Inhalation Anesthetics Flashcards
1
Q
Which anesthetic gases are ethers?
A
Des, Iso, Sevo, enflurane, Methoxyflurane, Ether
2
Q
Which anesthetic gases are alkanes?
A
halothane and chloroform
3
Q
Which anesthetic gases are simply gases?
A
N2O, cyclopropane, and xenon
4
Q
Name that gas
A
5
Q
Describe the structure of Iso.
A
5 fluorine atoms and 1 chlorine atom
6
Q
Describe the structure of Des.
A
6 fluorine atoms
7
Q
Describe the structure of Sevo.
A
7 fluorine atoms (sevo seven)
8
Q
Which anesthetic gases have chiral carbons?
A
Des and Iso
9
Q
How does the chlorine atom affect Iso?
A
increases potency, blood and tissue solubility
10
Q
Name that compound!
A
11
Q
What is the difference in the chemical structure of iso and Des?
A
the chlorine atom is replaced with a flourine atom
12
Q
What is the full fluorination of desflurane do?
A
decrease potency which increases MAC
increases vapor pressure
decreased metabolism
13
Q
How does fluorination affect the physical characteristics of halogenated agents?
A
decreases potency
14
Q
What anesthetic agents contains Bromine (Br)?
A
halothane
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
16
Q
Vapor pressure is directly related to ____.
A
temperature
17
Q
Will water boil at a higher or lower temperature at high altitude?
A
lower temperature due to reduced atmospheric pressure
18
Q
What is partial pressure?
A
the fractional amount of pressure that a single gas exerts with a gas mixture
19
Q
What law states that total gas pressure is equal to the sum of partial pressures exerted by each individual gas?
A
Dalton
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.
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
22
Q
How do you calculate partial pressure of a particular gas?
A
Vol% x total gas pressure
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
- 06 x 760 = 45.6 mmHg
0. 06 x 620 = 37.2 mmHg
24
Q
What are the vaporizer pressure of: Sevo Des Iso N2O
A
Sevo: 157
Des: 669
Iso: 238
N2O: 38,770
25
```
What is the boiling point of:
Sevo:
Des:
Iso:
N2O:
```
Sevo: 59
Des: 22
Iso: 49
N2O: 88
26
```
What is the molecular weight of:
Sevo:
Des:
Iso:
N2O:
```
Sevo: 200
Des: 168
Iso: 184
N2O: 44
27
```
What is the preservative of:
Sevo:
Des:
Iso:
N2O:
```
They dont have preservatives
28
```
What gases are stable in hydrated CO2 absorber?
Sevo:
Des:
Iso:
N2O:
```
Des:
Iso:
N2O:
29
```
What gases are stable in dehydrated CO2 absorber?
Sevo:
Des:
Iso:
N2O:
```
Only N2O.
| Sevo, Des, and Iso are UNSTABLE in DEhydrated CO2 absorber
30
```
What are the toxic byproducts of:
Sevo:
Des:
Iso:
N2O:
```
Sevo: compound A
Des: CO
Iso: CO
N2O: none
31
What is solubility?
the tendency of a solute to dissolve in a solvent
| "gas to dissolve in the blood"
32
Will a non polar or polar solute be more soluble in a hydrophilic solvent?
polar
33
Will a non polar or polar solute be more soluble in a lipophilic solvent?
non polar
34
What gas law describes the solubility of gases in solution?
Henry
35
How do we measure solubility?
partition coefficient
36
What is the blood:gas partition coefficient?
the relative solubility of an inhalation anesthetic in the blood vs. in the alveoli when the partial pressures of the two compartments are equal
37
What is the BLOOD : GAS PARTITION COEFFICIENT (λ) equation?
λ = Anesthetic dissolved in the blood /Anesthetic inside the alveoli
38
```
What are the blood:gas partition coefficients of:
Sevo:
Des:
Iso:
N2O:
```
Sevo: 0.65
Des: 0.42
Iso: 1.46
N2O: 0.46
39
```
What are the brain:blood partition coefficients of:
Sevo:
Des:
Iso:
N2O:
```
Sevo: 1.7
Des: 1.3
Iso: 1.6
N2O: 1.1
40
```
What are the muscle:blood partition coefficients of:
Sevo:
Des:
Iso:
N2O:
```
Sevo: 3.1
Des: 2
Iso: 2.9
N2O: 1.2
41
```
What are the fat:blood partition coefficients of:
Sevo:
Des:
Iso:
N2O:
```
Sevo: 47.5
Des: 27.2
Iso: 44.9
N2O: 2.3
42
```
What are the oil:gas partition coefficients of:
Sevo:
Des:
Iso:
N2O:
```
Sevo: 47
Des: 19
Iso: 91
N2O: 1.4
43
What is FA a function of?
rate of delivery to alveoli
| rate of removal from alveoli
44
What determines anesthetic gas delivery to alveoli?
vaporizer setting, time constant of delivery system, anatomic dead space, alveolar ventilation, FRC
45
What determines the removal of anesthetic gas from alveoli?
solubility of anesthetic in the blood, Cardiac output, pressure gradient between alveolar gas and mixed venous blood
46
How are anesthetic gases delivered to the body?
enters the blood and CO distributes it to the body
47
```
Rank the gases from fasted to slowest induction.
