Anesthesia services are not paid like surgical procedures. A surgeon’s code has a price, but the anesthesia code has weight which is base units. The time is added to it, then it is multiplied by a conversion factor which is a dollar rate. CPT 00170 is not worth anything by itself, it is 5 units plus how long the procedure took time. To understand this concept, picture it like a taxi fare. The base units are flag-drop. The units are the meter of the taxi which is running, the conversion factor is the price per unit, and the modifiers tell who was driving the taxi. Everything discussed in this article is one of these parts.
00170 CPT Code Description and Where It Sits
The descriptor says: CPT code 00170, “Anesthesia for intraoral procedures, including biopsy; not otherwise specified.” Intraoral procedure is inside the mouth which means this is an oral anesthesia. Including biopsy means that the same code covers the biopsy of mouth. Not otherwise specified is the default. If there is another code that is more specific to the intraoral anesthesia, it is used, otherwise 00170.
CPT 00170 belongs to anesthesia for procedures on the head (00100–00222), the first block of the anesthesia section. Here is the table that shows the CPT code and the related anesthesia:
| Code | Anesthesia for |
|---|---|
| 00170 | Intraoral procedures, including biopsy; not otherwise specified |
| 00172 | Intraoral; repair of cleft palate |
| 00174 | Intraoral; excision of retropharyngeal tumor |
| 00176 | Intraoral; radical surgery |
| 00100 | Salivary glands, including biopsy |
| 00160 | Nose and accessory sinuses; not otherwise specified |
| 00190 | Facial bones or skull; not otherwise specified |
The rule which is important to discuss here is that the site of the surgery picks the anesthesia code. The specialty of the surgery does not pick the code. An oral surgeon’s sinus lift is 00160, a mandible fracture is 00190, neither is 00170.
How CPT 00170 Is Paid: Base Units, Time and Conversion Factor
As discussed earlier, the surgical code has a fee but the anesthesia code has a weight. The time is added to it. The formula is: base units plus time units, multiplied by the anesthesia conversion factor, equals the allowed amount. CPT 00170 carries 5 base units in the CMS anesthesia base unit file. What do these 5 base units contain? Pre-anesthesia evaluation, induction, monitoring through the case, and the usual post-anesthesia care.
When does the anesthesia time start and when does it end? The time starts when the provider begins preparing the patient for induction and it ends when the patient is handed over to post-anesthesia care. Medicare counts one unit per 15 minutes and pays fractions. So, 47 minutes are equal to 3.13 units, not 4. Some commercial payers may round the figure but it depends on the contract. The time on the claim is reported in minutes, not in units.
CMS sets the conversion factor every year nationally and it is adjusted on the basis of locality. From 2026, there are two factors: one for qualifying APM participants and the other for everyone else.
Table
| Year | Qualifying APM participants | All other providers |
|---|---|---|
| 2025 | $20.3178 | $20.3178 |
| 2026 | $20.5998 | $20.4976 |
An example based on our discussion
00170, 47 minutes of anesthesia time, personally performed by an anesthesiologist, non-APM, national rate: 5 base units + 3.13 time units = 8.13 units × $20.4976 = $166.65 before locality adjustment.
Modifiers: Who Gave the Anesthesia
Why do anesthesia claims need a provider modifier? The claim of the surgeon shows what was done but the anesthesia claim tells a story about who did it. As the answer changes, the payment changes. Certified Registered Nurse Anesthetist (CRNA) is a registered nurse with a graduate degree in nurse anesthesia and a national certification, who gives anesthesia. CRNA is head of the table in many surgery centers and hospitals for the whole case. An anesthesiologist is a physician who completed an anesthesiology residency. This helps to reduce the Anesthesiologist / CRNA confusion. The table shows the modifiers along with their explanations:
| Modifier | Who | Medicare payment |
|---|---|---|
| AA | Anesthesiologist personally performed the whole case | 100% to the anesthesiologist |
| QY | Anesthesiologist medically directing one CRNA | 50% to the anesthesiologist |
| QK | Anesthesiologist medically directing 2–4 concurrent cases | 50% to the anesthesiologist on each |
| QX | CRNA working under medical direction | 50% to the CRNA |
| QZ | CRNA without medical direction | 100% to the CRNA |
| AD | Anesthesiologist supervising more than 4 concurrent cases | Reduced; 3 base units plus time rules |
| QS | Monitored anesthesia care | Informational; added with the provider modifier |
Physical Status and Qualifying Circumstances
There are two types of extra units that are a part of the anesthesia claim. Medicare pays for neither. The first one is the physical status modifier, P1 to P6, which tells us the condition of the patient. P1 is a patient who is healthy. P3 has a serious disease, P6 is an organ donor. Medicare accepts these on the claim and pays nothing extra for these physical status modifiers.
