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Inhalant anesthesia Flashcards

1
Q

What are the predictable effects of inhalant anesthesia?

A

Narcosis, muscle relaxation, not analgesic (with a few exceptions)

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2
Q

T/F: Inhalant anesthesia has rapid adjustment of anesthetic depth, minimal metabolism, and is economical

A

TRUE

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3
Q

What are 4 examples of vapor?

A

Halothane, isoflurane, sevoflurane, desflurane

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4
Q

What are the gas laws that govern inhalant anesthesia?

A

Boyle Charles Gay-Lussac Dalton’s law of partial pressure: total pressure of a gas mixture is equal to the sum of the partial pressure of the individual gases

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5
Q

Vapor pressure

A

Pressure exerted by vapor molecules when liquid and vapor phases are in equilibrium

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6
Q

T/F: Vapor pressures depends on temperature (increases with increasing temperature) and is inversely related to boiling point

A

TRUE

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7
Q

What is the solubility of anesthetic vapors? When is equilibrium reached?

A

Anesthetic vapors dissolve in liquids and solids. Equilibrium is reached when the partial pressure of the anesthetic is the same in each phase (partial pressures are equal; number of anesthetic molecules not equal)

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8
Q

What is solubility expressed as?

A

A partition coefficient Concentration ratio of an anesthetic in the solvent and gas phases Describes capacity of a given solvent to dissolve the anesthetic gas

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9
Q

T/F: The blood-gas partition coefficient is the most clinically useful number.

A

TRUE

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10
Q

What does the blood-gas partition coefficient describe?

A

Amount of an anesthetic in the blood vs. alveolar gas at equal partial pressure

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11
Q

What is the location of effect for the blood-gas partition coefficient?

A

The anesthetic in the alveolar gas represents brain concentration

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12
Q

T/F: In the blood-gas partition coefficient, anesthetic dissolved in blood is pharmacologically active.

A

FALSE–anesthetic dissolved in blood is pharmacologically INACTIVE

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13
Q

What is the most soluble agent? Least soluble?

A

Most soluble = halothane Least soluble = desflurane

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14
Q

Which is more soluble, isoflurane or sevoflurane?

A

Isoflurane

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15
Q

With a low blood-gas PC, there is ___ anesthetic dissolved in blood at equal partial pressure (___ in alveoli)

A

less; more

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16
Q

With a low blood-gas PC, there is a ____ time requird to attain a partial pressure in the brain and there is ____ induction and recovery.

A

shorter; short

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17
Q

What are some examples of low blood-gas PC?

A

Iso, sevo, desflurane

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18
Q

T/F: Low blood-gas PC is clinically more useful.

A

TRUE

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19
Q

What is a gas with a high blood-gas PC?

A

Halothane

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20
Q

In anesthetics with high blood-gas PC: There is ___ anesthetic dissolved in blood at equal partial pressure, a ___time is required to attain a partial pressure in the brain, and there is ___ induction and recovery.

A

more longer long

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21
Q

How is equilibrium achieved in inhaled anesthetics?

A

Inhaled anesthetics move down pressure gradients until equilibrium is achieved

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22
Q

What is the route of uptake for inhalant anesthetics?

A

Vaporizer–>breathing circuit–>alveoli–>arterial blood–>brain

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23
Q

T/F: partial pressure in the brain (P brain) is roughly equal to that in the alveoli (P A)

A

TRUE

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24
Q

Partial pressure in the alveoli (calculation)

