Inhalationals 1-3 Flashcards
(145 cards)
1
Q
What are the three chemical categories of inhalational agents?
A
Ethers (R-O-R)- Des,Sevo,Iso
Alkanes (R-H)- Halothane, Chloroform
and Gases- N20 and xenon
2
Q
What makes Isoflurane more potent compared to other agents?
A
Addition of a heavier chlorine atom increases its potency.
3
Q
What substitution differentiates Desflurane from Isoflurane?
A
Desflurane has fluorine replacing the chlorine atom in Isoflurane.
4
Q
What is unique about Sevoflurane’s structure?
A
It contains seven fluorine atoms.
5
Q
Define vapor pressure (VP) in anesthesia.
A
VP is the pressure exerted by a vapor in equilibrium with its liquid in a closed container; directly proportional to temperature.
6
Q
Vapor pressure is directly proportional to ____________
A
TEMPERATURE
higher temp = increased VP
7
Q
What determines an agent’s boiling point (BP)?
A
BP is reached when VP equals atmospheric pressure; BP decreases with altitude.
8
Q
What is the Vapor Pressure of
Iso
Des
Sevo
N20
i’d ask them separately but you know you’ll answer them all at once
A
Iso - 238 mmHg
Des- 669 mmHg (damn that’s close to 760)
Sevo - 157 mmHg
N20- wildin the f out over there at 38,770 mmHg
9
Q
T/F- a higher altitude will increase your boiling point
A
that is FALSE
high altitude make a liquid boil at a lower temp because there is decreased atmospheric pressure.
10
Q
Evaporation occurs when VP is ________ than ATM while boiling occurs when the VP __________ the ATM
A
evaporation occurs when VP is LESS than the ATM
Boiling is when VP is **equal or above **the ATM
11
Q
What are the Boiling Points of all our inhalationals?
A
Sevo- 59C
Des- 22.8C- dang thats close to OR temp- why its in a heater
ISO- 49C
N20- -88C- IE shes ALWAYS a gas
12
Q
What is partial pressure in gas mixtures?
A
Partial pressure (PP)- it’s the fractional amount of pressure a
single gas exerts within a gas mixture
Daltons Law of Partial Pressure- the total gas pressure in a
container is equal to the sum of the partial pressures exerted by
each gas
all need to add together to = 760 mmHg
13
Q
The goal of PP in setting your anesthetic is what?
idk if that made sense the answer should
A
you want the PP that gets to the BRAIN not the % of the agent alone
14
Q
Which agents are unstable with desiccated soda lime?
what are their biproducts
A
Desflurane and Isoflurane (produce carbon monoxide) (DES>ISO)
Sevoflurane (produces compound A).
15
Q
Fill this in
A
16
Q
what was the first inhalational used for surgery
A
Ether- first used for parties lol
17
Q
Problems with:
Ether and Cyclopropane
Chloroform
Methoxyflurane
A
Ether & Cyclopropane- flammable
Chloroform- cardio toxic
Methoxyflurane- renal toxic
18
Q
How do we “think” inhalational agents work?
A
Today- thought to facilitate GABA-A, Glycine,
Glutamate, Acetylcholine, Serotonin, Nitric Oxide,
Calcium, NMDA glutamate receptors, & ligand-gated
sodium ion channels
inhalationals disrupt transmission of neuronal impulses in the CNS
19
Q
what are the Macroscoping, Microscopic MOAs for inhalationals
A
- Macroscopic
- Spinal cord- stimulation of glycine channels & inhibition
of NMDA receptors and Na channels- * Brain- stereo selective receptors and facilitation of GABA-A receptors
-keeps CL channels open longer - Microscopic
- Synapses & axons
20
Q
T/F: N20 and Xenon stimulate Gaba-a
A
False- they sure don’t
21
Q
this looks important- name regions and functions
A
22
Q
3 pillars of anesthesia
A
analgesia- loss of pain
amnesia- loss of consciousness
akinesia- lack of mvmt
23
Q
Tell me about the idea agent and qualities she should have
does she exist?
