inhalational agents - MOA, effects on ventilation, and circulation Flashcards
1
Q
what defines anesthesia
A
- muscle relaxation
- unconsciousness
- analgesia
- suppression of autonomic reflexes
2
Q
what is absolutely essential according to Eger?
A
- immobility
- amnesia
3
Q
immobility site of action
A
spinal cord
4
Q
not exactly sure where in the cord, but one suggestion is the _____ _____
A
motor neuron
5
Q
there is a theory about the effect on receptors - not _____
A
directly
6
Q
depression of excitatory ______ _____
A
NMDA & AMPA
7
Q
enhancement of inhibitory -
[in the cord and brainstem]
A
glycine receptors
8
Q
Na+ ion channels - ________, inhibit release of ________
[Immobility theory]
A
hyperpolarization, inhibit release of glutamate
9
Q
MOA - immobility theory: site is likely ______ ______ of the membrane
A
lipid portion
10
Q
meyer-overton hypothesis states
A
that there is a direct correlation between the anesthetic potency and the lipophilicity (oil:gas partition coefficient)
this suggests that the site of action is on the neuronal lipid bilayers
11
Q
an indirect relationship between _____ and ____ ______ _____ _____
[meyer-overton]
A
MAC
oil:gas partition coefficient
12
Q
membrane expansion theory (M-O): agent moves into the ______ portion of the lipid bilayer causing a disruption of _________ _______ or ________ ________
A
lipid
synaptic transmission or receptor function
13
Q
1950s study showed that anesthetized animals could be awakened by ___________ them to _________ which restored the ________ ________ to the preanesthesia density
A
hyperpressurizing them to 100 atm
cell membranes
14
Q
problem was that some ________ _______ take much higher concentrations than M-O would suggest to cause immobility
A
transitional agents
15
Q
also, other ______________, never cause immobility although M-O would suggest that it could
A
nonimmobilizers
16
Q
________ have a greater potency than M-O would suggest
A
alcohol
17
Q
all three of these have a ______-solubility or ___________ component
A
water-solubility
hydrophilicity
18
Q
immobility modified theory - anesthetic agents must be ________ and ________ to work on both lipid and water portion of the lipid bilayer membrane
A
lipophilic and hydrophilic
19
Q
in doing so, inhalation agents change the amount or order of the motion of the lipid constituents. This changes the ______ ________ and the ________ and ________ function
A
surface tension
cellular and membrane
20
Q
5-angstrom theory - the site of action may actually be _____ _____ of action at either ______ of the molecule
A
2 sites
end
21
Q
maximum potency is achieved with a molecule ___ _______ long with ____ active sites at each end
A
5 carbons long with 2 active sites at each end
22
Q
(CF2)
[Immobility-MOA]
A
no anesthetic effect itself
23
Q
increased potency up to _____ ______, then started ______
[MOA-Immobility]
A
5 carbons
decreasing
24
Q
amnesia MOA - Not at the
A
spinal cord
25
possible site:
[MOA-Amnesia]
reticular activating system
26
enhance inhibitory synaptic transmission especially involving ______, the major _______ NT in the brain
GABA
inhibitory
27
hippocampus, ______, ______ _______, and parts of the cerebral ________
[MOA-Amnesia]
hippocampus, amygdala, caudate putamen, and parts of the cerebral cortex
28
_______, inhibitory NT in the cord and brainstem, is ________
glycine
enhanced
29
may be due to inhibition of release of _________ _______, specifically _______.
[MOA-Amnesia]
excitatory NTs
glutamate
30
which may be due to action on _______ _____ _______ or _______ _______ channels
[Inhibition of glutamate]
presynaptic Na+ channels or calcium ion channels
31
MOA - amnesia, unconsciousness, and immobility are not a single continuum of increasing anesthetic depth but rather
separate phenomena
32
analgesia has a biphasic dose response - volatiles at very low concentrations (approx. 10% MAC) increases response to ______ ______ and at higher doses they ________ the response
nociceptive pain
decrease
33
MOA amnesia theory - inhaled agents bind to specific sites on the membranes of _______ as opposed to disrupting ______ ________
proteins
lipid bilayers
34
sites may be _______ and _______ receptors
[MOA amnesia]
GABAa and glycine
35
guedel's stage 1 (analgesia)
ends with loss of eyelash reflex and unconsciousness
36
guedel's stage 2 (excitement) - _________ breathing, struggling, ______ _____, susceptible to _________, ________, ________, and ends with the onset of ______ _______ and the loss of _______ reflex
irregular breathing, struggling, dilated pupils, susceptible to vomiting, coughing, and laryngospasm. ends with onset of automatic breathing and the loss of eyelid reflex
37
guedel's stage 3 is preferred for _____ _____
surgical anesthesia
38
stage 3, plane 1 - until eyes ______ with loss of _______ _________, pupils normal or small, ________ increased, _________ reflex abolished
until eyes central with loss of conjunctival reflex, pupils normal or small, lacrimation increased, pharyngeal reflex abolished
39
stage 3, plan II - until onset of ______ _______, deep regular ________, ________ ________ abolished, loss of _______ reflex, pupils larger
intercostal paralysis
breathing
laryngeal reflexes abolished
