Mass-casualty incident

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Anniston, AL, January 21, 2011: Healthcare workers triage simulated victims during an MCI drill at the Center for Domestic Preparedness.

A mass casualty incident (often shortened to MCI and sometimes called a multiple-casualty incident or multiple-casualty situation) is any incident in which emergency medical services resources, such as personnel and equipment, are overwhelmed by the number and severity of casualties.[1] For example, an incident where a two-person crew is responding to a motor vehicle collision with three severely injured people could be considered a mass casualty incident. The general public more commonly recognizes events such as building collapses, train and bus collisions, plane crashes, earthquakes and other large-scale emergencies as mass casualty incidents. Events such as the Oklahoma City bombing in 1995 and the September 11 attacks in 2001 are well-publicized examples of mass casualty incidents. The most common types of MCIs are generally caused by terrorism, mass-transportation accidents, or natural disasters.


A mass casualty incident will usually be declared by the first arriving unit at the scene of the incident. However, it may alternately be declared by a dispatcher, based on the information available from people who call their local emergency telephone number about the incident. A formal declaration of an MCI is usually made by an officer or chief of the agency in charge. Initially, the senior paramedic at the scene will be in charge of the incident, but as additional resources arrive, a senior officer or chief will take command, usually using an incident command system structure to form a unified command to run all aspects of the incident.[1] In the United States, the Incident Command System is known as the National Incident Management System (NIMS). According to the Federal Emergency Management Agency, "NIMS provides the template for the management of incidents."[2]

Initial size-up[edit]

A size-up needs to be done by the initial person receiving an emergency call regarding a multitude of situations involving a large number of people or potentially involving a large number of people.

Scene size-up[edit]

After the proper agencies have arrived another size-up will be performed with this one involving more detail and following the M.E.T.H.A.N.E method.

M.E.T.H.A.N.E. method[edit]

This method provides an in depth result for the number of responders necessary and it allows for the scene to become clearer for the responders on the exact type of situation they are getting into.

  • Mass incident declared
  • Exact location
  • Type of incident
  • Hazards present
  • Access and egress
  • Number of casualties and severity
  • Emergency services required[3]

Agencies and responders[edit]

There are a throng of agencies involved in most mass casualty incidents which means many individuals that require training for these specific situations. The most common are listed below.

Emergency medical services[edit]

Fire and rescue[edit]

  • Firefighters will perform all initial rescue-related operations, as well as fire suppression and prevention. They may also provide medical care if they are trained and assigned to do so. They may arrive on a fire truck, in their personal vehicles, or from another agency. Many areas near airports will have automatic mutual aid agreements with airport fire departments in the event of a plane crash outside of the airport boundaries.

Public safety[edit]

  • Police officers will secure and control access to the scene, to ensure safety and smooth operations.
  • Utility services will ensure that utilities in the area are turned off as necessary, in order to prevent further injury or damage at the scene.

Specialized teams[edit]

HazMat specialists in Level II/B protection suits carry a patient out of the incident zone to be decontaminated.
  • Specialized rescue teams may be part of the local fire department; they may be associated with the state, provincial, or federal governments; or they may be privately operated teams. These teams are specialists in specific types of rescue, such as urban search and rescue (USAR) or confined space rescue.
  • Hazmat teams are responsible for cleaning up and neutralizing any hazardous materials at the scene. Sometimes these will be specialized CBRNE (chemical, biological, radiological, nuclear and high-yield explosives) teams.
  • National Guard units have medics specifically trained in mass-casualty triage who may be called in to respond to a disaster-related incident.

Public services[edit]

  • Railways and transportation agencies will be notified if an incident involves their tracks or right-of-way, or if they are required to cease operations in and through affected areas. Transportation agencies will provide buses to transport lightly injured people to the hospital. Buses can also provide shelter at the scene (for example, "warming buses") if required.
  • The media play an important role in keeping the general public informed about the incident and in keeping them away from the incident area. However, a Public Information Officer should be assigned as the only designated responder who communicates with the media, to prevent the spread of misinformation.
  • Non-governmental organizations such as St. John Ambulance, the Order of Malta, the Red Cross, the Red Crescent, the Medical Reserve Corps, and the Salvation Army will provide assistance with all aspects of a mass casualty incident, including trained medical staff, vehicles, individual registration and tracking, temporary shelter, food service, and many other important services.


  • Hospitals with emergency departments will have a mass casualty incident protocol which they initiate as soon as they are notified of an MCI in their community. They will have preparations in place to receive a massive number of casualties, like calling in more staff, pulling extra and spare equipment out of storage, and clearing non-acute patients out of the hospital. Some hospitals will send doctors to the scene of the incident to assist with triage, treatment, and transport of injured persons to the hospital.

