Inhalation Anesthetics Flashcards

1
Q

Which anesthetic gases are ethers?

A

Des, Iso, Sevo, enflurane, Methoxyflurane, Ether

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2
Q

Which anesthetic gases are alkanes?

A

halothane and chloroform

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3
Q

Which anesthetic gases are simply gases?

A

N2O, cyclopropane, and xenon

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4
Q

Name that gas

A
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5
Q

Describe the structure of Iso.

A

5 fluorine atoms and 1 chlorine atom

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6
Q

Describe the structure of Des.

A

6 fluorine atoms

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7
Q

Describe the structure of Sevo.

A

7 fluorine atoms (sevo seven)

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8
Q

Which anesthetic gases have chiral carbons?

A

Des and Iso

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9
Q

How does the chlorine atom affect Iso?

A

increases potency, blood and tissue solubility

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10
Q

Name that compound!

A
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11
Q

What is the difference in the chemical structure of iso and Des?

A

the chlorine atom is replaced with a flourine atom

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12
Q

What is the full fluorination of desflurane do?

A

decrease potency which increases MAC
increases vapor pressure
decreased metabolism

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13
Q

How does fluorination affect the physical characteristics of halogenated agents?

A

decreases potency

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14
Q

What anesthetic agents contains Bromine (Br)?

A

halothane

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15
Q

What is vapor pressure?

A

Pressure exerted by a vapor in equilibrium with its liquid or solid phase inside of a closed container

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16
Q

Vapor pressure is directly related to ____.

A

temperature

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17
Q

Will water boil at a higher or lower temperature at high altitude?

A

lower temperature due to reduced atmospheric pressure

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18
Q

What is partial pressure?

A

the fractional amount of pressure that a single gas exerts with a gas mixture

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19
Q

What law states that total gas pressure is equal to the sum of partial pressures exerted by each individual gas?

A

Dalton

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20
Q

What determines the depth of anesthesia?

A

the partial pressure of the anesthetic gas in the brain, not what you set the vaporizer to.

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21
Q

At elevation like Denver, is your delivered Volume % set on the vaporizer dial, higher or lower due to the altitude?

A

Lower, leading to underdosing

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22
Q

How do you calculate partial pressure of a particular gas?

A

Vol% x total gas pressure

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23
Q

What is the partial pressure of 6% Des at sea level?

What is the partial pressure of 6% Des at 620 atm?

A
  1. 06 x 760 = 45.6 mmHg

0. 06 x 620 = 37.2 mmHg

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24
Q
What are the vaporizer pressure of: 
Sevo
Des
Iso 
N2O
A

Sevo: 157
Des: 669
Iso: 238
N2O: 38,770

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25
Q
What is the boiling point of: 
Sevo:
Des:
Iso: 
N2O:
A

Sevo: 59
Des: 22
Iso: 49
N2O: 88

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26
Q
What is the molecular weight of: 
Sevo:
Des:
Iso: 
N2O:
A

Sevo: 200
Des: 168
Iso: 184
N2O: 44

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27
Q
What is the preservative of: 
Sevo:
Des:
Iso: 
N2O:
A

They dont have preservatives

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28
Q
What gases are stable in hydrated CO2 absorber?
Sevo:
Des:
Iso: 
N2O:
A

Des:
Iso:
N2O:

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29
Q
What gases are stable in dehydrated CO2 absorber? 
Sevo:
Des:
Iso: 
N2O:
A

Only N2O.

Sevo, Des, and Iso are UNSTABLE in DEhydrated CO2 absorber

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30
Q
What are the toxic byproducts of: 
Sevo:
Des:
Iso: 
N2O:
A

Sevo: compound A
Des: CO
Iso: CO
N2O: none

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31
Q

What is solubility?

A

the tendency of a solute to dissolve in a solvent

“gas to dissolve in the blood”

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32
Q

Will a non polar or polar solute be more soluble in a hydrophilic solvent?

A

polar

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33
Q

Will a non polar or polar solute be more soluble in a lipophilic solvent?

A

non polar

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34
Q

What gas law describes the solubility of gases in solution?

A

Henry

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35
Q

How do we measure solubility?

A

partition coefficient

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36
Q

What is the blood:gas partition coefficient?

