Monitored anesthesia care (MAC) refers to an anesthetic technique that involves a patient undergoing sedation without mechanical ventilatory support. . During MAC, patients typically do not need such support and usually retain control of their airways; however, they are sedated throughout the procedure . MAC usually requires fewer sedatives and analgesics than general anesthesia, however, patients are at risk of respiratory depression and airway obstruction because their airway is not externally secured . The anesthesia provider overseeing a patient’s sedation under monitored anesthesia care must continuously monitor the patient’s airway and breathing . In the event of an emergency, the provider must be well-equipped to convert to general anesthesia .
Beyond these broad differences, MAC also differs from general anesthesia when treating certain conditions. One such set of conditions is cardiovascular surgery. Managing sedation for cardiovascular patients–especially those that are critically ill–is very difficult, but MAC has proven successful in a number of such cases . For instance, dexmedetomidine, a drug commonly administered in MAC, typically instantiates only minimal respiratory depression . However, dexmedetomidine may result in transient hypertension or hypotension . In other specific surgeries, MAC may not be as beneficial. For instance, in patients undergoing transcatheter aortic valve replacement, MAC does not seem more advantageous than general anesthesia . Accordingly, the utility of MAC in cardiovascular patients requires taking into account the unique needs of each patient and the capabilities of his/her medical staff .
MAC has also been increasingly used in fetal surgery, with varying outcomes. In a review of 432 fetal interventions performed under MAC, only 11% required a mid-operation conversion to general anesthesia . The cause of those conversions was not necessarily an inherent deficiency in the MAC technique; they were largely due to poor pre-operative planning . Despite those particular cases, the vast majority of procedures were completed without complications and required the use of fewer drugs, therefore supporting MAC’s benefits in this context . In another comparative study between MAC and spinal anesthesia, the former was associated with reduced use of vasopressors, less fluid, and shorter pre-surgical times . In the fetal surgery context, MAC can be highly successful, assuming that pre-operative planning is meticulous and patient-specific.
In addition to cardiovascular and fetal surgery, MAC has been tested against other anesthesia techniques in a number of other contexts. MAC and the asleep-awake-asleep method have similar rates of success for awake craniotomies, but MAC is associated with shorter operative times . Similarly, when treating aortoiliac disease with an endovascular angioplasty, MAC is associated with lower morbidity and shorter hospital stays . A multitude of other case types have yielded similar results, but many researchers in this field acknowledge the need to conduct further research .
Current research suggests that MAC is a strong alternative to general anesthesia in many surgical contexts. Consequently, monitored anesthesia care should be used by practitioners when appropriate to improve efficiency and patient safety during surgery.
 H. Sohn and J. Ryu, “Trigeminal Neuralgia,” Korean Journal of Anesthesiology, vol. 69, no. 4, p. 319-326, Aug 2016. [Online]. Available: https://doi.org/10.4097/kjae.2016.69.4.319
 J. P. Wiener-Kronish and L. Fleisher, “Overview of Anesthesia,” Goldman’s Cecil Medicine, vol. 2, no. 1, p. 2483-2487, Jan 2012. [Online]. Available: https://doi.org/10.1016/B978-1-4377-1604-7.00440-1
 Committee of Economics, “Distinguishing Monitored Anesthesia Care (‘MAC’) from Moderate Sedation/Analgesia (Conscious Sedation),” American Society of Anesthesiologists, Oct 2018. [Online]. Available: https://www.asahq.org/standards-and-guidelines/distinguishing-monitored-anesthesia-care-mac-from-moderate-sedation analgesia-conscious-sedation
 J. W. Song, S. Soh, and J. Shim, “Monitored Anesthesia Care for Cardiovascular Interventions,” Korean Circulation Journal, vol. 50, no. 1, p. 1-11, Jan 2020. [Online]. Available: https://doi.org/10.4070/kcj.2019.0269
 C. Palermo et al., “Monitored Anesthesia Care Versus General Anesthesia: Experience With the Medtronic CoreValve,” Journal of Cardiothoracic & Vascular Anesthesia, vol. 30, no. 5, p. 1234-1237, Oct 2016. [Online]. Available: https://doi.org/10.1053/j.jvca.2016.02.006
 B. Frugoni and A. Mizuhuchi, “General, Regional, or Monitored Anesthesia Care for the Cardiac Patient Undergoing Noncardiac Surgery,” A Companion to Kaplan’s Cardiac Anesthesia, vol. 50, no. 1, p. 289-312, Oct 2018. [Online]. Available: https://doi.org/10.1016/B978-0-323-56716-9.00012-6
 D. Patel et al., “Monitored Anesthesia Care versus General Anesthesia for Intrauterine Fetal Interventions: Analysis of Conversions and Complications for 480 Cases,” Fetal Diagnosis and Therapy, vol. 47, no. 8, p. 597-603, July 2020. [Online]. Available: https://doi.org/10.1159/000504978
 M. B. Ferschl et al., “A Comparison of Spinal Anesthesia Versus Monitored Anesthesia Care With Local Anesthesia in Minimally Invasive Fetal Surgery,” Anesthesia and Analgesia, vol. 130, no. 2, p. 409-416, Feb 2020. [Online]. Available: https://doi.org/10.1213/ANE.0000000000003947
 C. I. Eseonu et al., “Awake Craniotomy Anesthesia: A Comparison of the Monitored Anesthesia Care and Asleep-Awake-Asleep Techniques,” World Neurosurgery, vol. 104, no. 1, p. 679-686, Aug 2017. [Online]. Available: https://doi.org/10.1016/j.wneu.2017.05.053
 N. M. Boulos et al., “Monitored Anesthesia Care Is Associated With a Decrease in Morbidity After Endovascular Angioplasty in Aortoiliac Disease,” Journal of Cardiothoracic & Vascular Anesthesia, vol. 34, no. 9, p. 2440-2445, Sep 2020. [Online]. Available: https://doi.org/10.1053/j.jvca.2020.02.025