Trauma centers[edit]

Trauma centers play a crucial role in the mass casualty incident timeline.[4] They are specific hospitals who have voluntarily applied to complete the verification process which is controlled and selected by the pertinent governmental forces and entities. Trauma centers have a multitude of levels ranging from level 1 all the way to level 5. Each level varying in different responsibilities and resources provided.

  • Level 1: level 1 facilities are able to offer complete care to the patients they receive from initial care to seeing the individual’s injury all the way out through rehabilitation.
  • Level 2: level 2 facilities are able to provide almost everything a level 1 facility offers except for tertiary care such as heart surgery.
  • Level 3: level 3 facilities being the next tier down in the trauma center hierarchy gives them the ability to provide prompt assessment of a patients injuries and respond quickly to decide whether they can perform the surgery or need to transport the individual to a level 1 or 2 facility.
  • Level 4: level 4 facilities are capable of performing advanced trauma life support and they are also capable of providing a diagnostics assessment of the individual’s injuries and transport them smoothly to a higher level facility.
  • Level 5: level 5 facilities are the bare minimum in terms of trauma centers but they still serve a vital role in the assessment stage and give the higher level facilities the proper information that they need to react correctly.

This is not an exhaustive list, and many other agencies and groups of people could be involved in a mass casualty incident.[5]


Ideally, once an MCI has been declared, a well-coordinated flow of events will occur, using three separate phases: triage, treatment, and transportation.


In an MCI drill aboard Naval Air Station Oceana, firefighter/EMT Greg Tetro breaks the rear glass of an automobile to rescue a trapped victim.

The first-arriving crew will conduct triage. Pre-hospital emergency triage generally consists of a check for immediate life-threatening concerns, usually lasting no more than one minute per patient. In North America, the START system (simple triage and rapid treatment) is the most common and is considered the easiest to use. Using START, the medical responder assigns each patient to one of four color-coded triage levels, based on their breathing, circulation, and mental status. The triage levels are:

  •   Immediate: Patients who have major life-threatening injuries, but are salvageable given the resources available
  •   Delayed: Patients who have non-life-threatening injuries, but are unable to walk or exhibit an altered mental status
  •   "Walking wounded": Patients who are able to ambulate out of the incident area to a treatment area
  •   Deceased or expectant: Used for victims who are dead, or whose injuries make survival unlikely.

Triage personnel do not conduct treatment, with the exception of:[6]

Generally, a small group of responders, usually the first two or three crews on scene, can complete triage.[6]

When responding to a chemical, biological, or radiological incident, the first-arriving crew must establish safety zones prior to entering the scene.[1] Safety zones include:

  • The hot zone: The contaminated area
  • The warm zone: The area where HazMat specialists will decontaminate patients and fellow responders
  • The cold zone: The safe zone, where any personnel who are not specially trained in HazMat and do not have chemical or biological protection gear must remain at all times. Depending on the contaminant, the cold zone should be roughly 200–300 yards from the incident, uphill and upwind. It should also be at least 50 yards uphill and upwind from the warm zone.

These zones should be clearly identified and with engineer tapes, lights, or cones. All responders and patients must leave the hot zone in designated pathways into the warm zone where they will be decontaminated. A designated officer should be posted at the hot zone and warm zone to make sure all contaminated personal are treated and decontaminated before entering the cold zone.


Once casualties have been triaged, they can be moved to appropriate treatment areas. Unless a patient is green-tagged and ambulatory, litter bearers will have to transport patients from the incident scene to safer treatment areas located nearby. These treatment areas must always be within walking distance, and will be staffed by appropriate numbers of properly certified medical personnel and support people. The litter bearers do not have to be advanced medical personnel; their role is to simply place casualties onto carrying devices and transport them to the appropriate treatment area. Casualties should be transported in order of treatment priority: red-tagged patients first, followed by yellow-tagged, then green-tagged, and finally black-tagged.

Each colored triage category will have its own treatment area. Treatment areas are often defined by coloured tarpaulins, flagging tape, signs, or tents. Upon arrival in the treatment area, the casualties are re-assessed and they are treated with the goal of stabilizing them until they can be transported to hospitals; transported to the morgue or medical examiner's office; or released.

On-site morgue[edit]

Some mass-casualty incidents require an on-site morgue, for several reasons:

  • To await transfer of these victims to a permanent morgue;
  • When the deceased must be removed to access injured victims;
  • To keep the deceased out of public sight and prevent heightening distress, fear, or panic in an already emotionally-charged scene

Most often, on-site morgues are set up on the far side of the incident, is in an enclosed area such as a temporary tent or nearby building.


