Mindray iPM-9800 - MAC Values

17-5
17.4 MAC Values
Minimum alveolar concentration (MAC) is the minimum concentration of the agent in the
alveoli. It is a basic index to indicate the depth of anesthesia. The standard ISO 21647 defines
MAC as this: alveolar concentration of an inhaled anesthetic agent that, in the absence of
other anesthetic agents and at equilibrium, prevents 50% of patients from moving in response
to a standard surgical stimulus.
Minimum alveolar concentration (MAC) values are listed below:
Agent DES ISO ENF SEV HAL N
2
O
1 MAC 7.3%* 1.15% 1.7% 2.1% 0.77% 105%**
* The data is taken from a patient of 25 years old.
** indicates 1 MAC nitrous oxide can only be reached in hyperbaric chamber.
NOTE
z The MAC values shown in the table above are those published by the U.S. Food
and Drug Administration for a healthy 40-year-old adult male patient.
z In actual applications, the MAC value may be affected by age, weight and other
factors.
The formula to calculate the MAC value is as follows:
∑
−
=
=
1
0
N
i
i
i
AgentVol
EtAgent
MAC
Where N is the number of all agents (including N
2
O) that the AG module can measure,
EtAgenti is the concentration of each agent and AgentVoli is the concentration of each agent
at 1 MAC.
For example, the AG module measures there are 4% of Des, 0.5% of Hal and 50% of N
2
O in
the patient’s end-tidal gas:
4.0% 0.5% 50%
1.67
7.3% 0.77% 105%
MAC =+ + =
NOTE
z The formula mentioned above is intended for adult patients only.