Sevo:
Des:
Iso:
N2O:
```
N2O fastest
Des
Sevo
Iso slowest
48
What is FA and FI?
FA is partial pressure of gas in the alveoli
| FI is anesthetic exiting the vaporizer
49
Concentration of an agent inside the ____ is proportional to its concentration inside the ____ and this is proportional to the anesthetic inside the ____.
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.
50
How does low gas solubility affect onset of anesthesia?
low solubility causes less uptake in the blood, increases the rate of rise leading to faster equilibrium of FA/FI leading to faster onset
51
How does high gas solubility affect onset of anesthesia?
high solubility causes more uptake in the blood, decreases the rate of rise leading to slower equilibrium of FA/FI leading to slower onset
52
What factors increase wash in of anesthetic gas leading to faster onset?
high FGF, high alveolar ventilation, Low FRC, low time constant, low Vd
53
What factors decrease uptake of anesthetic gas leading to faster onset?
low solubility, low CO, low Pa-Pv difference
54
What factors decrease wash in of anesthetic gas leading to slower onset?
low FGF, low alveolar ventilation, high FRC, high time constant, high Vd
55
What factors increase uptake of anesthetic gas leading to slower onset?
high solubility, high CO, high Pa-Pv difference
56
For each tissue type, what is uptake dependent on?
Tissue blood flow, Solubility of the anesthetic in the tissue, Arterial blood : tissue partial pressure gradient
57
What percentage of CO and body mass does the vessel rich group receive?
75% CO
| 10% body mass
58
What percentage of CO and body mass does muscle and skin consist of?
20% CO
| 50% body mass
59
What percentage of CO and body mass does the fat consist of?
5% CO
| 20% body mass
60
What percentage of CO and body mass does the vessel poor group consist of?
<1% CO
| 20% body mass
61
What does the vessel rich group consist of?
heart, brain, kidneys, liver, endocrine glands
62
What are the three ways inhaled anesthetics are removed from the body?
from alveoli, hepatic biotransformation, percutaneous loss
63
What percentage of hepatic biotransformation is responsible for metabolizing Des, Iso, and Sevo?
rule of 2's
Des 0.02%
Iso 0.2%
Sevo 2%
64
How are anesthetic gas metabolized in the liver?
P450 system by CYP 2E1
65
What are metabolites of Des and Iso?
inorganic fluoride ions and triflouracetic acid (TFA)
66
What is the cause of halothane hepatitis?
TFA
67
What are signs of high output renal failure as a result of sevo metabolism?
polyuria, hypernatremia, hyperosmolarity, increased plasma creatinine, & inability to concentrate urine
68
Which anesthetic gas creates compound A when exposed to soda lime?
Sevo
69
What explains why Nitrous have a high blood:gas partition coefficient than Desflurane but a faster onset?
concentration effect
70
What is the concentratION effect?
the higher the concentration of gas delivered to the alveolus, the faster its onset of action. Only w/ N2O
71
What is the concentratING effect?
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
What is augmented gas inflow?
The concentrating effect causes a temporary increase in alveolar ventilation and augments FA.
73
What is the ventilation effect?
describes how changes in alveolar ventilation can affect the rise in FA/FI.
74
What is the second gas effect?
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
How does N2O administration cause diffusion hypoxia?
as N2O is diffusing back into the alveoli for exhalation, it dilutes alveolar O2 and CO2, causing diffusion hypoxia and hypocarbia
76
How is diffusion hypoxia prevented?
100% FiO2 for 3-5 minutes
77
What is a right to left shunt?
deoxygenation blood bypasses the pulmonary circulation and lungs and leaves the body deoxygenated.
78
What is the net result of a right to left shunt?
reduction in PaO2 and reduced partial pressure of anesthetic in arterial blood
79
What are examples of right to left shunts?
Tetralogy of Fallot, Foramen ovale, Eisenmenger’s syndrome, Tricuspid atresia, Ebstein’s anomaly
80
Ranked the inhaled anesthetics from most to least affected by right to left shunts.
