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NUNA 681(pharm) > Inhalational Agents: MoA, Effects on Ventilation and Circulation > Flashcards

Inhalational Agents: MoA, Effects on Ventilation and Circulation Flashcards

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1
Q

what defines anesthesia?

A
  1. muscle relaxation
  2. unconsciousness
  3. analgesia
  4. suppression of autonomic reflexes
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2
Q

what is absolutely essential according to Eger to define anesthesia?

A
  1. immobility
  2. amnesia
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3
Q

mechanism of action of immobility- site of action is

A

spinal cord (not sure exactly where in the cord); one suggestion is the motor neuron

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4
Q

theory of immobility

A

effect on receptors
1. depression of excitatory- NMDA, AMPA
2. enhancement of inhibitory- glycine receptors
3. Na ion channels- hyper polarization, inhibit release of glutamate

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5
Q

mechanism of action- immobility theory- the site is likely

A

lipid portion of the membrane

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6
Q

Meyer-Overton hypothesis states that

A

there is a direct correlation between the anesthetic potency and the lipophilicity (oil:gas partition coefficient)

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7
Q

Meyer-Overton states that there is an ___ relationship between MAC and oil:gas partition coefficient

A

indirect

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8
Q

the membrane expansion theory on the MoA of immobility

A

agent moves into the lipid portion of the lipid bilayer causing a disruption of synaptic transmission or receptor function

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9
Q

in the membrane expansion theory, studies shows that anesthetized animals could

A

be awakened by hyperpressurixing them to 100atm which “restored the cell membranes to the preanesthesia density”

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10
Q

the problem with the membrane expansion theory was that

A

some transitional agents take much higher concentration than M-O would suggest to cause immobility

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11
Q

with the membrane expansion theory, nonimmobliizers ____ although M-O would suggest otherwise

A

never cause immobility

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12
Q

__ have greater potency with the membrane expansion theory than M-O would suggest

A

alcohols

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13
Q

transitional agents, non immobilizers, and alcohols have a ___ or ___ component

A

water-soluble or hydrophilicity

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14
Q

the modified theory for mechanism of action of immobility

A

anesthetic agents must be lipophilic and hydrophilic to work on both lipid and water portion of the lipid bilayer membrane

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15
Q

per the modified theory, inhalation agents change the amount or order of ___ which changes ___

A

the motion of the lipid constituents

the surface tension and the cellular and membrane function

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16
Q

5-angstrom theory says the site of action may actually be

A

two sites of action at either end of the molecule

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17
Q

5-angstrom theory says maximum potency is achieved

A

with a molecule 5 carbons long with 2 active sites at each end

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18
Q

5-angstrom theory says that CF2 has

A

no anesthetic effect itself

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19
Q

5-angstrom theory says increased potency up to

A

5 carbons, then started decreasing

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20
Q

amnesia is not possible at

A

the spinal cord

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21
Q

possible site of amnesia MoA

A

reticular activating system

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22
Q

reticular activating system is a site of amnesia MoA because

A

enhance inhibitory synaptic transmission especially involving GABA, the major inhibitory NT in the brain

