Advanced Pham II: Final Exam ACTUAL UPDATED QUESTIONS AND CORRECT
ANSWERS
MAC - minimum alveolar concentration required to achieve surgical anesthesia
(immobility) in 50% of patients exposed to a noxious stimulus (get cut)
- MAC is the dose of a gas
- equivalent to gas concentration in the brain
MAC-awake - alveolar concentration of anesthetic that inhibits responses to command in half
of patients
MAC-bar - alveolar concentration of anesthetic that blunts the autonomic response to
noxious stimuli
- ~1.6X higher than MAC
,atmosphere gas concentration (room air) ~ 79% Nitrogen
~ 21% Oxygen
What is the minimum amount of O2 your machine will - 30% O2
allow and why? - Anesthetic gases depress lung function (more shunting); must increase O2 to
prevent hypoxia
Why can't N2O be used as a sole anesthetic? - the MAC is too high (105%)
- its not strong enough to be used by itself
- low potency
- it is used as a "supplement"
Fa/Fi ratio - how fast the anesthetic rises in the lungs
- Fa = fraction of gas in the alveoli
- Fi = how much you turn the dial
- the Fa tries to equal the Fi (ratio of 1:1), but never truly does due to insensible loss
of gas
- get close to equilibrium but never do
True or False True
The Fa/Fi ratio rises more rapidly when ventilation is - The faster you breath, the faster you go to sleep
increased
True or False True
The Fa/Fi ratio rises more rapidly when gas concentration - The higher the dose, the faster it works
is increased.
, blood/gas partition coefficient - describes the ratio between amount of gas that stays in blood and amount
released into brain
- the lower the coefficient, the faster the gas works (N2O is an exception)
- smaller the coefficient = less soluble
- when gas enters blood
- some sticks to lipids within the blood
- some releases into tissues (brain)
Ex. Sevo blood/gas partition is 0.
- for every 0.6 molecules of sevo that stay in blood, 1 molecule is released into the
brain
True or False True
The smaller the blood/gas coefficient, the less soluble
and faster the drug.
Why is N20 the fastest gas despite not having the lowest - Nitrogen is given at a much higher concentration (concentration effect)
blood/gas partition coefficient? - N2O is given at 50-70%
- Des is given at <10%
List the gases from lowest blood/gas partition coefficient Des ← N2O ← Sevo ← Iso
to highest
List the gases from fastest to slowest N2O ← Des ← Sevo ← Iso
True or False False
A V/Q deficit (less than normal lungs) slows the delivery A V/Q deficit slows the delivery of all anesthetics BUT affects the gases with lower
of all anesthetics and effects them equally blood/gas partition more
less than normal lungs = pneumonia, COPD, etc.
ANSWERS
MAC - minimum alveolar concentration required to achieve surgical anesthesia
(immobility) in 50% of patients exposed to a noxious stimulus (get cut)
- MAC is the dose of a gas
- equivalent to gas concentration in the brain
MAC-awake - alveolar concentration of anesthetic that inhibits responses to command in half
of patients
MAC-bar - alveolar concentration of anesthetic that blunts the autonomic response to
noxious stimuli
- ~1.6X higher than MAC
,atmosphere gas concentration (room air) ~ 79% Nitrogen
~ 21% Oxygen
What is the minimum amount of O2 your machine will - 30% O2
allow and why? - Anesthetic gases depress lung function (more shunting); must increase O2 to
prevent hypoxia
Why can't N2O be used as a sole anesthetic? - the MAC is too high (105%)
- its not strong enough to be used by itself
- low potency
- it is used as a "supplement"
Fa/Fi ratio - how fast the anesthetic rises in the lungs
- Fa = fraction of gas in the alveoli
- Fi = how much you turn the dial
- the Fa tries to equal the Fi (ratio of 1:1), but never truly does due to insensible loss
of gas
- get close to equilibrium but never do
True or False True
The Fa/Fi ratio rises more rapidly when ventilation is - The faster you breath, the faster you go to sleep
increased
True or False True
The Fa/Fi ratio rises more rapidly when gas concentration - The higher the dose, the faster it works
is increased.
, blood/gas partition coefficient - describes the ratio between amount of gas that stays in blood and amount
released into brain
- the lower the coefficient, the faster the gas works (N2O is an exception)
- smaller the coefficient = less soluble
- when gas enters blood
- some sticks to lipids within the blood
- some releases into tissues (brain)
Ex. Sevo blood/gas partition is 0.
- for every 0.6 molecules of sevo that stay in blood, 1 molecule is released into the
brain
True or False True
The smaller the blood/gas coefficient, the less soluble
and faster the drug.
Why is N20 the fastest gas despite not having the lowest - Nitrogen is given at a much higher concentration (concentration effect)
blood/gas partition coefficient? - N2O is given at 50-70%
- Des is given at <10%
List the gases from lowest blood/gas partition coefficient Des ← N2O ← Sevo ← Iso
to highest
List the gases from fastest to slowest N2O ← Des ← Sevo ← Iso
True or False False
A V/Q deficit (less than normal lungs) slows the delivery A V/Q deficit slows the delivery of all anesthetics BUT affects the gases with lower
of all anesthetics and effects them equally blood/gas partition more
less than normal lungs = pneumonia, COPD, etc.
