CPT code 01140: Anesthesia for hindquarter amputation

Key Takeaways

CPT code 01140 describes anesthesia for interpelviabdominal amputation (hindquarter amputation), a major pelvic surgery requiring general anesthesia

Anesthesia billing uses the formula (base units + time units) x conversion factor; base units are fixed per code while time units accrue per 15-minute interval

Modifiers AA, AD, QK, QX, QY, and QZ govern who performed or medically directed the anesthesia; using the wrong modifier is the most common audit trigger for 01140

Pabau’s claims management software helps anesthesia billing teams track modifier assignments, document ASA physical status, and reduce claim denials

CPT code 01140 is the anesthesia code for interpelviabdominal amputation, commonly called a hindquarter amputation. It carries 15 base units, the highest value in its pelvis code family, and that dollar amount draws payer attention.

Most denials on this code don’t trace back to an undocumented procedure. They trace back to a mismatched modifier, a missing start or stop time, or an ASA physical status class that never reached the claim form.

CPT code 01140: Definition and clinical description

CPT code 01140 describes anesthesia services for interpelviabdominal amputation, commonly called a hindquarter amputation or hemipelvectomy.

The procedure involves removal of an entire lower extremity along with all or part of the hemipelvis. It is one of the most extensive oncologic or trauma surgeries performed on the pelvic region, requiring general anesthesia with full hemodynamic monitoring.

Within the AMA CPT code set, anesthesia codes occupy the 00100-01999 range, organized by anatomic region. CPT 01140 falls within the pelvis subgroup (01112–01173), which covers procedures on the pelvis except the hip.

The “except hip” qualifier matters: hip-specific anesthesia codes start at 01200 and are billed separately, so coding the wrong anatomic region is a straightforward audit flag.

How anesthesia billing works: The base unit + time unit formula

Unlike surgical CPT codes, anesthesia reimbursement is not a single flat fee. Payment is calculated using a three-variable formula that every anesthesia biller needs to know precisely. According to the CMS Physician Fee Schedule, the standard anesthesia payment formula is:

(Base Units + Time Units) x Conversion Factor = Allowable Payment

Each variable works differently. Base units are fixed per CPT code, reflecting procedural complexity. Time units accrue during the case, one time unit per 15 minutes of anesthesia time, with partial units typically rounded. The conversion factor is a dollar-per-unit value set by CMS for Medicare and negotiated separately by commercial payers.

Because all three variables interact, a small error in any one produces a proportionally larger underpayment or overpayment. Anesthesia practices using claims management software can automate the formula and flag missing time documentation before submission.

CPT 01140 base units

CPT 01140 carries a base unit value reflecting the high complexity of hindquarter amputation. Per the VA Table H and ASA Relative Value Guide, the base unit value for 01140 is 15 base units.

CMS assigns base unit values annually. Verify the current value against the FastRVU 2026 lookup tool before submitting claims, as values can change with fiscal year updates.

The table below compares 01140 against adjacent pelvis anesthesia codes to show how base units scale with procedural complexity.

Base unit values above are sourced from published reference tables and should be confirmed against the current ASA Relative Value Guide or CMS data before billing. Similar verification practices apply when billing coaching CPT codes or any specialty code with annual value updates.

Medicare fee schedule and reimbursement for CPT code 01140

Medicare anesthesia payment is locality-dependent. CMS applies a Geographic Practice Cost Index (GPCI) adjustment, so the allowable amount for CPT 01140 differs by payment locality. There is no single national rate that applies uniformly to every practice.

For current 2026 rates, query the CMS Physician Fee Schedule lookup tool using the modifier (AA for personally performed) and your MAC locality code.

CMS publishes an anesthesia conversion factor every year. For CY2026, the non-facility conversion factor is approximately $20.50 per unit, per the CMS Anesthesiologists Information Center. Confirm the current-year figure before billing. A 3-hour case for CPT 01140 accrues 12 time units (180 minutes / 15). With 15 base units, the total is 27 units.

At that conversion factor, the estimated allowable is roughly $553 before the GPCI adjustment. Commercial payers negotiate separate rates and may apply their own conversion factors. Practices billing other procedure codes, including IVF CPT codes, face similar locality-driven reimbursement variability.

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Applicable modifiers for CPT code 01140

Modifier selection for CPT 01140 depends on who administered the anesthesia and the supervisory relationship in place. Using the wrong modifier is the most common trigger for post-payment audits on anesthesia claims. Six modifiers apply to this code.

Medical direction and CRNA billing under CPT 01140

CMS requires anesthesiologists to meet seven specific criteria to qualify for the QK medical direction rate under Medicare. These are documented in Chapter 12 of the CMS Claims Processing Manual.

• Performed a pre-anesthesia examination and evaluation
• Prescribed the anesthesia plan
• Was physically present for induction and emergence
• Remained immediately available throughout the procedure
• Provided indicated post-anesthesia care
• Did not direct more than four concurrent procedures
• Documented all the above in the medical record

Failing any one of these criteria drops the claim to the AD modifier rate, which pays less. QZ applies whenever no anesthesiologist medically directs the case, whether or not the state has opted out of CMS physician supervision requirements. State opt-out status governs a separate, facility-level supervision requirement under Medicare Conditions of Participation.