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23
Q

other possible sites for MoA of amnesia

A

hippocampus, amygdala, caudate putamen, and parts of the cerebral cortex

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24
Q

during amnesia, __ is enhanced

A

glycine the inhibitory NT in the cord and brainstem

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25
amnesia may be due to
inhibition of release of excitatory NT, specifically glutamate; maybe be due to action on presynaptic Na channels or calcium ion channels
26
inhaled agents bind to
specific sites on the membrane of proteins as opposed to disrupting lipid bilayers
27
sites where inhaled agents bind may be
GABAa and glycine receptors
28
stage 1
analgesia
29
stage 1 ends with
loss of eyelash reflex and unconsciousness
30
stage 2
excitement
31
stage 2 signs
1. irregular breathing 2. struggling 3. dilating pupils
32
in stage 2, patients are susceptible to
vomiting, coughing, laryngospasm
33
stage 2 ends with
onset of automatic breathing and the loss of eyelid reflex
34
stage 3
surgical anesthesia
35
stage 3 plane 1 is until
eyes central with loss of conjunctival reflex, pupils normal are small, lacrimation increased, pharyngeal reflex abolished
36
stage 3 plane 2 is until
onset of intercostal paralysis, deep regular breathing, laryngeal reflexes abolished, loss of corneal reflex, pupils larger
37
stage 3 plane 3 is until
complete intercostal paralysis, shallow breathing, lacrimation depressed
38
stage3 plane 4 is until
diaphragmatic paralysis, carinal reflexes abolished
39
stage 4
overdose
40
stage 4 signs
apnea and dilated pupils
41
signs of light anesthesia
1. lacrimation, tearing 2. tachycardia 3. hypertension 4. sweating 5. reactive, dilated pupils 6. movement and laryngospasm (no NMB utilized)
42
inhaled agents cause ___ respiratory depression
dose-related
43
inhaled agents depress the ventilatory response to an increase in
carbon dioxide, dose dependent
44
inhaled agents depress the ventilatory response to a decrease in
oxygenation (oxyhemoglobin saturation), not dose-dependent
45
ventilation in light anesthesia
breath holding and irregular pattern or breathing and irregular depths of breaths
46
as anesthesia deepens, breathing changes to
regular, faster rate, smaller tidal volumes
47
in an even deeper plane, _____ muscle function fails
intercostal
48
minute ventilation may not change but ___ decrease with increased ___
alveolar ventilation dead space ventilation respiratory rate may be increased and tidal volume decreased
49
___ increased during spontaneous ventilation in proportion with the increase in the concentration of inhaled agent
PaCO2
50
___ does not increase the CO2
nitrous oxide
51
in an unanesthetied patient, the increased PaCO2 would stimulate
increased minute ventilation
52
in patients under inhaled anesthesia, increase PaCO2 response is
decreased; shifted to the right- it takes a higher CO2 to produce the increase in MV
53
studies have shown that the stimulation of surgery increases ___ and decreases ___
minute ventilation by 40% PaCO2 only by about 10%
54
increased production of CO2 offsets
increased MV
55
inhaled anesthetics cause depression of the response to
hypoxemia when PaO2 falls below 55 torr
56
the response to hypoxemia is blunted by
as little as 0.1 MAC of halothane, isoflurane, and sevoflurane (aka when they are waking up they won't respond to hypoxemia)
57
___ MAC causes 100% depression of hypoxic response
1.1
58
all agents cause broncho___
dilation
59
bronchodilating effect in order from most to least
sevo > iso > des
60
without preexisting bronchoconstriction, airway resistance is
essentially unchanged
61
may see 5% increase in bronchial resistance due to
low bronchomotor tone normally
62
desflurane causes increased bronchial resistance in
smokers
63
irritability of airways with des is blunted by
prior admin of fentanyl 1 mcg/kg or morphine 0.1 mg/kg or addition of nitrous
64
des and servo have been given to patient with asthma without
causing bronchoconstriction
65
airway diameter is reduced due to
reduced lung volumes and reduced elastic forces keeping small non-cartilaginous airways open
66
pungent desflurane is a bronchial irritant above
6% but does not cause irritation below 6%
67
airway irritation increases with
concentrations greater than MAC of isoflurane
68
airway irritation has a higher incidence in
smokers
69
minimize airway irritation by
