Inhaled Anesthetics

Front 1

Three distinct advantages of inhaled anesthetic over IV drugs are:

Back 1

Rapid onset/short duration

Easy to monitor end tidal gas

majority of elimination via lungs

(independent of liver or kidneys)

Front 2

Who discovered Nitrous Oxide

Back 2

Horace Wells

1840s

Front 3

Who discovered diethyl ether

Back 3

William morton

1840s

Front 4

WHo discovered Chloroform

Back 4

James Simpson

1840s

Front 5

Between 1920 and 1940, which three inhaled anesthetics were introduced into clinical practice?

Back 5

Ethylene

Cyclopropane

Divinyl Ether

Front 6

What advantage did Ethylene, cyclopropane, and divinyl ether have over older anesthetics?

Back 6

Less soluble in the blood - more rapid recovery

Front 7

Why did diethyl ether, chloroform, and ethylene vanish from clinical practice?

Back 7

Flammability

Front 8

Why did chlorform vanish from clinical practice?

Back 8

Hepatic toxicity

Front 9

Which anesthetics were introduced in the 1960s?

Back 9

Halogenated agents

Front 10

Substitution of fluorine, bromine, or chlorine on hydrocarbons allowed for what?

Back 10

Less toxicity

Less soluble in blood (rapid onset/recovery)

Front 11

List three advantages of halogenated agents:

Back 11

Less toxic

Lesss soluble in blood

Inflammable

Front 12

__________ was the prototype halogenated agent.

Back 12

Halothane

Front 13

Who synthesized over 700 fluorinated compounds between 1959 and 1980?

Back 13

Terrell and associates (Ohio Mecics)

*Later became Baxter

Front 14

Which two flourinated agents became the mainstays of anesthetic delivery in the 1970s and 1980s?

Back 14

Enflurane

Isoflurane

Front 15

What was the first agent halogenated exclusively with flourine?

Back 15

Desflurane

Front 16

Name two advantages of using flurane in an anesthetic?

Back 16

Less toxic

less soluble in the blood

Front 17

Why does desflurane need a special vaporizer

Back 17

Because it's saturated vapor pressure is near one atmosphere

Front 18

Desflurane is _________ as potent as isoflurane

Back 18

1/5th

Front 19

Why was desflurane intitially not introduced into use?

Back 19

Dangerous to synthesize (use of elemental fluorine)

Expensive

Front 20

As temperature increases, vapor pressure ______________

Back 20

increases

Front 21

What happens if an agent with a higher vapor pressure is accidentally added to a vaporizer of an agent with a lower vapor pressure?

Back 21

Will deliver more anesthetic than shown on the vaporizer.

Potential to deliver toxic levels

Front 22

Desflurane will degrade _______ in moist soda lime at temperatures above __________

Back 22

slightly

80 degrees Celsius

Front 23

Halothane and isoflurane will degrade _______ in moist soda lime at temperatures above ______

Back 23

moderately

80 degrees Celsius

Front 24

At what temperatures will sevoflurane degrade in moist soda lime?

Back 24

40 degrees = slight degradation

60 degrees = considerable degradation

80 degrees = massive degradation

Front 25

Degradation of an anesthetic is due to the interaction between the anesthetic and __________ bases in the absorbant, particularly:

________ and ___________

Back 25

monovalent bases

KOH

NaOH

Front 26

Anesthetic degradation depends on two factors:

Back 26

Moist vs dry soda lime

Temperature of soda lime

Front 27

What are two effects of dry soda lime

Back 27

Large amount of anesthetic degradation

Exothermic reaction = fire risk

Front 28

Which volatile anesthetic poses the greatest fire risk when reacting with dessicated soda lime?

Back 28

Sevoflurane

Front 29

Degradation of sevoflurane can result in production of what?

Back 29

Compound A

Front 30

Production of Degradation of isoflurane and desflurane can result in what?

Back 30

Carbon monoxide

Front 31

Compound A affects:

Back 31

The corticomedullary junction of the kidney

-enzymuria

-protinuria

-renal necrosis in rats

Front 32

Concentrations of compound A production correlated directly with (2)

And inversely with: (1)

Back 32

Direct correlation with:

-sevoflurane concentration

-absorbent temperature

Inverse correlation with FGF rates

Front 33

Recommended flow rates for sevoflurane

Back 33

1 LPM for up to 2 MAC hours

2 LPM after 2 MAC hours

Front 34

Production of significant CO requires ______ dessication of absorbent

Back 34

90%

-takes 1-2 days of high gas flows

Front 35

CO production is the result of the reaction with:

Back 35

monovalent bases in the absorbent

Front 36

Define MAC

Back 36

The minimum alveolar concentration of inhaled anesthetic that produces immobility in 50% of humans when exposed to noxious stimulus

Front 37

MAC is ___________across species

Back 37

constant

Front 38

How is MAC related to anesthetic potency?

Back 38

Inversely related

Front 39

Immobility due to MAC is mediated by the__________

Back 39

spinal cord

Front 40

What variables can increase MAC?

