Exam 2- Inhalational Agents Flashcards
1
Q
potent inhaled anesthetics are mostly in what state?
A
liquid state at normal room temperature
2
Q
what is vapor?
A
gaseous phase of a substance at a temperature which the substance can exist in either a liquid or a solid state below a critical temperature for that substance
3
Q
what is a variable bypass vaproizer?
A
one in which the total gas glow is divided in two streams by a variable resistance proportioning valve
4
Q
where does the majority of a volatile agent flow through?
A
the bypass line
5
Q
what does the Tech 6 vaporizer do?
A
contains an electrical filament that heats the desflurane to 39º C
6
Q
what what does the Tech 6 vaporizer do to the saturated vapor pressure?
A
raises it
7
Q
what does a higher pressure do to Desflurane?
A
removes the need for a pressurized carrier gas
8
Q
what would make an ideal agent?
A
non-pungent, non-flammable, fast induction, fast wake-up, no harmful metabolites
9
Q
3 main phases of anesthesia?
A
induction, maintenance, emergence
10
Q
how is an anesthetic state obtained?
A
combination of amnesia, analgesia, and lack of response to noxious stimuli
11
Q
what does the myer-overton theory state?
A
the lipid solubility is directly proportional to the potency of an inhaled anesthetic
12
Q
the ultimate effect of inhaled anesthetics depends on
A
reaching a therapeutic level in the CNS/brain/spinal cord
13
Q
unconsciousness is based on effects of what system?
A
the reticular activating system
14
Q
analgesia effect is based on what part of the body?
A
the spinothalamic tract
15
Q
amnesia affects what parts of the brain?
A
the amygdala and hippocampus
16
Q
immobility affects of anesthesia affect what part of the body?
A
the ventral horn of the spinal cord
17
Q
what are ideal characteristics of inhaled gases
A
pleasant to inhale, smooth induction and emergence
low solubility
easy to administer and analyze
stable in CO2 absorbers, inflammable, not metabolized
specific site of action
No CV or Resp side effects, non toxic, pain control, muscle relaxation
18
Q
amnesia and loss of conscious occur when?
A
at lower levels of anesthesia
19
Q
immobility occurs at what level of anesthesia?
A
higher levels than amnesia and loss of consciousness
20
Q
stage I
A
induction to loss of consciousness
21
Q
state II
A
delirium w a period of excitement
22
Q
pupils during stage II
A
dilated
23
Q
gaze during stage II
A
disconjugate
24
Q
in which stage will patient have an increase HR and RR
A
stage II
25
in which stage is the patient at highest risk for laryngospasm or bronchospasm?
stage II
26
stage III
surgical plane, fixed gaze, constricted pupils
27
stage IV
overdose
shallow/irregular RR
hypotension/profound CV collapse
dilated/unresponsive pupils
28
when is inhalational induction commonly seen?
pediatrics
29
vital capacity breath
prime entire circuit with the gas, quicker than tidal volume breathing
30
N2O/O2 induction
70% : 30% until induced
31
sevoflurane induction
7-8% until induced
32
can you use desflurane for mask induction?
yes? but it is pungent. patients may cough.
33
volatile agents effect on airway?
can relax airway smooth muscle and produce bronchodilation
34
what stages of anesthesia do patients undergoing inhaled induction experience?
stage I, II, and III
35
what stage of anesthesia do patients undergoing inhalational induction especially experience?
excitatory
36
which kind of induction bypasses the second stage?
IV induction
37
what are advantages of inhalation induction?
less trauma, no IV access, short pediatric cases, bronchodilator effect
38
what are disadvantages to inhalation induction?
smell
excitatory stage
delayed airway
gas bypassing scavenger system
39
what gas smells the best?
sevo
40
MAC
the inhalational anesthetic concentration at which 50% of the population will not move to painful or noxious stimuli
41
MAC is a direct measure of
the potency of the volatile anesthetic
42
how much does MAC vary among individuals
10-15%
43
how does MAC relate to brain partial pressure?
