What is the difference between Monitored Anesthesia Care (MAC) aware and MAC awake?

MAC Aware vs MAC Awake: Key Distinctions

MAC "aware" and MAC "awake" are not formally distinct anesthetic categories—both terms describe Monitored Anesthesia Care where the patient maintains spontaneous breathing through their own airway, but the critical difference lies in the level of consciousness and responsiveness during the procedure. 1

Defining the Spectrum

MAC Awake

• Patient maintains responsiveness to verbal or tactile stimulation throughout the procedure 2
• Patient can follow commands and communicate effectively with the surgical team 1
• Airway protective reflexes remain intact 3
• Represents lighter sedation on the continuum, often termed "conscious sedation" 3, 4
• The patient is able to answer orders appropriately and protect their airway 3

MAC Aware (Deep Sedation/Unresponsive MAC)

• Patient achieves a state of unresponsiveness to noxious stimuli (functionally equivalent to general anesthesia) while maintaining spontaneous breathing 1
• Responsiveness is significantly obtunded 1
• This represents deep sedation that requires identical monitoring to general anesthesia 1
• The constraint of spontaneous breathing helps prevent excessively deep anesthesia, but does not preclude unresponsiveness 1

Critical Clinical Distinction

The fundamental difference is that MAC "awake" maintains patient cooperation and communication, while MAC "aware" (deep sedation) produces unresponsiveness similar to general anesthesia but without airway control devices. 1, 3

Monitoring Requirements

For MAC Awake (Conscious Sedation)

• Standard monitoring: ECG, SpO₂, NIBP 1, 5
• Continuous presence of appropriately trained personnel 1
• Capnography when response to verbal contact is lost 5

For MAC Aware (Deep Sedation)

• Requires identical monitoring to general anesthesia 1
• Mandatory capnography throughout due to loss of verbal responsiveness 5
• Processed EEG monitoring (BIS targeting ~50) recommended when using propofol with opioids 5
• An anesthetist must remain present at all times, identical to general anesthesia requirements 1

Safety Considerations

Respiratory Risks

• MAC (particularly deep sedation/aware) is associated with more adverse respiratory events than general anesthesia 1
• Risk of apnea requiring airway rescue maneuvers is higher with deeper sedation 6
• Continuous capnography is essential during MAC aware to detect early respiratory depression 2

Hemodynamic Profile

• MAC (both levels) shows lower incidence of hypotension (14%) compared to general anesthesia (59%) 1, 2
• Vasopressor requirements are significantly reduced with MAC (7% vs 44% with GA) 1, 2
• Duration of hypotension when it occurs is brief (1 minute with MAC vs 4 minutes with GA) 1

Common Pitfalls

• Do not assume MAC always means the patient is communicative—deep sedation under MAC can render patients completely unresponsive 1
• Never reduce monitoring intensity for "MAC aware" compared to general anesthesia—the risks are equivalent 1
• Elderly patients (>60 years) require reduced propofol doses during MAC due to pharmacokinetic changes 5
• The term "sedation" is imprecise and means different things to different practitioners—always clarify the intended depth 1

Practical Algorithm for Depth Selection

For procedures requiring patient cooperation (e.g., awake craniotomy, regional anesthesia verification):

• Use MAC awake with maintained verbal responsiveness 7
• Patient must be conscious and communicating effectively 1

For procedures where patient movement is detrimental but airway access is maintained:

• MAC aware (deep sedation) may be appropriate 1
• Requires full anesthesia monitoring and immediate availability of airway rescue equipment 1

For procedures in prone position or with shared/compromised airway access (e.g., ERCP):

• Consider general anesthesia with secured airway to minimize critical hypoxemic events 6
• MAC aware in these positions carries higher risk of airway complications 6