Coding with asa crosswalk

I'm in search of a website or another place I maybe able to locate the answer. I was told previously that the Anesthesia crosswalk book is to be used only as a guide to cross the CPT codes to the ASA and that as long as the ASA fits within the description of the procedure, that ASA can be used, even if it is not listed as a valid cross in the crosswalk. Any input or insight into this matter would be of great help.

Thank you

Coding with asa crosswalk