The second type is qualifying circumstances. There are four add-on codes for conditions that make the anesthesia harder than the base units assume:
| Code | Circumstance | ASA units |
|---|---|---|
| 99100 | Patient under 1 year or over 70 | +1 |
| 99116 | Total body hypothermia | +5 |
| 99135 | Controlled hypotension | +5 |
| 99140 | Emergency conditions | +2 |
CRNA Opt-Out States and What They Change
There is a federal rule since 2001 which says that hospitals, ambulatory surgery centers, and critical access hospitals have had to keep CRNAs under the supervision of physicians to meet Medicare’s conditions. The state governor can opt out based on this rule by writing to CMS that the state consulted its boards of medicine and nursing, that the opt-out serves the state’s citizens, and that it is consistent with state law. As of July 2026, 27 states and Guam have opted out; Vermont and Ohio were the latest, both in July 2026. Three of the 27 are partial, limited to rural or critical access hospitals.
What happens to 00170 claims with this rule? It is an opt-out rule for a facility. It decides whether a hospital or a surgery center in that state runs with CRNA only and it can still be compliant with Medicare. It has no impact on the claim or changes the claim. A CRNA working without medical direction can do this: bills CPT 00170 with QZ in an opt-out state and in a non-opt-out state alike. It is paid the same way. The opt-out just removes the obligation to have a physician that supervises the CRNA.
Medical vs Dental Insurer and Prior Authorization
CDT codes are a category used by oral surgeons and dentists for their dental claims. Medical vs dental insurer can be understood here. The anesthesia provider bills CPT 00170 on a medical claim to the patient’s medical insurer. Dental plans have their own rules related to codes for sedation and general anesthesia codes, D9222 and D9223. Generally, they do not accept a CPT anesthesia code. Sending 00170 to the dental plan is one of the most common reasons why accurate anesthesia claim is rejected.
Now, there is a second layer as well added by Medicare. Routine dental work is excluded from Medicare and the anesthesia for it is excluded as well. Anesthesia for an oral procedure that Medicare does cover, such as a biopsy of a suspicious lesion, removal of a tumor, or dental work inextricably linked to a covered medical treatment, can be covered. The coverage of CPT 00170 follows the coverage of the procedure underneath it; it is never covered on its own.
Why CPT 00170 Claims Get Denied
Many claim denials related to CPT 00170 are based on where they went, which code they had, and who was in the room. Here are some common denials and how to avoid them:
- The claim went to the dental plan. Dental plans do not process 00170 claims as they have their separate codes.
- The code matched the surgeon and not the site. The code for anesthesia follows the site where surgery happened.
- Incorrect modifiers or missing them entirely can lead to claim denials. A CRNA case goes out with no QX or QZ, or an anesthesiologist directing two rooms bills AA instead of QK. The payer cannot tell who did the case or what share to pay, and the claim stops.
- The time is not correct. The time of anesthesia starts from where the patient is getting ready for induction to sending the patient to post-anesthesia care.
- Missing prior authorization is another denial reason. General anesthesia for an oral procedure required authorization on that plan but the case proceeded without it and the claim was sent. It leads to denial that is rarely overturned on appeal.
Final Thoughts
CPT 00170 is the default anesthesia code for work inside the mouth, with 5 base units, and a more specific intraoral code takes its place when one exists. What it pays depends on time, the year’s conversion factor, and the modifier that says whether an anesthesiologist, a CRNA or both were on the case. Most of the claims that fail went to the dental plan, carried the wrong head-section code, or left off the provider modifier, all of which an anesthesia billing services team checks before the claim leaves.
