This how I read and bring it to the discussion:
One rule of thumb, I remember, it is to report an anesthesia code if the block or injection is used as the anesthesia for the surgical procedure and use the appropriate pain-management, nerve block or injection code instead if it is a stand-alone injection or procedure.
In surgical situations, either the surgeon or the anesthesiologist might administer the nerve block. Often, however, the anesthesiologist is still likely to provide patient monitoring as well as additional medication to help calm the patient. Therefore, the anesthesiologist should bill the service with anesthesia codes that accurately reflect the level of care, Johnson says.
In this instance, you can bill nerve blocks only for pain management. Ruiz-Law cautions that some managed care companies will lump retrobulbar blocks into the ocular surgery payment. Other carriers consider the blocks local anesthesia and bundle it with the anesthesia code. (If the payment for a block is bundled into the surgical code, it is up to the surgeon and anesthesiologist to negotiate fees.)
A retrobulbar block, like other nerve blocks, cannot be billed separately if it is administered as monitored anesthesia care (MAC) for cataract or other surgeries. Instead, anesthesiologists should bill their time with the appropriate anesthesia code, even if care was provided in discontinuous time segments. For example, if the anesthesiologist placed a block from 7:50 until 8 a.m., then returned to monitor the patient from 8:30 until 9:20 a.m., billing is for the 60 minutes spent with the patient.