A

P a = gas delivery to alveoli - removal by blood from lungs

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25
How do you increase P a?
Increase anesthetic delivery to alveoli Decrease removal from alveoli
26
To increase inspired anesthetic concentration (Pi) you must:
Increase vaporizer setting Increase fresh gas flow Decrease breathing circuit volume
27
To increase alveolar ventilation:
Increase minute ventilation Decrease dead space ventilation
28
What is the concentration effect?
The higher the Pi, the more rapidly Pa approaches Pi
29
Is a high or low Pi required at the beginning of gas anesthesia? Why?
High--to quickly increase Pa
30
What does the concentration effect offset?
Impact of uptake (removal of anesthetic by pulmonary circulation)
31
T/F: According to the concentration effect, as uptake into blood increases, Pi can be decreased
FALSE--as uptake into blood DECREASES, Pi can be decreased
32
How do you decrease removal from alveoli?
(1) Decrease blood solubility of anesthetic (2) Decrease cardiac output (3) Decrease alveolar-venous anesthetic gradient
33
What does anesthetic elimination require?
Decrease in Pa
34
T/F: The same variables that affect a rise in Pa affect anesthetic elimination, except agent solubility (blood-gas PC) and alveolar ventilation.
FALSE--The same variables that affect a rise in Pa affect anesthetic elimination, ESPECIALLY agent solubility and alveolar ventilation
35
How do you quickly decreases Pa?
Turn off vaporizer Disconnect patient and flush O2 Turn up O2 flow (dilute anesthetic in circuit as it is exhaled from patient) Increase ventilation (IPPV)--increase fresh gas to alveoli
36
What is the hepatic metabolism for the following agents? Halothane Sevoflurane Isoflurane Desflurane
Halothane = 20-46% Sevoflurane = 2-5 Isoflurane = 0.2 Desflurane = 0.02
37
3 facts about N20
Low blood-gas PC (0.47) Mild analgesic Accumulates in closed gas spaces
38
Xenon--facts
Expensive, mostly experimental at this time
39
What is the minimum alveolar concentration (MAC)?
Minimum alveolar concentration of an anesthetic that prevents movement in 50% of patients exposed to a noxious stimulus
40
What does MAC allow?
Comparison of potency between agents--inverse relationship (high MAC = low potency)
41
T/F: Alveolar concentration can be approximated using a gas analyzer
TRUE
42
T/F: MAC measures percent of agent in inspired gas.
FALSE--expired gas
43
T/F: Alveolar concentration is the same as the vaporizer setting.
FALSE--it is NOT the same
44
What does an increase in MAC result in?
Hyperthermia Hypernatremia Drugs causing CNS stimulation Red hair in people
45
What does a decrease in MAC result in (8)?
Hypothermia Hyponatremia Drugs causing CNS depression MAP \< 50mmHg, PaO2 \< 40 mmHg, PaCO2 \> 95 mmHg Pregnancy Increasing adult age
46
What are MAC multiples used for?
To describe dose of gas in relation to pharmacologic and physiologic effect.
47
1.2-1.4 times MAC ensures what?
Immobility in 95% of patients
48
MAC is additive, therefore:
(0.5 x MACa) + (0.5 x MACb) = 1 MACab
49
When is the additive property of MAC important?
Changing gases in the middle of a case Using N2O Using a partial intravenous anesthesia (PIVA)
50
What are the 6 effects of the volatile anesthetics?
Cardiovascular Respiratory Neurologic Renal Hepatic Other
51
What are the 5 effects of volatile anesthetics on the cardiovascular system?
Decrease in CO Decrease in BP Decrease in systemic vascular resistance Decrease in contractility (inotropy) Ether no change or an increase in HR (chronotropy)
52
What are the 5 effects of volatile anesthetics on the respiratory system?
1. Decrease ventilation (depress central and peripheral chemoreceptors, decreased responsiveness to CO2) 2. Respiratory arrest at 1.5-3 MAC 3. Bronchodilation 4. Desflurane and isoflurane--irritating odor 5. Sevoflurane--least irritating
53
T/F: Inhalants cause significant hyperventilation
FALSE--hypOventilation
54
What are the 4 effects of volatile anesthetics on the neurologic system?
Increase intracranial pressure at \>1 MAC (increase cerebral blood flow) Decrease cerebral metabolic rate Act on brain and spinal cord to produce immobility (not analgesia) Suppress seizure activity (except Enflurane)
55
What are the 2 effects of volatile anesthetics on the renal system?
Decrease GFR and renal blood flow due to decreased CO Renal failure (methoxyflurane)
56
What is Compound A? What animal is it nephrotoxic in?
Produced from sevoflurane breakdown in CO2 absorbent (baralyme \> soda lime) Nephrotoxic in rats
57
Higher concentrations of Compound A are formed during:
Prolonged anesthesia Low fresh gas flows Desiccated absorbent
58
What are the 2 effects of volatile anesthetics on the hepatic system?
Reduce liver blood flow and O2 delivery (related to decrease in CO) Halothane can cause hepatotoxicity: (1) Increased liver enzymes--mild, self-limiting; (2) "halothane hepatitis"--immune-mediated, often fatal
59
Give me 4 facts about malignant hyperthermia
1. Myopathy occurring in genetically predisposed pigs, dogs, cats, horses, (people) 2. Exposure to inhalant anesthetic (esp. halothane, but also iso, sevo, des) 3. Uncontrolled muscle contraction--\>severe hyperthermia--\>death 4. First sign is often a rapid increase in EtCO2
60
What are the treatments for malignant hyperthermia?
1. Discontinue volatile anesthetic, flush with O2, switch to new circuit if possible 2. Provide 100% O2 3. Administer dantrolene--muscle relaxant 4. Fluids, active cooling
61
T/F: In malignant hyperthermia, death often occurs despite treatment
TRUE
62
T/F: Malignant hyperthermia is very common
FALSE--very rare
63
What is the max administration of N20?
75% (need \>/= 25% O2)
64
T/F: Nitrous oxide has a low solubility (blood-gas PC 0.47), minimal CV and resp. depression, and is a mild analgesic
TRUE
65
Why is nitrous oxide transfered to closed gas spaces?
Equilibration leads to N20 accumulating rapidly (more soluble in blood) while Nitrogen leaves slowly (less soluble) GI tract, sinuses, middle ear, pneumothorax, GDV, cuff of ET tube (avoid in disease states causing increased closed gas space)
66
Diffusion hypoxia (4 things)
1. When N2O administration is stopped, it diffuses quickly out of the blood into alveoli (down concentration gradient) 2. Displaces O2 from alveoli 3. If breathing room air--\> hypoxia 4. Provide 100% O2 supplementation for 5-10 minutes to prevent
67
What are the environmental safety concerns with inhalent anesthetics?
Concern exists that trace levels of inhalants cause adverse health effects (esp. fetal health and development, though data is inconclusive). Should reduce occupational exposure as much as possible
68
What are 7 ways to reduce gas exposure?
1. Utilize scavenging system 2. Minimize leaks 3. Avoid mask or chamber induction 4. Keep patient attached to circuit after anesthetic gas is turned off 5. Minimize exposure to exhaled gas from patient 6. Maximize ventilation 7. Monitor waste gas concentrations

Anesthesiology (16 decks)

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