Inhaled Anesthetics Flashcards
MAC highest at what age?
6 months
Effect on MAC: Hyperthermia
Increases
Effect on MAC: Hypernatermia
Increases
Effect on MAC: Hypercarbia
Decreases
Effect on MAC: Hypoxia
Decreases
MAC changes how much with each decade
Decreases 6% every decade after 40
Vapor Pressure Desflurane
660
Vapor Pressure Sevoflurane
160
Vapor Pressure Isoflurane
240
Vapor Pressure Halothane
240
Calculate the partial pressure of desflurane
delivered from the Tec 6 vaporizer at sea
level (atmospheric pressure = 760 mm Hg)
and also in the mountains where the atmospheric pressure is 600 mm Hg. Do your
calculations explain why delivering 5% in
the mountains results in lighter anesthesia?
If you set the dial on the Tec 6 at 5% and you are at sea level, the partial pressure of desflurane going to the patient is 0.05 x 760 mm Hg = 38 mm Hg (Dalton’s law of partial pressures permits this calculation); if you go
up into the mountains where the total atmospheric pressure is. let’s say. 600 mm Hg, the partial pressure of desflurane delivered to the patient when you set the Tec 6 dial at 5% is 0.05 x 600 mm Hg = 30 mm Hg. These calculations explain why setting the dial at 5% results in lighter anesthesia in the mountains than it does at sea level The partial pressure going to the patient for a given dial setting is lower in the mountains.
What is the temperature and pressure in the
desflurane vaporizer? Is the desflurane
vaporizer a flow-over vaporizer?
Desflurane is delivered from a heated (39 degrees C) and pressurized (1300 mmHg) vaporizer. The desflurane vaporizer is not a flow-over vaporizer.
State two reasons why desflurane needs a
specially-designed vaporizer?
1) Desflurane’s vapor pressure of 669 mm Hg is near atmospheric pressure, so it almost boils at sea level; (2) desflurane is only one-fifth as potent as the other volatile agents, so a relatively large volume of vapor must be
delivered to the patient.
**Required Dial Setting for Desflurane at Altitude
Required Setting = (Normal setting x 760) / Ambient Pressure
Partial Pressure Equation
Concentration(%) = Ppartial/Patm
