CPT Code 00450: Anesthesia for clavicle and scapula procedures

Key Takeaways

CPT Code 00450 covers anesthesia for surgical procedures on the clavicle and scapula, not otherwise specified, as defined by the American Medical Association (AMA).

Base units for 00450 are 5, used in the standard anesthesia reimbursement formula: (base units + time units) x conversion factor.

Modifier selection (AA, QK, QX, QZ) determines how the claim is paid under Medicare; incorrect modifier use is a leading audit trigger for this code.

Pabau’s claims management software helps practices track claim status, flag missing required details before submission, and reconcile insurer payments from one dashboard.

CPT Code 00450 is the anesthesia code for surgical procedures on the clavicle and scapula that don’t have a more specific code assigned. It carries 5 base units and covers a broad range of shoulder-girdle surgeries, from clavicle fracture repair to scapulectomy, delivered as general anesthesia, regional anesthesia, or monitored anesthesia care (MAC).

This reference covers the full clinical scope of CPT Code 00450, including its 2026 Medicare fee schedule, base unit value, applicable anesthesia modifiers, ICD-10 crosswalk, documentation requirements, and CRNA (Certified Registered Nurse Anesthetist) billing rules, along with the compliance pitfalls that most often trigger a payer audit or claim denial.

CPT Code 00450: definition and clinical scope

CPT Code 00450 describes anesthesia services for surgical procedures performed on the clavicle and scapula, not otherwise specified. It sits within the Anesthesia section of the AMA’s CPT code set, under the subsection covering procedures on the shoulder girdle.

The “not otherwise specified” (NOS) descriptor is important. It signals that no more specific anesthesia code exists for the procedure being performed. Coders should always verify whether a more specific code applies before defaulting to 00450.

Clinical procedures covered by CPT Code 00450

CPT Code 00450 applies when a patient undergoes surgery on the clavicle or scapula and requires anesthesia services. The range of qualifying procedures is broad, reflecting the NOS designation. Orthopedic and sports medicine practices bill it most often for post-injury clavicle repairs, while groups running plastic surgery caseloads use it for scapulectomy and reconstructive procedures.

• Clavicle fracture open reduction and internal fixation (ORIF) – the most frequently billed procedure paired with 00450
• Clavicle excision or resection – including distal clavicle excision for acromioclavicular joint pathology
• Scapula fracture repair – surgical stabilization of displaced scapular fractures
• Scapulectomy (partial or total) – resection procedures for tumor or chronic infection
• Clavicle biopsy – open biopsy for suspected neoplasm or infection
• Shoulder girdle decompression – procedures on the clavicle or scapula not covered by a more specific anesthesia code
• Pseudarthrosis repair – surgical correction of failed clavicle fracture union

If the procedure involves the glenohumeral joint, humeral head, or acromioclavicular joint as the primary surgical site, a different anesthesia code may apply. Head and neck procedures, such as those billed under 00212, fall under a separate anesthesia code family entirely. Always cross-reference the operative report against the CPT anesthesia code hierarchy before billing 00450.

Anesthesia base units for CPT Code 00450

The American Society of Anesthesiologists (ASA) assigns base units to each anesthesia CPT code based on the complexity and risk of the associated surgical procedure. CPT Code 00450 carries a base unit value of 5.

Base units are the starting point for every anesthesia reimbursement calculation. They reflect the inherent difficulty of providing anesthesia for that category of procedure, independent of how long the case takes. You can verify current base unit values through the FastRVU 2026 RVU lookup tool, which pulls CMS data directly.

How anesthesia reimbursement is calculated using CPT Code 00450

Medicare and most commercial payers use a standardized formula to calculate anesthesia reimbursement. The formula is: (Base Units + Time Units + Qualifying Circumstance Units) x Conversion Factor = Allowed Amount.

