Question: I have exhausted all my resources and wondered if you know whether the Medicare manuals offer any guidelines for billing time for two anesthesia personnel on a high-risk complex case, such as a liver transplant? Colorado Subscriber Answer: Medicare Claims Processing Manual, Chapter 12, Section 50.B, addresses payment when a physician and a Certified Registered Nurse Anesthetist (CRNA) or anesthesiologist’s assistant are medically necessary for a single case. In the sixth bullet, Section 50.B states that the Medicare contractor “must determine the fee schedule payment, recognizing the base unit for the anesthesia code and one time unit per 15 minutes of anesthesia time if … the physician and the CRNA (or anesthesiologist’s assistant) are involved in one anesthesia case and the services of each are found to be medically necessary. Documentation must be submitted by both the CRNA and the physician to support payment of the full fee for each of the two providers. The physician reports the AA modifier [Anesthesia services performed personally by anesthesiologist] and the CRNA reports the QZ modifier [CRNA service: without medical direction by a physician].” While the manual does not specifically address two anesthesiologists, if this situation occurs, you can try applying the same logic. Report modifier AA on each claim, and make sure documentation shows the services of each provider. The payer may initially deny the claim. An appeal with the information outlined above may be necessary to determine whether Medicare also recognizes two physicians under the same circumstances.