Five Questions for...

Fri, 03/18/2011 - 11:00 -- Stephanie

Five Questions for is a new feature on the EMS Classroom Blog.  We strive to bring interesting and relevant content to our readers.  This feature will bring some of the most important names in EMS to the blogosphere providing this information in an effective, no nonsense format.

We are thrilled to have Dr. Richard Hunt from the Centers for Disease Control as our first guest on Five Questions for... . Dr. Hunt leads the CDC’s Division of Injury Response at the National Center for Injury Prevention and Control.  He has a long history of involvement in EMS including being one of the familiar voices on the very popular (and visionary) EMS Journal Club. Read more about Dr. Hunt. We believe the National Trauma Triage Guidelines are an important step for EMS.  Instead of blindly using mechanism of injury as the determinant for transport to a trauma center, the CDC has presented a thoughtful plan to make our decisions more accurate and effective.

Again, we are please to present:

Five Questions for Dr. Richard Hunt, Director of Injury Response at the Centers for Disease Control.

1) Can you give us some background about the trauma triage guidelines and how they relate to EMS?

In 1976, America College of Surgeons-Committee on Trauma (ACS-COT) began publishing resource documents to provide guidance for designation of facilities as trauma centers and appropriate care of acutely injured patients. Before this guidance appeared, trauma victims were transported to the nearest hospital, regardless of the capability of that hospital, and often with little prehospital intervention.

ACS-COT regularly revised the resource document, which included the Decision Scheme. During each revision, the Decision Scheme was evaluated by a subcommittee of ACS-COT, which analyzed the available literature, considered expert opinion, and developed recommendations regarding additions and deletions to the Decision Scheme. Final approval of the recommendations rested with the ACS-COT Executive Committee. Since its initial publication in 1986, the Decision Scheme has been revised four times, in years: 1990, 1993, 1999, and 2006.

In recent years, CDC has taken an increasingly active role in the intersection between public health and acute injury care, including the publication in 2005 of an injury care research agenda. In 2005, with financial support from the National Highway Traffic Safety Administration (NHTSA), CDC convened a series of meetings of the National Expert Panel on Field Triage (the Panel) to guide the 2006 revision of the Decision Scheme. The Panel brought representatives with additional expertise to the revision process (e.g., persons in EMS, emergency medicine, public health, the automotive industry, and other federal agencies). The Panel had multiple objectives, including providing a vigorous review of the available evidence supporting the Decision Scheme, assisting with the dissemination of the revised scheme and the underlying rationale to the larger public health and acute injury care community, emphasizing the need for additional research in field triage, and establishing an evidence and decision base for future revisions. A major outcome of the Panel’s meetings was the creation of the 2006 Field Triage Decision Scheme

The development of field triage criteria paralleled the development of trauma centers, including the concept of bypassing closer facilities in favor of those with enhanced capabilities for treating severely injured patients. The initial 1976 guidance by ACS-COT contained no specific triage criteria but did include physiologic and anatomic measures that allowed stratification of patients by injury severity. Also in 1976, ACS-COT developed guidelines for the verification of trauma centers, including standards for personnel, facility, and processes deemed necessary for the optimal care of injured persons. Studies conducted in the 1970s and early to mid 1980s demonstrated a reduction in mortality in regions of the United States with specialized trauma centers. These studies led to a national consensus conference that resulted in publication of the first ACS field triage protocols, known as the Triage Decision Scheme, in 1986.

Since 1986, this Decision Scheme has served as the basis for the field triage of trauma patients in the majority of EMS systems in the United States. The Decision Scheme continues to serve as the template for field triage protocols in the majority of EMS systems across the United States, with some local and regional adaptation. Individual EMS systems may adapt the Decision Scheme to reflect the operational context in which they function. For example, the Decision Scheme may be modified to a specific environment (densely urban or extremely rural), to resources available (presence or absence of a specialized pediatric trauma center), or at the discretion of the local EMS medical director.

2) There has been a lot of talk about mechanism of injury - how reliable is MOI in predicting trauma?

