Question: Two of our anesthesiologists participated in a cased of separating 2-year-old conjoined twins. Anesthesiologist A placed a central line and administered general anesthesia when the surgeon completed a tracheostomy for Twin A. Anesthesiologist B monitored Twin B but didn't provide other services. How should I bill for each physician and baby? New York Subscriber Answer: For this case, you should report 00320 (Anesthesia for all procedures on esophagus, thyroid, larynx, trachea and lymphatic system of neck; not otherwise specified, age 1 year or older) for both anesthesiologists' services. Twin A's anesthesia affects Twin B, so your second anesthesiologist was probably there to monitor Twin B during the procedure. Report this service as monitored anesthesia care (MAC) with modifier QS (Monitored anesthesia care service), modifier 23 (Unusual anesthesia) or modifier 52 (Reduced services). Follow the carrier's guidelines to determine which modifier to report. Caution: Some carriers consider the twins as one patient until the surgeon separates them, which means they want to pay only one claim. Both anesthesiologists should be paid in full for their work, however, because both will be working very hard on their individual patient. Work with your carrier to ensure this happens.