Ambulance on scene with emergency lights on

The final stage in the pre-hospital management of a mass-casualty incident is the transport of casualties to hospitals for more definitive care. If there the number of ambulances available is inadequate, other vehicles may transport patients, such as police cars, firetrucks, air ambulances, transit buses, or personal vehicles. As with treatment, transport priority is determined based on the severity of the patient's injuries. Usually, the most seriously injured are transported first, with the least serious transported only after all the critical patients have been transported.

However, in an effort to remove as many lightly injured civilians as possible, an incident commander may choose to have those least seriously injured transported to local hospitals or interim-care centers in order to provide more room for emergency personnel to work. It is also possible that lightly-injured casualties will be transported first when access to those who are more severely injured will be delayed due to heavy or difficult rescue efforts.

Definitive care[edit]

The care that is rendered at the scene of an MCI is usually only temporary and is designed to stabilize the casualties until they can receive more definitive care at a hospital or an interim-care centre.

Interim-care centre[edit]

An interim-care centre is a temporary treatment centre which allows for the assessment and treatment of patients until they can either be discharged or transported to a hospital. These are often placed in gymnasiums, schools, arenas, community centres, hotels, and or other locations that can support a field hospital setup. Permanent buildings are preferred to tents as they provide shelter, power, and running water, but many governments maintain complete field hospital setups that can be deployed anywhere within their jurisdiction within 12–24 hours. While full field hospitals require a significant amount of time to deploy (in relation to the length of most incidents), emergency personnel can set up temporary interim-care centres fairly quickly if needed using the personnel and resources they have on-hand. These centres are usually staffed by a combination of doctors, nurses, paramedics/emergency medical technicians, first responders, and social workers (for example, from the Red Cross), who work to get families reunited after a disaster.

Mass casualty event[edit]

Generally, in the healthcare field, the term "mass casualty event" (MCE) is used when hospital resources are overwhelmed by the number or severity of casualties.[7] During these incidents, hospitals can discharge all fit patients, dedicate more resources to the emergency department, and expand their intensive care unit to accommodate anticipated long-term care needs.[8] While up to 80% of victims will be transported from the scene to hospitals, others who are less injured might walk themselves to these facilities and increase the load at the closest facility to the incident.[8]

MCEs can include epidemics, chemical emergencies, mass shootings, and natural disasters like weather.[9]


The final product of an MCI that happens to link up with the M.E.T.H.A.N.E. method is the act of demobilization which is crucial to the entire process. The demobilization process has to be in place from the beginning, once an area has been mobilized. This is critical, as a mass casualty incident can get out of hand quickly. Having everything planned out step-by-step can alleviate these concerns and help cover for the unexpected. The demobilization process also gives the local community and the corresponding agencies an idea for how long their city and specific areas will be consumed with emergency personnel and essentially blocked off. In many events, such as Hurricane Katrina, the demobilization process is not taken into account from the beginning. As a result, the process goes on much longer than necessary, which exacerbates financial costs, and puts a burden on local emergency and law enforcement services to uphold their everyday duties while also maintaining control of the mass casualty incident.[10]

See also[edit]


  1. ^ a b c Mistovich, Joseph J.; Karren, Keith J.; Hafen, Brent (2013). Prehospital Emergency Care. Prentice Hall. ISBN 978-0133369137.
  2. ^ National Incident Management System (PDF) (Report). United States Department of Homeland Security. p. 13. Retrieved January 3, 2016.
  3. ^ "Activating A Mass Casualty Response". DelValle Institute Knowledge Base. Retrieved 1 September 2017.
  4. ^
  5. ^ "Trauma Center Levels Explained". American Trauma Society. Retrieved 1 September 2017.
  6. ^ a b Sanders, Mick J.; McKenna, Kim D.; Lewis, Lawrence L.; Quick, Gary (December 1, 2011). Mosby’s Paramedic Textbook. Jones & Bartlett Publishers. ISBN 9780323072755.
  7. ^ Mattox, Kenneth (2013). Trauma (7th ed.). McGraw-Hill Education. p. 123. ISBN 978-0071663519.
  8. ^ a b Trunkey, Donald (2008). Current Therapy of Trauma and Surgical Critical Care (1st ed.). Philadelphia: Mosby. p. 68. ISBN 978-0-323-04418-9.
  9. ^ Niska RW; Shimizu IM 2011. "Hospital Preparedness for Emergency Response: United States, 2008". National Health Statistics Reports. 37: 1–16. Retrieved February 2, 2016.
  10. ^ "MCI Demobilization". DelValle Institute Knowledge Base. Retrieved 1 September 2017.