What is Monitoring Anesthesia Care (MAC)?

What is Monitoring Anesthesia Care (MAC)?

Monitored Anesthesia Care (MAC) is a planned anesthetic technique that combines local anesthesia with intravenous sedation and analgesia, administered by an anesthesiologist who provides continuous monitoring and remains present throughout the procedure. 1, 2

Core Definition and Components

MAC involves three fundamental elements that distinguish it from simple sedation:

• Sedation with maintained spontaneous breathing while achieving responsiveness to verbal or tactile stimulation 1
• Local anesthesia administered by the operator or anesthesiologist 2
• Continuous presence of an anesthesiologist who provides monitoring and is prepared to intervene if complications arise 1, 3

The critical distinction is that MAC is not merely "light sedation"—it exists on a spectrum from minimal sedation to deep sedation, and the depth must be clearly defined for each case 1.

The MAC Spectrum: "Awake" vs "Aware"

Understanding the depth of sedation is essential for appropriate monitoring:

MAC "Awake"

• Patient can follow commands and communicate effectively with the surgical team throughout the procedure 1
• Requires standard monitoring: ECG, SpO₂, NIBP, and continuous presence of trained personnel 1

MAC "Aware" (Deep Sedation)

• Patient is unresponsive to noxious stimuli while maintaining spontaneous breathing 1
• Requires identical monitoring to general anesthesia, including mandatory capnography throughout due to loss of verbal responsiveness 1
• An anesthesiologist must remain present at all times 1

Common pitfall: The term "MAC" is often used imprecisely—never assume MAC always means the patient is communicative, as deep sedation can render patients completely unresponsive 1. Always clarify the intended depth before the procedure begins.

Minimum Monitoring Requirements

The Association of Anaesthetists establishes that MAC requires:

• ECG, SpO₂, and NIBP as baseline minimum monitoring 4
• Waveform capnography must be added whenever there is loss of response to verbal contact 4, 1
• Continuous presence of an appropriately trained anesthesia provider throughout the procedure 3
• Monitoring must begin before sedation is initiated and continue throughout the procedure and recovery 3

Critical safety point: Capnography accurately detects apnea during MAC—studies show that 26% of patients develop apnea episodes lasting at least 20 seconds that go undetected by providers without capnography, but are reliably detected when capnography is used 5.

Clinical Advantages and Safety Profile

MAC offers specific benefits compared to general anesthesia:

• Lower incidence of hypotension (14% with MAC vs 59% with general anesthesia) 1
• Reduced vasopressor requirements (7% with MAC vs 44% with general anesthesia) 1
• Shorter duration of hypotension when it occurs (1 minute with MAC vs 4 minutes with general anesthesia) 1
• Rapid postoperative recovery with relatively small amounts of sedatives and analgesics 2

However, MAC is associated with more adverse respiratory events than general anesthesia, particularly with deep sedation 1. This underscores why monitoring intensity for "MAC aware" should not be reduced compared to general anesthesia 1.

Documentation Requirements

Maintain accurate records including:

• Heart rate, blood pressure, SpO₂, and ETCO₂ recorded at least every 5 minutes 4, 3
• All medications administered with timing and dosages 3
• Any complications and interventions performed 3
• Electronic anesthetic record systems are recommended when available 3

Key Clinical Pitfall

The most dangerous assumption is that MAC is "safer" or requires less vigilance than general anesthesia. Deep sedation under MAC can render patients completely unresponsive, and monitoring intensity must match the depth of sedation 1. The discretion and judgment of an experienced anesthesiologist are required because the airway is not secured 2.