loss of corneal reflex
pupils larger
40
stage 3, plane III - until complete ______ ______, shallow _______, _______ depressed
intercostal paralysis
shallow breathing
lacrimation depressed
41
stage 3, plane IV - until _______ _______, _______ reflexes abolished
diaphragmatic paralysis, carinal reflexes abolished
42
guedel's stage 4 is considered _______
overdose
43
stage 4 involves _____ and ______ ______
apnea and dilated pupils
44
indications that a patient is light:
- lacrimation, tearing
- tachycardia
- HTN
- sweating
- reactive, dilated pupils
- movement and laryngospasm
45
dose related _______ _______
[ventilation]
respiratory depression
46
depress the ventilatory response to an increase in CO2 is
dose dependent
47
depress the ventilatory response to a decrease in oxygenation (oxyhemoglobin saturation) is
NOT dose dependent
48
light anesthesia - _____ ______ and irregular depths and patterns of _________
breath holding
breathing
49
as anesthesia deepens, breathing changes to ________, ______ ______, and smaller _____ ______
regular, faster rate, and smaller tidal volumes
50
At an even deeper plane, ______ ______ _______ fails
intercostal muscle function fails
51
minute ventilation may not change, but ________ _______ decreases with increased _______ _______ ventilation
alveolar ventilation
dead space
52
respiratory rate may be
increased
53
tidal volume is
decreased
54
thus, PaCO2 ________ during spontaneous ventilation in proportion with the ______ in the ________ of _______ ________.
increases
increase in the concentration of inhaled agent
55
the ratio of ____ _____ ventilation to ______ ventilation increases
dead space
total
56
with spontaneous ventilation, the response to increasing _______ is diminished
CO2
57
N2O ______ ______ increase the CO2
DOES NOT
58
if N2O is used and the concentration of volatile is decreased, there is less _______ _______ compared to the equivalent ________ of the volatile alone.
ventilatory depression
MAC
(true with all volatiles)
59
______ patients will likely have an exaggerated increase in PaCO2
COPD
60
in an unanesthetized patient, the increased PaCO2 would stimulate ______ _______ ______
increased minute ventilation
61
in patients under inhaled anesthesia, that response is _________
[Ventilation]
decreased
62
the response curve is shifted to the ______ - it takes a higher ______ to produce an increase in _______
right
CO2
MV
63
des and sevo lead to apnea:
[response curve shift to R]
between 1.5 and 2.0 MAC
64
with surgical pts, this decreased response may:
not be so evident
65
studies have shown that the stimulation of surgery increases _____ ______ by ______ and decreases ________ only by _______
minute ventilation by 40%
PaCO2 only by 10%
66
increased production of ______ offsets increased ____
[Surgical patients, vent]
CO2
MV
67
inhaled anesthetics also cause depression of the response to _______, when PaO2 falls below ____
hypoxemia
55 torr
68
this response is blunted (50-70% depression) by as little as __________ of halothane/iso/sevo
[ventilation/hypoxemia]
0.1 MAC
69
1.1 MAC causes _______ depression of hypoxic response
100%
70
_____ has less effect on hypoxic drive than other agents
Desflurane
71
all agents cause
bronchodilation
72
in dogs, halo/iso/sevo prevented the _________ caused by ________
bronchoconstriction caused by histamine
73
bronchodilating effect (in order):
sevo > iso > des
"Help! SID needs his bronchodilator!"
74
without preexisting bronchoconstriction, airway resistance is
essentially unchanged
75
may see ____ ______ in resistance due to low bronchomotor tone normally
5% increase
76
Des causes increased
[ventilation]
resistance in smokers
77
irritability of airways with des is blunted by prior admin of _____ or ______, addition of ______ also blunts irritability
fentanyl 1 mcg/kg
morphine 0.1 mg/kg
N2O
78
_____ and ______ have been given to patients with asthma without causing bronchoconstriction
des and sevo
79
airway diameter is reduced due to reduced _____ ______ and reduced ______ _____ keeping small non-cartilaginous airways open
lung volumes
elastic forces
80
______ _____ is a bronchial irritant above ______ but does not cause irritation below _____
pungent des
6%
6%
81
Airway irritation increases with concentrations greater than ______ ____ ______
MAC of iso
82
higher incidences of airway irritation with
smokers
83
minimize irritation by premedicating with an ______ (_________)
opioid (fentanyl 1.5 mcg/kg)
84
minimize irritation with slower increases in _______ ______
desflurane concentrations
85
induction with ________ also minimizes irritation
propofol (vs inhaled agent)
86
_________ of inspired gases also helps
humidification
87
increases in ________ activity may reflect the effect of airway irritant _____ > ______ / ______
mucociliary
des > iso / halothane
88
cause _______ typically but have little effect on ______ ________
[HPV]
vasodilation
pulmonary vasculature (HPV)
89
concentrations that are used ________ of inhaled anesthetics ____ _____ prevent HPV
clinically
do NOT
90
dose dependent decrease in ______, at 2 MAC the ______ decreases by _______ without surgical stimulation
[cardiac]
MAP
BP
50%
91
surgical stimulation _______ ____ _______
[cardiac]
minimizes the decrease
