My wife told me about a famous dermatologist who flies in dread of getting that call and there being no other doctor available. When med school was 40 years ago, you're not necessarily going to be comfortable handling, say, a heart attack.
Apparently they were on shift one Saturday afternoon, when a call came through for a Code 2 (Cardiac Arrest) at a local racecourse.
Anyway, it was about 15 minutes away so they took off in a hurry, all the while receiving notes on their terminal regarding the job. Apparently it went along the lines of this:
Initial: Unknown Age, Cardiac Arrest, Racecourse etc Update: CPR in Progress Update: Doctor has self accounced at scene. Update: Doctor has called patient as deceased. CPR ceased.
It took another 5 minutes for the paramedics to get to the racecourse, and they still unloaded their gear and made their way to the patient. When asking for the doctor, they found that it was actually the racecourse veterinarian who had made the call.
The call was for a human, the 'doctor' who called it was a vet at the racecourse.
If I had a dollar for every time a dermatologist or podiatrist tried to be 'helpful' on an emergency scene... I could probably buy a coffee at Starbucks... The same goes for 'nurses.' If an ER nurse wants to help out, that's great. Invariably though, it's a nurse at a nursing home or dialysis center...
I don't mean to imply these folks aren't skilled professionals, but prehospital medical emergencies are generally well outside their experience, and the confusion that arises from that can be dangerous.
There are daft people in every field, but I would be delighted to have most of the derm residents and attendings I've met in an emergency (in fairness, I should note that this is a small sample, drawn from a couple top-tier hospitals, and biased towards people who do volunteer backcountry search and rescue).
Like I said, I'm not try to discredit these folks as skilled (and in many cases, extremely smart) individuals.
However, a couple weeks of a rotation through an ER during med school isn't really going to prepare you well for prehospital emergencies (SAR, on the other hand, can be great training for that). Making an assessment and clinical decisions based on fairly limited information isn't something I've found most physicians to be comfortable with, especially in an emergency setting.
My list of 'glad to see you' docs is pretty much: ER, OB, and Anesthesia.
I think I'd be happy for a vet to do some doctoring.