A patient who does not meet Step One or Step Two criteria might still have severe, but occult, injury. In field triage, the mechanism of injury should be evaluated next to determine whether the injured person should be transported to a trauma center. The criteria for mechanism of injury have been widely studied. A study of patients treated consecutively by the trauma service at a community hospital indicated that 206 (41.2%) of 500 patients suffered substantial injury (defined as ISS of >15, ED TS of <14, length of hospital stay of >3 days, or death). The sensitivity of various mechanisms of injury for predicting substantial injury ranged from 0.04 to 0.24, with specificity ranging from 0.72 to 0.96. A study of 1,839 trauma registry patients that evaluated the association between mechanism of injury and ISS indicated that the mechanism-of-injury criteria resulted in patients with ISS of >15 being routed to a trauma center and patients with ISS of <15 being routed to the nearest appropriate hospital 39%–84% of the time.

In this study, over triage of patients with ISS of <15 to a trauma center ranged from 16% to 61%. A review of South Carolina EMS registry data reported that 66 (16.1%) of 411 patients meeting mechanism-of-injury criteria had ISS of >15 and that 262 (63.7%) had mechanism of injury as the sole indication (i.e., with no physiologic or anatomic criteria) of serious injury. Mechanism-of-injury criteria alone had a sensitivity of 0.5 and a PPV of 16.1% for identifying severe injury. A prospective study of 3,147 trauma patients reported that mechanism-of-injury criteria alone had a sensitivity of 0.7 for identifying patients with ISS of >16 (91). Although substantial similarities existed between the mechanism-of-injury criteria used in these studies, they were not uniform, which limits the extent to which conclusions can be drawn.

However, the results of these studies considered together suggest that mechanism of injury is not an adequate sole criterion for triage but instead must be combined with other criteria (i.e., physiologic and anatomic).A retrospective analysis of patient data from 621 MVCs included in the Royal Melbourne Hospital trauma database in Victoria, Australia, that was conducted to determine if mechanism of injury alone accurately identified major injury among crash victims indicated that 52 (20.5%) of 253 patients with major injury after an MVC did not have a mechanism of injury suggestive of major injury. A retrospective review of 830 trauma admissions to one Level I trauma center reported that, of 414 patients who were triaged to the highest level of care only on the basis of mechanism-of-injury criteria, 8% had an ISS of >15, indicating an over triage rate of 92%.

Conversely, only 33 (35%) of 95 patients with ISS of >15 met mechanism-of-injury criteria, indicating an under triage rate of 65%. However, combining physiologic and anatomic criteria with mechanism-of-injury criteria identified at least 77 (81%) of 95 patients with ISS of >15. In addition, in a 1997 study of 3,147 patients transported from the City of Calgary EMS in Alberta, Canada, the mechanism-of-injury criteria alone would have missed 22 (26.5%) of 83 severely injured patients; combining mechanism of injury and physiologic criteria improved sensitivity for ISS of >15 to 0.8, and produced a specificity of 0.9.

3) The most recent guidelines reference vehicle telemetry data.  Can you define this term and tell us how it plays into triage decision making?

During the National Expert Panel on Field Triage meetings, members discussed the potential for vehicle telematics to more accurately guide trauma triage decisions.

Telematics is defined as the combination of telecommunications and computing. Vehicle telematics systems combine and integrate directly into the vehicle’s electrical architecture, cellular communications technology, Global Positioning System (GPS) satellite location capability, and sophisticated voice recognition while vehicle telematics provide a wide array of services, Advanced Automatic Collision Notification (AACN) was the telematics service that was of particular interest to the National Expert Panel members. AACN is the successor to Automatic Crash Notification (ACN) and is found on a number of motor vehicles. (Read more on AACN)

AACN is now installed in approximately 5 million vehicles in the United States and Canada. AACN alerts emergency services that a vehicle crash has occurred and automatically summons assistance. When a crash has occurred (as determined by various sensors, airbag deployment, or seatbelt pretensioners), the AACN system initiates an emergency wireless call to a telematics service provider (OnStar, ATX, etc.) to deliver the vehicle’s GPS location and crash-related data, and opens a voice communications channel to the emergency call center.

