Inhalation Anesthetics

Question 1

Inhalant Anesthetics

Answer 1

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

Question 2

How are inhalant anesthetic agents measured

Answer 2

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

Question 3

Vapor Pressure

Answer 3

Measurement of the tendency of a liquid to evaporate

Question 4

Vapor & Evaporation

Regarding Inhalant Agents

Answer 4

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

Low vapor pressure
* may be administered with nonprecision vaporizer

Question 5

Blood-gas Partition Coefficient

Answer 5

Measurement of the tendency of an agent to dissolve in blood

Question 6

Blood-gas Partition Coefficient

Associations

Answer 6

• Speed of induction
• Recovery
• Change in depth of anesthesia

Question 7

Low vs High Blood-gas Partition Coefficient

Answer 7

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

Low Partition Coefficient = Faster

High Partition Coefficient = Slower

Question 8

MAC

Answer 8

• Minimum Alveolar Concentration
• Percent concentration of an agent
• Measurement of potency of agent

Question 9

High vs Low MAC

Answer 9

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

Question 10

Halogenated Anesthetics
Function and Causes

Answer 10

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

Question 11

Halogenated Anesthetics

Examples

Answer 11

• Isoflurane
• Sevoflurane

Question 12

Halogenated Anesthetics

& the Heart

Answer 12

Cause myocardial depression
* cardiac function maintained close to preanesthetic levels

Question 13

Iso & Sevo

Vapor Pressure and Blood-gas Partition Coefficients

Answer 13

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

Question 14

Halogenated Anesthetics

Metabolism and Excretion

Answer 14

Both metabolized in Liver

Excreted primarily through lungs, but also by kidneys

Question 15

Iso & Sevo

Metabolism

Answer 15

Metabolized by liver

Iso = better choice for those with kidney or liver disease

Question 16

Sevoflurane and Fire/Heat

Answer 16

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

Question 17

Sevoflurane and Fire/Heat

Preventions

Answer 17

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

Question 18

Desflurane

Answer 18

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

Question 19

Desflurane

Vaporizer

Answer 19

Required expensive electronic vaporizer
* boiling point is near room temperature

Question 20

Desflurane Effects

Answer 20

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

Question 21

Advantages of Anesthesia

Answer 21

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

Question 22

Disadvantages of Anesthesia

Answer 22

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

Question 23

Inhalation Anesthetic Agents

Answer 23

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

Question 24

Alveolar Concentration

Answer 24

• 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

Question 25

MAC Factors | Cause Decrease

Answer 25

Decrease means more sensitivity to anesthetic * hypotension * hypothermia * aging | Lower the need for anesthetic levels

Question 26

Partition Coefficient

Answer 26

Entry of anesthetic into body fluids and tissues More soluable agent = slower induction/recovery * slower it takes to get to brain tissues

Question 27

Partition Coefficient & Anesthetic Gas

Answer 27

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

Question 28

Diffusion Hypoxia

Answer 28

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

Question 29

Vapor Pressue | Definition

Answer 29

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

Question 30

Equilibrium | Regarding Vapor Pressure

Answer 30

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

Question 31

Votality & Vapor Pressure

Answer 31

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

Question 32

Vapor Pressure Variations

Answer 32

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

Question 33

High Vapor Pressure Agents

Answer 33

Require precision vaporizer * halothane * isoflurane * sevoflurane

Question 34

Inhalation Anesthetic Drugs | Desired Properties

Answer 34

* 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

Question 35

Nitrous Oxide

Answer 35

* Weak anesthetic drug - no anesthesia by itself * Tank color is Blue * Referred to as "laughing gas"

Question 36

Nitrous Oxide | Anesthetic Effects

Answer 36

* Some depression of cerebral cortex * Unchanged HR, cardiac output, BP * Tachycardia will occur with hypoxia

Question 37

Nitrous Oxide | Elimination & Metabolism

Answer 37

* Eliminated through lungs * Very little is metabolized * Completely gone within 2 minutes

Question 38

Nitrous Oxide | Diffusion Hypoxia

Answer 38

* Occurs when N2O floods alveoli when turned off - rapid outflow of N2O * Suppliment with O2 for 2-5 minutes after N2O turned off

Question 39

Nitrous Oxide | Abuse

Answer 39

Potential for human abuse * may cause death by hypoxia

Question 40

Nitrous Oxide | Hollow body structures

Answer 40

Will rapidly diffuse into hollow structures and cause distention Use caution with * pneumothorax * GI obstruction * gastric torsion * lung cyst * diaphragmatic hernia

Question 41

Ether

Answer 41

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

Question 42

Methoxyflurane

Answer 42

* Inhalant anesthetic agent * Potent, highly soluble * Slow induction and recovery * Delayed kidney toxicity in humans

Question 43

Halothane

Answer 43

* Inhalation anesthetic agent * Lost popularity because it sensitizes the heart to epinephrine induced arrhythmias

Question 44

Isoflurane

Answer 44

* Inhalation anesthetic agent * Insoluble in tissues (blood and muscles)* * Physically stable | More soluble in fat than blood

Question 45

Isoflurane | Chemical Properties

Answer 45

* Colorless * Ether-like odor * Mild irritation to mm * Heavier than air * Non-flammable

Question 46

Isoflurane | Patients & Protocol

Answer 46

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

Question 47

Sevoflurane Characteristics

Answer 47

* Non-pungent odor * Less irritating to mm * Suited for mask induction

Question 48

Sevoflurane | Effects

Answer 48

High insoluble * quick induction/recovery * quick alteration to anesthetic depth Low tendancy for cardiac arrhythmias

Question 49

Sevoflurane | Concentrations

Answer 49

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