CRNA orders

Any practicing CRNA's have input on this issue?

http://allnurses.com/forums/showthre...threadid=54292

When a CRNA gives orders to an RN do they have to be cosigned by an MDA or ok'd by an MDA? I wouldn't think so because some facilities don't have MDA's but I thought this issue would be best answered by practicing CRNA's.