I agree with Jurassicpark.
As a paramedic, I can tell you that many physicians never learn to handle emergencies. In the same way that I'm not much good without a lot of my toys, an ER doc would be fairly out of his element outside of the hospital.
The key thing outside of the hospital would be to focus on the BLS and keep the person alive until more help arrives. With experience, you might have a better idea of what is going on, but I doubt that would help you manage an out-of-hospital emergency very much.