A

the relative solubility of an inhalation anesthetic in the blood vs. in the alveoli when the partial pressures of the two compartments are equal

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37
Q

What is the BLOOD : GAS PARTITION COEFFICIENT (λ) equation?

A

λ = Anesthetic dissolved in the blood /Anesthetic inside the alveoli

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38
Q
What are the blood:gas partition coefficients of: 
Sevo:
Des:
Iso: 
N2O:
A

Sevo: 0.65
Des: 0.42
Iso: 1.46
N2O: 0.46

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39
Q
What are the brain:blood partition coefficients of: 
Sevo:
Des:
Iso: 
N2O:
A

Sevo: 1.7
Des: 1.3
Iso: 1.6
N2O: 1.1

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40
Q
What are the muscle:blood partition coefficients of: 
Sevo:
Des:
Iso: 
N2O:
A

Sevo: 3.1
Des: 2
Iso: 2.9
N2O: 1.2

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41
Q
What are the fat:blood partition coefficients of: 
Sevo:
Des:
Iso: 
N2O:
A

Sevo: 47.5
Des: 27.2
Iso: 44.9
N2O: 2.3

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42
Q
What are the oil:gas partition coefficients of: 
Sevo:
Des:
Iso: 
N2O:
A

Sevo: 47
Des: 19
Iso: 91
N2O: 1.4

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43
Q

What is FA a function of?

A

rate of delivery to alveoli

rate of removal from alveoli

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44
Q

What determines anesthetic gas delivery to alveoli?

A

vaporizer setting, time constant of delivery system, anatomic dead space, alveolar ventilation, FRC

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45
Q

What determines the removal of anesthetic gas from alveoli?

A

solubility of anesthetic in the blood, Cardiac output, pressure gradient between alveolar gas and mixed venous blood

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46
Q

How are anesthetic gases delivered to the body?

A

enters the blood and CO distributes it to the body

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47
Q
Rank the gases from fasted to slowest induction.
Sevo:
Des:
Iso: 
N2O:
A

N2O fastest
Des
Sevo
Iso slowest

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48
Q

What is FA and FI?

A

FA is partial pressure of gas in the alveoli

FI is anesthetic exiting the vaporizer

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49
Q

Concentration of an agent inside the ____ is proportional to its concentration inside the ____ and this is proportional to the anesthetic inside the ____.

A

Concentration of an agent inside the alveoli is proportional to its concentration inside the blood and this is proportional to the anesthetic inside the brain.

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50
Q

How does low gas solubility affect onset of anesthesia?

A

low solubility causes less uptake in the blood, increases the rate of rise leading to faster equilibrium of FA/FI leading to faster onset

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51
Q

How does high gas solubility affect onset of anesthesia?

A

high solubility causes more uptake in the blood, decreases the rate of rise leading to slower equilibrium of FA/FI leading to slower onset

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52
Q

What factors increase wash in of anesthetic gas leading to faster onset?

A

high FGF, high alveolar ventilation, Low FRC, low time constant, low Vd

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53
Q

What factors decrease uptake of anesthetic gas leading to faster onset?

A

low solubility, low CO, low Pa-Pv difference

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54
Q

What factors decrease wash in of anesthetic gas leading to slower onset?

A

low FGF, low alveolar ventilation, high FRC, high time constant, high Vd

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55
Q

What factors increase uptake of anesthetic gas leading to slower onset?

A

high solubility, high CO, high Pa-Pv difference

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56
Q

For each tissue type, what is uptake dependent on?

A

Tissue blood flow, Solubility of the anesthetic in the tissue, Arterial blood : tissue partial pressure gradient

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57
Q

What percentage of CO and body mass does the vessel rich group receive?

A

75% CO

10% body mass

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58
Q

What percentage of CO and body mass does muscle and skin consist of?

A

20% CO

50% body mass

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59
Q

What percentage of CO and body mass does the fat consist of?

A

5% CO

20% body mass

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60
Q

What percentage of CO and body mass does the vessel poor group consist of?

A

<1% CO

20% body mass

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61
Q

What does the vessel rich group consist of?

A

heart, brain, kidneys, liver, endocrine glands

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62
Q

What are the three ways inhaled anesthetics are removed from the body?

A

from alveoli, hepatic biotransformation, percutaneous loss

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63
Q

What percentage of hepatic biotransformation is responsible for metabolizing Des, Iso, and Sevo?