Des - most
N2O
Sevo
Iso - least
81
How does Right to left shunts affect IV induction? Faster or slower
faster
82
How do left to right shunts affect inhalation induction?
no effect
83
How do left to right shunts affect IV induction?
slow induction
84
N2O is ____x more soluble than N
34
85
What is the NITROGEN blood:gas partition coefficient?
0.014
86
What is the N2O blood:gas partition coefficient?
0.46
87
In Compliant airspaces
Volume ____
Pressure _____
Volume increases
| Pressure unchanged
88
In noncompliant airspaces
Volume ____
Pressure _____
Volume unchanged
| Pressure increases
89
What factors (4) determine pressure change in a airspace?
compliance, partial pressure of N2O, perfusion of surrounding tissue, time
90
What are considerations for N2O with retinal surgery?
stop 15 minutes before bubble
| avoided for 7-10 days after retinal surgery
91
N2O inhibits vitamin B12, which inhibits what?
methionine synthase
92
What are consequences of N2O inhibiting vitamin B12?
megaloblastic anemia, neuropathy, immunocompromise, impaired DNA synthesis, spontaneous abortion
93
N2O causes _____ equilibrium of volume in compliant air filled spaces.
fast
94
N2O causes slow equilibrium in what two spaces?
bowel and pneumoperitoneum
95
N2O increases pressure rapidly in what spaces?
middle ear, brain during intracranial procedures
96
What are two ear complications of N2O administration?
damage to tympanic membrane, serous otitis
97
What are the alternatives to SF6 & how long should N2O be avoided?
Air - 5 days
Perfluoropropane - 30 days
Silicone oil - No contraindications
98
What procedures should N2O be avoided in because it support combustion?
laparoscopy with pneumoperitoneum if cautery is used
99
What trimesters of pregnancy should N2O be avoided?
first and second
100
MAC is inversely related to ____
potency
101
The higher the MAC the ___ the potency?
lower
102
Which inhaled anesthetic is the most potent?
Iso, MAC 1.2
103
What is MAC?
concentration of inhaled anesthetic that prevents pain withdrawal reflex in 50% of the population.
104
```
What are the MAC values of:
Iso
Sevo
Des
N2O
```
Iso: 1.2
Sevo: 2
Des: 6.6
N2O: 104%
105
What is the MAC awake during induction and during emergence?
induction: 0.4-0.5
Emergence: 0.15
106
Arrange the inhalation anesthetics from most to least potent.
Iso - most
Sevo
Des
N2O least
107
What is MAC bar?
value to block autonomic response following a supra maximal stimulus. 1.5 MAC
108
Movement is prevented in 95% of the population at what MAC value?
1.3
109
Awareness is prevented at what MAC value?
0.4-0.5
110
What drugs and conditions increase MAC?
chronic EtOH use, amphetamine intoxication, cocaine use, MAOIs, ephedrine, levodopa
111
What drugs and conditions decrease MAC?
acute EtOH intoxication, IV anesthetics, N2O, opioids, alpha 2 agonists, lithium, lidocaine, hydroxyzine
112
How does hyperNa and hypoNa affect MAC?
hyper increase MAC
| hypo decreases MAC
113
What electrolytes do not affect MAC?
potassium and mag
114
What ages increase and decrease MAC?
increases: 1-6months
decreases: old age, premature
115
MAC decreases by _% for each decade after ___
MAC decreases by 6% for each decade after 40.
116
How does temperature affect MAC?
hyperthermia increases MAC
| hypothermia decreases MAC
117
What factors do not affect MAC?
thyroid, gender, PaCO2 15-95, HTN
118
How can thyroid disease affect MAC?
hypothyroid has decreased CO leading to faster rise in FA/FI
119
What is the Meyer-Overton rule?
lipid solubility is directly proportional to potency of gas. Greater solubility lower MAC. (Iso)
120
What is the unitary hypothesis?
all anesthetics share a similar mechanism of action, but work at different sites
121
What do volatile anesthetics do to inhibitory and stimulatory receptors?
stimulate inhibitory receptors
| inhibit stimulatory receptors
122
What are the inhibitory pathways volatiles stimulate?
GABA-A, Glycine channels, Potassium channels
123
What are the stimulatory pathways volatiles inhibit?
NMDA, Nicotinic, Sodium, dendritic spine function and motility
124
What is the most important receptor site of volatile action in the brain?
GABA-A
125
What do volatiles do the GABA-A receptors?
bind to the chloride channels and inhibit their closure, leading to hyperpolarization, impairing neurons from firing.