92
lower MAP due to changes in _____ ______, _______ ________, and_______ __________ _______
cardiac output
venous capacitance
systemic vascular resistance
93
different agents alter
BP by different mechanisms
94
substitution of _______ of the volatile agent decreases the extent of the decrease in MAP compared to the same ________ of the volatile alone
N2O
MAC concentration
95
decreases in myocardial contractility and CO
halothane
96
decrease in SVR causes decrease in BP
iso/des/sevo
97
all agents cause ______ ______ to some degree in a dose-dependent manner
[cardiac]
myocardial depression
98
calculated _____ _____ _____ decreased 15-30%
LV stroke volume
99
halothane causes _______-_________ decrease in ______ in healthy volunteers
dose-dependent
CO
100
decreased LV stroke volume may not translate into _____ _______ due to the ______ and decreased _______ caused by des, iso, sevo
decreased CO
vasodilation
SVR
101
the decreased myocardial contractility results in a ______-______ reduction in ______ ______
dose-dependent reduction in oxygen demand
102
however, excessive concentrations can cause ______ ______
CV collapse
103
N2O increase ______ reflecting mild ____________ effects
[cardiac]
CO
sympathomimetic
104
all agents but sevo cause increased
RAP
105
decreased forward pump causes higher pressures in the _______ ______ or ______ _____
venous side or right atrium
106
_______ increases RAP due to increased PVR
N2O
107
inhaled agents decrease the resistance to the ______, _______, and the _____; but increase resistance to the ________ system
skin, muscles, and the brain
splanchnic
108
inhaled agents are ________ and can be used to our advantage to dilate _________ _______
venodilators
peripheral veins (for IV start)
109
they also attenuate __________ r/t sympathetic stimulation
vasoconstriction
110
more exaggerated hypotension is seen with ________ patients over ________ patients
hypertensive
normotensive
111
they increase peripheral blood flow (muscle and cutaneous) which has multiple effects: (3)
- temp decrease and heat loss r/t vasodilation (increased risk of shivering)
- better delivery of NMB to NMJ
- waster perfusion compared to needs
112
isoflurane has a _____ ______ effect
beta agonist
113
N2O does not decrease _____ and may actually cause __________ of cutaneous vessels
SVR
vasoconstriction
114
little effect of volatile agents on ______ _______
pulmonary vasculature
115
N2O causes increased ____ ______ ______
pulmonary vascular resistance
116
_______ are vulnerable
[PVR]
neonates
117
congenital ______ _____ / ______
[PVR]
heart defects / shunts
118
agent specific effect and concentration specific effect for
[Cardiac]
heart rate
119
______ increases HR only at concentrations > 1.5 MAC
sevo
120
____ and ____ increase HR at a lower concentration
Iso and Des
121
________ does not increase HR - conduction effects
halothane
122
increases in HR are more frequently seen with _______ patients and accentuated by ______ agents like _______ and __________
younger patients
vagolytic agents
atropine and pancuronium
123
_____ activity, ___ ____ firing, and ______ ______ are all affected by inhalational agents
ANS activity, SA node firing, and myocardial conduction
124
_____ can alter the increase in HR
opioids
125
increased _____ ______ (______) can enhance increased HR
sympathetic activity (anxiety)
126
dose-dependent depression of the ______-______ response
baroreceptor-reflex
127
some agents _______the baroreceptor-reflex at low concentrations
eliminate
128
_____ attenuates baroreceptor response, but doesnt abolish
des
129
______ - studies differ - abolishes baroreceptor reflex at 1.25 MAC v some response at 1.5 MAC
iso
130
_____ - increasing to 4% (2 MAC) decreases baroreceptor response
sevo
131
when BP decreases, there is no ______ _____ of an increase in ______
reflex response
HR
132
this impacts us clinically related to ______ _____ or ____ ______ during anesthesia
volume loss or position changes
133
coronary vasodilators acting on small coronary arteries can cause shift of blood from _______ to _______ ______
ischemic to non ischemic
134
this shift is called
coronary steal syndrome
135
however, the syndrome is
clinically insignificant unless MAP < 60
136
preconditioning can be done for
cardioprotection
137
brief exposure of the myocardium to volatile agents ________ myocardial ischemia results in _______ recovery after reperfusion of ischemic myocardium and reduction in _____ _____
before
faster
infarct size
138
similar effect on ______ _______ may provide protection to other side too
vascular epithelium
139
_______ as low as 0.25 MAC may be effective
iso
140
______ has been shown to be protective for CPB patients
sevo
141
brief exposure to volatile agents can activate ____ ______ resulting in cardioprotection
K channels
142
reperfusion injury
cellular injury caused by reinstitution of the blood flow, not due to ischemia itself
143
signs of reperfusion injury (3)
cardiac dysrhythmias, contractile dysfunction, and microvascular injury
144
the protection probably results from an action on ______ ________ ______ ______
ATP dependent potassium channels
145
if given during reperfusion, _____ may slightly increase myocardial ATP
sevo
