Just before being gas-ed for anesthesia.

Here’s Why Anesthesia Coding/Billing Is More Complex Than You Might Think 

By Marsha S. DiamondDirector of Coding Solutions

While anesthesia coding/billing should perhaps be a relatively simple task due to the small number of CPT codes utilized compared to, for example, the surgery codes, payer and claims submission requirements necessitates that the anesthesia coder be diligent in ensuring that specific third party guidelines are followed for all the additional elements needed on anesthesia claims.

In addition to reporting the correct anesthesia CPT code(s) and accompanying ICD-10-CM diagnosis(es), the world of anesthesia coding/billing extends well beyond those two elements needed on other claims.  The coder/biller is often responsible for assigning, or at least ensuring that other vital information utilized in processing the anesthesia claim are included such as:

Physical Status Modifier

Modifiers P1 through P5

Describes the overall physical status of the patient as assessed by the anesthesiologist at the time of the surgical event.  This may or may not be required for some payers.

Qualifying Circumstances

Codes 99100, 99116, 99135, 99140

Assigned as an additional CPT code when the anesthesia is performed under unusually difficult circumstances, such as extreme age, emergency situations or utilization of hypothermia and/or controlled hypotension.  Again, these may or may not be utilized by some carriers.

Anesthesia Providers

Often services are performed by CRNAs under the direction of an anesthesiologist.  Therefore, coders/billers must determine what provider(s) can provider/supervise services for a specific carrier.

Anesthesia Direction

Since multiple providers may be involved in the case, modifiers indicating who the provider was and/or the medical direction that occurred are also necessary. Examples are:

  • AA: Personally provided by anesthesiologist
  • AD: Medical supervision by a physician; more than 4 concurrent anesthesia procedures
  • QK: Medical direction of 2, 3 or 4 concurrent anesthesia procedures involving qualified individuals
  • QX: Qualified nonphysician anesthetist service with direction by a physician
  • QY: Medical direction of one qualified nonphysician anesthetist by a physician
  • QZ: CRNA service, without medical direction by physician

Time and Units of Service

Anesthesia services are reported in time units, usually one unit is equal to 15 minutes. However, there are some carriers that utilize ten minute units instead. In addition to the time units, all anesthesia procedures are also assigned base units, which are added to the time units and the total reported in the days/units category on the claim.

These units of services are essential in ensuring proper reimbursement for the extent of services performed.  Usually only one anesthesia code is reported for services performed, so the coder/biller needs to determine the most significant service to place on the claim. Some exceptions are made such as in the case of obstetrics and nerve blocks in some instances in addition to the main surgical procedure.

CPT Surgery Code Conversion

Usually the anesthesia coder/biller is also responsible for reviewing the surgical procedure performed and “crosswalking” the CPT surgical code to the appropriate anesthesia code.

Other Services

Often anesthesia groups not only perform supportive anesthesia care during a surgical procedure, but also perform other services such as critical care, pain management, postoperative pain blocks, as well as evaluation and management services. Therefore, the anesthesia coders/billers must not only be knowledgeable in anesthesia coding, but, other areas of coding as well.


All of the above additional requirements for anesthesia require the coder/biller to be proficient at assigning the usual CPT/ICD-10-CM codes as well as identifying or verifying many other anesthesia elements required on the anesthesia claim for proper payment. It also requires the anesthesia coder/biller to utilize specific third party guidelines in determining what elements are required for each carrier when submitting anesthesia claims.

In summary, the world of anesthesia coding/billing becomes a very complicated, intricate and involved process beyond the assigning of CPT andICD-10 codes.  This process requires extensive organizational skills, knowledge and thoroughness on the part of the coder, or a computerized process such as AI to correctly identify, capture and ensure that all the elements necessary for proper reimbursement are submitted.

Marsha S. Diamond is Director of Coding Solutions at Aidéo Technologies. Find her on LinkedIn here.