Workforce issues were a key concern in health care in 2021, and they continue to be a focus of attention among clinical specialties in 2022. Relevant to anesthesiology were headlines about potential shortages of anesthesiologists, certified registered nurse anesthetists (CRNAs), and certified anesthesiologist assistants (CAAs). The concern for potential workforce shortages exists despite a record-setting number of physicians entering anesthesiology residency programs in each of the last five years (ASA Monitor 2021;85:40-1). In addition, the growth rate in the number of CRNAs and CAAs continues to outpace the growth rate in the number of anesthesiologists. Given the elevated competition for anesthesia professionals among academic medical centers, large national group practices, and smaller regional and local practices, I was curious about where new anesthesia professionals initially practice.

I identified a sample of “new” anesthesia professionals in 2021 based on new National Provider Identifiers (NPIs) present in the 11 Centers for Medicare & Medicaid Services (CMS) National Downloadable Files (NDFs) between July 16, 2021, and December 4, 2021 ( These files include NPIs and related information for anesthesiologists, CRNAs, and CAAs who submitted Medicare fee-for-service claims in the previous six months. I designated clinicians as “new” if their NPI was present in one or more of these 11 files but not in any of the previous 135 NDFs between March 2014 (the first available NDF) and July 2, 2021. I created a similar sample of new providers in 2016. For NDFs before February 15, 2018, the Medicare “look back” period is 12 months rather than six months.

The information in each NDF includes the clinician’s name, credentials, specialty, address, gender, medical school, graduation year, affiliated group practice, and up to four hospitals associated with the Medicare claims. I excluded professionals not practicing in the conterminous United States, Alaska, or Hawaii. In addition, I linked the hospitals in the NDF to the 2020 hospital data in the American Hospital Association’s (AHA’s) most recent annual survey database (

The NDF data include the organization’s legal name and group identification number associated with the clinician’s practice. For some group practices, this represents a local or regional organization that is part of a large national group but operates with a different legal name and group identification number than those of the “umbrella” group under which it operates. For example, U.S. Anesthesia Partners (USAP) is generally identified at a state level (e.g., USAP of Texas and USAP of Florida); North American Partners in Anesthesia (NAPA) has several different organization names (groups) within the NDF; and Sheridan, although part of Envision Physician Services, is listed as Sheridan Healthcorp. The component organizations within some large national groups can only be identified through additional primary research. However, for small, medium, and most large groups, there is typically only a single organization name within the NDF.

I identified 2,620 “new” anesthesia professionals in the 2021 NDFs. Of these new professionals, 52.5% were anesthesiologists, 43.8% were CRNAs, and 3.7% were CAAs. The ratio of new CRNAs to new anesthesiologists was 0.83. Approximately 60% of CRNAs and CAAs, and 30% of the new anesthesiologists, were women (Table 1).


At least one new anesthesia professional went to each state. Approximately one-third of the new anesthesia professionals were in five states, and 50% of the new anesthesia professionals were in 10 states (Table 2). These percentages are not surprising since 37% of the 2020 U.S. population was in the same top five states, and 54% was in the top 10 most populous states ( Although Indiana is among the top 10 states for new anesthesia professionals, it ranks 17th based on population. Georgia is among the top 10 most populous states but ranks 13th based on new anesthesia professionals in 2021.

For the top 10 states, the ratio of CRNAs to anesthesiologists was 0.69; however, the ratio for North Carolina was 2.28, and the ratio for California was 0.20. New York and Massachusetts also had CRNA-to-anesthesiologists ratios below 0.5. Four of the top 10 states had CAAs (Florida, Texas, Ohio, and Indiana) representing more than 50% of the new CAAs. More than three-fourths of the new CAAs were in five states (Georgia, Texas, Florida, Ohio, and Missouri).

In 2021, 15% of the non-federal hospitals had a new anesthesia professional, and 83% of these clinicians billed Medicare for services provided at a hospital (Table 3). Thirty percent of the new hospital-affiliated anesthesia professionals went to Council of Teaching Hospitals (COTH) members, with 72% of COTH hospitals getting at least one new anesthesia professional. Five percent of the new anesthesia professionals went to small bed-size hospitals, with only 3% of small hospitals receiving a new anesthesia professional.


Almost all (97%) of the new anesthesia professionals had an identified group practice. Table 4 presents the distribution of new anesthesia professionals among group practices. Not surprisingly, academic medical centers and the very large national groups received the greatest number of new anesthesia professionals. In 2019, the Center for Anesthesia Workforce Studies (CAWS) undertook primary research to identify and link local group practices to the large national umbrella groups under which they operate. Based on these linkages, the top five organizations for the new anesthesia professionals would be NAPA, USAP, Envision, TeamHealth, and Mayo Clinic.

In an analysis of “new” anesthesia professionals in 2016, there was a similar sample size and gender distribution to the 2021 cohort (Table 1). After five years, 85% remained in the NDF. Of those anesthesia professionals new in 2016 and in the December 2021 NDF, 77% were in the same state, 46% were at the same hospital, and 44% were in the same group. Group differences could be due to acquisitions or other legal organization name changes rather than differences in practice operations or location.

We examined the geographic, hospital, and practice distribution of a cohort of 2,620 anesthesia professionals newly billing Medicare in 2021. Of these clinicians, 1,375 were anesthesiologists. However, the Accreditation Council for Graduate Medical Education (ACGME) reported that 2,874 anesthesiology residents graduated in the 2019-2020 academic year ( Why is the number of graduating residents substantially greater than the number of anesthesiologists showing up as “new” in the NDFs?

There are several potential reasons for this difference. The overarching reason is that the 2021 NDFs include clinicians only if they have submitted claims for services provided to Medicare fee-for-service patients in the previous six months. Therefore, the NDFs may exclude recently graduated residents who:

  • Provide clinical services only at a military or Veterans Affairs facility
  • Enter a fellowship program
  • Have little to no clinical work and focus on research
  • Assume an administrative or other health care leadership position
  • Enter a specialty practice focused on cosmetic surgery, pediatrics, or pain medicine that does serve Medicare fee-for-service patients
  • Join a practice model or health system that does serve Medicare fee-for-service patients
  • Join a practice that also employs CRNAs using the care team model where supervised CRNAs bill Medicare with the QZ modifier (A A Case Rep 2016;6:217-9)
  • Take extended parental or other leave before joining a practice
  • Develop a disability or die before being able to practice medicine
  • Leave the U.S. to practice in another country
  • Decide to pursue a different career path.

Nonetheless, this 2021 analysis provides insight into the distribution of a large sample of anesthesia professionals billing Medicare for the first time (at least since late 2013). Over the next few years, CAWS will follow these 2016 and 2021 cohorts of new anesthesia professionals. We will look for changes in hospital and practice types and geographical settings such as urban to rural and vice versa. Although CAWS does not have access to individual compensation data, we will try to identify direct and indirect economic drivers of changes in settings for anesthesia professionals early in their careers.