There are over 5,800 Centers for Medicare & Medicaid Services (CMS)-certified ambulatory surgery centers (ASCs) in the United States, which are located in every state, each of which has its own laws and rules that govern ambulatory surgery ( Every year in the U.S., the number of ambulatory procedural and surgical suites grows by almost 1%. Between 2017 and 2018, this number grew to 2.6% given changes to the Medicare payment policy, thus dramatically increasing the capacity to provide ambulatory surgical and procedural services ( Presently, 68% of surgical procedures performed in the U.S. are performed on an outpatient basis ( It is estimated that ASC procedure volume will grow by at least 6% in 2021 and that orthopedic, spine, and cardiac procedures will increase the fastest through the mid-2020s ( This expansion will drive growth in ambulatory anesthesiology staffing and will create new opportunities for anesthesiologists and allied health providers.

Like those in many other countries, our health care system also operates under a veil of constant downward economic pressure. Within the perioperative space specifically, this pressure often manifests as a shift from hospital-based inpatient procedural and surgical care to either hospital outpatient departments (HOPD), ASCs, or freestanding surgery centers where the cost of care is lower (;

Shifting surgical patients from the inpatient to the outpatient space, however, is not a straightforward administrative decision, especially for patients with significant comorbidities who may not meet ASC patient selection criteria. Furthermore, the majority of ASCs lack laboratory, radiology, pharmacy, or blood bank services. Additionally, when required for the management of critically ill patients, most ASCs also lack the tools that are requisite for functional hemodynamic monitoring, such as the measurement of cardiac output, dynamic indices, invasive arterial pressures, or central venous pressures. Finally, given a relatively low serious adverse event rate, ASC staff are rarely exposed to critical events and, thus, rely on quarterly or annual drills to maintain staff proficiency (;; Anesthesiology 2013;119:1310-21).

Anesthesiologists working within the ambulatory anesthesiology space require a different skill set than those working within the inpatient setting. While anesthesiologists working within the inpatient space make complex clinical decisions daily, such as administering a blood transfusion, these decisions become critical within the ASC space, where blood is generally unavailable. Patient and procedure selection for ambulatory surgery thus represent critical elements of safe ASC care. Additionally, optimal outpatient care also requires that ASC anesthesia staff consider the skill and knowledge of the facility staff, equipment (or lack thereof), ability of the surgeon to perform a procedure in an efficient and safe manner, and knowledge of both the outpatient management of several common co-morbidities, including hypertension, diabetes, and chronic lung and kidney disease, as well as the impact of outpatient medications on anesthetic delivery.

“It is estimated that ASC procedure volume will grow by at least 6% in 2021 and that orthopedic, spine, and cardiac procedures will increase the fastest through the mid-2020s.”

From a holistic perspective, optimizing the experience of providing and receiving care within an ASC requires that facility administration (and its staff) as well as the surgeons, proceduralists, and anesthesia providers work seamlessly together and are aligned on the mission of delivering safe, effective, high-value, evidence-based perioperative care. To this point, however, complex clinical and operational decisions can and do affect relationships within the ASC setting, which, at the end of the day, may not only impact patient care but the economic viability of a given center. Too conservative and demanding an approach to facility medical management can lead to lower surgical and procedural volumes in addition to disgruntled facility staff, surgeons, proceduralists, and patients who may all prefer to provide and receive care respectively within the ambulatory setting. On the other hand, too liberal an approach may lead to unnecessary complications or transfers to higher levels of care. Finally, in addition to the aforementioned downward economic pressure, decision-making within the ambulatory anesthesiology space represents a balance of clinical and operational pressures that touch all ASC stakeholders and can dramatically affect the economic viability of the facility. Forethought, attitude, and approach to patient care and facility management require a fine balance.

