I would hope having a letter or some sort of official documentation from your PM about your health status & dx's would be helpful.

At least it would help to verify to ER personnel that you are under the care of a PM and do have legitimate reasons for needing extra pain control at times.
Especially if ER visit is during off hours or your PM can't be reached for verification.

There should be some way to have something on record ahead of time and verified at the hospital, just in case a ER trip is needed.

Might be just a case of asking the PM office to prepare a letter for you, or to fax it right to the hospital in question.

But it is also a good idea to have something official on your person in case of accidents or if away from home and an emergency happens, then you have the info with you.

Some print up a medical ID card with main dx, meds & drs listed, and carry that in the wallet or billfold.