while what you say is true, that "NA" is often used to mean "nursing assistent" or "nurses aide" it is not being used in that context here. It is being used to mean "Nurse Anesthetist" in these discussions.
Another example of this is "AANA." That is being used to mean the "American Association of Nurse Anesthetists" in these discussions and not the "Arthroscopy Association of North America." www.aana.org
I think anyone reading posts on a discussion board talking about anesthesia is going to realize "NA" means "Nurse Anesthetist" and not be confused with some other designation. Just as they are going to realize "MDA" means physician anesthesiologist and not the "Muscular Distropy Association."
Lets not muddy the waters and go off on tangents. K?