EMS Evacuation Triage


Triage is the sorting and categorizing of patients based on clinical severity to maximize the results for the most number of patients when there are limited resources available.  It is a tried and true method that is used in multiple scenarios in multiple practice environments throughout the world.  Most are familiar with the process of triage upon initial arrival of patients to a medical facility or upon arrival to the scene when there are multiple casualties.  Triage in these situations involves using the START method or similar clinically based tool tailored to the individual practice environment such as emergency departments and refined during training events as discussed in separate articles.  Triage, however, does not stop after the first iteration.  It must be continually used and reevaluated during any transition of care or when resources or situations change. 

When patients arrive at a treatment area, they undergo triage as discussed above.  What this article will cover is the process of triage prior to moving patients out from one area of care to another.  This is done to prioritize which patients are to be moved first and determines by what means they are transported based on available resources, acuity of the patients, and treatments or monitoring needed in route; hence the term "evacuation triage."

Issues of Concern

Just as patients undergo triage when entering a medical treatment area, triage of patients is necessary before transferring them to other treatment areas or different facilities.  The same principles necessitating triage upon arrival drive essential components of evacuation triage.  When the needs outstrip resources, triage must be utilized to maximize the results for the number of patients.  There are unique characteristics for evacuation triage that separate it from its counterpart though that must be discussed and well understood prior to implementation.

The first key difference is to understand that providers are not triaging patients to prioritize treatments. Instead, they are triaging to prioritize evacuation.  It is essential to recognize that the patients are already in a treatment area and receiving medical care at this point.  The reasons that would necessitate evacuation include being transferred to receive definitive care, go to a higher level of care with further resources or sub-specialization, or to clear space at the forward treatment area to make room for new patients coming in.

The other significant difference is in recognizing into what categories to triage patients. Evacuation triage does not follow the medical triage designations such as 1-5 of the Emergency Severity Index or the color-coded Red Yellow Green Black methodology of (Jump) START.[1]These emphasize how quickly patients need to be seen, reexamined, or have an intervention. Instead, patients are sorted into categories designating prioritized timelines for evacuation. The US military and NATO partners have been utilizing this method for several decades with great success. There are variations on the theme, and updates to the tools have occurred over the years, but it essentially boils down to “how quickly do we need to move this patient from their current location to the next?”

The 9 Line Medevac of the military is the report and request for resources used once it is determined there is a need to evacuate patients. It has several essential pieces of information that we will discuss further but which merit consideration in all evacuation cases.  Other pieces of information are not applicable to most civilian situations but raise the point that there are often other factors in even the most routine evacuation that should be accounted for prior to execution.

The first portion of evacuation triage is to recognize how many patients there will be to move and by what means they will need transport. Can the patients walk and move on their own? Are they on a backboard? Are they bed bound? These questions help determine what type of vehicle they will fit into and if personnel is needed to help move them.

 The next step in evacuation triage is recognizing how quickly each patient needs removal from the current treatment area.  Patients may be sick, but as long as they are receiving care at the current level, they may be stable enough to hold off evacuation while other patients who are not able to be maintained in the current treatment area obtain transport.

Next, there needs to be synchronization regarding which patient will require removal. What resources will are necessary in route? Will patients require ventilators? Will they require medicine pumps? Will there be special equipment required to move or extricate the patient?

Understanding of all resources available is essential to this portion of evacuation triage.  There may be medical evacuation assets including ambulances and helicopters that are available for normal use in evacuation plans.  These assets should be well known and hopefully rehearsed in their employment by those who will be utilizing them to manage evacuations.  In a triage scenario, these resources are likely overwhelmed or insufficient to handle the volume of patients that need evacuation during a specific period. 

Use of casualty evacuation, discussed in different articles, may not only be necessary but the most appropriate use of resources.  The use of nonstandard evacuation methods can help facilitate the quick movement of a large number of patients; all patients should get matched to a specific resource.  Those requiring medical treatment in route should be prioritized for the medical evacuation vehicles while those who are stable enough to be transported by casualty evacuation can utilize nonstandard forms as discussed.

