Jeanette, you're overthinking this.

Anxiety attacks are quite easy to diagnose, as a rule. Even more so if you tell the provider "Hey, I have anxiety!" or "I take Ativan!" As far as I know, no EMS agency allows their medics to give Ativan for anxiety only, so being in an acute attack wouldn't change most treatment options.

If your attack does get to the point you pass out, well, you'll have stopped hyperventilating, and likely awoken, by the time EMS arrives.

As for your drugs, if you feel it's a potential issue, then get the tag with your meds. If you've got concurrent depression, then concievably you could OD on them. It won't help EMS (they don't carry the antidote) but it may help the ED. Assuming you don't have someone with you to tell them what you take.

Ditto Pete - he's pretty much spot on in my experiences.