Background: The American Society of Anesthesiologists (ASA) defines MAC as an anesthesia service for diagnostic or therapeutic procedures where indications include the nature of the procedure, the patient’s clinical condition, and potential need to convert to a regional or general anesthetic. MAC “includes all aspects of anesthesia care” such as a pre-procedure visit, intra-procedure monitoring and management, and post-procedure anesthesia care.
The ASA levels of sedation/analgesia are: Minimal sedation (anxiolysis) — responds normally to verbal commands; Moderate sedation/analgesia (conscious sedation) — purposeful response to verbal commands with adequate ventilation and cardiovascular function; Deep sedation/analgesia — not easily arousable, may require assistance maintaining airway and ventilation; and General anesthesia — unarousable even to painful stimulation, often requiring airway support and positive-pressure ventilation.
Scope of MAC: MAC may include varying levels of sedation, analgesia, and anxiolysis as needed for outpatient procedures (e.g., endoscopy, colonoscopy, bronchoscopy, interventional procedures). Sedation in outpatient settings should be administered by qualified and appropriately trained personnel; providers of MAC must be prepared and qualified to convert to general anesthesia if necessary.
Personnel and risks: ASA standards call for MAC to be provided by qualified anesthesia personnel in addition to the proceduralist, present continuously to monitor and provide care. Because sedation is a continuum, practitioners must be able to rescue patients who progress to deeper levels of sedation than intended. Common moderate sedation regimens include combinations of benzodiazepines and opioids (with available reversal agents). Propofol is increasingly used for procedural sedation due to rapid onset and recovery but raises safety concerns when administered by non-anesthesiologists because it can induce general anesthesia and has no pharmacologic antagonist; ASA guidelines stress that personnel must be prepared to respond to loss of airway protection or deeper levels of sedation.