A

rule of 2’s
Des 0.02%
Iso 0.2%
Sevo 2%

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64
Q

How are anesthetic gas metabolized in the liver?

A

P450 system by CYP 2E1

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65
Q

What are metabolites of Des and Iso?

A

inorganic fluoride ions and triflouracetic acid (TFA)

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66
Q

What is the cause of halothane hepatitis?

A

TFA

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67
Q

What are signs of high output renal failure as a result of sevo metabolism?

A

polyuria, hypernatremia, hyperosmolarity, increased plasma creatinine, & inability to concentrate urine

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68
Q

Which anesthetic gas creates compound A when exposed to soda lime?

A

Sevo

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69
Q

What explains why Nitrous have a high blood:gas partition coefficient than Desflurane but a faster onset?

A

concentration effect

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70
Q

What is the concentratION effect?

A

the higher the concentration of gas delivered to the alveolus, the faster its onset of action. Only w/ N2O

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71
Q

What is the concentratING effect?

A

The large volume of N2O entering the alveoli compared to the small amount of Nitrogen leaving the alveoli causes the alveoli to shrink, causing a relative increase in FA.

72
Q

What is augmented gas inflow?

A

The concentrating effect causes a temporary increase in alveolar ventilation and augments FA.

73
Q

What is the ventilation effect?

A

describes how changes in alveolar ventilation can affect the rise in FA/FI.

74
Q

What is the second gas effect?

A

The use of N2O with another gas during an inhalation induction will speed the onset of the second gas.
Leads to a higher convention of gas in the alveoli.

75
Q

How does N2O administration cause diffusion hypoxia?

A

as N2O is diffusing back into the alveoli for exhalation, it dilutes alveolar O2 and CO2, causing diffusion hypoxia and hypocarbia

76
Q

How is diffusion hypoxia prevented?

A

100% FiO2 for 3-5 minutes

77
Q

What is a right to left shunt?

A

deoxygenation blood bypasses the pulmonary circulation and lungs and leaves the body deoxygenated.

78
Q

What is the net result of a right to left shunt?

A

reduction in PaO2 and reduced partial pressure of anesthetic in arterial blood

79
Q

What are examples of right to left shunts?

A

Tetralogy of Fallot, Foramen ovale, Eisenmenger’s syndrome, Tricuspid atresia, Ebstein’s anomaly

80
Q

Ranked the inhaled anesthetics from most to least affected by right to left shunts.

A

Des - most
N2O
Sevo
Iso - least

81
Q

How does Right to left shunts affect IV induction? Faster or slower

A

faster

82
Q

How do left to right shunts affect inhalation induction?

A

no effect

83
Q

How do left to right shunts affect IV induction?

A

slow induction

84
Q

N2O is ____x more soluble than N

A

34

85
Q

What is the NITROGEN blood:gas partition coefficient?

A

0.014

86
Q

What is the N2O blood:gas partition coefficient?

A

0.46

87
Q

In Compliant airspaces
Volume ____
Pressure _____

A

Volume increases

Pressure unchanged

88
Q

In noncompliant airspaces
Volume ____
Pressure _____

A

Volume unchanged

Pressure increases

89
Q

What factors (4) determine pressure change in a airspace?

A

compliance, partial pressure of N2O, perfusion of surrounding tissue, time

90
Q

What are considerations for N2O with retinal surgery?

A

stop 15 minutes before bubble

avoided for 7-10 days after retinal surgery

91
Q

N2O inhibits vitamin B12, which inhibits what?

A

methionine synthase

92
Q

What are consequences of N2O inhibiting vitamin B12?

A

megaloblastic anemia, neuropathy, immunocompromise, impaired DNA synthesis, spontaneous abortion

93
Q

N2O causes _____ equilibrium of volume in compliant air filled spaces.

A

fast

94
Q

N2O causes slow equilibrium in what two spaces?

A

bowel and pneumoperitoneum

95
Q

N2O increases pressure rapidly in what spaces?

A

middle ear, brain during intracranial procedures

96
Q

What are two ear complications of N2O administration?

A

damage to tympanic membrane, serous otitis

97
Q

What are the alternatives to SF6 & how long should N2O be avoided?

A

Air - 5 days
Perfluoropropane - 30 days
Silicone oil - No contraindications

98
Q

What procedures should N2O be avoided in because it support combustion?

