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The definition of wilderness medicine, and wilderness EMS, has surprisingly not been well-established in our field.

In the twentieth century, definitions largely utilized time characteristics, and these definitions persist in some publications, organizations, and protocols to the current day. These would often cite one (or sometimes two) hours “until definitive care” as the defining feature of wilderness medicine. However, more modern scholarship and inquiry has questioned the ability for time alone to define our work.

First, it is unclear what precisely the start and stop time is for this measurement. If the start time is considered point of injury, and the stop time is a hospital or clinic, a huge number of cases will be included that nobody would think is wilderness. It might surprise some readers that one large national database determines average traditional (non-wilderness) EMS call time by this start-and-stop metric to be a mean of about 40 minutes, with fully 10% of calls occurring over 60 minutes. This data suggests that even outside the wilderness, traditional EMS calls may be longer from 911 activation to arrival at definitive care than people suspect. On the other hand, if the start time is 911 activation, and the stop time is transport from the scene, some cases that are certainly wilderness could be clocked at less than one hour.

Second, time-based definitions don't recognize that a startling number of wilderness EMS calls—including ALS calls—don't involve transport. For example, in one database published by the National Park Service, 77% of wilderness EMS patients were released by EMS personnel at the scene and not transported. It's not clear what the time measurement end point should be if a hospital or clinic is never utilized.

Third, even if a hospital or clinic is utilized, it's not clear what the definition of “definitive” is. Many critical access hospitals don't even define themselves to be “definitive”, and when they transfer the patient further, the literal reason for transfer to a larger center is to acquire “definitive care”. On the other hand, some programs will choose to define the end point as EMS arrival, but most EMS systems would not define themselves as “definitive care” either. This is also regionally contextual—in some parts of the country, and some countries, no “definitive care” exists as it would be defined in a major American metropolitan center.

Fourth, a time-based definition puts unreasonable expectations on field EMS clinicians and first aiders. There is really no way prospectively to know for sure, at the time of injury or even at the time of 911 activation, how long the arbitrary end point will be reached. Tasking those in the field with knowing transport times depends on too many variables (including just baseline knowledge of the area and the destination facility) to be able to make this calculation with the precision required for an hour or two hour window. However, there are prospective operational needs for a definition—for example, EMS clinicians may need to know if they are allowed to activate wilderness protocols that differ from traditional protocols. This argues that time should be one among a number of considerations. In this model, protocol activation could be accomplished in a number of ways. One would be through on-line medical oversight. Another would be to create geofences in specific response areas that define front country and backcountry protocol areas accounting for terrain and expected care time windows. Alternately, programs could define specific regions or operations as wilderness or not wilderness prospectively, including anticipated time with specific definitions of start and stop time within that assignment. It's important to recognize that all these are contextually-driven definitions that would not appear in a textbook for the definition of “wilderness medicine” or “wilderness EMS”, but rather would be operationally-determine for specific cases.

Because of this, a consensus definition is needed for dialogue about the work that we do in these spaces. It needs to be one that transcends and includes these operationally-specific definitions, while at the same time not flattening all cases to an unreasonable categorization (e.g., all cases where more than hour elapses between time of injury and arrival at the final receiving hospital/clinic).

It is interesting to note that, while we consider EMS to be a very familiar and well-established institution, it is also a very recent development in the United States, only becoming formalized and widespread in the early 1970s. Even more amazingly, a consensus definition was not published until 2012, when the National Association of State EMS Officials (NASEMSO) published their consensus definition of EMS as “the integrated system of medical response established and designed to respond, assess, treat, monitor, observe, and determine the disposition of patients with injury or illness and those in need of medically safe transportation”.

A growing number of publications, including Auerbach's Wilderness Medicine 7e (2017), Wilderness EMS 1e (2018), Emergency Medical Services Clinical Practice & System Oversight 3e (2021), Prehospital Trauma Life Support 10e (2022), and Nancy Caroline's Care in the Streets 9e (2022) have adopted a new consensus definition for wilderness medicine, as have freestanding courses such as the Wilderness EMS Medical Director Course. That consensus definition is:

Even Wikipedia, the well-known crowd-sourced encyclopedia, has adopted this consensus definition. The Wilderness Medical Society used this definition during their recent rebrand and adopted a modified, everyday version of it as “medical care delivered amidst geographic challenges and/or limited resources.”

Key elements of this consensus definition include its focus on geography and the fact that the impact is measured in terms of patient movement and medical resources and requirements, the two most common operational adaptations of wilderness medicine. Terrain and geography seem more meaningful as a primary element of what we do than time, and time can neatly be captured when terrain and geography compromise speed of operations. It's also critical to note that geographic obstacles can be fixed or transient… fixed obstacles like rivers or mountains are familiar to us, but a major US city can become a wilderness medicine environment during a disaster when transient geographic changes occur like flooding or earthquake or snowstorm.

Then, combining the NASEMSO consensus of EMS with the consensus definition of wilderness medicine, the following consensus definition of wilderness EMS was first published in 2018 (specifically citing the prior consensus definition of “wilderness medicine” when that term is used here):

This represents the first multiauthor, multireference consensus definition of both wilderness medicine and wilderness EMS. Having shared definitions is critically important for us to understand amongst each other, and explain to others, the precise nature of what we do in our field (wilderness medicine) and our subdiscipline (wilderness EMS). This definition is robust enough to include all those parameters we think of as wilderness but discriminating enough to hopefully exclude unnecessary care types that are really outside our work. More importantly, while it has more operational utility than other definitions (such as the anthropologically-driven definition found in Wilderness EMS 1e), it still leaves the critical operational definitions to be made by individual agencies in the context of their own operations… where it most properly belongs. While we need universal definitions, those definitions need to acknowledge (as strict time-based definitions do not) that all wilderness medicine, and wilderness EMS, is fundamentally contextual and resistant to broad generalizations.

We hope you will consider integrating this consensus definition into your protocols, operations, and publications!

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