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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

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
Q

amnesia may be due to

A

inhibition of release of excitatory NT, specifically glutamate; maybe be due to action on presynaptic Na channels or calcium ion channels

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26
Q

inhaled agents bind to

A

specific sites on the membrane of proteins as opposed to disrupting lipid bilayers

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27
Q

sites where inhaled agents bind may be

A

GABAa and glycine receptors

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28
Q

stage 1

A

analgesia

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29
Q

stage 1 ends with

A

loss of eyelash reflex and unconsciousness

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30
Q

stage 2

A

excitement

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31
Q

stage 2 signs

A
  1. irregular breathing
  2. struggling
  3. dilating pupils
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32
Q

in stage 2, patients are susceptible to

A

vomiting, coughing, laryngospasm

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33
Q

stage 2 ends with

A

onset of automatic breathing and the loss of eyelid reflex

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34
Q

stage 3

A

surgical anesthesia

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35
Q

stage 3 plane 1 is until

A

eyes central with loss of conjunctival reflex, pupils normal are small, lacrimation increased, pharyngeal reflex abolished

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36
Q

stage 3 plane 2 is until

A

onset of intercostal paralysis, deep regular breathing, laryngeal reflexes abolished, loss of corneal reflex, pupils larger

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37
Q

stage 3 plane 3 is until

A

complete intercostal paralysis, shallow breathing, lacrimation depressed

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38
Q

stage3 plane 4 is until

A

diaphragmatic paralysis, carinal reflexes abolished

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39
Q

stage 4

A

overdose

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40
Q

stage 4 signs

A

apnea and dilated pupils

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41
Q

signs of light anesthesia

A
  1. lacrimation, tearing
  2. tachycardia
  3. hypertension
  4. sweating
  5. reactive, dilated pupils
  6. movement and laryngospasm (no NMB utilized)
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42
Q

inhaled agents cause ___ respiratory depression

A

dose-related

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43
Q

inhaled agents depress the ventilatory response to an increase in

A

carbon dioxide, dose dependent

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44
Q

inhaled agents depress the ventilatory response to a decrease in

A

oxygenation (oxyhemoglobin saturation), not dose-dependent

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45
Q

ventilation in light anesthesia

A

breath holding and irregular pattern or breathing and irregular depths of breaths

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46
Q

as anesthesia deepens, breathing changes to

A

regular, faster rate, smaller tidal volumes

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47
Q

in an even deeper plane, _____ muscle function fails

A

intercostal

48
Q

minute ventilation may not change but ___ decrease with increased ___

A

alveolar ventilation

dead space ventilation

respiratory rate may be increased and tidal volume decreased

49
Q

___ increased during spontaneous ventilation in proportion with the increase in the concentration of inhaled agent

A

PaCO2

50
Q

___ does not increase the CO2

A

nitrous oxide

51
Q

in an unanesthetied patient, the increased PaCO2 would stimulate

A

increased minute ventilation

52
Q

in patients under inhaled anesthesia, increase PaCO2 response is

A

decreased; shifted to the right- it takes a higher CO2 to produce the increase in MV

53
Q

studies have shown that the stimulation of surgery increases ___ and decreases ___

A

minute ventilation by 40%

PaCO2 only by about 10%

54
Q

increased production of CO2 offsets

A

increased MV

55
Q

inhaled anesthetics cause depression of the response to

A

hypoxemia when PaO2 falls below 55 torr

56
Q

the response to hypoxemia is blunted by

A

as little as 0.1 MAC of halothane, isoflurane, and sevoflurane (aka when they are waking up they won’t respond to hypoxemia)

57
Q

___ MAC causes 100% depression of hypoxic response

A

1.1

58
Q

all agents cause broncho___

A

dilation

59
Q

bronchodilating effect in order from most to least

A

sevo > iso > des

60
Q

without preexisting bronchoconstriction, airway resistance is

A

essentially unchanged

61
Q

may see 5% increase in bronchial resistance due to

A

low bronchomotor tone normally

62
Q

desflurane causes increased bronchial resistance in

A

smokers

63
Q

irritability of airways with des is blunted by

A

prior admin of fentanyl 1 mcg/kg or morphine 0.1 mg/kg or addition of nitrous

64
Q

des and servo have been given to patient with asthma without

A

causing bronchoconstriction

65
Q

airway diameter is reduced due to

A

reduced lung volumes and reduced elastic forces keeping small non-cartilaginous airways open

