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Mechanism of Injury & Level One Trauma Centers


Review Of: Lerner EB, Shah MN, Cushman J, et al. Does mechanism of injury predict trauma center need? Prehosp Emerg Care. 2011;15(4):518–525.

The authors interviewed EMTs who brought major trauma patient to three Level I Trauma centers in Milwaukee, Wis.; Rochester, N.Y.; and Royal Oak, Mich. They excluded those patients that met the 1999 CDC Trauma Triage Anatomic & Physiologic criteria, which include the following:

Glasgow Coma Scale <14 or systolic blood pressure <90 or respiratory rate <10 or >29 (<20 in infant < one year)

•All penetrating injuries to head, neck, torso and extremities proximal to elbow and knee
•Two or more proximal long bone fractures
•Crushed, degloved or mangled extremity
•Amputation proximal to wrist and ankle
•Pelvic fractures
•Open or depressed skull fracture

They then examined the Mechanism of Injury (MOI) that was associated with the admission and determined whether or not the patient needed the resources of the Level One Trauma center. They defined trauma center need as 1) Died, 2) ICU admission, and/or 3) Non-orthopedic surgery within 24 hours of admission.

They determined that of all of the MOIs listed in the CDC triage criteria only three reliably predicted the need for a Level One Trauma center. They included 1) Death of an occupant in the vehicle; 2) Fall greater than 20 feet; and 3) Extrication time > 20 minutes

Dr. Wesley: This study provides us with insight into the value or lack thereof to using Mechanism of Injury (MOI) as the sole determinant for deciding to transport a trauma patient to a Level One trauma center. To appreciate this study, it’s important to recognize some of its limitations. First, all the patients studied were taken to a Level One Center, and the authors determined that 91% of the patients transported solely based on MOI didn’t need Level One Center resources. Why were these patients not transported to other hospitals?

The Centers for Disease Control & Prevention (CDC) criteria states that only those meeting anatomic and/or physiologic criteria should be transported to the highest level trauma center in the system. Patients who meet the MOI criteria should be taken to the closest appropriate hospital, which does not necessarily mean the highest level of care. What this means is that these three Level One Trauma centers appear to be used exclusively for all trauma patients and may not be using Level Two or Three centers to receive patients with MOI criteria alone.

Despite this limitation, the authors provide some clarity as to the value of each of the CDC mechanisms they list. The mechanisms that the CDC recommends should go to the closest facility include the following:

• Adults: > 20 ft. (one story is equal to 10 ft.)
• Children: >10 ft., or 2–3 times the height of the child

High-Risk Auto Crashes
• Intrusion: > 12 in. occupant site; > 18 in. any site
• Ejection (partial or complete) from automobile
• Death in same passenger compartment
• Vehicle telemetry data consistent with high risk of injury
• Auto v. pedestrian/bicyclist thrown, run over, or with significant (> 20 miles per hour) impact

Motorcycle Crash
• > 20 miles per hour

Three of these MOI consistently identified those patients who might benefit from being transported directly to a Level One Trauma center.

Despite all of this data, it’s vital to remember that this study applies only to patients without anatomic or physiologic criteria consistent with a major traumatic injury. If these criteria are absent, however, then perhaps you should consider transporting the patients with the three highest risk MOIs to a Level One Center. Otherwise, you can probably feel comfortable taking the rest of your trauma patients to the nearest appropriate facility and not over burden the Level One Center with patients who don’t need that level of care.

Medic Marshall: The Doc hit this one on the head. From my perspective, I think it can be difficult to properly triage patients when you’re looking at the scene of an accident. At times, there is so much damage and destruction to a vehicle or at the scene of the accident that you can’t help but think the patient has to be severely injured and in need of a trauma center. So the safe thing to do is default to the Level One despite the fact that a nearby hospital is perfectly capable of handling the patient.

The over-triage rate of this study did and did not surprise me. I expected EMS providers to over-triage trauma patients. I’m sure I’ve done it several times in my EMS career. But to have an over triage rate of 91% was what struck me. It’s important to remember that this study is not “generalizable” to the entire “trauma population” per se, but it provides an interesting insight into what is more than likely occurring across the country.

From a study perspective, I applaud the investigators for taking a stronger approach to studying trauma. Although this is still an observational study, the data were collected prospectively by interviewers who were stationed at emergency departments (EDs). One downfall is the lack of interviewers in the EDs on overnights; the investigators relied on the information from paper forms for EMS providers to complete if there wasn’t an interviewer at the site. From the sounds of it, it seems as though many of these forms were not filled out, which excluded a significant number of patients from the study.

To determine the predictive value of the mechanism-of-injury step of the American College of Surgeons Field Triage Decision Scheme for determining trauma center need.

Emergency medical services (EMS) providers caring for injured adult patients transported to the regional trauma center in three midsized communities over two years were interviewed upon emergency department (ED) arrival. Included was any injured patient, regardless of injury severity. The interview collected patient physiologic condition, apparent anatomic injury, and mechanism of injury. Using the 1999 Scheme, patients who met the physiologic or anatomic steps were excluded. Patients were considered to need a trauma center if they had non-orthopedic surgery within 24 hours, had intensive care unit admission, or died prior to hospital discharge. Data were analyzed by calculating positive likelihood ratios (+LRs) and 95% confidence intervals (CIs) for each mechanism-of-injury criterion.

A total of 11,892 provider interviews were conducted. Of those, one was excluded because outcome data were not available, and 2,408 were excluded because they met the other steps of the Field Triage Decision Scheme. Of the remaining 9,483 cases, 2,363 met one of the mechanisms of injury criteria, 204 (9%) of whom needed the resources of a trauma center. Criteria with a +LR ≥5 were death of another occupant in the same vehicle (6.8; CI: 2.7–16.7), fall >20 feet (5.3; CI: 2.4–11.4), and motor vehicle crash (MVC) extrication time >20 minutes (5.1; CI: 3.2–8.1). Criteria with a+LR between >2 and <5 were intrusion >12 inches (4.2; CI: 2.9–5.9), ejection (3.2; CI: 1.3–8.2), and deformity >20 inches (2.5; CI: 1.9–3.2).

The criteria with a +LR ≤2wereMVC speed >40 mph (2.0; CI: 1.7–2.4), pedestrian/bicyclist struck at a speed >5 mph (1.2; CI:1.1–1.4), bicyclist/pedestrian thrown or run over (1.2; CI: 0.9–1.6), motorcycle crash at a speed >20 mph (1.2; CI: 1.1–1.4), rider separated from motorcycle (1.0; CI: 0.9–1.2), and MVC rollover (1.0; CI: 0.7–1.5).

Death of another occupant, fall distance, and extrication time were good predictors of trauma center need when a patient did not meet the anatomic or physiologic conditions. Intrusion, ejection, and vehicle deformity were moderate predictors.


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