"Trauma by mechanism" is my least favourite phrase I hear in my trauma bay. That just means that the mechanism of injury ought to be severe enough to cause some harm. Even if the patient is found walking around the scene of the accident with no complaints whatsoever, if the EMT deems that the mechanism is severe enough, that patient will be called a "trauma" and it'll drop into my lap.
Don't misunderstand me - I have a tremendous amount of respect for the emergency response personnel. They save lives, they get people to the hospital quickly, they do some amazing things. But I've met a few who aren't the sharpest tool in the shed.
I always try to keep in mind that these hardworking people are not doctors. I can usually assess someone and determine if that person is critically ill and/or will need surgery in about 15 seconds. But I've had 9+ years of formal, rigorous medical training, so it's an apples-to-rutabaga comparison.
The emergency medical technicians have to make a judgment when they first get on the scene - is this person injured to the point of requiring an evaluation by a trauma surgeon, or can we take him to the ER where he or she will likely sit in the waiting room for 3 or 4 hours before an ER physician can do the initial evaluation. It's doubtless a difficult determination, but in some cases it should be much easier than others. And sometimes, they just make boneheaded decisions.
The ambulance dropped off a patient this past week after he was in a car accident. He was wearing his seatbelt when he lost control and his car rolled over. He didn't lose consciousness, he was able to get out of the car by himself, and he had no complaints whatsoever when EMS arrived. They still slapped a cervical collar on him, strapped him to a backboard, and shipped him to me. I discharged him about 10 minutes later, no doubt with a headache and frustration of being sent to the hospital for no damned reason.
Even worse was a lady whose car was hit on the passenger side, again wearing her seatbelt. She appeared to have no injuries, and indeed when I asked her, she had no pain at all. I asked the EMT why she was called a trauma, and he told me it was by mechanism of a head-on collision. I tried to explain that she was T-boned, not hit head on. He told me that it was a "trauma by mechanism" (my blood started boiling) of the other car involved...not hers. She was actually upgraded to a trauma based on the amount of damage to the car that hit her car, which was minimally damaged. I had to control my rage or else he would have been my next trauma patient after I kicked him in the shin.
I discharged her about 10 minutes later too.