Modifier code 23 (unusual anesthesia) should be used to indicate anesthesia services complicated by procedures performed in the prone position or by field avoidance. When used for this purpose, modifier code 23 has a unit value of 1.
Documentation
When submitting a claim with a modifier 23, please include the operative report, anesthesia records as well as the indication justifying its use.
Claims Filing Information
Example
The patient had surgery on the popliteal vein due to phlebitis. The administration of the anesthesia was complicated by the patient’s prone position. The anesthesiologist was in attendance for one hour (60 minutes).
Note: Two modifiers have been used -- modifier AA, to indicate that the procedure was performed by an anesthesiologist, and modifier 23, indicating anesthesia services complicated by procedures performed in the prone position or by field avoidance. A multiple modifier indicator such as 99 is not required.
Recognized Procedures
The following list represents the CPT codes with which modifier code 23 (indicating prone position or field avoidance) may be used. This modifier may be used for other purposes.
| Code | Description |
|---|---|
| 00210 | Anesthesia for intracranial procedures, not otherwise specified |
| 00215 | Anesthesia for intracranial procedures, not otherwise specified; cranioplasty or elevation of depressed skull fracture, extradural (simple or compound) |
| 00600 | Anesthesia for procedures on cervical spine and cord, not otherwise specified |
| 01430 | Anesthesia for procedures on veins of knee and popliteal area; not otherwise specified |
| 01462 | Anesthesia for all closed procedures on lower leg, ankle and foot |
| 01464 | Anesthesia for arthroscopic procedures of ankle and or foot |
| 01470 | Anesthesia for procedures on nerves, muscles, tendons, and fascia of lower leg, ankle, and foot; not otherwise specified |
| 01480 | Anesthesia for open procedures on bones of lower leg, ankle, and foot; not otherwise specified |
| 01520 | Anesthesia for procedures on veins of lower leg; not otherwise specified |
| 01680 | Anesthesia for shoulder cast application, removal or repair; not otherwise specified |
| 01710 | Anesthesia for procedures on nerves, muscles, tendons, fascia, and bursae of upper arm and elbow; not otherwise specified |
| 01730 | Anesthesia for all closed procedures on humerus and elbow |
| 01732 | Anesthesia for diagnostic arthroscopic procedures of elbow joint |
| 01780 | Anesthesia for procedures on veins of upper arm and elbow; not otherwise specified |
| 01951 | Anesthesia for second- and third-degree burn excision or debridement with or without skin grafting, any site, for total body surface area (TBSA) treated during anesthesia and surgery; less than 4% total body surface area |
| 01952 | Anesthesia for second- and third-degree burn excision or debridement with or without skin grafting, any site, for total body surface area (TBSA) treated during anesthesia and surgery; between 4% and 9% of total body surface area |
Note: Anesthesia risk modifiers should be billed only by the practitioner actually administering the anesthesia. In cases where a CRNA is administering anesthesia under the supervision of an anesthesiologist, the CRNA may bill for the anesthesia risk modifier, but the supervising anesthesiologist may not.
Revision History
| Date | Nature of Revision |
|---|---|
| 08/03/2026 | Migrated to new platform. |