A

laparoscopy with pneumoperitoneum if cautery is used

99
Q

What trimesters of pregnancy should N2O be avoided?

A

first and second

100
Q

MAC is inversely related to ____

A

potency

101
Q

The higher the MAC the ___ the potency?

A

lower

102
Q

Which inhaled anesthetic is the most potent?

A

Iso, MAC 1.2

103
Q

What is MAC?

A

concentration of inhaled anesthetic that prevents pain withdrawal reflex in 50% of the population.

104
Q
What are the MAC values of:
Iso
Sevo
Des
N2O
A

Iso: 1.2
Sevo: 2
Des: 6.6
N2O: 104%

105
Q

What is the MAC awake during induction and during emergence?

A

induction: 0.4-0.5
Emergence: 0.15

106
Q

Arrange the inhalation anesthetics from most to least potent.

A

Iso - most
Sevo
Des
N2O least

107
Q

What is MAC bar?

A

value to block autonomic response following a supra maximal stimulus. 1.5 MAC

108
Q

Movement is prevented in 95% of the population at what MAC value?

A

1.3

109
Q

Awareness is prevented at what MAC value?

A

0.4-0.5

110
Q

What drugs and conditions increase MAC?

A

chronic EtOH use, amphetamine intoxication, cocaine use, MAOIs, ephedrine, levodopa

111
Q

What drugs and conditions decrease MAC?

A

acute EtOH intoxication, IV anesthetics, N2O, opioids, alpha 2 agonists, lithium, lidocaine, hydroxyzine

112
Q

How does hyperNa and hypoNa affect MAC?

A

hyper increase MAC

hypo decreases MAC

113
Q

What electrolytes do not affect MAC?

A

potassium and mag

114
Q

What ages increase and decrease MAC?

A

increases: 1-6months
decreases: old age, premature

115
Q

MAC decreases by _% for each decade after ___

A

MAC decreases by 6% for each decade after 40.

116
Q

How does temperature affect MAC?

A

hyperthermia increases MAC

hypothermia decreases MAC

117
Q

What factors do not affect MAC?

A

thyroid, gender, PaCO2 15-95, HTN

118
Q

How can thyroid disease affect MAC?

A

hypothyroid has decreased CO leading to faster rise in FA/FI

119
Q

What is the Meyer-Overton rule?

A

lipid solubility is directly proportional to potency of gas. Greater solubility lower MAC. (Iso)

120
Q

What is the unitary hypothesis?

A

all anesthetics share a similar mechanism of action, but work at different sites

121
Q

What do volatile anesthetics do to inhibitory and stimulatory receptors?

A

stimulate inhibitory receptors

inhibit stimulatory receptors

122
Q

What are the inhibitory pathways volatiles stimulate?

A

GABA-A, Glycine channels, Potassium channels

123
Q

What are the stimulatory pathways volatiles inhibit?

A

NMDA, Nicotinic, Sodium, dendritic spine function and motility

124
Q

What is the most important receptor site of volatile action in the brain?

A

GABA-A

125
Q

What do volatiles do the GABA-A receptors?

A

bind to the chloride channels and inhibit their closure, leading to hyperpolarization, impairing neurons from firing.

126
Q

Where do volatile produce immobility in the spinal cord?

A

ventral horn

127
Q

Where are the sites of action of volatiles in the spinal cord?

A

glycine receptors, NMDA, Na channels

128
Q

What is the triad of general anesthetic action?

A

unconsciousness, amnesia, immobility

129
Q

What regions of the brain are responsible for anesthetics causing unconsciousness?

A

cerebral cortex, thalamus, RAS

130
Q

What regions of the brain are responsible for anesthetics causing amnesia?

A

amygdala, hippocampus

131
Q

What regions of the brain are responsible for anesthetics causing immobility?

A

ventral horn

132
Q

What regions of the brain are responsible for anesthetics causing analgesia?

A

spinothalamic tract

133
Q

What regions of the brain are responsible for anesthetics causing autonomic modulation?

A

pons and medulla

134
Q

What are the two effects of volatiles on cardiac muscle and vascular smooth muscle?

A

decrease Ca influx, reduce Ca release from sarcoplasmic reticulum

135
Q

What is the effect of volatiles on heart rate? Except which one?

A

increase HR.

Sevo does not increase HR.

136
Q

What is the effect of volatiles on blood pressure? Except which one?

