Field triage in the civilian arena

History and evolution of trauma triage systems

Prior to the 1970s, trauma patients were transported to the nearest hospital without regard for institutional capability or resource utilization. By 1976, the American College of Surgeons (ACS) identified the need for specialized hospitals dedicated to the care of the injured patients. Termed “trauma centers,” these hospitals were created with certain standards of personnel, critical care resources, and processes designed specifically for the care of traumatically injured patients. Currently, trauma centers are organized into four different levels. The highest level of care (Level I) provides definitive trauma resuscitation from injury prevention through rehabilitation and discharge, and at the other end of the range, Level IV hospitals, with fewer resources, provide initial care and then subsequent transfer to facilities with higher levels of care as necessary ( Table 1 ).

The development of specialized trauma centers caused an important question to surface: which patients should be transported to the highest-level trauma centers and who should continue to receive care at nonspecialized regional hospitals? To help answer this question, the ACS published the first version of the “Optimal Resources for the Care of the Seriously Injured” in 1976. This document outlined a set of injuries and accompanying physiologic measures of injury severity, allowing for some degree of injury stratification. Concurrently, one of the first studies to support the concept of triage was published. Following a motor vehicle crash, all victims in San Francisco were taken to a single trauma center, but those occurring in Orange County were taken to the closest receiving hospital. After reviewing the deaths from each county, the authors determined that two thirds of the non–brain injury–related deaths and one third of the deaths related to brain injuries could have been potentially prevented in the group who received care at nondesignated trauma centers. Other studies emerged in the early 1980s suggesting that severely injured patients received better care following treatment from an organized system of care and as a result, the ACS published the first true triage decision scheme in 1986. This document called for the field assessment of the patient in three separate steps (physiologic, anatomic, and mechanism of injury), with each step connected to the determination of the patient’s need for the highest level of trauma center care. Since its initial publication, this decision scheme has served as the primary resource for triage of the injured patient for trauma systems across the United States. The original scheme has since been revised five times (1990, 1993, 1999, 2006, and 2011). In 2005, the Centers for Disease Control and Prevention (CDC), in concert with the National Highway Traffic Safety Administration and ACS Committee on Trauma, began facilitating this revision process, and the result is a collaborative effort from a nationally representative, multidisciplinary expert panel using best available data and consensus opinion. Originally published in the Resources for the Optimal Care of the Injured Patient in 2006 and last revised in 2011, the most current triage decision scheme calls for the step-by-step evaluation of four components of an injured patient. Steps 1 and 2 assess the severity of physiologic and anatomic signs of injury. These signs include initial vital signs, such as systolic blood pressure, pulse, respiratory rate, and the patient’s level of consciousness using the Glasgow Coma Scale. The anatomic evaluation looks for high-risk injuries such as penetrating trauma proximal to the elbows and knees, severe musculoskeletal injuries including amputation and pelvic fracture, and new-onset paralysis. Step 3 assesses high-risk mechanisms of injury, such as falls greater than 20 feet, pedestrians or bicyclists struck by vehicles, and high-risk vehicular crashes as indicated by extensive external vehicle deformity, patient ejection, or death of another passenger. Step 4 assesses for patient-specific characteristics that may contribute to increased morbidity and mortality risks. Examples include extremes of age, end-stage kidney disease, burns, and pregnancy ( Fig. 1 ).

Despite the best efforts to match the needs of the injured patient with the resources of the hospital, two principal problems have emerged: overtriage and undertriage. Overtriage, or the transporting of patients with minor injury not requiring higher level care to a trauma center, has the potential to overburden the trauma center. In addition, it is an inefficient use of EMS resources, may displace patients from their communities, is a source of lost revenue at the hospital bypassed, and constitutes an unnecessary risk of injury to patient and EMS crew during transport. Conversely, undertriage can be defined as the inappropriate transport to a lower-level trauma center or nontrauma center and can lead to treatment delays, errors, missed injuries, and increased morbidity and higher mortality rates. As an example, the National Study on Costs and Outcomes of Trauma completed in 2006 found that, for severely injured patients, care at a designated trauma center reduced mortality rate by 25%.

In 2014, the ACS Committee on Trauma (ACS-COT) suggested that a 5% rate of undertriage and a 25% to 35% rate of overtriage are acceptable goals for field triage. This suggests that trauma center need can be accurately identified and that the rates of over- and undertriage should be the same for all trauma systems. Yet, no gold standard measurement is available that defines the need for a trauma center, and this may differ by the number of higher-level trauma centers within a given system. Previous studies have used an Injury Severity Score (ISS) greater than 15 as an estimation of trauma center need. ISS is an anatomic scoring system ranging from 0 to 75, which assigns a numerical value (1–5) to each one of six body regions (head, face, chest, abdomen, extremities, and external). The scores of the three most severely injured body regions are squared and then added together to produce a composite score. Other studies have used resource utilization as a proxy for the need for a trauma center. For example, whether or not the patient needed admission to the intensive care unit, required emergent nonorthopedic surgery within 24 hours of presentation to the hospital, or died prior to hospital discharge are surrogates of resource utilization. Finally, early studies used death alone as a measure of trauma center need. However, relative to the high morbidity many trauma patients sustain, few patients actually die. As such, this measure is now rarely used to approximate trauma center need.

The accuracy of the ACS-COT/CDC triage criteria can be evaluated in its entirety or by evaluating each criterion separately. A study using the National Trauma Database sought to determine whether or not the physiologic and anatomic criteria alone (versus the complete scheme) were sufficient to accurately predict need for a trauma center. Defining trauma center need as an ISS of greater than 15 or the need for emergent surgery or an intensive care unit admission greater than 24 hours, overtriage rates for the physiologic criteria were 9% and undertriage rates were 68%. The anatomic criteria alone resulted in overtriage rates of 15% and undertriage rates of 74%. Even when combining both the physiologic and anatomic steps in succession (as an EMS worker would perform in the field), overtriage would have occurred 22% of the time and undertriage would have occurred in 51% of injured patients. Because more than half of the patients in the study would not have been identified as needing a trauma center using the anatomic and physiologic criteria alone, authors concluded that mechanism of injury and special considerations criteria contribute significantly to the triage guideline by limiting undertriage. This emphasizes the fact that all four steps in the decision scheme are important to the overall accuracy of the algorithm. It also describes an important concept: improving the rates of undertriage come at the expense of increasing overtriage. As pointed out by the CDC, additional research efforts were needed specifically related to field triage and predictors of trauma center need. In turn, a recent study funded by the CDC sought to prospectively validate field trauma triage guidelines. Importantly, the study found that the sensitivity and specificity of the guidelines were 66.2% and 87.8% for those with an ISS greater than 15 and 80.1% and 87.3% for early critical resource use. The study also found that triage guideline sensitivity decreased with age, from 87.4% in children to 51.8% in older adults. The authors concluded that the national field triage guidelines are relatively insensitive for identifying seriously injured patients who require critical resource use, particularly among older patients. Accordingly, ongoing research in these areas should continue and ought to involve acute care, public health, and public safety practitioners and researchers to improve continuing analysis, valuation, and revisions of the current field decision scheme.