Monitored Anesthesia Care
Monitored anesthesia care (MAC) is a set of anesthesia services defined by the type of anesthesia personnel present during a procedure, not specifically by the level of anesthesia needed. The American Society of Anesthesiologists (ASA) defined MAC, and the following is derived from the ASA's statements:
"Monitored anesthesia care is a specific anesthesia service for a diagnostic or therapeutic procedure. Indications for monitored anesthesia care include the nature of the procedure, the individual's clinical condition and/or the potential need to convert to a general or regional anesthetic.
Monitored anesthesia care 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.
Monitored anesthesia care 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 individual loses consciousness and the ability to respond purposefully, the anesthesia care is a general anesthetic, irrespective of whether airway instrumentation is required."
In 2004 (amended in 2014), ASA defined 4 levels of sedation and analgesia, as shown in Table 1.
Table 1. ASA's Definitions of General Anesthesia and Levels of Sedation and Analgesia
||Minimal Sedation (Anxiolysis)
||Moderate Sedation or Analgesia (Conscious Sedation)
||Deep Sedation or Analgesia
||Normal response to verbal stimulation
||Purposeful response to verbal or tactile stimulation
||Purposeful response following repeated or painful stimulation
||Unarousable even with painful stimulation
||No intervention required
||Intervention may be required
||Intervention often required
||May be inadequate
||May be impaired
Adapted from American Society of Anesthesiologists (2013).
ASA: American Society of Anesthesiologists.
Because sedation is a continuum, it is not always possible to predict how an individual will respond. Hence, practitioners intending to produce a given level of sedation should be able to rescue individuals whose level of sedation becomes deeper than initially intended. Individuals administering moderate sedation or analgesia (conscious sedation) should be able to rescue individuals who enter a state of deep sedation or analgesia, while those administering deep sedation or analgesia should be able to rescue individuals who enter a state of general anesthesia.
Sedation for Diagnostic and Therapeutic Procedures
Multiple diagnostic and therapeutic procedures performed in the outpatient setting (e.g., endoscopy, colonoscopy, bronchoscopy, interventional pain management procedures) rely on some degree of sedation for anxiolysis and pain control. Regardless of sedation depth, sedation and anesthesia services provided in outpatient settings should be administered by qualified and appropriately trained personnel. Moderate sedation is generally sufficient for many diagnostic and uncomplicated therapeutic procedures. Moderate sedation using benzodiazepines, with or without narcotics, is frequently administered under the supervision of the proceduralist.
According to the ASA's standard for monitoring, MAC should be provided by qualified anesthesia personnel, including physicians and nurse specialists. By this standard, the personnel must be, in addition to the proceduralist, present continuously to monitor the individual and provide anesthesia care. For individuals at high risk of an unsuccessful procedure under moderate sedation, this allows for the safe continuation of the procedure under deep sedation or general anesthesia by trained personnel.
Moderate sedation can be achieved using pharmacologic agents for sedation, anxiolysis, and analgesia. A frequently used combination is an opioid and benzodiazepine (e.g., fentanyl with midazolam) at doses individualized to obtain the desired sedative effect. Other combinations have also been used. While benzodiazepines and opioids can cause respiratory depression, effective reversal agents exist for both.
Propofol has increasingly been used to provide sedation for procedures. It is associated with a rapid onset of action and fast recovery from sedation. However, there are concerns about potential adverse effects and safety when used by non-anesthesiologists. Propofol has the potential to induce general anesthesia, and there is no pharmacologic antagonist to reverse its action. When used as moderate sedation, propofol may be administered by anesthesia personnel or under the direction of the proceduralist. ASA has offered practice guidelines for the provision of sedation by non-anesthesiologists, stating that personnel must be prepared to respond to deep sedation and loss of airway protection should these complications inadvertently occur during sedation.
In 1989, propofol Diprivan® (AstraZeneca) was approved by the U.S. Food and Drug Administration (FDA) through the premarket approval process for the induction and maintenance of anesthesia. The current FDA-approved label for Diprivan® states that it is indicated for initiation and maintenance of MAC sedation, combined sedation, and regional anesthesia; the label also states that Diprivan® is indicated for the sedation of adults in the intensive care unit who have been intubated or mechanically ventilated. Moreover, Diprivan® is also approved for induction of general anesthesia in individuals three (3) years of age and older and maintenance of general anesthesia in individuals two (2) months of age and older.
Many other FDA-approved medications for pain relief, anxiolysis, and sedation may be used in outpatient sedation.
Summary of Evidence
For individuals who have planned endoscopy and certain risk factors or significant medical conditions who receive MAC, the evidence includes systematic reviews, randomized controlled trials (RCTs) , and observational studies. Relevant outcomes are overall survival (OS), morbid events, hospitalizations, and treatment-related mortality and morbidity. A literature review for the American Gastroenterological Association Institute identified potential indications requiring an anesthesia specialist. Systematic reviews comparing general anesthesia to MAC in individuals undergoing endoscopic retrograde cholangiopancreatography have found few differences between these modalities. However, the evidence from RCTs is sparse. A RCT comparing propofol administration by anesthesiologists for the purpose of anesthesia with propofol administered by nonanesthesiologists for sedation during colonoscopy reported that individuals receiving propofol from anesthesiologists indicated greater willingness to undergo further colonoscopies under the same conditions. This trial did not show any differences in procedure time or individual satisfaction and reported a higher rate of hypoxia in individuals treated by anesthesiologists with propofol. However, this trial may have been underpowered to detect differences in complication rates. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome.
For individuals who have planned bronchoscopy and certain risk factors or significant medical conditions who receive MAC, the evidence includes no studies that directly address this issue. Relevant outcomes are OS, morbid events, hospitalizations, and treatment-related mortality and morbidity. There is a lack of published evidence on MAC for bronchoscopy procedures; no RCTs, nonrandomized comparative studies, or large case series were identified. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome.
For individuals who have planned interventional pain management procedures and certain risk factors or significant medical conditions who receive MAC, the evidence includes no studies that directly address this issue. Relevant outcomes are OS, morbid events, hospitalizations, and treatment-related mortality and morbidity. There is a lack of published evidence on MAC for interventional pain management procedures; no RCTs, nonrandomized comparative studies, or large case series were identified. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome.
National guidelines (e.g., from the American Society of Anesthesiologists) support the use of MAC for individuals undergoing outpatient procedures who have certain risk factors or significant medical conditions. Therefore, MAC is considered medically necessary in these situations.