In simple words: This code is used when a patient receives monitored anesthesia care (MAC) during a procedure. MAC involves a combination of local anesthetic and sedation, along with continuous monitoring of the patient's vital signs.

Modifier QS indicates that the anesthesia provider performs monitored anesthesia care (MAC). MAC involves monitoring the patient’s vital signs while in the operating room, examination prior to anesthesia, the prescription for anesthesia care, and postoperative care.

Example 1: A patient receives a local anesthetic and sedation for a colonoscopy. The anesthesia provider monitors the patient's vital signs throughout the procedure. Modifier QS is appended to the anesthesia code., A patient undergoes a carpal tunnel release with MAC anesthesia. Modifier QS is appended to the anesthesia code to indicate that MAC was provided., A patient with a history of severe cardiac disease requires MAC for a minor surgical procedure. Modifier QS is used to specify the anesthesia type. Because of the patient's cardiac history, G9 modifier is also used.

Documentation should support the medical necessity of MAC and include details of the patient's condition, the procedure performed, and the anesthesia services provided.

** Some payers may provide additional reimbursement for the use of this modifier, but only if the reasons for providing MAC are medically necessary and well-documented.