A

decrease. except N2O

137
Q

What is the effect of volatiles on CO?

A

decrease

138
Q

What is the effect of volatiles on SVR? Except which one?

A

decrease. Except N2O

139
Q

What is the primary mechanism for volatiles decreasing BP?

A

decreased intracellular Ca causing a decrease in inotropy

140
Q

What is the mechanism for volatiles decreasing HR?

A

decreased SA node automaticity, decrease conduction velocity, increased repolarization

141
Q

Volatiles decrease contractility but they remain responsive to what?

A

preload

142
Q

What volatile causes the least amount of decrease in SVR?

A

Sevo

143
Q

Rank the volatiles from greatest to least potency of coronary artery dilation?

A

Iso > Des > Sevo

144
Q

What is the hearts oxygen extraction ratio?

A

75%

145
Q

Iso may cause coronary steal. What is coronary steal?

A

coronary blood flow is preferentially directed to healthy tissues at the expense of diseased vessels

146
Q

For every _mmHg increase in PaCO2 above baseline, VE increases by _L/min.

A

For every 1mmHg increase in PaCO2 above baseline, VE increases by 3L/min.

147
Q

What is the effect on volatiles on Vt and RR?

A

increase RR and decreased Vt

148
Q

How do volatiles affect the CO2 response curve?

A

decreased response to CO2, increased apnea threshold. Shift down and to the right

149
Q

What volatiles impair hypoxic ventilator drive the most?

A

Sevo > Iso > Des

150
Q

What volatile impaired hypoxic ventilatory drive the least?

A

Des

151
Q

What agent is best to use on patients that rely on hypoxia to drive ventilation like emphysema and sleep apnea? Why

A

Desflurane. It impaired hypoxic ventilatory drive the least.

152
Q

What are causes of a right shift on the CO2 response curve?

A

general anesthetics, opioids, metabolic alkalosis, denervation of peripheral chemoreceptors.

153
Q

What are causes of a left shift on the CO2 response curve?

A

anxiety, surgical stimulation, metabolic acidosis, increased ICP, salicylates, aminophylline, doxapram

154
Q

What muscles do volatiles inhibit leading to upper airway obstruction?

A

tensor palatine and genioglossus

155
Q

A PaO2 less than ____ is a stimulus to increase minute ventilation.

A

< 60 mmHg

156
Q

Carotid bodies relay afferent input to the Respiratory center via which cranial nerve?

A

9, glossopharyngeal

157
Q

Aortic bodies relay afferent information via which CN?

A

x, vagus

158
Q

What type of cells provide the sensory arm of the hypoxic drive?

A

glomus type 1

159
Q

How do volatiles affect CMRO2?

A

reduce CMRO2, because they reduce electrical activity

160
Q

What MAC value produces an isoelectric EEG?

A

1.5-2

161
Q

What volatile can cause seizure activity at 2 MAC? What population is this common?

A

Sevo, pediatric inhalation induction

162
Q

How do volatiles affect cerebral blood flow?

A

increase by decreasing cerebrovascular resistance

163
Q

What volatile increases CMRO2 and cerebral blood flow?

A

N2O

164
Q

How do most volatiles affect CMRO2 and cerebral blood flow?

A

reduce CMRO2 and increase cerebral blood flow

165
Q

CPP is auto regulated at what pressures?

A

50-150

166
Q

How do volatiles affect CSF absorption and production.

A

Iso: increases absorption
Des: increases production
Sevo: decreases production

167
Q

Where is CSF absorbed and secreted?

A

secretion by choroid plexus

absorption by arachnoid villi

168
Q

How do volatiles affected EEG amplitude and latency?

A

decrease amplitude

increase latency

169
Q

What EEG changes are concerning?

A

50% decrease in amplitude

10% increase in latency

170
Q

What evoked potential monitors the dorsal column?

A

SSEP

171
Q

What evoked potential monitors integrity of the corticospinal tract?

A

MEP

172
Q

Do volatiles affect SSEP, MEPs or both?

A

SSEP

173
Q

Besides volatiles, what three factors affect evoked potentials?

A

hypoxia, hypercarbia, hypothermia

174
Q

What anesthetic enhances evoked potential signals?

A

ketamine

175
Q

What evoked potentials are most and least sensitive to anesthetics?

A

BAEP: least
VEP: most