An advance medical directive is something entirely different than a physician's "Do not attempt resuscitation" order entered into your medical record once you are in the hospital. They have very different rules. MDinana is entirely correct that a physician's DNAR may not be honored elsewhere, and it will likely to cease having any effect once you are discharged.

But, an advance medical directive, properly prepared and legally sufficient, is a binding legal document. It must be honored at ANY hospital. If some hospital refuses to honor one of my client's directives simply because it's not on their own form, I'll have their posterior in front of a judge so fast their heads will spin, and that's one advantage of having a lawyer prepare the document with you. Mine have my after hours cell phone printed on it for just such emergencies, along with many other provisions covering all sorts of circumstances that I've not seen anyone else include.

Also, because they have neither the time nor the ability to review the legal sufficiency of your advance medical directive in an out of hospital emergency, paramedics in most jurisdictions are trained to simply ignore it, and let the hospital folks sort it out. However, as MDinana correctly points out, some jurisdictions have special out of hospital forms aimed at paramedics. Florida does. Check for this in your jurisdiction.

MDinana gives wise advice to "make sure you understand the legalities in your area about when it does and doesn't apply." The rules can vary in different jurisdictions. I'm not offering legal advice here, just information for you to discuss with your own attorney familiar with your jurisdiction.

Jeff