Inhalation Agents Flashcards
Potency is directly related to what?
lipid solubility
what provides a quantitative measure of lipid solubility (aka potency)
oil:gas partition coefficient
what is minimal alveolar concentration (MAC)?
the alveolar concentration of an inhalation agent at which 50% of patients do not move in response to skin incision or similar noxious stimuli
is MAC inversely or directly proportional to potency (lipid solubility)
inversely proportional
the lower the MAC the higher the potency
list the MAC's and put the following in order from least to most potent. halothane Des Sevo iso Enf N20
N20- 104% Des- 6.6% Sevo-1.7% Iso- 1.2 (1.15)% Enf- 1.6 % Hal- 0.75%
enflurane is the one exception
temp and solubility:
what happens to solubility of gas in a liquid as temp increases
decreases
temp and solubility:
the solubility of gas decreases in a liquid as temp increases. how does this apply to out pts
less inhalation agent will dissolve in blood if pt hyperthermic
more inhalation agent will dissolve in blood if pt hypothermic
Uptake and elimination:
what determines speed of onset and elimination
blood solubility
Uptake and elimination:
what provides a quantitative measure of blood solubility?
blood:gas partition coefficient
Uptake and elimination:
which inhalation agents have the faster uptake thus onset the one with a high or low blood:gas
low
Uptake and elimination:
what are the 3 determinants of brain uptake and induction speed? and explain how?
- blood solubility- lower blood:gas faster onset
- Alveolar ventilation- the greater the ventilation the faster uptake
- Cardiac output- inversely related- decreased CO faster onset
Uptake and elimination:
old people with low CO will their IV inhalation be slow or fast? will there inhalation agent onset be slow or fast?
IV- slow
Inhalation agent- fast
Blood:gas partition coefficient:
agents with high blood solubility means they are more soluble where?
in blood
they prefer to be in the blood not gas
Blood:gas partition coefficient:
agents with low blood solubility means thay are more soluble where?
in gas
prefer to be in gas
Blood:gas partition coefficient:
explain the blood:gas partition coefficent for halothane 2.50 and then nitrous oxide 0.46
halothane 2.50:1 = 250:100 (250 molecules in blood and 100 in gas) - means the affinity (solubility) in blood is 2.5 x’s higher than the gas state
nitrous 0.46:1 = 46:100 (46 molecules in blood and 100 in gas)- means solubilty in blood is 0.46 x’s that in gas state)
aka nitrous oxide has a much faster onset than halothane
Blood:gas partition coefficient:
why is it that the lower the blood:gas the faster the onset
b/c the alveoli or the windows to the brain (AKA more in the alveoli=more in the brain), thus more in the gas phase the more in the alveoli
what is the Blood:Gas:
N20
0.46
what is the Blood:Gas:
des
0.42
what is the Blood:Gas:
sevo
0.7
what is the Blood:Gas:
iso
1.46
what is the Blood:Gas:
enflurane
1.9
what is the Blood:Gas:
halothane
2.5
after 30 min, halothane will be how close in % to equilibration?
think 50%
but actual answer 58%
after 30 min, isoflurane will be how close in % to equilibration?
think 70’s
actual answer 73%
