What modifier should be used when a CRNA performs services without medical direction?

The correct modifier used when a Certified Registered Nurse Anesthetist (CRNA) performs anesthesia services without medical direction is QZ. This modifier indicates that the CRNA is acting independently and is solely responsible for the anesthesia services provided, without the supervision of a physician. It allows for proper billing that reflects the level of autonomy under which the CRNA operates, ensuring that they are appropriately reimbursed for their work in situations where they are not following physician directives.

In contrast, the other modifiers serve distinct purposes: the QX modifier signifies that the services were performed with medical direction, the AD modifier is used to indicate medical supervision by a physician for multiple anesthesia services, and G9 indicates that the anesthesia service was for a procedure that is typically considered high risk. Therefore, in the context of services rendered independently by a CRNA, the QZ modifier is the appropriate choice.