Draw a Line Between Moderate (Conscious) Sedation and Monitored Anesthesia Care

Knowing where the line is can clear up hazy anesthesia reporting.

By Kelly Dennis, MBA, CPC, CPC-I, CANPC, ACS-AN

Coding moderate sedation (or conscious sedation) and monitored anesthesia care (MAC) is not difficult; however, distinguishing what the services provided are and deciphering conflicted information about which physicians can report what codes can be confusing.

Anesthesia and Pain Management CANPC

Misinterpretation Clouds Payer Judgment

History and changing terminology play a role in the confusion. Until the mid-1980s, anesthesiologists classified anesthesia into three types: general, regional, and local standby. Some payers, however, interpreted “standby” in the literal sense—mistakenly thinking the anesthesiologist was “standing by” and not providing a service—and would not pay for local standby services.

To clear up the confusion, the American Society of Anesthesiologists (ASA) replaced the term “standby” anesthesia with “monitored anesthesia care,” approving its first position statement on MAC in 1986. Both the new term and position statement demonstrated active involvement in patient care. In 1998, the MAC position statement was revised (www.asahq.org/Newsletters/1998/12_98/ASAupdates_1298.html) and the concept of a sedation continuum as illustrated by L. Charles Novak, M.D. became part of ASA’s efforts to educate non-anesthesiologists about conscious sedation (Cohen/McMichael, 2004 www.asahq.org/Newsletters/2004/06_04/whatsNew06_04.html). The MAC position statement was last updated Sept. 2, 2008.

MAC vs. Conscious Sedation

MAC services are rendered by anesthesia providers who aren’t involved in the diagnostic or procedural service, and include the same care as any other anesthesia service: a pre-anesthesia assessment, documentation of vital signs during the procedure, and post anesthesia patient care. If necessary, the anesthesia provider must convert to a general anesthetic, which requires anesthesia training.

In contrast, moderate (conscious) sedation, as defined by the CPT®, closely matches the ASA’s definition of a drug induced depression of consciousness. CPT® further indicates that moderate sedation does not include the MAC codes (00100-01999) found in the anesthesia section of the CPT® book.

Moderate sedation codes 99143-99145 require the sedation service be provided by the same physician performing the diagnostic or therapeutic service, along with an independent trained observer to assist in monitoring the patient. Codes 99148-99150 require the sedation service be provided by a physician other than the one performing the diagnostic or therapeutic codes, but an independent trained observer is not required. There are additional CPT® instructions for services performed in a facility or non-facility setting, as well as exclusions for codes listed in Appendix G of the CPT® book.

Although a coder may expect that anesthesia codes are only reported by trained anesthesia providers, existing insurance policies indicate non-anesthesia providers will be reimbursed when billing the appropriate anesthesia codes. The billing physician, however, must report anesthesia time in minutes and meet the requirements for MAC as defined by the ASA. An anesthesia modifier (G8 Monitored anesthesia care (MAC) for deep complex, complicated, or markedly invasive surgical procedure, G9 Monitored anesthesia care for a patient who has a history of severe cardio-pulmonary condition, or QS Monitored anesthesia care service) identifying the service must also be appended. See Oxford Health Plans (March 1) Medical and Administrative Policies (Moderate (Conscious) Sedation and Monitored Anesthesia Care (MAC), (www.oxhp.com/secure/policy/moderate_sedation_309.html) for more information.

Several Medicare Administrative Contractors (also known as MACs), formerly known as fiscal intermediaries, have published Local Coverage Determinations (LCD) related to MAC services. Statistical anesthesia modifiers are required to track MAC cases. Since 1992, all Medicare contractors require the anesthesia modifier QS, and LCD’s will identify those carriers that require G8 and G9. Usually, it isn’t necessary to report both modifier QS and either modifier G8 or modifier G9 (as applicable to the patient) because each of these anesthesia modifiers indicate MAC was used during the procedure. If the procedure converts from a MAC to general anesthesia, no modifier is necessary.

In a 1991 report (www.oig.hhs.gov/oei/reports/oei-02-89-00050.pdf), Richard P. Kusserow of the Office of Inspector General (OIG) indicated that a carrier private business plan identified over 700 procedures for which the services of an anesthetist customarily are not required. Anesthesia claims for those procedures may be denied unless documentation is provided to support the medical necessity for an anesthetist (defined in this report as anesthesia services are rendered by anesthesiologists, other qualified physicians, certified registered nurse anesthetists (CRNAs), and anesthesiologist assistants (AAs)). Coders must understand the reported and billed service, and ensure documentation supports the reported service, whether it is moderate sedation or MAC. It is also important to follow Medicare LCD and medical necessity guidelines for any procedure performed. American Society of
Anesthesiologists (ASA) Definitions

Monitored anesthesia care and moderate sedation are clinically distinct services. Here’s how the ASA defines each:

Moderate sedation/analgesia (conscious sedation) is a drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation. No interventions are required to maintain a patent airway, and spontaneous ventilation is adequate. Cardiovascular function is usually maintained.

Note: Reflex withdrawal from a painful stimulus is NOT considered a purposeful response.

Monitored anesthesia care (MAC) is a specific anesthesia service for a diagnostic or therapeutic procedure. Indications for monitored anesthesia care include the nature of the procedure, the patient’s clinical condition and/or the potential need to convert to a general or regional anesthetic.

MAC includes all aspects of anesthesia care: a pre-procedure visit, intra-procedure care, and post-procedure anesthesia management. During monitored anesthesia care, the anesthesiologist provides or medically directs a number of specific services, including but not limited to:

  • Diagnosis and treatment of clinical problems that occur during the procedure
  • Support of vital functions
  • Administration of sedatives, analgesics, hypnotics, anesthetic agents, or other medications as necessary for patient safety
  • Psychological support and physical comfort
  • Provision of other medical services as needed to complete the procedure safely

MAC may include varying levels of sedation, analgesia, and anxiolysis as necessary. The provider of monitored anesthesia care must be prepared and qualified to convert to general anesthesia when necessary. If the patient loses consciousness and the ability to respond purposefully, the anesthesia care is a general anesthetic, irrespective of whether airway instrumentation is required.

MAC is a physician service provided to an individual patient. It should be subject to the same level of payment as general or regional anesthesia. Accordingly, the ASA Relative Value Guide® provides for the use of proper base procedural units, time units and modifier units as the basis for determining payment.

To see the ASA’s anesthesia’s definitions online, go to www.asahq.org/publicationsAndServices/standards/20.pdf and www.asahq.org/publicationsAndServices/standards/35.pdf.


Kelly Dennis, MBA, CPC, CPC-I, CANPC, ACS-AN, has over 26 years experience in anesthesia billing. She serves as lead anesthesia advisor for the Board of Medical Specialty Coding and is an active member of several associations, including past legislative liaison and past president of Florida Anesthesia Administrators’ Association, past-president of Medical Group Management Association’s Anesthesia Administrators Assembly and a member of AAPC since 2000. She is president of Perfect Office Solutions, Inc.


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