10 basic steps in Anesthesia coding

In this article, you can check and follow the basic steps that involved in Anesthesia coding. Why do I need to follow these steps? You may have a question and I have an answer for you.

Anesthesia coding is different from other specialities as it includes several factors in deriving the final fee values for Anesthesia. Missing any of the below steps will lead to improper units assignment thereby affecting the reimbursement for Anesthesia practitioners.

Anesthesia coding is not just the coding of CPT and ICD -10 with modifiers, it also requires other essential elements like ASA codes, physical status modifiers and qualifying circumstances to derive the final fee value for Anesthesia services. In this article, you can learn about the steps involved in Anesthesia coding.

You can also read the general introduction to Anesthesia coding in the below link:



Whether you are a new or an experienced Anesthesia coder, you must follow these steps while coding Anesthesia claims. These steps will help you out in deriving the accurate fee values for the Anesthesia services.

1. Determine the appropriate CPT code(s) for the surgical procedure(s) performed.

First determine the CPT code for the surgical procedure performed in the operative session. This is the most important step as the correct CPT code for the surgery would crosswalk to the correct ASA code.

2. Crosswalk the CPT code(s) to the appropriate ASA code.

The appropriate CPT should be cross walked to the ASA code by using the RVG guide. Remember that you are going to bill only the ASA codes for the Anesthesiologist providers and not the surgical CPT codes. However CPT assignment is necessary to select the appropriate ASA codes.

3. Determine the appropriate number of base units.

Each CPT anesthesia code (00100-01999) is assigned a base value by the ASA. The Base Value of each code is comprised of units referred to as the Base Unit Value. Only one Anesthesia code with high base unit value should be reported per Anesthesia claim. Therefore when multiple procedures are performed in a single session, you must crosswalk all surgical procedures performed and the anesthesia code with the highest base unit value is reported for the case.

4. Determine the appropriate number of time units.

“Time Unit” is a measure of each 15-minute interval, or fraction thereof, during which anesthesia services are performed. It is important to anesthesia coding and reimbursement as the charge and reimbursement increases based on the time reported.

5. Assign the appropriate anesthesia modifier to identify the anesthesia provider.

Anesthesia services are performed by Anesthesiologist or CRNA or a combination of both.

An anesthesia modifier is used to identify whether the service was personally performed, medically supervised, or under medical direction. These modifiers are also referred as “payment modifiers” and should be billed in the first modifier position.

6. Assign the appropriate modifier to identify MAC services, when appropriate.

Monitored Anesthesia care is a specialized type of Anesthesia service and payers require HCPCS modifier to denote MAC services. The modifiers are QS, G8 and G9 and are considered to be informational only. These modifiers should be billed in the second modifier position when a payment anesthesia modifier accompanies it in the first modifier position.

7. Assign the appropriate physical status modifier :

The physical status modifiers identify levels of complexity of the anesthesia services, and are reported in conjunction with anesthesia services codes when appropriate. Physical status modifiers are represented by the initial letter “P” followed by the appropriate single digit from 1 to 6 (P1-P6). These modifiers are also considered as “Informational only”.

8. Assign the appropriate Qualifying circumstances if applicable:

Qualifying circumstances for anesthesia: These codes 99100-99140 are add-on codes that include a list of important qualifying circumstances that significantly affect the character of the anesthesia service provided. These circumstances would be reported as additional procedure numbers qualifying an anesthesia procedure or service. More than one code in the section may be selected, if applicable.

9. Determine the appropriate CPT code(s) for any additional services or procedures performed.

Anesthesiologist can also perform additional procedures besides anesthesia administration. These additional procedures are not included in the base unit value and can be billed separately. Examples would include Insertion of central venous catheter, Insertion of intra-arterial catheter, Insertion of swan-ganz and TEE placements.

10. Determine the total units for the anesthesia services.

Anesthesia fees are the result of a formula. This is payer-specific information that is not contained in the CPT manual but is included in this article for the benefit of exposing you to the formula commonly used to calculate charges and payment for anesthesia services. Generally this calculation is accomplished by means of a computer program and is not manually calculated by the coding or billing personnel. However the coders should feed all the data into the claim for proper and accurate reimbursement.


Final Fee (FF) = (Base units + Time units + Additional units) X conversion factor CF

Case Example:

Mr John is a 72 years old patient with severe hypertension. He underwent right total knee arthroplasty under general anesthesia. Prior to induction of Anesthesia, Dr.Ken has completed a preoperative visit and documented a detailed history, detailed examination and low complexity decision. The anesthesiologist begins to prepare the patient for surgery at 10.00am and the surgery begins at 10.15am, and the surgery ends at 10.45am.The anesthesiologist transfers patient care to the recovery room nurse at 11.00am.

Final Fee (FF) = (Base units + Time units + Additional units) X conversion factor CF

= (7+4+2) X conversion factor (specific to the locality)

Though the Anesthesia billing software use the final fee calculation, it is responsible for the coder to feed all the appropriate unit values into the system. Missing of any single unit will affect the Anesthesia reimbursement.



1 Comment

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