AACN improves the data sent from the ACN version by including crash severity data collected by in-vehicle sensors. In earlier versions of the Decision Scheme, a number of vehicle crash characteristics were incorporated into the prehospital triage decision evaluation. These included, among others, high vehicle speed, vehicle deformity >20 inches, and intrusion >12 inches for unbelted occupants as mechanism of injury criteria. National Automotive Sampling System Crashworthiness Data System (NASS-CDS) data indicate that risk for injury, impact direction, and increasing crash severity are linked. An analysis of 621 Australian motor vehicle crashes indicated that high-speed impacts (>60 km/hr [>35 mph]) were associated with major injury, defined as Injury Severity Score [ISS >15], ICU admission >24 hours requiring mechanical ventilation, urgent surgery, or death (OR = 1.5; CI: 1.1–2.2).9

Previously, the usefulness of vehicle speed had been limited because of the challenges to EMS personnel in estimating impact speed accurately. New AACN technology installed in some automobiles can, however, identify vehicle location, measure change in velocity (“delta V”), and detect the crash’s principal direction of force, airbag deployment, rollover, and the occurrence of multiple collisions. As a result, and in recognition that this information might become more available in the future, vehicle telemetry data consistent with a high risk for injury (e.g., change in velocity and principal direction of force) was added as a triage criterion.

4) Some of the information you presented in Baltimore dealt with the relationship between injury severity score (ISS) and telemetry data. Since the ISS has not been routinely used the field, could you explain it and how it may relate to trauma triage in the future?

While not calculated in the field, the ISS gives us critical information. Various standardized definitions and systems have been developed to classify the type and severity of injuries. These permit comparison of the medical outcomes of patients with different types and extent of injuries who receive different treatment and care regimens.

Worldwide, the most widely accepted injury-severity scale is the Abbreviated Injury Scale (AIS), which ranks each injury in every body region with a numerical score according to an ordinal scale (range: 1 [minor injury]–6 [probably lethal/maximum injury]). In 1974, the Injury Severity Score (ISS) was developed as a way to summarize and take account of the effect of multiple injuries. The ISS was derived from AIS scores and uses an ordinal scale (range: 1–75), which is calculated by assigning AIS scores to injuries in each of six body regions (head/neck, face, thorax, abdomen/visceral pelvis, bony pelvis/extremities, and external structures) and then adding the squares of the highest AIS scores in each of the three most severely injured body regions (i.e., the three body regions with the highest AIS scores). Only the most severe injury in each body region is used in the score. If an AIS score of 6 is assigned to any body region, the maximal ISS of 75 is assigned. ISS is an accepted method of determining the overall severity of injury and correlates with mortality, morbidity, and length of hospital stay.

For example, ISS has been used to predict mortality and risk for post injury multiple organ failure. In trauma research, ISS also has been used to dichotomize trauma patients into severe injuries (ISS of >15) and non-severe injuries (ISS of <15) and to evaluate outcomes of patients with similar degrees of injury severity. For example, during 1982–1987, data for 80,544 trauma patients from 139 North American hospitals indicated that survival from blunt and penetrating injuries decreased with increasing ISS score; this decrease was more marked in persons aged >55 years. Patients with ISS of <15 had survival rates of >94%. For patients with blunt trauma, survival decreased with increasing ISS score (>16) and age (>55 years).

5) We know you spend a lot of time in Emergency Medicine and have been involved with EMS in the past. Is there anything you would like to tell us about how the CDC and EMS may collaborate in the future?

Injury is the leading cause of death in the United States.  Primary prevention of injuries, surveillance, prehospital emergency care, emergency medicine, trauma surgery, and rehabilitation are all critical components in our efforts to decrease morbidity and mortality from injury.   The approximately one million EMS providers in the United States work 24/7 on the streets, in homes, and in our places of work to save lives and decrease the consequences of injury.

 CDC has enjoyed successful collaboration with EMS to date. In the future, we will continue to work with our nation's EMS providers, medical directors, administrators, and national organizations on matters related to field triage of injured patients, the utilization of crash notification data to predict injury severity, and in our efforts regarding the clinical and systems response to terrorist bombings.  The work together on these issues serve as an excellent foundation for any future initiatives that will serve our common mission to decrease morbidity and mortality.

For more information:

For CECBEMS approved CE on the Field Triage Decision Scheme:

We extend our sincere thanks to Dr. Hunt and Terica Scott at the CDC for the insightful responses to our questions and for making this segment possible.

If you have suggestions for future guests on our Five Questions for please send them to us.

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