126
Where do volatile produce immobility in the spinal cord?
ventral horn
127
Where are the sites of action of volatiles in the spinal cord?
glycine receptors, NMDA, Na channels
128
What is the triad of general anesthetic action?
unconsciousness, amnesia, immobility
129
What regions of the brain are responsible for anesthetics causing unconsciousness?
cerebral cortex, thalamus, RAS
130
What regions of the brain are responsible for anesthetics causing amnesia?
amygdala, hippocampus
131
What regions of the brain are responsible for anesthetics causing immobility?
ventral horn
132
What regions of the brain are responsible for anesthetics causing analgesia?
spinothalamic tract
133
What regions of the brain are responsible for anesthetics causing autonomic modulation?
pons and medulla
134
What are the two effects of volatiles on cardiac muscle and vascular smooth muscle?
decrease Ca influx, reduce Ca release from sarcoplasmic reticulum
135
What is the effect of volatiles on heart rate? Except which one?
increase HR.
| Sevo does not increase HR.
136
What is the effect of volatiles on blood pressure? Except which one?
decrease. except N2O
137
What is the effect of volatiles on CO?
decrease
138
What is the effect of volatiles on SVR? Except which one?
decrease. Except N2O
139
What is the primary mechanism for volatiles decreasing BP?
decreased intracellular Ca causing a decrease in inotropy
140
What is the mechanism for volatiles decreasing HR?
decreased SA node automaticity, decrease conduction velocity, increased repolarization
141
Volatiles decrease contractility but they remain responsive to what?
preload
142
What volatile causes the least amount of decrease in SVR?
Sevo
143
Rank the volatiles from greatest to least potency of coronary artery dilation?
Iso > Des > Sevo
144
What is the hearts oxygen extraction ratio?
75%
145
Iso may cause coronary steal. What is coronary steal?
coronary blood flow is preferentially directed to healthy tissues at the expense of diseased vessels
146
For every _mmHg increase in PaCO2 above baseline, VE increases by _L/min.
For every 1mmHg increase in PaCO2 above baseline, VE increases by 3L/min.
147
What is the effect on volatiles on Vt and RR?
increase RR and decreased Vt
148
How do volatiles affect the CO2 response curve?
decreased response to CO2, increased apnea threshold. Shift down and to the right
149
What volatiles impair hypoxic ventilator drive the most?
Sevo > Iso > Des
150
What volatile impaired hypoxic ventilatory drive the least?
Des
151
What agent is best to use on patients that rely on hypoxia to drive ventilation like emphysema and sleep apnea? Why
Desflurane. It impaired hypoxic ventilatory drive the least.
152
What are causes of a right shift on the CO2 response curve?
general anesthetics, opioids, metabolic alkalosis, denervation of peripheral chemoreceptors.
153
What are causes of a left shift on the CO2 response curve?
anxiety, surgical stimulation, metabolic acidosis, increased ICP, salicylates, aminophylline, doxapram
154
What muscles do volatiles inhibit leading to upper airway obstruction?
tensor palatine and genioglossus
155
A PaO2 less than ____ is a stimulus to increase minute ventilation.
< 60 mmHg
156
Carotid bodies relay afferent input to the Respiratory center via which cranial nerve?
9, glossopharyngeal
157
Aortic bodies relay afferent information via which CN?
x, vagus
158
What type of cells provide the sensory arm of the hypoxic drive?
glomus type 1
159
How do volatiles affect CMRO2?
reduce CMRO2, because they reduce electrical activity
160
What MAC value produces an isoelectric EEG?
1.5-2
161
What volatile can cause seizure activity at 2 MAC? What population is this common?
Sevo, pediatric inhalation induction
162
How do volatiles affect cerebral blood flow?
increase by decreasing cerebrovascular resistance
163
What volatile increases CMRO2 and cerebral blood flow?
N2O
164
How do most volatiles affect CMRO2 and cerebral blood flow?
reduce CMRO2 and increase cerebral blood flow
165
CPP is auto regulated at what pressures?
50-150
166
How do volatiles affect CSF absorption and production.
Iso: increases absorption
Des: increases production
Sevo: decreases production
167
Where is CSF absorbed and secreted?
secretion by choroid plexus
| absorption by arachnoid villi
168
How do volatiles affected EEG amplitude and latency?
decrease amplitude
| increase latency
169
What EEG changes are concerning?
50% decrease in amplitude
| 10% increase in latency
170
What evoked potential monitors the dorsal column?
SSEP
171
What evoked potential monitors integrity of the corticospinal tract?
MEP
172
Do volatiles affect SSEP, MEPs or both?
SSEP
173
Besides volatiles, what three factors affect evoked potentials?
hypoxia, hypercarbia, hypothermia
174
What anesthetic enhances evoked potential signals?
ketamine
175
What evoked potentials are most and least sensitive to anesthetics?
BAEP: least
VEP: most