Here is a worked example for CPT Code 00450 under Medicare:

1. Base units: 5 (fixed for 00450)
2. Time units: 4 (a 60-minute procedure at 1 unit per 15 minutes)
3. Qualifying circumstances: 1 (if the patient is under age 1 or over age 70, add 1 unit via code 99100)
4. Total units: 5 + 4 + 1 = 10
5. Conversion factor (example): $20.32 per unit (2025 national rate; the 2026 rate is set annually by CMS via the Physician Fee Schedule)
6. Allowed amount: 10 x $20.32 = $203.20

Actual reimbursement varies by locality, payer contract, and whether qualifying circumstance add-on codes apply. The conversion factor changes each January 1 under the Medicare Physician Fee Schedule Final Rule.

2026 Medicare fee schedule for CPT Code 00450

Medicare publishes locality-adjusted anesthesia conversion factors annually. The national rate below is illustrative; your actual reimbursement depends on the CMS locality for your practice’s billing address. Check the procedure code fee schedule reference for multi-payer context.

*Approximate figures based on a national conversion factor near $20.32 per unit. Always verify the current CMS-published rate for your locality before submitting claims. The 2026 final conversion factor is set in the CMS Physician Fee Schedule Final Rule. QC in the table above stands for qualifying circumstances, the add-on units covered in detail below.

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Applicable modifiers for CPT Code 00450

Anesthesia modifier selection is the most consequential billing decision for CPT Code 00450. The modifier tells the payer who performed the anesthesia and under what supervisory arrangement. Selecting the wrong modifier is one of the top reasons for denied and down-coded claims.

QK and QX are always billed as a pair: the supervising anesthesiologist bills QK, and the CRNA bills QX on a separate claim for the same case. Billing them separately on the same claim line triggers an automatic edit.

ASA physical status and qualifying circumstances

The ASA physical status classification documents the patient’s pre-operative health status. It is required on every anesthesia claim and affects documentation, not the base unit calculation directly. However, qualifying circumstance add-on codes tied to patient characteristics do affect total reimbursable units.

The four qualifying circumstance add-on codes recognized by CMS and the AMA are:

• 99100 – Anesthesia for patient of extreme age (younger than 1 year or older than 70): +1 unit
• 99116 – Anesthesia complicated by utilization of total body hypothermia: +5 units
• 99135 – Anesthesia complicated by utilization of controlled hypotension: +5 units
• 99140 – Anesthesia complicated by emergency conditions: +2 units

Never bill a qualifying circumstance code without clinical documentation to support it. 99116 (total body hypothermia) and 99135 (controlled hypotension) are distinct circumstances, so both can be reported on the same case if each is separately documented.

Billing either one without supporting documentation is an overbilling pattern CMS flags in audits. This is documented in the billing compliance requirements for medical offices.

ICD-10 codes commonly used with CPT Code 00450

The ICD-10 diagnosis code on the claim must support the medical necessity of both the surgical procedure and the anesthesia service. For CPT Code 00450, the most common pairings involve clavicle fractures, scapular injuries, and shoulder girdle conditions requiring surgery.

A cardiac comorbidity code such as I49.9 illustrates how a secondary diagnosis can also influence ASA physical status documentation. Bone-fragility conditions such as M83.8 are another comorbidity worth flagging when a pathological clavicle or scapula fracture is part of the surgical picture.

Payer Local Coverage Determinations (LCDs) may restrict certain ICD-10/CPT pairings. Always verify diagnosis-to-procedure pairing against the applicable MAC’s LCD before submitting. The AAPC CPT-to-ICD-10 crosswalk tool provides a starting point; payer-specific LCD acceptance is the final arbiter. For an example of diagnosis coding in complex oncologic cases, see M36.0.

Documentation requirements for billing CPT Code 00450

Incomplete documentation is the second-most-cited reason for anesthesia claim denial after modifier errors. Every CPT Code 00450 claim needs a complete anesthesia record, starting with a signed consent for medical treatment before the case begins. Storing these records in Pabau’s digital forms and documentation tools reduces the risk of missing paper-based records during audits.