An effective ambulatory anesthesia practice is one that understands that to be successful it has to provide high-quality, high-value, and highly efficient service while adapting and responding to the changing demands of patients, surgeons, and the facility. Since many ASCs are also jointly owned by surgeons and proceduralists, they often have more input into facility operations than in the inpatient space. This input occasionally impacts the aforementioned finely tuned ASC stakeholder balance needed to provide safe, effective ambulatory care, such as demanding that patient selection criteria be ignored or the desire to perform complex procedures generally reserved for the inpatient space. While this pressure can be difficult to manage, significant advances in the delivery of ambulatory surgery to older patients undergoing complex surgery, once thought impossible to perform in the ASC realm, is becoming more commonplace, such as ambulatory total joint replacements, spine surgery, and colorectal surgery (J Spine Surg 2019;5:S124-S132). Additionally, as the list of ASC procedures has grown, so has the expectation to perform these procedures on patients with increasing comorbidities, thus requiring providers with enhanced skillsets and funds of knowledge. Additionally, enhanced procedural and surgical care challenges ASCs to purchase and educate staff on the use of new equipment requisite for the care of these ever-more complex patients. It goes without saying that patient-selection and care, as well as professional relationship-building and maintenance, represent critical aspects of what an ambulatory anesthesiologist does daily and where anesthesia providers who are dedicated and geared to ambulatory anesthesia excel. This is where we perceive the value of having a dedicated core group of anesthesia providers who are geared toward providing ambulatory anesthesia, are familiar with the unique decisions required of them, and can benefit from being part of a larger anesthesia group with additional clinical resources, such as clinicians with pediatric or geriatric training. Additionally, leveraging the knowledge and skill sets of other ambulatory anesthesia providers within the larger organization allows for efficient transfer of knowledge between clinicians, such as when new invasive procedures are to be performed within the ASC. Collaboration of this type can yield better patient experience and outcomes and enhance surgeon and facility satisfaction and experience.

Staffing models

State laws and regulations define who may take care of patients during surgery – physicians, physicians and allied health, or allied health alone. Additionally, the state also determines how physicians and clinicians may care for patients: Solo, medically directed, supervised, or collaborating. Also, ASCs with anesthesiology departments generally follow one of three administrative models:

  • Open system: In this model, surgeons work with specific anesthesiologists either directly or leading a care team model of CAAs or CRNAs. In some states, CRNAs may work independently, collaboratively, or supervised by the surgeon.
  • Closed system with small group (single facility coverage): May include care rendered by physicians, CRNAs, or an anesthesia care team model. The facility contracts with a group of anesthesiologists or CRNAs who then determine the best staffing model for the facility. In some states, CRNAs may work independently, collaboratively, or supervised by the surgeon.
  • Closed system with large group (covers multiple facilities): Most common in corporate-owned or managed ambulatory surgery centers. These ASCs generally contract with a large group of anesthesiology providers to manage perioperative services. In this case, the anesthesiology group works with the facility to determine the most appropriate staffing model.

Each of these models has strengths and weaknesses for the surgeon or proceduralist, the facility, and the anesthesia provider. Surgeon satisfaction is often high when facilities rely on independent anesthesiologists or anesthetists to provide care because the providers are often chosen by the surgeon. This system, however, often leaves facilities burdened when independent clinicians run late from other facilities, impacting patient, surgeon, and facility staff satisfaction and efficiency. Additionally, when ASCs lack facility-based anesthesia providers, critical department needs may go unattended, such as defining and maintaining best-practices, policies and procedures, oversight of high-value supply chain needs, and participation in regulatory inspections, not to mention having dedicated clinical staff to focus on preoperative patient evaluation and optimization, daily operational efficiency, and guiding the management of both intraoperative and postoperative adverse events.

“Prehabilitation not only enhances patient outcomes, but enhances facility efficiency by reducing costly day-of-surgery case cancellations.”

When facilities contract with small groups, facility staff satisfaction often increases because the facility administrative needs and operational efficiencies are usually taken care of. But as facility volume increases either in patient volume or by service line procedural expansion, there may not be enough providers or sufficient providers with necessary skill sets to manage patient volume. In this scenario, surgeons are often left unsatisfied when operational inefficiencies occur or when particular providers are unavailable.