It does not decide which modifier a CRNA bills under Part B. A CRNA can properly bill QZ in a non-opt-out state any time the medical direction criteria were not met. This distinction shows up in other scope-of-practice billing questions too, including the documentation rules for ADHD screening CPT codes.

Billing and documentation requirements for CPT 01140

Anesthesia claims are among the most documentation-intensive in outpatient and surgical billing. For CPT 01140, the following items must be present in the record before claim submission. Missing any one creates grounds for denial or post-payment recovery.

• Pre-anesthesia evaluation: completed before the procedure, documenting patient history, physical examination, and planned anesthetic approach
• ASA physical status classification: documented by the anesthesiologist at the pre-anesthesia evaluation (ASA I through VI)
• Anesthesia start and stop times: exact times entered in the anesthesia record; these drive time unit calculation
• Intraoperative anesthesia record: continuous documentation of vital signs, agents administered, and significant events
• Post-anesthesia note: evaluation of patient status in the PACU or recovery area
• Informed consent: signed prior to procedure
• Modifier justification: documentation supporting the modifier billed (e.g., the seven QK criteria for medical direction)

Solid documentation practices protect against audit exposure and support the healthcare compliance documentation standards that apply across surgical specialties.

That discipline carries into the rehabilitation phase too, where practices using physical therapy EMR keep the mobility and prosthetic-fitting timeline linked to the same patient record.

ASA physical status classification and its role in anesthesia coding

The ASA Physical Status (PS) classification, maintained by the American Society of Anesthesiologists, describes the patient’s pre-operative physical condition. It does not directly change the base unit value for CPT 01140, but it is required documentation and affects qualifying circumstance add-on code selection.

Qualifying circumstance add-on codes (99100 for extreme age, 99140 for emergency conditions) can be billed alongside CPT 01140 when clinically supported. Each one needs its own documentation in the anesthesia record, tied to the condition documented in the chart rather than assumed from the case type.

CPT code 01140 vs related pelvis anesthesia codes

Selecting the wrong pelvis anesthesia code is a common error, particularly between 01112, 01140, and 01150. The distinctions are procedural. The table below lays out the key differentiators to help coders choose correctly.

Code selection depends entirely on what the surgeon performed, not on what the anesthesiologist anticipated. If the operative report documents a hindquarter amputation, CPT 01140 is the only defensible code. Using 01112 or 01150 when 01140 is clinically supported constitutes undercoding and leaves reimbursement on the table.

For broader procedure code context, practices can also review how procedure code fee schedules are structured across different billing environments. Similarly, surgical practices managing pelvic oncology workflows may benefit from dedicated surgical practice management tools that integrate billing and clinical documentation.

Common billing errors and compliance pitfalls for CPT 01140

CPT 01140 generates a higher dollar claim than most anesthesia codes. That visibility attracts payer scrutiny. These are the errors that appear most frequently in post-payment audits and claim denials.

• Wrong modifier: Billing AA when QK was required (or vice versa) is the single most common trigger. Modifier choice must match the actual supervisory arrangement documented in the record, not what the biller assumed.
• Missing start/stop times: Without exact anesthesia start and stop times, payers cannot verify time unit calculations. Claims without this documentation are routinely flagged or denied.
• Incorrect time unit calculation: Rounding partial units inconsistently, or counting time from surgical incision rather than anesthesia induction, produces calculation errors that differ from payer expectations.
• Missing ASA physical status: ASA PS classification must be explicitly documented; “patient was in good health” is not sufficient. The anesthesiologist must record the classification (ASA I through VI) by class number.
• Exceeding the four-procedure QK limit: If the anesthesiologist directed five or more concurrent cases, modifier QK cannot be used. AD is required. Billing QK for a five-case scenario constitutes a false claim.
• Assuming QZ needs an opt-out state: QZ depends on whether an anesthesiologist medically directed the case, not on state opt-out status. A CRNA can bill QZ in a non-opt-out state whenever no anesthesiologist medically directed the case.

Practices using dedicated medical practice scheduling software integrated with billing workflows can build modifier selection prompts and documentation checklists into pre-submission review, reducing manual error rates. The same systematic approach that prevents errors on CPT 01140 applies across all high-value specialty codes.

Conclusion

CPT code 01140 is a high-complexity, high-value anesthesia code with narrow documentation tolerances. The billing formula itself is simple. The compliance exposure comes from modifier selection errors and missing record elements. Get the modifier right, capture exact times, document ASA physical status by class number, and check the base unit value and conversion factor every year.

Anesthesia claims like this one carry a lot of moving parts in one record. The modifier, the times, the ASA class, the qualifying circumstances all have to line up.

Practice management software like Pabau keeps those pieces attached to the same patient file, so a biller can check the modifier against the documented supervisory arrangement before the claim goes out, not after a payer sends it back.

If that fits how your anesthesia or surgical billing team works, book a demo.

Continue your research

Need the rest of the pelvis-except-hip family? CPT code 01120 covers the bony-pelvis code most often confused with 01140.

Coding the leg instead of the pelvis? CPT code 01230 breaks down anesthesia base units for the upper-femur family next door.

Want the documentation standards behind the anesthesia record? Nursing documentation covers the charting standards anesthesia records lean on too.

Frequently asked questions