for the current scenario, lack of on-scene or surrounding hospital resources, etc. A.J. Heightman, Editor and Chief of JEMS, developed a table of “Multipliers that Affect MCIs” that should be identified and managed as early as possible in the course of an MCI, and are listed below:

  1. Physical location and access/egress complications
  2. Several access points and distance between exits on a highway
  3. Location, speed, and density of traffic
  4. The weather or roadway conditions
  5. Time of day
  6. Staffing levels
  7. Massive debris field
  8. Other simultaneous incidents drain on available resources.
  9. Location of specialty teams and resources
  10. Ambulances are unfamiliar with a district’s MCI operational procedures
  11. Ambulances from another system arriving on the scene or self-dispatching
  12. Hospital backlogs, closures, or lack of resources or capabilities
  13. Communication coverage gaps or inability to communicate with mutual response resources
  14. Failure to establish incident command, divisions, or groups early enough
  15. Lack of scene vests or identification of triage, treatment, or transportation areas
  16. Late or improper access directions or staging instructions to incoming units
  17. Complicating factors, such as ongoing crashes, gunfire, or explosions

To combat these roadblocks, early-on-scene role establishment is essential.

Hierarchical Approach

Response and management to an MCI are dependent on hierarchy. The Incident Commander of the National Incident Management System Incident Command System controls the operations of the entire MCI. Where available, Interprofessional Regional Medical Coordinating Systems meet to coordinate patient transfers during patient surges when the nearest facilities' demands exceed their resources. Regional Medical Coordinating Systems coordinate hospital resources based on the number of emergent and non-emergent patient surges each surrounding facility can accommodate.

Once on the scene, the EMS Branch Director or the Incident Command oversees all on-scene operations (safety, scene size-up, communications, and so forth), which should be established early. While law enforcement is responsible for maintaining the security of the scene, the Safety Officer is responsible for assessing current and potential hazards and maintaining responding crews’ safety. The radio officer works directly with the incident command to provide frequently updated scene reports and coordinate communications with the transportation officer to local hospitals to assess their ability to accommodate their ongoing needs. The Medical Supervisor must oversee and coordinate the scene's triage, treatment, and transport sectors; they are responsible for creating patient flow and managing patient resource allocation. The Triage Officer coordinates patient flow to the transportation area based on the clinical condition designated by the triage team. They are in charge of performing a final scene sweep to ensure no patient who has been rescued has been left without being triaged. The Treatment Officer establishes the treatment zone and allocates supplies. They are responsible for anticipating resource needs and updating the Transportation Officer on the number of “green, yellow, red, and black” triage designations and when those numbers change based on patients’ worsening clinical conditions. The Transportation Officer is responsible for patient tracking, transportation, assistance from local responding units, directions, and hospital designations based on resource availability and needs.

Mutual aid ambulance services, first responder units, and EMS personnel provide transportation and evacuation of MCI patients as dispatched per the established regional policy and communications center. Individual EMS personnel are prohibited from self-dispatching to the scene. The first available responder squad on the scene should be responsible for gauging the extent of the catastrophe, providing a scene report, and alerting nearby hospitals to determine resource and bed availability at those facilities. To quickly and efficiently gauge the extent of the MCI, the Massachusetts Department of Public Health recommends employing the “METHANE” mnemonic, and is as follows:

  • M: Major incident declaration
  • E: Exact location; the precise location of the incident, staging area, if applicable
  • Type of incident: the nature of the incident, including how many vehicles, buildings, and so forth are involved
  • H: Hazards, both present and potential
  • A: Access; best route for emergency services to access the site or obstructions and bottlenecks to avoid
  • N: Numbers of casualties, dead and injured, on the scene
  • E: Emergency services; which services are already on scene and which are still required (Mass Casualty Incident trailer, Regional EMS Council staff, Task Force, and so forth)

Adapted from the Massachusetts Department of Public Health Emergency Medical Services Mass Casualty Incident Plan.

Scene identification vests should be distributed to the IC, Safety Officer, Staging Officer, Medical Supervisor, Radio Officer, Triage Officer, Treatment Officer, Transportation Officer, and all rescue and responder personnel, branding them in their roles so they can be easily identified by the current on-scene personnel, newly incoming crews, and MCI victims. In the event of a terrorist-based MCI, ballistic tactical vests should be highly considered for distribution.

On the scene, determine safe areas that can serve as a staging area, a specialty vehicle loading zone, a triage, and a treatment zone removed from the accident scene or “hot zone,” and secure these areas with a police command. In addition, a region for a morgue that is out of the way but remains easily accessible for temporary body disposal and later removal from the scene should be created. To continuously direct patient triage without necessitating the designation of a worker to remain in the staging area, stage the triage zones with color-coded green, yellow, and red tarps to delineate minor, delayed, and immediate care zones, respectively. This tactic frees up available first responder resources and allows the remaining walking wounded to locate emergency medical personnel.

Specifically, concerning MCIs created by a mass shooting, more than 250 people were killed over 114 years from 1999 to 2013. In response, the American College of Surgeons and the Federal Bureau of Investigation (FBI) in Hartford, Connecticut, gathered to create an efficient set of critical actions to be employed on the scene to maximize the survivability of mass shootings. These critical actions were summarized within the acronym THREAT:

  • T: Threat suppression
  • H: Hemorrhage control
  • RE: Rapid Extrication to safety
  • A: Assessment by medical providers
  • T: Transport to definitive care

Adapted from “Fire/Emergency Medical Services Department Operational Considerations and Guide for Active Shooter and Mass Casualty Incidents.” Federal Emergency Management Agency


The allocation of resources is based on the difficult decisions of patient triage. The START adult algorithm constitutes the basis of MCI triage. In total, there are 4 categories in START: minor (green), delayed (yellow), immediate (red), and expectant (black). All patients should be tracked with START Triage Tags. The color designating the patient’s clinical condition is the color remaining after tearing off the other colors that do not match the patient’s condition. Persons that can be tagged green for “Minor” injuries are known as the “walking wounded”: they have relatively minor injuries, are unlikely to deteriorate over days, and may be able to assist in their care. Those triaged to the “Delayed” category are those with potentially serious and life-threatening injuries. However, these patients should be able to follow simple commands, have a capillary refill under 2 seconds, and have a respiratory rate of under 30 breaths per minute. Their status is not expected to deteriorate significantly over several hours, and transport can be delayed on this basis. Persons triaged in the “Immediate” category require immediate transportation and medical attention within minutes for survival (up to 60 minutes) for compromised airway, breathing, and circulation. These patients meet “Immediate” care criteria if they have respirations over 30 breaths per minute, signs of active hemorrhage, capillary refill over 2 seconds, or have altered mental status in which they cannot follow simple commands. Expectants are those who are dead or inevitably dying and are triaged as “Black.” A jaw thrust maneuver may be implemented to determine if spontaneous respirations resume. If not, palliative medications only should be provided.


Inventory of resources is as paramount as resource allocation. Inventory methods should be adaptable and scalable. Inventory lists can be created on paper or electronic spreadsheets on the scene or in the hospital setting. The Incident Resource Inventory System provided by the Federal Emergency Management Agency at no cost is a standards-based information software tool that “allows users to identify & inventory their resources, consistently with National Incident Management System resource typing definitions, for mutual aid operations based on mission needs and each resource’s capabilities, availability and response time, and share information with other agencies.”



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