Review of: Petrie DA, Tallon JM, Crowell W, et al: Medically appropriate use of helicopter EMS: The mission acceptance/triage process. Air Medical Journal. 26(1):50 54, 2007.
This study from Nova Scotia examined the appropriateness of helicopter EMS (HEMS) in the region during a 21-month period with the goal to determine the current level of overtriage. They determined flights to be appropriate if the patient required ICU admission, died during transport or within 24 hours, and, in the case of trauma, an injury severity scale (ISS) score was 12 or less. Overtriage was defined as not meeting these criteria.
They transported 584 patients using a mission acceptance process that relied on outreach education, dispatcher oversight and clinician-to-clinician discussion about each case.
They report their overall overtriage rate was 13.1%
The American College of Surgeons has suggested that for major trauma an overtriage rate of 50% would generally result in an undertriage of 10%. That is, in order to feel comfortable that you re missing less than 10% of the patients who need a trauma center, the patients you do transport will have only a 50% chance of actually needing a trauma center. Although this may apply to EMS as a whole, the risk and benefit of air medical transport probably dictate a more conservative approach.
This study is another example of why we must read the entire study to determine its value. Of the 584 patients transported, only 199 were for trauma; of those, 49 were from the scene. The overtriage of the medical cases was 3.4% for cardiac and 14.3% for other medical.
For the trauma patients, the overtriage rate was 19.1% overall and 34.7% for those transported from the scene. Trauma patients transported from a facility had an overtriage rate of 14%, which is similar to that of medical.
In Canada, multiple trauma is defined as an ISS score of 12 and higher, whereas in the U.S. it s a score of 16 and higher. Had the authors applied the U.S. criteria to the study, the overtriage rate for trauma would have been even higher.
I m not suggesting we stop calling for helicopters. Instead, let s look at the implications of the study. Clearly, there s a difference between medical and trauma cases. Perhaps we need better definitions of appropriateness, such as requiring time-dependent imaging or requiring potentially life-saving procedure. However, this would result in worsening of the debate. The study clearly indicates that once patients arrive at a hospital, the physicians are able to make a better determination of the need for HEMS.
This system used an auto-launch program based on dispatch criteria. Perhaps what s needed is a closer examination of these criteria as well as that used by rescuers on scene.