MAC mirrors brain pressure
44
potency is directly related to
solubility
45
are MAC anesthesia values additive?
yes
46
MAC-BAR
MAC needed to block autonomic responsiveness to painful stimuli
47
MAC-BAR values
1.5-2.0 MAC
48
MAC-awake
alveolar concentration at which patients open their eyes
49
MAC-awake values
0.4-0.5 to lose consciousness and 0.15 to regain it
50
awareness and recall are usually thought to be prevented at what MAC?
0..4-0.5 MAC
51
what MAC will prevent movement in 95% of surgical patients?
1.2-1.3
52
nitrous oxide MAC and vapor pressure
MAC- 104
vapor pressure- 38,770
53
halothane MAC and vapor pressure
MAC- 0.75
vapor pressure- 244
54
isoflurane MAC and vapor pressure
MAC- 1.17
vapor pressure- 240
55
sevoflurane MAC and vapor pressure
MAC- 1.8
vapor pressure- 157
56
desflurane MAC and vapor pressure
MAC- 6.6
vapor pressure- 660
57
does duration of anesthesia change MAC?
no
58
does anesthetic metabolism change MAC
no
59
does hyperkalemia change MAC
no
60
does hyper or hypo carbia change MAC
no
61
does gender change MAC
no
62
does thyroid function change MAC
no
63
does metabolic alkalosis change MAC
no
64
which population requires a higher MAC requirement?
young, healthy patients
65
what factors may increase MAC
hyperthermia, drugs, natural red hair, hypernatremia, chronic alcohol abuse
66
what drugs might increase mac
drugs that increase CNS catecholamine levels
- MAOI
-cocaine
-ephedrine
-levodopa
-amphetamine abuse
67
what factors may decrease MAC
hypothermia, Benzos, older age, pregnancy, alpha agonists (precedex), acute alcohol ingestion, hyponatremia, hypotension, drugs, severe anemia, low MAP <50mmHg
68
what is the only true gas?
N2O
69
inhaled anesthetic properties
nonionized, low molecular weights, rapid diffusion
70
sevoflurane boiling point
59º C
71
sevoflurane vapor pressure at 20º C
157 mmHg
72
sevoflurane blood: gas partition coefficient
0.65
73
sevoflurane oil: gas partition coefficient
47
74
sevoflurane MAC
1.8
75
sevoflurane % metabolized in the body
2-5%
76
desflurane boiling point
24º C
77
desflurane vapor pressure
669 mmHg
78
desflurane blood:gas partition coefficient
0.43
79
desflurane oil:gas partition coefficient
19
80
desflurane MAC
6.6
81
desflurane % metabolized in the body
0.02%
82
isoflurane boiling point
49º C
83
isoflurane vapor pressure
238 mmHg
84
isoflurane blood:gas partition coefficient
1.46
85
isoflurane oil:gas partition coefficient
91
86
isoflurane MAC
1.17
87
isoflurane % metabolized in the body
0.2%
88
nitrous oxide boiling point
-88ºC
89
nitrous oxide vapor pressure
38,770 mmHg
90
nitrous oxide blood:gas partition coefficient
0.46
91
nitrous oxide oil: gas partition coefficient
1.4
92
nitrous oxide MAC
104
93
nitrous oxide % metabolized in the body
0%
94
can plasma and tissues absorb the anesthetic well?
no.
95
at equilibrium, CNS partial pressure equals
blood partial pressure which equals alveolar partial pressure
96
which factors increase the speed of onset of inhaled anesthetics?
high inspired concentration
high alveolar minute ventilation
low blood solubility
high MAC
97
FGF
fresh gas flow; determined by flowmeter settings and vaporizer
98
FI
inspired gas concentration, determined by fresh gas flow, breathing circuit volume, and circuit absorption
99
FA
alveolar gas; determined by uptake, ventilation, the concentration effect and second gas effect
100
Fa
arterial gas, affected by ventilation perfusion mismatch
101
Goal of inhalational anesthesia
anesthetic state in the CNS/brain
to achieve optimal and constant partial pressure of anesthetic in the brain
102
inspired gas concentration depends on
Fresh gas flow and rate
Breathing system volume
Absorption of machine circuit
103
what determines the speed of onset for inhalation agents?
