Inhalation Anesthetics Flashcards

1
Q

Inhalant Anesthetics

A
  • Liquid agents vaporized in oxygen
  • Administered via anesthetic breathing system by ET-tube, mask, or chamber
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2
Q

How are inhalant anesthetic agents measured

A
  • Vapor pressure
  • Blood-gas partition coefficient
  • Minimum alveolar concentration (MAC)
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3
Q

Vapor Pressure

A

Measurement of the tendency of a liquid to evaporate

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4
Q

Vapor & Evaporation

Regarding Inhalant Agents

A

High vapor pressure = readily evaporate
* reach dangerously high concentrations
* administer using agent-specific precision vaporizer

Low vapor pressure
* may be administered with nonprecision vaporizer

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5
Q

Blood-gas Partition Coefficient

A

Measurement of the tendency of an agent to dissolve in blood

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6
Q

Blood-gas Partition Coefficient

Associations

A
  • Speed of induction
  • Recovery
  • Change in depth of anesthesia
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7
Q

Low vs High Blood-gas Partition Coefficient

A

In regards to speed of induction, recovery, and change in depth of anesthesia

Low Partition Coefficient = Faster

High Partition Coefficient = Slower

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8
Q

MAC

A
  • Minimum Alveolar Concentration
  • Percent concentration of an agent
  • Measurement of potency of agent
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9
Q

High vs Low MAC

A

High MAC = less potent
* more required to attain surgical anesthesia

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10
Q

Halogenated Anesthetics
Function and Causes

A
  • Induce and maintain general anesthesia
  • CNS depression
  • Respiratory depression
  • Hypothermia
  • Hypotension
  • Muscle relaxation
  • No analgesic postoperatively
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11
Q

Halogenated Anesthetics

Examples

A
  • Isoflurane
  • Sevoflurane
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12
Q

Halogenated Anesthetics

& the Heart

A

Cause myocardial depression
* cardiac function maintained close to preanesthetic levels

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13
Q

Iso & Sevo

Vapor Pressure and Blood-gas Partition Coefficients

A

Both have:
* High vapor pressure - need precision vaporizer
* Low blood-gas partition coefficients - rapid induction, recovery, and change in anesthetic depth

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14
Q

Halogenated Anesthetics

Metabolism and Excretion

A

Both metabolized in Liver

Excreted primarily through lungs, but also by kidneys

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15
Q

Iso & Sevo

Metabolism

A

Metabolized by liver

Iso = better choice for those with kidney or liver disease

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16
Q

Sevoflurane and Fire/Heat

A
  • Fire / heat production produced when used with dry CO2 absorbent
  • More common when low oxygen flow rates used over long time
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17
Q

Sevoflurane and Fire/Heat

Preventions

A
  • Turn machine off when not in use
  • Replace absorbent granules regularly
  • Avoid low oxygen flow rates for extended periods
  • Monitor temperature of abosrbent canister
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18
Q

Desflurane

A
  • Similar to Isoflurane
  • Extremely high vapor pressure
  • Low blood-gas partition coefficient
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19
Q

Desflurane

Vaporizer

A

Required expensive electronic vaporizer
* boiling point is near room temperature

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20
Q

Desflurane Effects

A
  • More rapid inductions and recovery compared to sevoflurane
  • Causes dose-related respiratory depression
21
Q

Advantages of Anesthesia

A
  • Elimination through lungs - liver and kidneys not as crucial
  • Good control of aneshetic depth
  • Newer agents less irritating to respiratory system
  • Well tolerated
22
Q

Disadvantages of Anesthesia

A
  • Require constant monitoring
  • Requires complex and expensive equipment
  • Muscle relaxation
  • No long term analgesia
23
Q

Inhalation Anesthetic Agents

A

No longer commonly used
* diethyl ether
* methoxyflurane
* nitrous oxide
* halothane

24
Q

Alveolar Concentration

A
  • Inhalation anesthetic effects in brain related to anesthetic concentration in lungs
  • Low concentration needed
  • Concentration needed to prevent muscle movement in response to surgical stimuli
25
Q

MAC Factors

Cause Decrease

A

Decrease means more sensitivity to anesthetic
* hypotension
* hypothermia
* aging