• Anesthesia start and stop times – exact times (hours and minutes) that anesthesia was initiated and discontinued; used to calculate time units
• Name and CPT code of the surgical procedure – must match the operative report exactly
• ASA physical status classification – P1 through P6, documented by the anesthesiologist pre-operatively
• Type of anesthesia administered – general, regional, MAC, or a combination
• Provider credentials – whether the service was personally performed (AA), medically directed (QK/QX), or independently performed by a CRNA (QZ)
• Qualifying circumstances documentation – clinical evidence for any 99100, 99116, 99135, or 99140 add-on code billed
• Pre-anesthesia evaluation note – patient assessment, planned anesthetic technique, and risk discussion
• Post-anesthesia note – patient status at handoff to recovery

CMS requires that every element listed above be present in the medical record before the claim is submitted. See billing compliance requirements for how HIPAA intersects with billing documentation standards. The ADHD screening CPT code documentation framework illustrates how structured pre-service documentation reduces audit exposure across CPT categories.

CRNA and medical direction billing rules

Whether a CRNA can bill CPT Code 00450 independently depends on two factors: whether the state has opted out of the federal physician supervision requirement, and the payer’s specific policy. CMS allows states to waive the federal supervision mandate for Medicare patients, and as of the most recent CMS policy update, over 20 states have exercised that opt-out.

Medical direction requires the anesthesiologist to meet seven specific CMS conditions for each case:

• Performing the pre-anesthesia evaluation
• Prescribing the anesthesia plan
• Being present for induction
• Being available throughout the procedure
• Providing post-anesthesia care
• Not concurrently directing more than four procedures
• Not performing any other services during the case

Failure to document any one of these conditions reduces the claim to the AD supervision rate or triggers denial.

Related anesthesia CPT codes

When 00450 does not precisely describe the procedure performed, check these adjacent codes. Selecting a more specific code when available is always preferable to the NOS descriptor. Browse coaching CPT codes for an example of how to navigate adjacent code families, and see the IVF CPT codes reference for multi-procedure anesthesia context.

For anesthesia on immediately adjoining anatomy, see 01710 and 01730, which cover the upper arm, humerus, and elbow.

Common billing errors and compliance tips for CPT Code 00450

These are the patterns most likely to trigger a payer audit or claim denial for CPT Code 00450.

• Using 00450 when a more specific code exists: The NOS descriptor is a last resort. If the procedure involves the glenohumeral joint or acromioclavicular joint as the primary site, 01630 or 01638 is likely more appropriate. Defaulting to 00450 for all shoulder-region cases is a coding error.
• Mismatched modifier pairs: QK must always appear on the physician’s claim when QX appears on the CRNA’s claim for the same case. Submitting QX alone or QK alone triggers an edit.
• Stacking qualifying circumstances without documentation: Billing 99100 for a patient over age 70 requires the chart to confirm the patient’s age. Billing 99140 for an emergency requires documentation that the emergency existed. Unsupported add-ons are a RAC (Recovery Audit Contractor) audit target.
• Wrong ICD-10 seventh character: For fracture repair at an initial surgical encounter, the 7th character must be A. Using D (subsequent encounter) or S (sequela) on a fresh surgical case will deny.
• Time unit rounding errors: Round time units down, not up, unless your payer explicitly allows rounding up. Rounding up 58 minutes to 4 units (60 minutes) instead of 3 units is overbilling under most payer policies.
• Missing pre-anesthesia evaluation note: CMS requires a pre-anesthesia evaluation documented before the procedure begins for medical direction claims. Post-dated notes are a compliance risk.

Practices billing a high volume of orthopedic anesthesia cases should use claims management software to flag missing documentation fields and track claim status before submission. Proactive checks at the claim level catch most of these errors before they become denials or audits.

Conclusion

CPT Code 00450 draws payer scrutiny because of its NOS descriptor, and the anesthesia modifier framework is strict enough that one missing documentation detail can convert a full AA claim into a 3-unit AD payment. Getting the base units, time calculation, modifier pair, and ICD-10 7th character right every time requires a consistent, auditable workflow.

Pabau’s claims management software gives surgical and anesthesia practices a structured way to track claim status, flag missing required fields before submission, and reconcile insurer payments from one dashboard. To see how it works for your billing workflow, book a demo.

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