Dräger Primus - Page 81

Anaesthetic agents
The anaesthetic agents are side-stream measured in the same
way as CO2 and O2.
MAC” definition
1 MAC is equal to the anaesthetic gas concentration at
1013 hPa at which 50 % of all patients no longer respond to
a stimulation of the nerves.
The values listed in the table below are used to calculate the
MAC value. These values are merely guideline values and are
still subject to debate. The current MAC values listed in the
instructions enclosed with the anaesthetic gases are binding!
1 MAC
Halothane 0.77 %
Enflurane 17%
Isoflurane 1.15 %
Desflurane 6.65 %
Sevoflurane 21%
N20 105 %
The MAC value depends on the patient's age. The above
values refer to age 40 years.
Primus automaticaliy identifies the anaesthetic agent used and
adjusts the measurement and monitoring of the anaesthetic
gas concentration to suit the gas identified.
If there is a mixture of two volatile anaesthetic agents, the
concentration of the secondary anaesthetic agent is displayed
if the MAC value is 0.1 MAC or greater. The gas with the
higher expiratory MAC value is displayed above the secondary
gas.
A secondary anaesthetic agent becomes the main anaesthetic
agent if its MAC value exceeds the MAC value of the main
anaesthetic agent by 0.2 MAC.
A mixture of more than two voiatile anaesthetic agents cannot
be reliably detected.
Calculating the MAC values
The MAC value is a simple navigation aid for determining the
dosage of anaesthetic agent.
Primus takes into account age correction, altitude correction
and mixture calculation. The influence of other medication
(opiates or intravenous hypnotics) is not taken into account
when calculating MAC values.
The measured values used for calculating the MAC factor are
the end-expiratory concentrations. Partial pressures are taken
into account.
The displayed value is calculated for 1013 hPa as follows:
_ exp. conc. agent; + ep. cone. agent)
Monitoring
influence of age on the MAC value
+ exp. conc. N20
© MAC (age) agent; MAC (age) agent,
1} Minimum alveolar concentration, MAC
Instructions for Use Primus SW 2.n
MAC (age) N20
Desflurana
0.2*N20
Sevoflurane
i Enflurane
loflurane
Halothane
19 20 20 如 so w 20 so
Age (years)
0036
mon