Lower the need for anesthetic levels

26
Q

Partition Coefficient

A

Entry of anesthetic into body fluids and tissues

More soluable agent = slower induction/recovery
* slower it takes to get to brain tissues

27
Q

Partition Coefficient & Anesthetic Gas

A

Volume of gas absorbed by a unit volume of liquid
* High concentration during induction
* Low concentration for maintanence

28
Q

Diffusion Hypoxia

A

Occurs if a gas other than oxygen floods alveoli and displaced O2
* occurs with very insoluable gases

29
Q

Vapor Pressue

Definition

A

Amount of pressure exerted by the gas form when gas and liquid are in equilibrium

30
Q

Equilibrium

Regarding Vapor Pressure

A

Reached when the number of molecules going to gas and returning to liquid is equal

31
Q

Votality & Vapor Pressure

A

High vapor pressure = high tendency to evaporate
* easily evaporate = High votality

32
Q

Vapor Pressure Variations

A

Will vary with:
* physical property of the liquid
* temperature of the liquid

33
Q

High Vapor Pressure Agents

A

Require precision vaporizer
* halothane
* isoflurane
* sevoflurane

34
Q

Inhalation Anesthetic Drugs

Desired Properties

A
  • Safe, no delayed toxicity
  • Non-flammable/ Non-explosive
  • Chemically stabe, no reaction to soda-lime
  • Low MAC value
  • Low blood solubility
  • No irritation to mm
  • No nausea
  • Inexpensive
35
Q

Nitrous Oxide

A
  • Weak anesthetic drug - no anesthesia by itself
  • Tank color is Blue
  • Referred to as “laughing gas”
36
Q

Nitrous Oxide

Anesthetic Effects

A
  • Some depression of cerebral cortex
  • Unchanged HR, cardiac output, BP
  • Tachycardia will occur with hypoxia
37
Q

Nitrous Oxide

Elimination & Metabolism

A
  • Eliminated through lungs
  • Very little is metabolized
  • Completely gone within 2 minutes
38
Q

Nitrous Oxide

Diffusion Hypoxia

A
  • Occurs when N2O floods alveoli when turned off - rapid outflow of N2O
  • Suppliment with O2 for 2-5 minutes after N2O turned off
39
Q

Nitrous Oxide

Abuse

A

Potential for human abuse
* may cause death by hypoxia

40
Q

Nitrous Oxide

Hollow body structures

A

Will rapidly diffuse into hollow structures and cause distention

Use caution with
* pneumothorax
* GI obstruction
* gastric torsion
* lung cyst
* diaphragmatic hernia

41
Q

Ether

A
  • Used as main inhalant anesthetic up until 1956
  • Highly flammable
  • Heavier than air; sink and form vapor cloud
  • Good analgesia and margin of safety
42
Q

Methoxyflurane

A
  • Inhalant anesthetic agent
  • Potent, highly soluble
  • Slow induction and recovery
  • Delayed kidney toxicity in humans
43
Q

Halothane

A
  • Inhalation anesthetic agent
  • Lost popularity because it sensitizes the heart to epinephrine induced arrhythmias
44
Q

Isoflurane

A
  • Inhalation anesthetic agent
  • Insoluble in tissues (blood and muscles)*
  • Physically stable

More soluble in fat than blood

45
Q

Isoflurane

Chemical Properties

A
  • Colorless
  • Ether-like odor
  • Mild irritation to mm
  • Heavier than air
  • Non-flammable
46
Q

Isoflurane

Patients & Protocol

A

Protocol for brachycephalics & high-risk
* pre-oxygenate for 3-5 minutes
* flow 3L/min
* calm patient during this time

47
Q

Sevoflurane
Characteristics

A
  • Non-pungent odor
  • Less irritating to mm
  • Suited for mask induction
48
Q

Sevoflurane

Effects

A

High insoluble
* quick induction/recovery
* quick alteration to anesthetic depth

Low tendancy for cardiac arrhythmias

49
Q

Sevoflurane

Concentrations

A

Higher concentrations cause rapid change in anesthetic depth
* may cause hypotension and respiratory depression