Each evacuation resource will have an intrinsic number of patients that they can move depending on severity and resources required.  For instance, patients who can sit upright will take up less space in a ground vehicle, and more may be transportable in one trip.  Patients are generally not able to sit up in air ambulances, and air ambulances have inherent limitations on the number of patients that they can carry.  Their use in evacuation triage must give priority for those requiring the most care in route for the most expedient evacuation.

A detailed understanding of the current situation and the environment, along with broad situational awareness is essential to maintain the flow of patients through the evacuation process.  Below is a basic flow that one can use to help visualize the process of evacuation and be aware of where triage is often necessary to help those managing the scene ensure that they are aware of potential bottlenecks and can come up with workarounds to improve flow.

  • Phase 1 – Patients undergo identification in the field. They receive point of care treatment. They can then evacuate to a casualty collection point
  • Phase 2 – CCPs are the first receiving points for groups of patients. They get triaged on arrival and receive further care. CCPs are often temporary and hastily put together in a disaster. Patients will need a transfer for more definitive care
  • Phase 3 – Patients undergo triage for evacuation to a higher level of care. Further planning and resources should begin in this phase. While casualty evacuation was likely all that was available at the point of injury, medical evacuation assets can begin to be utilized and appropriated into the plan.
  • Phase 4 – During an evacuation, multiple inflection points should be utilized to maximize turnaround times. Exchange points and asset release triggers are some of the most common.
  • Phase 5 – After arrival to a higher level of care, patients undergo another triage process for evaluation and treatment. After stabilization, some patients may require additional evacuation, cycling back to Phase 3.

Clinical Significance

Once the determination of the need to evacuate is complete, planning for its implementation must begin in earnest. Ideally, there will have been prepared and rehearsed plans in place already, but every scenario is different and may not proceed as expected. The ability to adapt to the current situation is vital. Having a rehearsed plan, regardless of its fidelity to the real-life condition, sets a baseline from which all providers can branch out.[2]

As can be seen in the evacuation phases, there are multiple transitions of care along with the periods of evacuation.  If one of the legs of evacuation is known to be a prolonged process, it may become necessary to establish exchange points along the route of evacuation.  Ambulance exchange points can work in two general ways.  First, one evacuation asset will move to an established location and then transfer their patients to another waiting evacuation asset before returning to the pickup point.  This method may be most useful in situations such as HAZMAT contamination.[3] The "dirty" ambulance can drop off patients at a decontamination site before further evacuation and then return to the scene faster.  It is perhaps most commonly used when there is a need for air ambulance evacuation, but there is not a suitable helicopter landing zone nearby.  An ambulance may drive to the point that the helicopter can land, exchange patients, and then return to the pickup point of the original scene.[4] Another way to utilize ambulance exchange points is to have evacuation assets that emply release triggers. An asset will wait at one location and then be triggered to go to the point of pickup by either a call for further resources or with known events such as being passed by one ambulance in the process of evacuation. That site can serve as a staging point for evacuation assets without any physical exchange of patients.

As can be seen in the 9 Line Medevac report, there may be multiple issues affecting an evacuation. Communication between sites and moving assets is essential. Appropriate backup communication methods, including being told to go to a designated staging area and awaiting further instructions, should be part of the plan. The routes that assets will take should be known. It is not inconceivable that one route becomes unusable after an evacuation chain has already been put in to use. If there is a backlog on one route, prioritizing routes for the highest triaged patients may also become necessary. Various safety issues such as terrain, weather, contamination, or violence may need to be anticipated, and a balance between the need to evacuate and not should always merit consideration.

When utilizing evacuation triage, consideration of all these factors is crucial, and incorporation during the execution of the plan established on the scene is vital. It will be incumbent on the scene or incident commander to take charge of the evacuation chain or delegate this role to an appropriate party with authority and situational awareness. When executed properly, evacuation triage moves patients to appropriate treatment centers in a safe and timely fashion and ultimately helps to save resources and lives.

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9-Line MEDEVAC Request
9-Line MEDEVAC Request
Contributed by the United States Army (Military)
Article Details

Article Author

Brandon W. Koser

Article Editor:

Maureen Suchenski


9/19/2022 11:56:02 AM



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