A
Ideal agent- produce analgesia, amnesia, hypnosis,
Co pyright- information can not be used without the authors written permission
muscle relaxation loss of reflex activity. Should have wide safety range, rapid, not be unpleasant, rapid recovery, easy to control, stable, nonflammatory, free of side effects, nonirritating, cheap
Does NOT exist- just like the perfect man
24
Q
A
thank god amnesia is so low
25
Tell me about the blood Gas partition Coefficient
| if you can
* Partition coefficient is a measure of **solubility**
* Blood:gas partition coefficient describes the solubility of
an inhalational agent in the blood vs alveolar gas when
the pp between the two are equal
alveoli and blood are EQUAL- that's the goal
when u first turn your gas on theres more goes into the blood and we want it in the alveoli
Distribution of an agent at equilibrium between two
substances (blood & alveolar gas) at the same temperature, pressure and volume
26
What three factors determine the uptake of inhalational agents?
1) Blood/gas solubility
2) Cardiac output
3) Alveolar to venous partial pressure gradient.
27
Tell a girl the MAC and B/G coeffecient of all the inhaleds we use
MAC. B/G
N20. 104. .47
ISO. 1.14. 1.4
Des. 6.6 .42
Sevo 2 .65
28
what is the Oil:Gas partition coefficient
ISO- 99
Sevo- 50
Des - 19
Nitrous- 1.4-- that LOW
29
What does a high blood/gas (B/G) solubility coefficient indicate?
Greater solubility in blood, slower induction b/c there is more uptake by the blood
more for a resevoir tho too- longer offset
30
what is the isoflurane blood gas partition coefficient
1.4
31
How does cardiac output affect uptake?
Higher CO leads to greater uptake and slower induction.
32
What is the 'Fa/Fi' ratio?
Ratio of alveolar concentration (Fa) to inspired concentration (Fi); reflects speed of induction.
Fa= alveolar gas- pp of agent to brain and tissue
Fi = inspired gas controlled by delivery at a high inflow to prevent rebreathing (this is set by dial)
33
What is overpressurization?
A technique where a higher Fi is delivered to accelerate induction.
can compensate for high BG solubility coeffienct by increasing the % delivered
like a bolus
34
Increased FA/FI =
35
Decreased Fa/FI =
36
I had it starred- know which is which
37
What is Va
alveolar ventilation
normal is 4L
38
FRC
functional residual capacity- how much is left in the lungs after normal exhalation
normal = 2L
39
Ve
ventilation/min or MV
normal is 6-8 LPM
40
Define time constant in gas kinetics.
Time to achieve 63% change in concentration; 1 T.C. = 63%, 2 T.C. = 86%, etc.
3= 95% change
4= 98 % change
41
What effect does solubility have on elimination?
Less soluble agents are eliminated more quickly, allowing faster emergence.
42
How does ventilation affect the rate of rise of Fa?
Increased ventilation speeds the rise of Fa, especially for soluble agents.
43
How does the concentration effect enhance uptake?
A higher Fi leads to increased Fa due to increased driving pressure and second gas effect.
44
uptake is the product of what 3 factors
solubility- more soluble the agent = more in blood/less in lung
CO- CO big= uptake big
diff b/t pp of agent in alveoli and venous blood
IF ANY 3 are 0 = UPTAKE = O
45
say the concentration of an agent in the blood is 3% and there is 6% in the lung, what is the affinity of agent for blood
3/6 = 0.5 THIS IS GOOD
46
T/F: elimination is more rapid with a LESS soluble agent than a MORE soluble agent
TRUE- becuase it less in the blood
47
LOW B/G coefficient = _______onset
HIGH BG coefficient = ______ onset
faster
slower
48
What is the second gas effect?
A phenomenon where N₂O speeds the uptake of a second gas by increasing alveolar concentration.