solubility in the blood
104
more insoluble inhaled agents
are taken up much slower by the blood SO INDUCTION IS FASTER
105
how is the solubility of an anesthetic expressed?
partition coefficients
106
does isoflurane have a high blood : gas coefficient
yes, 1.4
it is soluble; slower induction/wakeup
107
which inhaled anesthetic has a low blood : gas coefficient
desflurane (0.42)
poor solubility
rapid induction/wake up
108
what parallels anesthetic requirements
oil:gas partition coefficient
109
higher MAC level
lower B:G coefficient
110
decrease in potency
associated with a decrease in the oil:gas partition coefficient
111
as cardiac output increases what happens to anesthetic uptake?
it increases
112
what % cardiac output does the vessel rich group recieve?
75%
113
what % cardiac output does the muscle recieve?
19%
114
what % cardiac output does fat recieve?
6%
115
how much blood flow does the vessel poor group recieve?
less than 1%
116
are inhalational agents lipid soluble?
yes, very
117
ways to speed up the equilibrium of FA/FI
increase minute ventilation
decrease FRC
for mask inductions: breathe deeply before applying the mask, breathe deeply and quickly after applying the mask
118
describe the second gas effect
Uptake of a large volume of a first or primary gas (usually Nitrous) from alveoli accelerates the rate of increase of the PA of a co-administered second gas
119
concentration of inhaled anesthetics in the tissues at the end of anesthetic depends on
solubility of the agent and time of administration
120
exhaled gases from the patient will be rebreathed uneless
fresh gas flow rates are >5L/min
121
which anesthetics are non-pungent?
sevoflurane, halothane, and nitrous
122
which anesthetic agents are pungent?
desflurane and isoflurane
123
why might PaCO2 increasee?
dose dependent depression of the ventilatory response to hypercarbia
124
which anesthetic agent might be irritating to smokers?
desflurane
125
inhalational agent cardiovascular effects
reduce MAP, CO, and Cl in dose dependent ways
myocardial depression
decreased SVR --> hypotension from vasodilation
reduce BP via relaxation of vascular smooth muscle causing a decrease in SVR
126
which agent activates the sympathetic nervous system and increases SVR?
N2O
127
which inhalation agent can lead to increases in CVP and arterial pressures?
N2O
128
which inhalation agents can increase HR and BP due to sympathetic stimulation?
isoflurane and desflurane
129
which inhalation agent demonstrates initial tachycardia?
desflurane
130
what do inhalational agents do to the CNS?
dose dependent increases in cerebral blood flow by direct vasodilation
increased ICP
131
how is increased ICP from inhalational agents attenuated?
hyperventilation
132
inhalational agent obstetric effects?
dose-dependent decreases in uterine smooth muscle contractility and blood flow
133
what MAC are obstetric effects seen at?
>1 MAC
134
inhalational agent effect on kidneys?
decreased GFR
135
do inhaled anesthetics undergo liver metabolism?
minimally
136
how are inhaled anesthetics most commonly biodegraded?
CYP450 oxidation
137
inhalational anesthetic neuromuscular system effects
dose dependent skeletal muscle relaxation
138
what can inhalational agents do to recovery from nondepolarizing muscle relaxants?
delay recovery because of synergistic effects
139
when is post-op cognitive dysfunction an increased concern?
elderly and pediatric patients
140
what is emergence delirium
acute state of confusion/agitation after anesthesia
141
when is emergence delirium more commonly seen?
20-80% in pediatrics in both sexed 2-6 yrs old
142
what inhalational agents more commonly have emergence delirium effects?
sevoflurane and desflurane
143
how long does emergence delirium last and how does it end?