Unlike facility contracting with small groups, when ASCs are supported by large groups, not only are anesthesia providers often dedicated to the ASC, but they are able to flex staff with specific skill sets to the ASC, which not only enhances operational efficiency, but allows for a greater variety of patient and procedural complexity.

Anesthesia staffing ratios should be determined by the complexity of the procedure and patient comorbidity. Glance compared five different anesthesia staffing models using a cost effectiveness analysis and found that the optimal staffing model is one in which high-risk patients are managed by anesthesiologists alone, intermediate-risk patients by anesthesia care teams with a physician to CRNA ratio of 1:2, and low-risk patients by ACTs with a physician to CRNA ratio of 1:4. Relative to cost-effectiveness, increasing the physician-to-CRNA ratio for low-risk patients from 1:4 to 1:2 was not cost-effective (Anesth Analg 2000;90:584-92). It is important for patients, surgeons and proceduralists, and facility staff to recognize that when referring to the anesthesia care team model, including CRNAs and CAAs, the composition of the team is not associated with significant differences in mortality, length of stay, or inpatient spending (Anesthesiology 2018;129:700-9). Large group practices are better able to adapt to the need for changing staffing ratios based on external factors, such as scheduling, patient comorbidities, and procedure complexity.

Large group practices go beyond just providing patient care. They mitigate the immense administrative burden imposed upon today’s providers by relieving clinicians of payer negotiations, providing robust revenue cycle management, and providing clinicians with tools to enhance their own physical, emotional, and psychological well-being. Additionally, many of these groups participate in both quality measures development and testing, and some maintain their own CMS-certified qualified clinical data registries, which, aside from participating in the MACRA program, are used to identify local, regional, and national quality performance variation and to target quality improvement (Anesthesiol Clin 2019;37:361-72). Additionally, large groups often have robust internal peer-review systems fed by claims data, self-reported occurrence data, and post-surgical outcomes data that drive continuous quality improvement. Altogether, large group practices have the tools to achieve the quadruple aim by improving the experience of care, enhancing population health, decreasing the total cost of care, and improving the experience of delivering care for their clinicians. Furthermore, large group practices often have the infrastructure to support and perform robust clinical research, even within the ambulatory surgery center space, which helps to define and deliver tomorrow’s health care today.

ASCs may be physically located on a hospital campus or in the same building. In this case, ASC anesthesia staffing may come from the hospital, a different group, or a shared model between groups. Contracting with the same group in both locations provides flexibility to both surgical departments because of the ability to float providers, both in number and with different skill sets between areas. This flexibility for coverage can also be achieved if the group providing anesthesia services at the ASC has the capability to float providers from other local facilities.

Perioperative medicine

To optimize patient outcomes, facilities must have a way to receive and review patient-related clinical information prior to the day of surgery. Patients with significant comorbidities should be evaluated by a facility-based anesthesiologist prior to surgery and, where appropriate, their PCP or specialty clinician in order to guide prehabilitation, medical optimization, and to play a role in presurgical risk assessment, shared-decision making, and informed consent. Prehabilitation not only enhances patient outcomes, but enhances facility efficiency by reducing costly day-of-surgery case cancellations. ASC medical directors should be involved in every aspect of patient management along the care continuum and with facility operations to ensure optimal patient care, facility efficiency and effectiveness, and anesthesia staff satisfaction (; J Arthroplasty 2017;32:S150-S156.e1; Anesthesiology 2020;133:645-52).

As we look to the future, increasing patient and procedural complexity in addition to downward economic pressures demand that ASCs grow in their overall capacity to care for patients once thought to be appropriate only for the inpatient setting. As ambulatory surgical volumes rise, ASCs must meet this challenge by enhancing facility staffing skillsets, incorporating complex equipment, altering drug formularies, and working with anesthesia providers capable of driving and sustaining perioperative practice transformation while ensuring the delivery of high-quality, high-value, highly efficient patient care.