It depends on if you are billing for the anesthesiologist or the center the services are being performed. if you are billing for the dr/crna, you do not use G codes--only medicare pts for the reimbursement. i.e., G8427--documentation of medication, this has NO value to it, just a reporting code. How is your billing system setup? Does it crosswalk the actual surg code to the anesthesia code? or do you have to add the anesthesia code in? (send me a private message if you want to discuss further) the only modifer you can use to distinguish its a MAC case is, "QS". there is no ASA code. Do you have the ASA crosswalk book from the american society of anesthesiology? that would help you out alot too. Like i said, send me a Private message if you want, or feel free to contact me via telephone, would be glad to help.