Developed By: Committee on Anesthesia Care Team
Last Amended: October 26, 2022 (Original Approval: October 17, 2007)
Certified anesthesiologist assistants (CAA) and certified registered nurse anesthetists (CRNA) are both non-physician members of the anesthesia care team (ACT). Their role in patient care is described in the American Society of Anesthesiologists (ASA) “Statement on the Anesthesia Care Team.” The ASA document entitled “Recommended Scope of Practice of Nurse Anesthetists and Anesthesiologist Assistants” further delineates the recommended and safe limits of clinical practice. These documents summarize ASA's view that anesthesiologist assistants and nurse anesthetists share identical patient care responsibilities, and commensurate knowledge and technical skills, a view in harmony with their equivalent treatment by the Centers for Medicare and Medicaid Services (CMS). The proven safety of the team approach to anesthesia when physician anesthesiologists work with anesthesiologist assistants and/or nurse anesthetists confirms the enduring wisdom of this view.
Nonetheless, differences exist between anesthesiologist assistants and nurse anesthetists regarding educational program prerequisites, instruction, and requirements for supervised clinical practice. The purpose of this document is to review these for purposes of comparison, to summarize changes that have taken place in the respective curricula, and to assess their current and potential future significance.
- Historical Background of Certified Anesthesiologist Assistants and Certified Registered Nurse Anesthetists
- Certified Registered Nurse Anesthetists
The discipline of nurse anesthesia developed in the late 1800s and early 1900s. The first formal nurse anesthesia program was founded at St. Vincent’s Hospital in Portland, Oregon, in 1909. The first certification examinations were administered in 1945. A nursing diploma was sufficient for entry into nurse anesthesia programs until 1986, when the prerequisite was established for a bachelor’s degree in nursing or a related field. By 1998, all programs were required to provide a graduate level of education, awarding a “Master of Science in Nurse Anesthesia” or MSNA degree. At that time, nurse anesthetists who had graduated from non-master’s degree programs were “grandfathered” into the new system and allowed to continue practicing without further graduate education. Once an accredited nurse anesthesia educational program has been completed, the graduate nurse anesthetist must pass a certification examination administered by the National Board of Certification and Recertification for Nurse Anesthetists (NBCRNA).
In 2007, the American Association of Nurse Anesthetists (AANA) adopted a position statement supporting further graduate education and recommending that the entry to practice degree for nurse anesthetists be moved to the “doctoral” level by 2025. The degree to be awarded is the “practice doctorate”, usually termed the “Doctor of Nursing Practice” degree (DNP) or the “Doctor of Nurse Anesthesia Practice” degree (DNAP). These “practice” or “clinical” degrees differ in rigor and requirements from the more demanding research doctorate (PhD) or the education doctorate (EdD), which are typically required for nurses who wish to ascend in academic rank.
A nurse anesthetist with a master’s degree may complete a DNP degree with one additional year of online course work, and no additional requirement for in person education or additional clinical requirements. As of August 2021, there are 128 nurse anesthesia programs in the U.S. and Puerto Rico, and 113 of the programs are approved to award doctoral degrees. These programs typically have extended their educational time requirement by six to 12 months, to a total of three years of full-time study or the part-time equivalent. The curricula are described in more detail later in this document.
- Certified Anesthesiologist Assistants
The anesthesiologist assistant profession was established in the 1960s by three chairs of academic anesthesiology departments: Joachim Gravenstein, MD; John Steinhaus, MD, PhD; and Perry Volpitto, MD. Concerned with the shortage of anesthesiologists in the U.S., they analyzed the tasks and skills required during anesthesia care and studied the educational pathway for physician anesthesiologists and nurse anesthetists. The result of this anesthesia workforce analysis was to introduce the formal concept of the anesthesia care team, and to define a new type of anesthesia practitioner, the anesthesiologist assistant. The three founders of the anesthesiologist assistant profession created a new educational paradigm for a master’s degree anesthesia practitioner, emphasizing a premedical college background in science rather than in nursing. Their vision came to fruition in 1969, when the first training programs for anesthesiologist assistants began to accept students at Emory University in Atlanta, Georgia, and at Case Western Reserve University in Cleveland, Ohio. It was the founders’ belief that all patients deserved physician anesthesiologist supervised care, that they would become members of the anesthesia care team, and never a substitute for physician-led care.
Today, anesthesiologist assistant training programs are 24 to 28 months in duration, and the degree awarded is a Master of Science in Anesthesia or a Master of Medical Science. There are currently 15 anesthesiologist assistant educational programs accredited by the Commission for Accreditation of Allied Health Education Programs (CAAHEP). All the anesthesiologist assistant programs are associated with the anesthesiology department of a medical school and have a board-certified physician anesthesiologist as the medical director. The anesthesiology department must have the educational resources to qualify it to meet the criteria of the Accreditation Council for Graduate Medical Education (ACGME) for sponsorship of an anesthesiology residency program. Graduates or senior students in their last semester must pass a certifying examination administered by the National Commission for Certification of Anesthesiologist Assistants (NCCAA) in collaboration with the National Board of Medical Examiners (NBME).