10-15 mins; terminated spontaneously or after IV dose of propofol, midazolam, clonidine, precedex, ketamine, opioids, etc
144
when is there a higher probability of Compound A production?
low flow rates
closed circuit breathing systems
warm/dry CO2 absorbers
Sevoflurane use
144
how much CO2 can soda lime absorb
23 L of CO2 per 100g of absorbent
144
what are the final products of CO2 neutralization
carbonates, heat, water
145
what type of capnography would you see in a patient when the CO2 absorbent is exhausted?
rising ETCO2 waveform
146
isoflurane chemical makeup
5 fluorine atoms and 1 chlorine atom
147
desflurane chemical makeup
6 fluorine atoms
148
sevoflurane chemical makeup
7 fluorine atoms
149
which inhaled agents are chiral?
desflurane and isoflurane
150
which inhaled agent has no chiral carbon?
sevoflurane
151
what is a coronary steal
diversion of blood from a myocardial bed with limited or inadequate perfusion to a bed with more perfusion
152
which inhalation agent is associated with a coronary steal?
isoflurane
153
which inhalation agent is associated with a dose dependent decrease in mean arterial pressure?
isoflurane
154
which inhalation agent is associated with a dose dependent increase in cerebral blood flow?
isoflurane
155
which inhalation agent is associated with a resistance to degradation?
isoflurane
156
which inhalation agent is non-pungent
sevoflurane
157
which inhalation agent is associated with minimal sympathetic activation?
sevoflurane
158
which inhalation agent is insoluble in blood
desfluranew
159
which inhalation agent is associated with faster to sleep and wake up times
desflurane
160
which inhalation agent is a potential airway irritant?
desflurane
161
TEC6 vaporizer
dual-circuit, NOT variable bypass
162
what temperature is the TEC6 vaporizer heated to?
39º C
163
can you fill the TEC6 vaporizer during use?
yes
164
inhalation agents should be avoided in what population?
patients w a high risk of PONV
165
characteristics of N2O
Colorless, non-pungent, non-explosive, non-flammable
166
which inhalation agent has minimal CV effects but can increase bp?
nitrous oxide
167
which inhalation agent can increase RR and decrease TV?
nitrous oxide
168
does N2O trigger MH?
no
169
nitrous oxide musculoskeletal effects
no muscle relaxation or uterine relaxation
170
when is N2O use contraindicated?
bowel cases, pneumothorax/blebs, venous air emboli, middle ear surgery, some eye surgeries
171
is N2O a good analgesic?
yes
172
what inactivates methionine synthease?
N2O
173
what is the best approach to prevent OR pollution with anesthetic gases and reduce waste?
shutting off the fresh gas flows
174
when does diffusion hypoxia occur?
when nitrous is discontinued abruptly, usually occurs in the first 5 min after stopping nitrous
175
when should nitrous be discontinued during an anesthesia case
early to filly the lungs with oxygen and decrease the chance of arterial hypoxemia
176
risk factors for intraoperative awareness?
age, gender, substance use, paralytic use, type of surgery,
177
what MAC will decrease potential for intra-op awareness?
0.4-0.5 MAC of gas
178
malignant hyperthermia
profound uncontrolled release of Ca from the sarcoplasmic reticulum
179
what induces MH?
succinylcholine and inhalational agents
180
what does MH do to capnography?
unexplained increase in ETCO2
181
what is a late sign of MH?
increased temp
182
what kind of gas needs less fresh gas flow?
low solubility anesthetics
183
what volatile agent is the most destructive to climate change?
desflurane
184
how long can desflurane last in the atmosphere?
up to 14 years
185
how long can isoflurane and sevoflurane last in the atmosphere?
3.2 years for isoflurane and 1.1 year for sevoflurane
186
what gas directly relates to destruction of the O-zone
nitrous oxide
187
MAC decreases at what rate
approx. 6% per decade
188
what is a potential risk with high, long-lasting concentrations of secoflurane
can trigger EEG abnormalities ...unsure
189
is N2O associated with POCD and delirium?
yes
190
is N2o meant to be a complete anesthetic itself?
no, it is a co-anesthetic used to supplement
191
by what % does O2 consumption decrease during general anesthesia?
10-15%
192
what happens to FRC during general anesthesia?
it is decreased
193
what do volatile anesthetics and N2O do to ciliary movement?
they reduce it, and alter the characteristics of mucus
194
where are inhaled anesthetics primarily excreted?
the lungs
195
NIOSH exposure limits
25 ppm for N2O and 2 ppm for volatile anesthetics
196
what can halothane cause
hepatotoxicity
197
