One could carry such a letter. It will only be as effective as the attitude of the ER you go to and the attitude of the attending ER doctor.

I have been a chronic pain patient for 30 years and have been officially disabled since 1995. I have been in a disciplined relationship with my current pain doc for almost seven years now. I had my 8th spinal surgery two weeks ago and this was the third time this particular spinal surgeon had worked on me. Prior to discharge, the surgeon discontinued my Fentanyl patch, throwing me into withdrawl. He also advised me that I was not disabled but a dead beat as I was an addict. I was further advised that I did not deserve rehab., home health etc. These services were also discontinued by this illustrious surgeon. My primary and pain docs were able to re-establish these services but it has taken time and I have been out on a limb post operatively. Best wishes.