Once fully trained, certified anesthesiologist assistants work exclusively under the medical direction of the physician anesthesiologist, incorporating learned principles of anesthesia patient care, as an integral member of the physician-led anesthesia care team (ACT) model.
Anesthesiologist assistant education was designed to incorporate the basic principles supportive of the ACT. The founders recognized the advantages of a strong premedical background and anticipated that some anesthesiologist assistants would choose to go on to medical school and continue their careers as physician anesthesiologists.
- Prerequisites for Entry
- CRNA school prerequisites
- Undergraduate baccalaureate degree (3-4 years) in nursing
- Minimum GPA 3.0 may be required
- Graduate Record Exam (GRE) may be required
- Active registered nurse (RN) licensure
- Minimum 1-year acute care experience (ICU, PACU, ER). As of January 2022, all CRNA programs must include a doctoral degree: a 1-2 year clinical or non-clinical, web-based certification focused in either nursing, nurse anesthesia, philosophy, education, or nursing science.
- AA school prerequisites
- Undergraduate baccalaureate degree, with pre-medical science requirements that include biology, chemistry, organic chemistry, anatomy, physiology, physics, and statistics
- Minimum GPA 3.0 may be required
- Satisfactory completion of the MCAT and/or GRE may be required depending on the program.
- Prior health care experience is preferred, but not required, similar to the requirement for students entering medical school. Currently, the majority of students entering AA programs, do have health care experience.
Despite differences in prerequisite requirements between AA and CRNA training programs, there is no evidence that differences exist in either care team members ability to attain necessary clinical skills, knowledge, and complete education training in either program.
CRNA vs. CAA Clinical Curriculum
|Number of months in program
||24-36 months, master’s or doctorate level program
||24-28 months, master's level program
|Number of didactic hours
||34-80 hours, program dependent
||56-132 hours, program dependent
|Minimum number of anesthesia cases
|Minimum number of clinical hours
||1700, average 2000
||2000, average 2500
|Minimum number of neuraxial anesthetics on live patients
|Minimum number of peripheral nerve blocks on live patients
|Central venous line insertion on live patients
CRNA vs CAA Clinical Curriculum
|Use of Ultrasound, Fluoroscopy, or other diagnostic technologies
|Scholarly work (i.e., research, manuscript, poster, innovative model, clinical publication)
||“One substantial final written work product”
|Certification in doctoral degree
||By Jan 2022, required to complete a 1-2 year
non-clinical, web-based certification in either nursing, nurse anesthesia, philosophy, education, or nursing
- Council on Accreditation of Nurse Anesthesia Educational Programs. 2019. Standards for Accreditation of Nurse Anesthesia Programs – Practice Doctorate. Accessed July 22, 2022. https://www.coacrna.org/wp-content/uploads/2020/01/Standards-for-Accreditation-of-Nurse-Anesthesia-Programs-Practice-Doctorate-revised-October-2019.pdf
- Council on Accreditation. 2020. Index of WP Content Uploads. Accessed July 22, 2022. CRNA requirements: https://www.coacrna.org/wp-content/uploads/ 2021/03/Standards-for-Accreditation-of-Nurse-Anesthesia-Programs-Practice-Doctorate-revised-January-2021.pdf
- Commission on Accreditation of Allied Health Education Programs. 2016. Standards and Guidelines for the Accreditation of Educational Programs for the Anesthesiology Assistant. Accessed July 22, 2022. https://www.caahep.org/CAAHEP/media/CAAHEP- Documents/AnesthesiologistAssistantStandards.pdf
- Physician Involvement in Anesthesia Care Delivery
The ASA strongly supports the practice of safe, high-quality anesthesia care and thus the Society’s recommendation will always be to maintain physician involvement in anesthesia care, wherever and whenever possible. Physicians have the highest level of education and training. The delivery of safe high-quality anesthesia care is tied directly to that level of education. Having a physician-led team is especially important in specialties such as anesthesiology and critical care, where decisions being made within seconds may mean the difference between a patient’s life or death.
The principle of physician supervision, present since the beginning of nurse anesthesia, has been maintained to this day, now primarily through federal regulation, state statute and licensing regulations, and hospital medical bylaws and/or staff rules. The majority of anesthetics in the US are delivered using the physician-led care team model, where a physician anesthesiologist supervises and directs anesthesiology residents, CAAs, and/or CRNAs.
A study published in Anesthesiology in October 2018 (Sun, E, et al) concluded: “The specific composition of the anesthesia care team (whether made up of physician anesthesiologist and an AA [sic] or a physician anesthesiologist and a CRNA was not associated with any significant differences in mortality, length of stay, or inpatient spending.”
