MAC, the minimum alveolar concentration of an inhaled anesthetic, provides anesthesiologists with a convenient mental model of anesthetic potency as a basis for clinical decisions. Philips IntelliVue patient monitors calculate MAC and MAC-awake* values for display on the monitor using the gas concentration measurements provided by Philips gas modules.
Anesthesia decision support at the point of care
The partial pressure of the brain and alveoli are in equilibrium; therefore, alveolar concentrations can be used to gauge the anesthetic effect of an inhaled agent.
A MAC value of 1 is defined as the alveolar concentration at which 50% of a patient population does not respond with movement to a noxious stimulus, such as skin incision. MAC is a valuable measure because it applies to any inhaled agent, including N2O.
Similarly, a MAC-awake* value of 1 signifies the anesthetic agent concentration at which 50% of patients respond again to verbal comment.
MAC is a useful indicator of anesthetic potency in one normalized value since the required concentrations of different agents to achieve a MAC value of 1 varies widely.
An algorithm to help control the patient’s anesthetic status
In addition to the standard MAC calculation, our algorithm can also calculate a corrected and enhanced MAC* value.
Corrected MAC takes into account:
- ambient barometric pressure
Enhanced MAC* that also takes into account:
- patient age
- body temperature
A coherent overview of patient status
The IntelliVue patient monitors display waveforms and numerics for MAC values, anesthetic and respiratory gases plus vital signs, providing a comprehensive patient overview in one glance.
References
Eger II, Edmond.
Age, Minimum
Alveolar Anesthetic Concentration, and Minimum Alveolar Anesthetic Concentration- Awake. Anesth Analg. 2001 Oct;93(4):947-53. Review.
* Not available in the United States