CPT Code 01670: Anesthesia for Shoulder and Axilla Procedures

Key takeaways

CPT code 01670 covers anesthesia for procedures on the veins of the shoulder and axilla, billed by anesthesiologists and CRNAs.

The code carries 4 base units; reimbursement follows (Base Units + Time Units) x Conversion Factor, at one time unit per 15 minutes.

Modifier AA (personal performance by anesthesiologist) or QZ (unsupervised CRNA) must be appended to every 01670 claim; missing modifiers are the top denial reason.

Pabau’s practice management software keeps anesthesia records structured and audit-ready, helping staff catch missing time data or modifier errors before an 01670 claim goes out.

Central line and port placement in the axillary or subclavian vein is routine in oncology, dialysis, and vascular access care. CPT code 01670 is the anesthesia code that goes with it. The code itself is rarely the problem on a denied claim. What trips up billing staff is the modifier stack, the time-unit count, and the ICD-10 pairing. All three variables must align perfectly before CMS or a commercial payer approves payment.

This reference covers the official code description, base unit value, and the reimbursement formula with a worked example. It also covers applicable modifiers, Medicare rates, ICD-10 pairings, documentation requirements, and the errors that cause the most claim denials.

CPT code 01670: definition and clinical description

CPT code 01670 describes anesthesia services for procedures on the shoulder and axilla. It specifically covers procedures on the veins in that region, such as central venous catheter or port placement. The code sits within the AMA’s CPT code set anesthesia section, which spans the 00100-01999 range. That section organizes anesthesia codes by the anatomical region of the surgical procedure, not the anesthesia technique used.

Both anesthesiologists and Certified Registered Nurse Anesthetists (CRNAs) bill this code, with the appropriate supervision modifier determining which provider type is the billing entity. The code applies to anesthesia care, not the surgical procedure itself.

Procedures covered by CPT code 01670

The following venous procedures of the shoulder and axilla are commonly reported with CPT code 01670 as the anesthesia code:

• Axillary or subclavian vein catheter placement for central venous access
• Insertion of an implantable venous access port via the axillary or subclavian vein
• Axillary vein thrombectomy or catheter-directed thrombolysis
• Axillary-subclavian vein repair or venous reconstruction
• Removal of a chronically implanted axillary or subclavian venous catheter
• Venography or venous mapping of the axillary or subclavian vein
• Revision or exchange of a tunneled central venous catheter placed through the axillary vein
• Venous access procedures for hemodialysis performed via the axillary or subclavian vein

Coders should confirm the operative note documents a venous procedure rather than an arterial or musculoskeletal one. Procedures on shoulder arteries, or on nerves, muscles, tendons, and bursae, fall under adjacent codes in the 01610-01680 range instead.

CPT code 01670 base units and the anesthesia billing formula

CPT code 01670 carries a base unit value of 4. Base units reflect the inherent complexity of providing anesthesia for a given type of procedure. They are assigned by the AMA CPT Editorial Panel and ratified against CMS’s Medicare Physician Fee Schedule.

Anesthesia reimbursement does not use the standard RVU-based formula. Instead, CMS calculates payment using the anesthesia-specific formula below.

Worked calculation: 90-minute axillary vein thrombectomy

Most reference pages state the formula without applying it. Here is a concrete worked example for a 90-minute axillary vein thrombectomy billed to Medicare in a mid-range locality (conversion factor $23.00):

Medicare payment varies by geographic locality. Use the CMS fee schedule lookup to find the current conversion factor for your Medicare Administrative Contractor (MAC) region. Commercial payer rates are negotiated separately and typically exceed Medicare rates.

Applicable modifiers for CPT code 01670

Every anesthesia claim requires at least two modifiers: one indicating the supervision level of care and one indicating the patient’s physical status. Missing either is a near-certain denial. CPT code 01670 follows the same modifier rules as all anesthesia codes under CMS billing guidelines.

Provider supervision modifiers (AA, AD, QK, QX, QY, QZ)

QZ modifier eligibility depends on whether the state has submitted a letter to CMS opting out of the federal physician supervision requirement for CRNAs. Practices should confirm their state’s opt-out status before submitting QZ on a 01670 claim. State-level rules vary; blanket use of QZ across all states is a compliance risk.

Physical status modifiers (P1 through P6)

Physical status modifiers, defined by the American Society of Anesthesiologists (ASA), are appended to CPT code 01670 to document the patient’s pre-anesthesia health classification. Not all payers add units for higher-acuity classifications, but the modifiers must still be present for documentation purposes.