49
name vessel rich groups
and poor
and how much CO they take up
rich - brain, haeart, lung, liver, kideny
(10% body mass) (75% CO)
Muscle/skln
(50% body mass)(20% CO)
Fat
(20%body mass)( 5% CO)
Vessel poor- bones, ligaments, tendons, cartilage
(20% Body mass) (<1% CO)
50
What is the Meyer-Overton rule?
It states that anesthetic potency is proportional to lipid solubility.
51
What is the Ferguson rule?
Potency correlates with solubility and vapor pressure.
52
Where do inhaled agents act in the CNS?
On GABA-A, glycine, NMDA, glutamate, serotonin, acetylcholine receptors, and ligand-gated ion channels.
53
What are the main macroscopic and molecular targets of volatile agents?
Macroscopically: GABA-A, glycine, NMDA inhibition; Microscopically: synapses/axons; Molecularly: CNS proteins.
54
Do N₂O and xenon act via GABA-A?
No, they antagonize NMDA and stimulate K+ channels without acting on GABA-A.
55
Which agents are considered volatile anesthetics?
Isoflurane, Desflurane, Sevoflurane.
56
Which agent is not potent enough for full anesthesia?
Nitrous oxide (N₂O); it provides analgesia but not full anesthesia.
57
Which agent has the highest MAC?
N₂O (MAC ~104%).
58
Which agent has the lowest blood/gas solubility?
Desflurane (0.42).
59
What is MAC?
Minimum Alveolar Concentration that prevents movement in 50% of subjects exposed to a noxious stimulus.
60
What is MAC-awake?
Concentration at which 50% of patients respond to command (≈0.4–0.5 MAC on induction).
61
what can prolong wash out and wake up
FAT- fat continuously uptakes the agent and acts as a big ol resevoir
62
What is MAC-BAR?
Concentration that blocks autonomic responses in 50% of patients (≈1.5 MAC).
63
How does age affect MAC?
MAC decreases 6% per decade after age 40.
64
How do volatile agents affect CBF and ICP?
They increase cerebral blood flow and intracranial pressure; blunted by hyperventilation.
65
Which agent increases CSF absorption?
Isoflurane (Forane).
66
Which agent may cause seizure-like EEG activity?
Sevoflurane at >2 MAC.
67
How do inhaled agents affect cardiovascular system?
Cause vasodilation, decrease MAP, CO, SVR; dose-dependent.
68
Which agent causes the most coronary vasodilation?
Isoflurane.
69
What is the effect of volatile agents on QT interval?
All prolong QT; avoid Sevoflurane in long QT syndrome.
70
How do inhaled agents affect respiration?
Dose-dependent respiratory depression, decreased TV, increased RR, impaired response to CO₂.
71
Which agent is most irritating to the airway?
Desflurane.
72
Which agent is preferred for inhalational induction?
Sevoflurane.
73
Which agent has the highest metabolism rate?
Sevoflurane (2-5%).
74
What is compound A and which agent forms it?
A nephrotoxic byproduct formed when Sevoflurane is degraded in soda lime.
75
Which agent produces the most carbon monoxide when exposed to dry soda lime?
Desflurane.
76
Which agent requires a special vaporizer?
Desflurane (TEC-6 vaporizer).
77
What is the metabolism rate of Isoflurane?
~0.2%.
78
What is the metabolism rate of Desflurane?
~0.02%.
79
What are the benefits of N₂O?
Rapid onset, analgesia, second gas effect, minimal CV effects.
80
What are risks of N₂O?
Diffusional hypoxia, expansion in closed gas spaces, PONV, teratogenic risk with prolonged exposure.
81
What causes diffusional hypoxia with N₂O?
Rapid diffusion into alveoli dilutes oxygen after discontinuation; mitigated by 100% O₂.
82
What metabolic pathway does N₂O inhibit?
Methionine synthase; affects DNA synthesis and B12 metabolism.
83
What are the four tissue compartments for anesthetic distribution?
Vessel-rich group (VRG), muscle, fat, vessel-poor group (VPG).
84
What is the time constant for VRG equilibrium?