66
Q

pungent desflurane is a bronchial irritant above

A

6% but does not cause irritation below 6%

67
Q

airway irritation increases with

A

concentrations greater than MAC of isoflurane

68
Q

airway irritation has a higher incidence in

A

smokers

69
Q

minimize airway irritation by

A
  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
Q

hypoxic pulmonary vasoconstriction (HPV) causes ___ but has little effect on ___

A

vasodilation typically

pulmonary vasculature

71
Q

HPV is not prevented by

A

concentrations that are used clinically of inhaled anesthetics

72
Q

___ decrease in MAP

A

dose-dependent

73
Q

at 2 MAC the BP decreases by

A

50% without surgical stimulation

74
Q

___ minimizes the decrease in MAP

A

surgical stimulation

75
Q

lower MAP due to changes in

A

cardiac output, venous capacitance, and systemic vascular resistance

76
Q

halothane decreases

A

myocardial contractility and cardiac output

77
Q

isoflurane, desflurane, and sevoflurane decrease

A

SVR which causes decreases in BP

78
Q

all agents cause myocardial depression to some degree in a ___ manner

A

dose-dependent

79
Q

halothane causes dose-dependent decrease in

A

CO

80
Q

decreased LV stroke volume may not translate into decreased CO due to

A

the vasodilation and decreased SVR caused by des, iso, sevo

81
Q

the decreased myocardial contractility results in a dose-dependent reduction in

A

oxygen demand (agent variable)

82
Q

excessive concentrations of agents can cause ___ collapse

A

cardiovascular

83
Q

___ increased CO reflecting mild sympathomimetic effects

A

nitrous oxide

84
Q

___ cause increased RAP

A

all agents but sevo

85
Q

decreased forward pump causes

A

higher pressures in the venous side or right atrium

86
Q

nitrous oxide increase RAP due to

A

increased pulmonary vascular resistance

87
Q

inhaled agents decreased the vascular resistance to __, ___, ___

A

skin

muscle

brain

88
Q

inhaled agents increase the vascular resistance to the

A

splanchnic system

89
Q

inhaled agents are veno___

A

dilators

90
Q

inhaled agents attenuate vasoconstriction related to ___ and is more exaggerated in ____

A

sympathetic stimulation

hypotension seen with hypertensive patients than normotensive patients

91
Q

increased peripheral blood flow effects

A
  1. temperature decrease and heat loss due to vasodilation
  2. better delivery of NMB and NMJ
  3. wasted perfusion compared to needs
92
Q

isoflurane has __ effect

A

beta agonist

93
Q

nitrous oxide does not decrease __ and may actually cause ___

A

SVR

vasoconstriction of cutaneous vessels

94
Q

pulmonary vascular resistance has little effect of volatile agents on

A

pulmonary vasculature

95
Q

___ causes increased pulmonary vascular resistance

A

nitrous oxide

96
Q

at risk populations for increased pulmonary vascular resistance from nitrous oxide

A
  1. neonates
  2. congenital heart defects/shunts
97
Q

sevo increases HR only at concentrations

A

great than 1.5 MAC

98
Q

iso and des increase HR at

A

lower concentration

99
Q

halothane effect on heart rate

A

does not increase

100
Q

increases in HR are more frequently seen with

A

younger patients

101
Q

increased in HR are accentuated by

A

vagolytic agents like atropine and pancuronium

102
Q

___ activity, ___ firing, ___ conduction are all affected by inhalation agents

A

ANS

SA node

myocardial

103
Q

___ depression of the baroreceptor-reflex response

A

dose-dependent

104
Q

__ attenuates baroreceptor-reflex response at low concentrations

A

des

105
Q

___ abolishes baroreceptor-reflex response at 1.25 MAC versus some response at 1.5 MAC

A

iso

106
Q

___ increasing to 4% decreases baroreceptor-reflex response

A

sevo

107
Q

when BP decrease, there is no

A

baroreceptor-reflex response of an increase in HR which impacts us clinically related to volume loss or position changes during anesthesia

108
Q

coronary vasodilators acting on small coronary arteries can cause

A

shift of blood from ischemic areas to non-ischemic areas; “Coronary Steal Syndrome”

109
Q

Coronary Steel Syndrome is only going to happen if

A

MAP < 60

110
Q

preconditioning for cardioprotection

A

brief exposure of the myocardium to volatile agents before myocardial ischemia

111
Q

brief exposure of the myocardium to volatile agents before myocardial ischemia results in

A

faster recovery after reperfusion of ischemic myocardium and reduction in infarct size

112
Q

____ as low as 0.25 MAC may be effective as cardioprotectant

A

isoflurane

113
Q

__ have been shown to be protective in CPB patients

A

sevo

114
Q

reperfusion injury

A

cellular injury caused by the reinstitution of the blood flow, not due to the ischemia itself

115
Q

signs of reversible reperfusion injury

A
  1. cardiac dysrhythmias
  2. contractile dysfunction
  3. microvasucalr injury
116
Q

the cardioprotection probably results from

A

an action on ATP-dependent potassium channels

117
Q

if given during reperfusion, __ may slightly increase myocardial ATP

A

sevo

NUNA 681(pharm) (12 decks)

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