Qualifying circumstances add-on codes for CPT 01670

Qualifying circumstances codes (99100-99140) may be reported alongside CPT code 01670 when the clinical situation adds unusual complexity to the anesthesia service. These are add-on codes, not standalone, and payer acceptance varies. Medicare has specific rules governing their use.

• 99100: Anesthesia for patient of extreme age, younger than 1 year and older than 70
• 99116: Anesthesia complicated by utilization of total body hypothermia
• 99135: Anesthesia complicated by utilization of controlled hypotension
• 99140: Anesthesia for emergency conditions

Report 99100 when the venous procedure is performed on a patient younger than 1 year or older than 70. This applies often, since central-line and port placement is common in oncology, dialysis, and neonatal care. Verify the specific payer’s policy before adding these codes, as some commercial payers bundle them without additional payment.

ICD-10 codes commonly paired with CPT code 01670

Selecting an ICD-10 code that matches the surgical diagnosis is essential for medical necessity on 01670 claims. The anesthesia provider typically uses the same principal diagnosis listed on the surgeon’s claim. Mismatched diagnosis codes are a common source of payer denials for venous access anesthesia claims. Pabau’s coding library also covers diagnostic codes across other specialties, including ICD-10 code O62.2.

Always use the most specific code available. Laterality matters. Unspecified axillary or subclavian vein codes (without right/left designation) are increasingly flagged by commercial payers. The ICD-10-CM coding guidelines require laterality designation whenever the condition is unilateral and the side is known. Central line placement for hemodialysis access also comes up often in outpatient infusion and IV therapy settings that manage long-term vascular access. Severe catheter-site infections that progress to needing surgical debridement are billed separately under CPT code 11005.

Who can bill CPT code 01670: anesthesiologists and CRNAs

Both anesthesiologists and CRNAs are eligible to bill CPT code 01670. The provider type determines which supervision modifier is appended, which then affects the Medicare payment percentage. Understanding provider eligibility rules is especially important for practices running anesthesia care team models, including surgical specialties such as those using plastic surgery EMR software.

• Anesthesiologist, personally performing (AA): Bills for 100% of the allowed amount. The anesthesiologist must be continuously present and personally administering the anesthesia throughout the case.
• CRNA without physician direction (QZ): Bills for 100% of the allowed amount in states that have opted out of the CMS physician supervision requirement. Eligibility depends on state opt-out status.
• Medically directed CRNA + anesthesiologist (QX + QK): Each party bills at 50% of the allowed amount. Both claims must be submitted with matching modifiers. Submitted separately by each provider.

Anesthesiologists billing under medical direction (QK modifier) must document that they performed all seven required pre-anesthesia steps defined by CMS’s TEFRA rules. Missing documentation of any one step can void the medical direction modifier and reduce payment.

• Perform a pre-anesthesia evaluation.
• Prescribe the anesthesia plan.
• Personally participate in the most demanding portions of the plan, including induction and emergence.
• Ensure a qualified individual performs any part of the plan the anesthesiologist doesn’t handle personally.
• Monitor the course of anesthesia at frequent intervals.
• Remain physically present and available for emergencies.
• Provide indicated post-anesthesia care.

For related CPT billing workflows and how different supervision models affect reimbursement across specialties, Pabau’s procedure code library covers multiple code types.

Documentation requirements for CPT code 01670 claims

Payer audits of anesthesia claims focus almost entirely on the anesthesia record. A claim that cannot be fully supported by the record is subject to recoupment, even if the service was performed correctly. The anesthesia record must document specific data points to support 01670. Using digital anesthesia record forms that capture time-stamped data fields significantly cuts missing documentation at the point of care.

• Pre-anesthesia evaluation: Date, time, patient health history, physical status classification (P1-P6), planned anesthetic technique, consent documentation
• Anesthesia start time: The exact time the provider began preparing the patient for induction (not the surgical incision time)
• Anesthesia end time: The time the provider’s personal attendance ends (typically transfer of care to the PACU team)
• Intraoperative monitoring records: Vital signs, blood pressure, oxygen saturation, EKG, temperature, and administered agents at regular timed intervals
• Medications administered: Drug name, dose, route, time of administration
• Complications or significant events: Any change in anesthetic management, physiologic changes, or emergency interventions
• Post-anesthesia evaluation note: Patient’s status upon transfer to recovery
• Provider signature and credentials

For HIPAA-compliant record retention, anesthesia records must be maintained according to state law for the applicable retention period, typically a minimum of seven years. For anesthesia practices handling these records digitally, HIPAA compliance guide is a useful operational reference.

Related anesthesia CPT codes for shoulder and axilla procedures

CPT code 01670 sits within the 01610-01680 shoulder and axilla anesthesia range. Selecting the wrong adjacent code is a preventable billing error. The distinctions between these codes are anatomical: whether the procedure addresses nerve, artery, bone/joint, or vein determines the correct code. For reference on how procedure code fee schedules work across different payer systems, Pabau’s billing reference library covers the comparison in detail.