~1.5 min (63%), ~6 min (98%).
85
How does fat affect emergence?
Acts as a reservoir, slowing elimination especially for soluble agents like Isoflurane.
86
How do changes in ventilation-perfusion (V/Q) ratios affect uptake?
Impaired V/Q (e.g., pneumonia) delays agent delivery and uptake.
87
How does high altitude affect vaporizer output?
Decreased atmospheric pressure lowers the partial pressure of agents delivered.
88
Why is Sevoflurane preferred in pediatric inductions?
Non-pungent, rapid onset, minimal airway irritation.
89
Which agents are best for outpatient surgery?
Desflurane and Sevoflurane due to rapid emergence.
90
Which agent should be avoided in suspected increased ICP?
N₂O and high-dose volatile agents.
91
Which patients are at risk from N₂O exposure?
Those with B12 deficiency, pregnancy (especially first trimester), or closed gas spaces.
92
What are strategies to reduce environmental impact of inhaled agents?
Use low fresh gas flows, avoid Desflurane, consider TIVA when feasible.
93
who this?
Isoflurane
Look at that CL tho- thats what makes it heavier/more potent
94
name the gas
Desflurane- only diff than iso is the CL is replaced by fluorine
95
# name the gas
Sevoflurane- look at all them Fs, there's 7!
96
why is fluoride good for anesthetics
more fluorinated = less absorbed by the body
what we want
lower that BG coefficient!
97
what are things that have NO effect on >MAC
gender
BMI
BP above 50 mmHg
HCT > 10
Pa02
> 50
thyroid fxn
hyper/hypokalemia
hypertension
Hyper/Hypocapnia
98
things other than age that decrease mac
Hypothermia - 2-5% decrease w/ each 1C drop in temp
Hyponatremia, preggo up to 72 hrs postpartum
drunkenness
meds- clonidine, BB, Ca Blockers, adenosine, opioids, benzo, barb, prop, N20, Locals, Lithium
Hypotension Map <50
hypoxia
CPB, PaCO2 > 95, hypoxia, metabolic acidosis, anemia (<4.3)
99
things that increase MAC
chronic alcohol consumption
infants 1-6m
hypers- hyperthermia, hypernatremia, hyperthryroidism
MAO inhibitors, Cocaine, ephedrine, levodopa
being a red head - 19% increase in MAC requriement
100
How do volatile anesthetics affect cerebral blood flow (CBF) and intracranial pressure (ICP)?
They increase CBF and ICP via cerebral vasodilation; can be blunted with hyperventilation (PaCO₂ ~30 mmHg).
101
Which volatile anesthetic increases ICP only at >1.6 MAC?
Isoflurane (Forane).
102
How do volatile anesthetics affect cerebral metabolic rate of oxygen (CMRO₂)?
They decrease CMRO₂ by reducing neuronal activity; isoflurane decreases it the most.
103
Which volatile anesthetic increases CSF reabsorption?
Isoflurane (Forane).
104
Which volatile anesthetic increases CSF production?
Desflurane.
105
Which volatile agent has anticonvulsant effects?
Isoflurane (Forane).
106
Which volatile agent may cause seizure-like activity, especially >2 MAC or with hypercapnia?
Sevoflurane.
107
Which agents can produce burst suppression on EEG at 1.5–2 MAC?
Desflurane and Isoflurane.
108
How do volatile agents affect evoked potentials?
↓ Amplitude and ↑ latency, suggesting neural pathway compromise.
109
Which evoked potential is most sensitive to volatile anesthetics?
Visual Evoked Potentials (VEPs).
110
Which evoked potential is least affected by volatile anesthetics?
Brainstem Auditory Evoked Potentials (BAEPs).
111
How do SSEPs rank in sensitivity to volatile agents?
Intermediate sensitivity: Iso > Des > Sevo.
112
What is the key anesthetic consideration for Motor Evoked Potentials (MEPs)?
Avoid muscle relaxants.
113
What anesthetic technique is preferred for EP monitoring?
