The modifier that includes the term "unusual anesthesia" is Modifier 23. This specific modifier is used to indicate that a procedure usually performed under local anesthesia was carried out under general anesthesia due to unusual circumstances. The presence of unusual conditions necessitating general anesthesia reflects a significant deviation from the norm, which is crucial for proper coding and reimbursement.
In contrast, the other modifiers listed have different purposes. The QX modifier is used to indicate that a qualified non-physician anesthetist is providing anesthesia under the medical direction of a physician. The G9 modifier is applied when there is a procedure that typically requires general anesthesia but is performed under local anesthesia due to the patient's specific circumstances. The AD modifier is not commonly associated with anesthesia; it usually denotes a specific type of visit or service adjustment.
Thus, understanding the specific context of modifier 23 clarifies why it is the appropriate choice for denoting situations involving unusual anesthesia requirements.