A coder encountering a shoulder arthroscopy claim should note that 01630 carries 5 base units. It applies to open or arthroscopic procedures on the humeral head, sternoclavicular joint, or acromioclavicular joint. Anesthesia for a venous procedure in the same region, such as axillary vein catheter placement or thrombectomy, is reported with 01670 (4 base units) instead. When in doubt, review the operative note to confirm whether the procedure addressed bone and joint, artery, or vein. For IVF or other surgical contexts where code selection follows similar anatomical specificity logic, the IVF CPT codes reference illustrates the same approach. Anesthesia coders working across multiple specialties will also encounter CPT code 00756, which follows the same base-unit and modifier logic in a different anatomical region.

Common billing errors and compliance pitfalls for CPT code 01670

Anesthesia claims are denied at higher rates than most other claim types. Venous access procedures generate a specific subset of errors that repeat across practices. Understanding the most common CPT code 01670 billing pitfalls helps billing staff build claim review protocols that catch these before submission.

• Missing supervision modifier: Submitting 01670 without AA, QZ, QK, QX, or QY results in near-universal denial. The modifier is mandatory, not optional.
• Incorrect time unit count: Miscounting anesthesia start or stop time by even one 15-minute interval affects the total units billed. A discrepancy between the claimed time and the operative report time is a top OIG audit trigger.
• Mismatched ICD-10 code: Using a non-specific or incorrect diagnosis code breaks medical necessity. For lateralized venous conditions, using an unspecified code (e.g., I82.A19 instead of I82.A11 for right-side pathology) is increasingly flagged.
• Incomplete medical-direction documentation: Claims with QK + QX must be supported by documentation proving the anesthesiologist performed all seven required medical-direction steps. That includes ensuring a qualified individual performs any part they don’t personally handle, and providing indicated post-anesthesia care. Partial documentation typically results in the claim being reprocessed at a lower rate or denied.
• Wrong adjacent code selection: Using 01630 (5 base units) for a joint procedure creates a mismatch when the case was actually venous work. That work belongs under 01670 (4 base units) instead.
• Unbundling qualifying circumstances: Some practices routinely append 99100 for all patients over 70 without confirming payer policy. Medicare does reimburse 99100 in most cases, but commercial payer policies vary and some bundle it without additional payment.

Building a billing compliance protocol around these six failure modes significantly reduces denial rates for CPT code 01670 claims. A well-structured medical practice billing plan should include pre-submission claim review rules specific to anesthesia codes. The ADHD screening CPT code reference shows how systematic, code-specific documentation requirements reduce errors across different CPT categories.

How anesthesia billing software simplifies CPT code 01670 claims

Manual anesthesia billing requires staff to track three separate data points per claim. These are base units, time units calculated from the anesthesia record, and the correct modifier combination. Getting any one of these wrong generates a denial, and practices using disconnected tools repeat this calculation at every claim submission.

Pabau’s practice management software keeps the anesthesia record structured, connecting documented start and stop times, modifier rationale, and the physical status classification in one place. That removes the manual re-entry from a paper anesthesia record, which is where most 01670 documentation errors originate.

Practices that standardize anesthesia documentation in automated billing workflows also benefit from audit-ready records. Every anesthesia record captures start time, stop time, provider credentials, and modifier rationale in one structured format. That format supports both claim submission and payer audit responses. For practices evaluating practice management software for billing workflow automation, the key criteria are time-unit automation, modifier rule libraries, and integrated claim scrubbing.

Keep anesthesia records audit-ready with structured documentation

Pabau's practice management software keeps anesthesia records structured, from the pre-anesthesia evaluation through start and stop times, so the documentation behind every CPT code 01670 claim stays complete and audit-ready.

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Conclusion

CPT code 01670 is a straightforward code with a well-defined scope: anesthesia for procedures on the veins of the shoulder and axilla. It carries 4 base units and is billed using the (B+T)xCF formula. The complexity is in the execution, specifically the modifier stack, time-unit accuracy, and ICD-10 specificity that payers scrutinize most closely.

Pabau’s practice management software helps anesthesia practices reduce those errors. It keeps anesthesia record documentation structured and connected to the billing record, cutting the manual re-entry that generates most preventable denials. To see how it works for your billing workflow, book a demo and ask about anesthesia documentation workflows.

Continue your research

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Need the diagnosis code for a shoulder injury with a retained foreign body? ICD-10 code S41.022A covers laceration with a foreign body of the left shoulder.

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