In simple words: This code is used when an anesthesiologist is supervising more than four operations at the same time that require anesthesia.

This modifier is used when an anesthesiologist provides medical supervision for more than four concurrent anesthesia procedures. Concurrent means there is some overlap, possibly as little as one minute, between the procedures. The anesthesiologist may also be performing other services while directing the concurrent procedures.

Example 1: An anesthesiologist is supervising five concurrent procedures involving certified registered nurse anesthetists (CRNAs). The procedures have overlapping times, making them concurrent. The anesthesiologist performs the pre-anesthetic evaluation, prescribes the anesthesia plan, and is available to intervene if necessary., An anesthesiologist is supervising four concurrent procedures with CRNAs while simultaneously performing other tasks, such as reviewing patient charts or consulting with other physicians. Even though only four procedures are being supervised, modifier AD is used because the anesthesiologist is performing other services concurrently., An anesthesiologist is called to the operating room to medically supervise six ongoing procedures performed by CRNAs because of unexpected complications in several patients.

Documentation should support the number of concurrent procedures being supervised, the time overlap, and any other services the anesthesiologist performed concurrently. If claiming the additional time unit for being present at induction, this also needs to be documented.