In this study, we explored out-of-hospital triage decisions, field cognitive reasoning and other factors affecting the distribution of injured patients transported in a well-established trauma system. While previous studies on cognitive reasoning in acute care settings have focused on reducing medical errors and understanding diagnostic reasoning,19-22
we evaluated cognitive processes as they apply to field triage and hospital selection in a regionalized trauma system. The current approach to trauma triage is assumed to follow an algorithmic, risk-based process for identifying patients with serious injuries, yet our results demonstrate that actual triage decision-making is complex and dynamic, relying on high-level cognition to generate rapid decisions. EMS provider “gut feeling” (provider judgment) had the greatest influence on identifying seriously injured patients in this system, a finding that was supported by both quantitative and qualitative study results. For injured patients not felt to have serious injuries, patient/family preference and proximity were the dominant factors in hospital selection, with modification by provider perceptions about hospital resources and quality of care. Our findings also demonstrate that a substantial number of injured patients not meeting field triage criteria are still transported to high-resource hospitals, most commonly based on patient/family preference (i.e., request).
This study demonstrates that out-of-hospital triage involves more independent thinking by field providers than has previously been understood. Studies assessing the utility of paramedic judgment in identifying seriously injured patients have shown mixed results.23-27
However, the cognitive processes behind such “judgment” have not been previously described. As opposed to the current algorithmic model for identifying seriously injured patients,6,7
we demonstrate that the cognitive processes for arriving at this determination are fast, intuitive, heuristic, and based largely on early scene information and visual cues, rather than specific criteria. Early information, often obtained and processed before patient contact, feeds the cognitive reasoning process, while information that cannot be assessed with rapid visual or auditory assessment (e.g., blood pressure, heart rate, respiratory rate, non-obvious anatomic injuries, detailed history) is generally not part of the primary triage decision-making process. This type of decision-making model has been termed “System 1” by Croskerry,28,29
with thought processes similar to experienced clinicians,19,20,22,28
and illustrates a form of “forward thinking” where a provisional hypothesis is rapidly formed (e.g., by dispatch information), then quickly tested with a smaller number of data points (e.g., visual cues from the scene) that allows the provider to expedite care.22
In the frequently chaotic and time-constrained environment of out-of-hospital care, quick decision-making and efficient critical thinking are rewarded and reflected in these cognitive processes. While the System 1 model of diagnostic reasoning can occasionally fail, “sometimes catastrophically,”28
this risk is accommodated by a trauma system culture that accepts high rates of over-triage. EMS provider judgment is included as a triage criterion in the most recent version of the ACSCOT Field Decision Scheme, referred to as “EMS Provider Judgment.”6,7
When there is not an immediate “gut feeling” regarding serious injury, EMS providers move into a “System 2” decision-making approach using a slower, deductive process based on additional data and more time-consuming, analytic cognitive functions.20,28
Our findings suggest that such “gray area” cases using System 2 processes are relatively uncommon and present impractical scenarios in a setting that favors rapid decision-making and short time intervals. When System 1 and 2 processing suggest no serious injuries, patient preference for hospital selection is given priority. While patient autonomy is minimized in patients believed to have serious injury, it is otherwise maximized similar to medical decision-making that weighs outcomes according to patient preference and satisfaction.
Our findings are notable because the ACSCOT Field Triage Decision Scheme, which has been used as the basis for field trauma triage in most U.S. trauma systems since 1987, was generally replaced by higher level decision-making among EMS providers. Although the field triage guidelines are comprehensive and sensible from a scientific perspective, the algorithmic format does not match the flow of information to field providers and does not cater to the fast, heuristic cognitive processes favored in the out-of-hospital setting. Providers in this system tend to proceed through the Field Triage Decision Scheme in generally reverse order, starting with EMS provider judgment (integrated with mechanism of injury and visual cues from the scene), then anatomic criteria (i.e., by physical exam, unless these injuries were apparent by visual assessment), and vital signs. These findings suggest that small modifications to individual triage criteria (e.g., the exact height of a fall or the specific Glasgow Coma Scale (GCS) value) may have little impact on triage processes, particularly among experienced out-of-hospital providers. Field provider insights and perceptions about patient needs and hospital resources (or lack thereof) also appear to play a role in hospital selection. Our findings suggest that provider perceptions about the availability, quality, staffing, cost, and comprehensiveness of hospital care can influence hospital selection for some patients. In addition, hospital proximity is an important factor, which may explain why hospitals that reside in areas with heavier EMS call volumes may see larger volumes of patients.
Provider intuition in this system is based on training and previous experience. While we did not assess the amount of experience needed to reach this level of intuition, there is likely some point at which EMS providers transition from a “learner” model requiring proscribed algorithms and highly structured protocols to more experienced providers with higher-level, faster, and less algorithmic decision-making. David and Brachet evaluated the relationship between EMS work experience, volume of trauma patients cared for (both recent and cumulative), and out-of-hospital time intervals (a proxy for provider performance).30
These authors found that more than two years of field experience, plus past and recent volume of trauma patients were all associated with reductions in out-of-hospital time.30
While the highly structured format of the ACSCOT Field Triage Decision Scheme appears to work well for learners, more experienced providers in this system use cognitive processes that match the flow of information, integrate provider experience and yield rapid, intuitive decision-making.
Our sample was limited to patients and EMS providers from a single trauma system. While this region includes urban, suburban, and some rural areas, most patients presented within reasonable proximity to a major trauma center. The decision-making process and order of priorities may be different in settings far from major trauma centers (e.g., rural or frontier regions), in regions where trauma resources are more constrained, or where EMS systems and respective protocols are inherently different. In addition, we did not assess other out-of-hospital decision-making topics, such as when to activate air medical transport from the scene. In this 4-county sample, only a small proportion of patients (0.1%) were transported from the scene by helicopter.
EMS provider experience surfaced as an important aspect of cognitive processing for trauma triage, however we did not collect information on provider experience. It is possible that the EMS crews participating in interviews were generally more experienced, which was reflected in development of the cognitive model. However, less experienced EMS personnel (e.g., first-year EMS personnel) were included in the field observation and interview process, particularly among the fire crews interviewed. Because the more senior EMS providers on-scene tend to guide the trauma triage process, we believe our findings are representative of actual field decision-making processes, where teams of EMS providers have a mix of experience levels. EMS systems or regions with fewer personnel on-scene or operating with less experienced providers may behave differently.
Finally, this study was designed to assess the process
of out-of-hospital triage and hospital selection, rather than outcomes or the accuracy of such cognitive processing, though studies addressing these questions have been published.23-27
We do note that the survival benefit of this trauma system, as well as the effective redistribution of seriously injured patients with trauma system implementation, have been previously demonstrated.3,4
Additional studies to further explore the predictive value of EMS provider “gut feeling” relative to other triage criteria in identifying seriously injured patients are underway.
In summary, we derived an empirical, out-of-hospital cognitive reasoning model of trauma triage decision-making rooted in provider intuition, experience, and early informative cues. In this system, EMS provider judgment was the most frequently cited criteria for entering patients into the trauma system, a finding what was consistent with qualitative results from interviews and focus groups. For patients not felt to have serious injuries, patient/family preference and hospital proximity were the most important factors in selecting hospitals. It will be important to replicate this study in other EMS and trauma systems to assess whether the cognitive processing demonstrated here is similar in other systems. Understanding the flow of information to field providers, cognitive processing, consumer choice, and geographic location is likely critical in further modifying the regional distribution of injured patients and other persons with high-acuity clinical conditions served by EMS providers.