Vaporizers Flashcards
Only inhalation agent that can be used for induction
Sevoflurane - ultane
Known for rapid induction and awakening
Sevoflurane (Ultane®)
What 2 things is sevo used for?
Used for peds/inhalation
induction
Can react with CO2 absorbents to form nephrotoxic
compound A.
Sevoflurane (Ultane®)
Requires specially designed electrically heated
vaporizer
Desflurane (Suprane®)
2 bad side effects desflurane causes:
Airway irritant (during induction,
combine with IV agents)
Can cause tachycardia (caution
with coronary artery disease)
Rapid elimination of des results in
quick awakening
Once considered the “gold standard” of
inhalation agents, especially for
neurosurgery
Isoflurane (Forane®)
What BAD thing can isoflurane cause?
Can cause coronary artery steal
syndrome
isoflurane causes significant
peripheral vasodilation
can cause hypotension
was agent of choice
for inhalation induction
(now replaced by sevoflurane)
Halothane
Halothane is good for use in asthmatics, why?
Potent bronchodilator
What serious implication did halothane have on organ that is not the heart?
Halothane hepatitis
Why does halothane Increase risk of dysrhythmias
decrease sensitivity to catecholamines - real bad if local anesthetic and epi given
halothane Emergence is significantly
slower than other agents
NOT a volatile agent
Used to supplement inhalation
agents
NITROUS OXIDE
Only inhalation agent with
sympathomimetic activity
nitrous
What is important concept to understand about nitrous?
Diffuses into air-filled spaces
(increases pressure)
what should be given during emergence to avoid
diffusion hypoxia with nitrous
high fio2
A device for converting a volatile
anesthetic agent into breathable vapor
vaporizer
where are vaporizers located?
between flow meters and common gas outlet
Gaseous molecules from a
substance that is liquid at room
temp at 1 atm (760 mmHg)
pressure
vapor
if you increase temperature, what happens to vaporization?
it increases
if you increase vaporization, what happens to the liquid below?
decreases the temp of the liquid below
if you decrease temperature, what happens to vaporization?
will decrease vaporization unless heat is added (increased temp = increased vaporization)
[think energy]
Equilibrium pressure of a vapor above
its liquid or solid
Vapor Pressure
This term is temperature and agent specific?
Vapor Pressure
When equilibrium is met, the anesthetic is at its
saturated vapor pressure
why do we want volatiles at saturated vapor pressure
so that we can control the amount of agent that we give
when you increase temperature, what happens to vapor pressure?
vapor pressure increases
Temp at which vapor pressure = atm pressure
Boiling Point
when you decrease atm pressure, what happens to boiling point?
decreases boiling point
[things will boil at lower temp]
Calories needed to convert 1g of liquid to vapor without temperature change in the remaining liquid
Latent Heat of Vaporization
Calories needed to increase the temperature of 1g of a
substance by 1°C
Specific Heat
what do we want our vaporizers to be constructed with?
materials with high specific heat and conductivity to minimize temp changes associated with vaporization
Alveolar concentration that prevents movement
in 50% of patients in response to surgical stimuli
(incision)
MAC (minimum alveolar concentration):
Measured-flow (operator controls flow bubbled
through agent from 2nd O2 flowmeter)
COPPER KETTLE (VERNITROL)
what material has high specific heat (heat needed to
raise 1g by 1°C) and high thermal conductivity
(speed of heat conductance)
Copper
Amount of fresh gas allowed to come in contact with liquid vapor is controlled
VARIABLE-BYPASS
with VARIABLE-BYPASS Gas entering the vaporizing chamber is
a carrier gas
what is Splitting ratio determined by
internal resistance to flow
(controlled by vaporizer dial) and temp compensating
mechanism (inside vaporizer)
what 2 things cause full saturation in variable bypass vaporizer?
Wicks/baffles
Saturated gas combines with fresh gas at
vaporizer outlet
to consistently produce final desired concentration
regardless of total fresh gas flow (FGF)
does FGF have anything to do with % of volatile pt receives when using variable bypass vaporizer?
NO NO NO
independent of FGF
explain Temperature Compensation with variable bypass vaporizers
temp change causes strip bending which produces ↑ or ↓ in gas
passing through vaporizer
Vapor Blender vaporizer
ELECTRONIC (TEC 6)
requires electronic (heated) vaporizer, why?
desflurane, so it doesn’t crystalize
mechanism of ELECTRONIC (TEC 6) with des?
injects tiny amounts of vaporizer into FGF that goes to pt, no carrier gas used, no flow going into vaporizer - just injects
what is electronic tec 6 controlled by?
dial and internal transducer
only vaporizer you can refill while still on?
Tec 6
One central electronic control
mechanism for all agents
ELECTRONIC (ALADIN CASSETTE)
Variable bypass, even for
desflurane
ELECTRONIC (ALADIN CASSETTE)
what happens if A sevoflurane (VP: 157) vaporizer was filled with isoflurane (VP: 240)
you would give less sevo bc of the lower VP
[sevo does not want to escape as badly]
what happens if you fill isoflurane (vp 240) with sevoflurance (vp 157)
you would give a lethal dose of the sevo
what are the 6 safety mechanisms?
- Color-coding (although not FDA required)
- Keyed fillers
- Low filling port
- Secured vaporizers
(minimizes tipping) - Concentration dial increases output in all when
rotated counterclockwise - Interlocks
Ensures that only one vaporizer is turned on and that gas can only enter if vaporizer in an on position
VAPORIZER INTERLOCK
5 risks of vaporizers?
- tipping
- out of calibration
- leaks
- pumping
- electronic dysfunction
what side are vaporizers on anesthesia machine?
low pressure side
