CPT Code 99100: Under Qualifying Circumstances for Anesthesia

What is CPT Code 99100?

CPT code 99100 is an anesthesia add-on code. It is used when anesthesia services are provided to patients who are at the extremes of age, either younger than one year or older than seventy. Administering anesthesia care to these age groups typically involves increased attention to managing anesthesia depth, maintaining stable blood pressure, and addressing age-specific sensitivities to medications. CPT 99100 ensures that these age-related risks and necessary adjustments to anesthesia techniques are clearly recognized during anesthesia billing. Anesthesiologists and nurse anesthetists use this code along with the primary anesthesia procedure to account for the additional complexity and heightened risk associated with very young or elderly patients.  

CPT code 99100 documentation requirements

Comprehensive documentation in the medical record is essential to justify the application of CPT code 99100 and ensure appropriate anesthesia billing.

Patient age (under 1 or over 70)

Clearly document the patient's age in the medical record. Indicate explicitly if the patient is younger than one year old or older than seventy at the time anesthesia services were provided, as this is critical for billing code 99100.

Date/time of surgery and anesthesia start

Include the exact date and anesthesia time start clearly in the patient’s medical record. This documentation supports proper reporting of qualifying circumstances alongside the primary anesthesia procedure.

Associated primary anesthesia code

Specify the primary anesthesia CPT code (within the range 00100-01999) linked to the qualifying circumstance code 99100. Clearly linking both codes illustrates the additional complexity due to age-related anesthesia risks.

Notes on age-related risk/considerations

Document specific age-related anesthesia risks or considerations, such as heightened sensitivity to anesthetics, difficulty managing blood pressure, or increased likelihood of complications. Explicit notes on these unusual risk factors support medical necessity for billing code 99100.

CPT code 99100 billing guidelines

Correct billing practices for CPT code 99100 are crucial to ensure compliance and appropriate reimbursement.

Must be paired with a primary anesthesia code

CPT code 99100 is an add-on code and must be reported with a primary anesthesia procedure code (00100–01999). It is always listed separately in addition to the primary anesthesia procedure.

Only used once per anesthesia event

Report CPT 99100 only once per anesthesia service, regardless of the duration or complexity of the anesthesia time. It is billed per anesthesia event, not per hour or time increments.

Not payable by all payers (some bundle it)

Certain insurance companies consider 99100 bundled with the primary anesthesia CPT code and may not reimburse it separately. Verify individual payer policies before billing to avoid payment denials.

No modifiers required

This qualifying circumstance add-on code does not require anesthesia or physical status modifiers. Modifiers are applied only to the primary anesthesia procedure code, not the add-on code itself.

Related CPT codes

• 99116 – Anesthesia complicated by utilization of controlled hypotension
• 99135 – Anesthesia complicated by utilization of total body hypothermia
• 99140 – Anesthesia complicated by emergency conditions
• 00126 – Anesthesia for tympanotomy in pediatric patients
• 00561 – Anesthesia for cardiac procedures on pump oxygenator