Wiki Arterial line VS 59 Modifier

[beulastella]

We use 59 modifier along with nerve block to denote it as a distinct procedure when it is done with a main procedure, but why Can't we append 59 modifier with arterial line (cpt procedure) in anesthesia when it is done with another main procedure.? kindly suggest if any specific reason behind it.

Thanks,

 

[dwaldman]

Can you give an example of a "main procedure"?