In the majority of states, nurse anesthetists function in an ACT model with a physician anesthesiologist or under the supervision of the operating surgeon, dentist, or other nonanesthesiologist physician, thereby satisfying CMS requirements for physician supervision of nurse anesthesia. In limited circumstances, nurse anesthetists are authorized to practice without the involvement of a physician as a result of state law or governor opt-out.
CMS has structured its payment system for physician anesthesiologist services into four categories: personally performed, teaching, medical direction, and medical supervision. These are indicated by different Medicare billing modifiers, and most commercial payers utilize the same payment system. CMS uses the term “qualified non-physician anesthetists” to refer to nurse anesthetists and anesthesiologist assistants as a combined group, since in most billing circumstances the rules of payment for their services are the same. One exception is that the “QZ” modifier is specific to CRNAs and does not apply to cases involving care by CAAs. The “QZ” modifier is defined as nurse anesthetist service “without medical direction by a physician.”
The use of the “QZ” modifier in billing does not necessarily mean that a nurse anesthetist was practicing solo without any involvement of a physician anesthesiologist For 2019, the QZ for Medicare billing was used for 28.5% of payments and 34.5% of claims-based units. A 2016 study showed that among 538 hospitals that filed all of their anesthesia claims using the modifier “QZ” in 2013, 48 percent had affiliated physician anesthesiologists. The authors concluded, “It seems likely that the physician anesthesiologists were involved in patient care and had some relationship with nurse anesthetists practicing at the hospitals.”4 Thus, use of the “QZ” modifier in billing for a case does not imply or prove that a physician anesthesiologist was never involved with the management of the anesthesia care. Outcomes data from cases billed using the “QZ” modifier cannot be used accurately as a surrogate for independent nurse anesthesia practice. The results of this study underscore the continuing influence and widespread acceptance of the anesthesia care team concept as critical to patient safety.
- Maintenance of Certification
Once certified, every CRNA and CAA must be continually involved in ongoing education and the recertification process, though the requirements vary between each type of ACT member. The table below outlines these differences.
Licensing requirements and Maintenance of Certification
||National Board of Certification and Recertification for Nurse Anesthetists (NBCRNA)
||National Commission for Certification of Anesthesiologist Assistants (NCCAA)
||All 50 states and the District of Columbia
||Licensing allowed in 18 jurisdictions
||Board of Nursing
||Board of Medicine
|Average number of CME/year
||1st 4 years – 40 CEUs
2nd 4 years – recertification exam
|40 credits over 2 years
||No requirement prior to 2016. The "Continued Professional Certification (CPC) program" is now oﬀered, but no negative impact on certification regardless of score in its first oﬀering between 2020-2024. Second “Passing Standard Exam” will be given 2028-2032.
||Must initially pass the
“Continued Demonstration of Qualifications (CDQ)” after 6 years of graduation, then on an ongoing basis every 10 years. ii
- National Board of Certification and Recertification for Nurse Anesthetists. 2022. Accessed July 25, 2022. https://www.nbcrna.com/docs/default-source/publications-documentation/handbooks/nce_hb(1).pdf?sfvrsn=5ed2310c_30.
- National Commission for Certification of Anesthesiologist Assistants. 2022. Accessed July 22, 2022. https://www.nccaatest.org/. (Exam administered by the NBME and addresses 16 core competencies.)
The Committee on the ACT studied and compared the prerequisites for program admission, the didactic curricula, and the clinical components of anesthesiologist assistant and nurse anesthetist educational programs with regard to scope of practice and overall quality. Reference was made to published program prerequisites, curricula, graduation requirements, the laws and regulations governing clinical practice, requirements for maintenance of certification, and available information on the safety of anesthesiologist assistant and nurse anesthetist practice.
The Committee concludes that differences do exist between anesthesiologist assistants and nurse anesthetists with regard to the educational program prerequisites, instruction, and requirements for supervision in practice as well as maintenance of certification. These are the result of the different backgrounds associated with the two professions related to development, and the stated preference of anesthesiologist assistants to work exclusively on teams with physician anesthesiologists. The committee found no evidence that any of these differences result in disparity in knowledge base, technical skills, or quality of care when supervised by a physician anesthesiologist.
- Council on Accreditation of Nurse Anesthesia Educational Programs. Standards for accreditation of nurse anesthesia educational programs. Approved 2004, revised June 2016.
- Council on Accreditation of Nurse Anesthesia Educational Programs. Standards for accreditation of nurse anesthesia educational programs – Practice Doctorate. Approved 2015, revised June 2016.
- Commission on Accreditation of Allied Health Education Programs. Standards and guidelines for the accreditation of educational programs for the anesthesiologist assistant. Approved 1987, revised 2009.
- Sun E, Miller T, Moshfegh J, Baker L. Anesthesia Care Team Composition and Surgical Outcomes. Anesthesiology 2018; 129:700-9.
- Miller T, Abouleish A, Halzack N. Anesthesiologists are affiliated with many hospitals only reporting anesthesia claims using modifier QZ for Medicare claims in 2013. A&A Case Reports: April 1, 2016, Vol 6 No 7, 217-219.