1. premeditate with an opioid (fentanyl 1.5 mcg/kg) 2. slower increase in desflurane concentration 3. induction with propofol (v. inhalation induction) 4. humidification of inspired gases (HME)
70
hypoxic pulmonary vasoconstriction (HPV) causes ___ but has little effect on ___
vasodilation typically pulmonary vasculature
71
HPV is not prevented by
concentrations that are used clinically of inhaled anesthetics
72
___ decrease in MAP
dose-dependent
73
at 2 MAC the BP decreases by
50% without surgical stimulation
74
___ minimizes the decrease in MAP
surgical stimulation
75
lower MAP due to changes in
cardiac output, venous capacitance, and systemic vascular resistance
76
halothane decreases
myocardial contractility and cardiac output
77
isoflurane, desflurane, and sevoflurane decrease
SVR which causes decreases in BP
78
all agents cause myocardial depression to some degree in a ___ manner
dose-dependent
79
halothane causes dose-dependent decrease in
CO
80
decreased LV stroke volume may not translate into decreased CO due to
the vasodilation and decreased SVR caused by des, iso, sevo
81
the decreased myocardial contractility results in a dose-dependent reduction in
oxygen demand (agent variable)
82
excessive concentrations of agents can cause ___ collapse
cardiovascular
83
___ increased CO reflecting mild sympathomimetic effects
nitrous oxide
84
___ cause increased RAP
all agents but sevo
85
decreased forward pump causes
higher pressures in the venous side or right atrium
86
nitrous oxide increase RAP due to
increased pulmonary vascular resistance
87
inhaled agents decreased the vascular resistance to __, ___, ___
skin muscle brain
88
inhaled agents increase the vascular resistance to the
splanchnic system
89
inhaled agents are veno___
dilators
90
inhaled agents attenuate vasoconstriction related to ___ and is more exaggerated in ____
sympathetic stimulation hypotension seen with hypertensive patients than normotensive patients
91
increased peripheral blood flow effects
1. temperature decrease and heat loss due to vasodilation 2. better delivery of NMB and NMJ 3. wasted perfusion compared to needs
92
isoflurane has __ effect
beta agonist
93
nitrous oxide does not decrease __ and may actually cause ___
SVR vasoconstriction of cutaneous vessels
94
pulmonary vascular resistance has little effect of volatile agents on
pulmonary vasculature
95
___ causes increased pulmonary vascular resistance
nitrous oxide
96
at risk populations for increased pulmonary vascular resistance from nitrous oxide
1. neonates 2. congenital heart defects/shunts
97
sevo increases HR only at concentrations
great than 1.5 MAC
98
iso and des increase HR at
lower concentration
99
halothane effect on heart rate
does not increase
100
increases in HR are more frequently seen with
younger patients
101
increased in HR are accentuated by
vagolytic agents like atropine and pancuronium
102
___ activity, ___ firing, ___ conduction are all affected by inhalation agents
ANS SA node myocardial
103
___ depression of the baroreceptor-reflex response
dose-dependent
104
__ attenuates baroreceptor-reflex response at low concentrations
des
105
___ abolishes baroreceptor-reflex response at 1.25 MAC versus some response at 1.5 MAC
iso
106
___ increasing to 4% decreases baroreceptor-reflex response
sevo
107
when BP decrease, there is no
baroreceptor-reflex response of an increase in HR which impacts us clinically related to volume loss or position changes during anesthesia
108
coronary vasodilators acting on small coronary arteries can cause
shift of blood from ischemic areas to non-ischemic areas; "Coronary Steal Syndrome"
109
Coronary Steel Syndrome is only going to happen if
MAP < 60
110
preconditioning for cardioprotection
brief exposure of the myocardium to volatile agents before myocardial ischemia
111
brief exposure of the myocardium to volatile agents before myocardial ischemia results in
faster recovery after reperfusion of ischemic myocardium and reduction in infarct size
112
____ as low as 0.25 MAC may be effective as cardioprotectant
isoflurane
113
__ have been shown to be protective in CPB patients
sevo
114
reperfusion injury
cellular injury caused by the reinstitution of the blood flow, not due to the ischemia itself
115
signs of reversible reperfusion injury
1. cardiac dysrhythmias 2. contractile dysfunction 3. microvasucalr injury
116
the cardioprotection probably results from
an action on ATP-dependent potassium channels
117
if given during reperfusion, __ may slightly increase myocardial ATP
sevo

NUNA 681(pharm) (12 decks)

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