A mass casualty incident (often shortened to MCI) describes an 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, the September 11 attacks in 2001, and the Boston Marathon bombing in 2013 are well-publicized examples of mass casualty incidents. The most common types of MCIs are generally caused by terrorism, mass-transportation accidents, fires or natural disasters. A multiple casualty incident is one in which there are multiple casualties. The key difference from a mass casualty incident is that in a multiple casualty incident the resources available are sufficient to manage the needs of the victims. The issue of resource availability is therefore critical to the understanding of these concepts. One crosses over from a multiple to a mass casualty incident when resources are exceeded and the systems are overwhelmed.
A mass casualty incident will usually be declared by the first arriving unit at the scene of the incident, and less usually by an emergency call dispatcher, depending on the information that is provided by emergency units. 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]
After the proper agencies have arrived, a more detailed assessment of the scene will be performed using the M.E.T.H.A.N.E method, which summarizes information necessary for responders:
There are multiple agencies involved in most mass casualty incidents, which means there are many individuals that require training for these specific situations. The most common types of agencies and responders are listed below.
Trauma centers play a crucial role in the mass casualty incident timeline.[6] A hospital can receive trauma center status by meeting specific criteria established by the American College of Surgeons (ACS) and passing a site review. Trauma centers have levels ranging from level 1 to level 4, with each level varying in different responsibilities and resources provided:
This is not an exhaustive list of agencies, and many other agencies and groups of people could be involved in a mass casualty incident.[7]
Ideally, once an MCI has been declared, a well-coordinated flow of events will occur, using three separate phases: triage, treatment, and transportation.
See main article: Triage.
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:
Triage personnel do not conduct treatment, with the exception of:[8]
Generally, a small group of responders, usually the first two or three crews on scene, can complete triage.[8]
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:
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 colored 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.
Some mass casualty incidents require an onsite morgue to await transfer of bodies to a permanent morgue, when they must be removed to access injured victims or to keep them out of public sight and prevent heightening emotions further. They are usually far aside the incident, in an existing building or pitched tent.
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 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.
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.
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 center.
An interim-care center is a temporary treatment center 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 centers, 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 centers fairly quickly if needed using the personnel and resources they have on-hand. These centers 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.
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.[9] 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.[10] 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.
MCEs can include epidemics, chemical emergencies, mass shootings, and natural disasters like weather.[11]
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.[12]