TIVA (Total Intravenous Anesthesia), with volatile agent <0.5 MAC and no N₂O.
114
What cardiovascular effects are common to all volatile anesthetics?
Vasodilation → ↓ SVR, ↓ venous return, ↓ MAP/CO/CI, and heat loss.
115
Rank volatile anesthetics by their hypotensive effect.
Isoflurane = Desflurane > Sevoflurane.
116
What is unique about isoflurane’s effect on skeletal muscle blood flow?
It causes a 2–3 fold increase, contributing to ↓ SVR.
117
How does N₂O affect blood pressure?
May cause slight ↑ BP via sympathetic stimulation and ↑ SVR.
118
Do modern inhaled anesthetics cause coronary steal at ≤1.5 MAC?
No coronary steal is observed at ≤1.5 MAC with any volatile agents.
119
What is a shared organ-protective property of all potent inhalational agents?
They decrease mortality and protect the heart, lungs, brain, and kidneys.
120
What concern has been raised in animal studies regarding inhalational agents in pediatrics?
Potential for long-term cognitive dysfunction.
121
How do inhalational agents affect hypoxic pulmonary vasoconstriction (HPV)?
Decrease HPV in animal studies; in humans, effects are dose-dependent or minimal (<1.5 MAC).
122
What is the effect of volatile agents on breathing pattern?
Initial ↑ RR and ↓ tidal volume, followed by decreased MV, FRC, and TV.
123
Which agent is most airway-irritating?
Desflurane.
124
At what concentration does apnea typically occur?
Around 1.5–2.0 MAC.
125
Do volatile agents increase or decrease airway resistance?
Decrease airway resistance (bronchodilation)—beneficial in status asthmaticus.
126
What percentage of unmedicated patients reported respiratory irritation at 2 MAC of Sevoflurane?
0%.
127
How does opioid premedication affect coughing with Desflurane induction?
Decreases incidence; fentanyl/morphine reduce coughing significantly.
128
Which patients are more likely to cough during Desflurane anesthesia—smokers or nonsmokers?
Smokers (up to 100% in some studies).
129
What is the effect of inhalational agents on mucociliary function?
Impairment—of particular concern in patients with pulmonary disease.
130
By how much do inhalational agents decrease hepatic blood flow without surgery?
20–30%.
131
What exacerbates hepatic blood flow reduction during surgery?
Surgical stimulation and catecholamine release.
132
What enzymes mediate volatile anesthetic metabolism in the liver?
CYP3A4 and CYP3A5 via oxidation/hydrolysis (Phase I reactions).
133
What enzymes are involved in kidney metabolism of volatile agents?
CYP2E1.
134
What chemical bonds are most susceptible to metabolism?
Ether and carbon-halogen bonds.
135
Which agent provides the fastest recovery in obese patients?
Desflurane (faster than Isoflurane).
136
Why might volatile agents be avoided in trauma patients?
Due to risk of worsening hypotension from hypovolemia.
137
What is the main fetal concern with volatile anesthetics?
Risk only if maternal hypotension or hypoxia occurs.
138
What is a recommended dose of Forane during C-section?
0.75%.
139
Which agents are best for outpatient/ambulatory procedures?
Sevoflurane and Desflurane (rapid onset, emergence, and discharge).
140
What renal effects are seen with volatile agents?
Dose-dependent ↓ renal blood flow, ↓ GFR, ↓ urine output.
141
Which agent produces the most fluoride ions?
Sevoflurane (Forane & Desflurane = minimal fluoride).
142
How do volatile agents affect neuromuscular blockade?
Potentiate both depolarizing and non-depolarizing agents; ↓ NDMR dose by 25–50%.
143
Do volatile agents provide muscle relaxation at >1 MAC?
Yes—adequate for most surgeries.
144
What serious complication is associated with all volatile agents?
Malignant Hyperthermia (MH).
145
What rare hepatic complication has been reported with Desflurane?
Acute liver injury resembling halothane hepatitis.
