Goodbye to Mechanism of Injury?

By Mike McEvoy, Ph.D., RN, CCRN, REMT-P

Mechanism of Injury (MOI) criteria has been used for years to predict seriousness of injury and expected outcomes of trauma patients. Recently, trauma researchers came to the same conclusion made years ago in surgery and critical care: Predictions for individual patients can’t be made solely on statistically derived criteria. MOI is a statistically derived method of guessing patient outcomes. In the United States, resources to treat trauma patients are shrinking, and reductions will continue. Hospitals must now be more selective in where they apply their resources. As a result, you may soon be saying goodbye to MOI, at least as exclusive triage and transport criteria.

The writing on the wall came in 1999 when the American College of Surgeons (ACS) drafted revised criteria for trauma resuscitation. In its document, “Resources for Optimal Care of the Injured Patient: 1999,” the ACS changed its definition of minimum criteria for a major trauma resuscitation to include blood pressure

Missing from these revised criteria were the old and familiar: ejected from a vehicle, rollover vehicle crashes, long falls, motorcycle crashes, pedestrians thrown great distances, and the like. Three reasons are driving the shift in focus away from exclusive use of MOI. First, injury severity is difficult to quantify. Second, every patient responds differently to injury, making models very difficult to develop. Third, MOI does not account for the strengths or weaknesses of EMS providers and EMS systems. Both may significantly impact outcomes.

EMS providers are hardly surprised that MOI is incredibly limited in predicting outcomes. Routinely, we arrive at rollover motor vehicle crashes to find apparently uninjured drivers walking around their demolished vehicles. We have seen victims fall several stories and land unscathed. Indeed, intuition has long taught EMS providers that decisions about the severity of a patient’s injuries can’t be based solely on a single set of criteria.

In 2001, the truth about MOI was told. The National Trauma Data Bank established by the American College of Surgeons to study trauma in the United States published a report that, among other items, reviewed Mechanism of Injury data from 1994 through 1999. This data set confirmed the inclusion of gunshot wounds in the 1999 trauma criteria and continued to question the validity of other MOI criteria. What may well be the future of trauma triage decision making are schemes that use both MOI criteria and patient assessment findings. Such a system would eliminate the issue of how different people react to trauma by combining the seeming seriousness of an injury with competent assessment of how an individual patient responds.

We would all do well to make a note of this trend. By incorporating real patient assessment findings with MOI criteria, it would seem that decisions could actually result in better outcomes not only for our patients but also for utilization of trauma care resources that are becoming increasingly scarce. If your present trauma triage and transport protocols rely exclusively on MOI, changes are coming!

American College of Surgeons. National Trauma Data Bank Report 2001. [On-Line] Available:

Mike McEvoy, Ph.D., RN, CCRN, REMT-P, is the EMS coordinator for Saratoga County, New York. A former forensic psychologist, he now works in the Cardiac Surgical ICU at Albany Medical Center and teaches at Albany Medical College in NY. He is a paramedic for Clifton Park-Halfmoon Ambulance Corps and medical advisor for West Crescent Fire Department. He presently serves as a member of the New York State EMS Council and the State Emergency Medical Advisory Council and chairs the EMS Section of the New York State Association of Fire Chiefs.

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