From my friend V. Ramirez, CPC, CHC
Reduced service modifiers used in ASCs are 73 and 74. Modifier 52 is used for in office procedures.
73
Discontinued Outpatient Hospital/Ambulatory Surgery Center (ASC) Procedure Prior to the Administration of Anesthesia
(Note that under OPPS, anesthesia includes general, local and regional block(s), moderate sedation/analgesia (conscious sedation), and deep sedation/analgesia. ~Used to indicate a discontinued procedure and is applicable for surgical procedures and certain diagnostic procedures only. This modifier is not used to indicate discontinued radiology procedures.~Used to report a discontinued outpatient hospital/ASC procedure prior to the administration of anesthesia (local, regional blocks, general).~Never report the elective cancellation of procedures. This modifier applies in extenuating circumstances and when the well-being of the patient is threatened. The patient must be taken to the room where the procedure is to be performed to report modifier 73.~If available, use a CPT code that classifies the extent of the procedure performed instead of reporting the intended procedure. When one or more of the planned procedures is completed, report the completed procedure as usual. Any others that were planned and not started are not reported. When none of the procedures that were planned are completed, the first procedure that was planned to be done is reported with this modifier.)
Due to extenuating circumstances or those that threaten the well being of the patient, the physician may cancel a surgical or diagnostic procedure subsequent to the patient's surgical preparation (including sedation when provided, and being taken to the room where the procedure is to be performed), but prior to the administration of anesthesia (local, regional block(s) or general). Under these circumstances, the intended service that is prepared for but cancelled can be reported by its usual procedure number and the addition of modifier 73. Note: The elective cancellation of a service prior to the administration of anesthesia and/or surgical preparation of the patient should not be reported. For physician reporting of a discontinued procedure, see modifier 53.
74
Discontinued Outpatient Hospital/Ambulatory Surgery Center (ASC) Procedure After Administration of Anesthesia
(Note that under OPPS anesthesia includes general, local and regional block(s), moderate sedation/analgesia (conscious sedation), and deep sedation/analgesia. ~When used to indicate a discontinued procedure, modifier 74 is used for surgical procedures and certain diagnostic procedures only. This modifier is not used to indicate discontinued radiology procedures.~Used to report a discontinued outpatient hospital/ASC procedure after the administration of anesthesia or after the procedure was started (incision made, intubation started, scope inserted).~Never report the elective cancellation of procedures. This modifier applies in extenuating circumstances and when the well-being of the patient is threatened. The patient must be taken to the room where the procedure is to be performed to report modifier 74.~If available, use a CPT code that classifies the extent of the procedure performed instead of reporting the intended procedure. When one or more of the planned procedures is completed, report the completed procedure as usual. Any others that were planned and not started are not reported. When none of the procedures that were planned are completed, the first procedure that was planned to be done is reported with this modifier.)
Due to extenuating circumstances or those that threaten the well being of the patient, the physician may terminate a surgical or diagnostic procedure after the administration of anesthesia (local, regional block(s), general) or after the procedure was started (incision made, intubation started, scope inserted, etc). Under these circumstances, the procedure started but terminated can be reported by its usual procedure number and the addition of modifier 74. Note: The elective cancellation of a service prior to the administration of anesthesia and/or surgical preparation of the patient should not be reported. For physician reporting of a discontinued procedure, see modifier 53.