Back 40

Young age

hyperthermia

chronic alcohol abuse

Acute cocaine & amphetamine intoxication

hypernatremia

Front 41

What variables can decrease MAC

Back 41

Old age

hypothermia

acute alcohol intoxication

PaO2 < 40, pCO2 >95, HCT <10%

Local anesthetics, opoids, ketamine, barbituates, verapamil, lithium, clonidine, dexmeditomidine, chronic amphetamine/cocaine use

Front 42

What variables do NOT affect MAC?

Back 42

Gender

Height/weight

Duration of anesthesia

Hyper/hypothyroid

Front 43

MAC of halothane (in 100% O2 and 70% N20)

Back 43

.75 %

.29 %

Front 44

MAC of isoflurane (in 100% O2 and 70% N20)

Back 44

1.2

.50

Front 45

MAC of Sevoflurane (in 100% O2 and 70% N20)

Back 45

2.0

.66

Front 46

MAC of desflurane (in 100% O2 and 70% N20)

Back 46

6.0

2.8

Front 47

MAC of N2O

Back 47

105%

Front 48

Surgical anesthesia approximates ______ MAC

Back 48

1.3 MAC

Front 49

What is MAC Awake?

Back 49

The average concentration permitting voluntary response to command.

~1/3 MAC

Front 50

What is MAC BAR

Back 50

The avleolar concentration that blocks autonomic response to stimuli

~1.5 MAC (or higher)

Front 51

What is anesthesia?

Back 51

Immobility

Amnesia

Front 52

How do anesthetics produce amnesia?

Back 52

By their affect on the brain

Front 53

How do anesthetics produce immobility?

Back 53

By their affects on the spinal cord.

Front 54

What is the Meyer-Overton hypothesis?

Back 54

Anesthetic potency correlates directly with lipid solubility.

Anesthetics must disrtupt neruonal transmission at hydrophobic sites in the lipid bilayer

Front 55

What is one weakness of the Meyer-Overton hypothesis

Back 55

Not all lipid soluble agents are anesthetics

Front 56

What is the 5 angstrom (5 Carbon) theory?

Back 56

Suggests that anesthetics act on two different sites separated by a distance of 5 angstroms.

Front 57

What evidence supports the 5 angstrom theory

Back 57

In a series of anesthetic compounds, potency increases to a maximum at 5 carbon lengths, then decreases.

Also true for barbituates

Front 58

Which excitatory receptors are believed to be depressed by inhaled anesthetics?

Back 58

5-HT

ACh

Glutamate (NMDA)

Front 59

Which inhibitory receptors are believed to be enhanced by inhaled anesthetics?

Back 59

GABA

Glycine

Front 60

Anesthetic uptake from the lungs is a product of which three factors?

Back 60

Solubility (blood:gas KP)

Cardiac output

Alveolar-venous partial pressure gradient

Front 61

Solubility of anesthetic gas in the blood is denoted by___________

Back 61

blood: gas partition coefficeint.

Describes the affinity of the anesthetic for two phases of equilibrium

Front 62

What does a larger blood: gas partition coefficient indicate?

What does this cause?

Back 62

Greater solubility in the blood.

Faster uptake

Front 63

A larger blood:gas partition coeficient will produce a ___________ FA/FI ratio

Back 63

lower

Front 64

What means are available to compensate for uptake of the anesthetic by the blood?

Back 64

Increase % inspired (FI)

Increase Flow

Increase respiratory rate (alveolar ventilation)

Front 65

What is the blood:gas partition coeficeint of Desflurane?

Back 65

0.42

Front 66

What is the blood:gas partition coeficeint of N2O?

Back 66

0.47

Front 67

What is the blood:gas partition coeficeint of Sevoflurane?

Back 67

0.69

Front 68

What is the blood:gas partition coeficeint of Isoflurane?

Back 68

1.4

Front 69

What is the blood:gas partition coeficeint of Halothane?

Back 69

2.4

Front 70

Uptake is _________ proportional to cardiac output

Back 70

directly

Front 71

doubling cardiac output ___________ the amount of blood exposed to anesthetic

Back 71

doubles

Front 72

Why do low cardiac output states pre-dispose to toxic levels of anesthetic

Back 72

what is affect in blood

what is affect on brain

Front 73

What does the alveolar-venous partial pressure gradient arise from?

Back 73

Tissue uptake

Front 74

What three factors affect tissue uptake of anesthetic?

Back 74

Tissue blood flow

Solubility of anesthetic in the tissue

Arterial-tissue partial pressure gradient

Front 75

What is the main determinant of tissue uptake of anesthetic?

Back 75

Tissue blood flow

Front 76

The vessel rich group is composed of:

Back 76

brain, heart, lungs, liver, kidneys

Front 77

How much blood flow is received by the vessel rich group?

Back 77

70% of cardiac output

(only 10% of body mass)

Front 78

How long does it take for the muscle group to acheive equilibrium?

Back 78

1-4 hours

Front 79

How long does the fat group take to reach equilibrium

Back 79

up to 30 hours

Front 80

How do we compensate for anesthetic uptake?

Back 80

Increase alveolar ventilation

Increase inspired concentration (FI)

[increasing flows will also increase FI]

Front 81

Increasing alveolar ventilation causes more rapid "wash-in" of anesthetic. Why is this more pronounced with higher solubility agents?

Back 81

Because a greater percentage of anesthetic is uptaken by the blood.

Front 82

What is the concentration effect (overpressuring)

Back 82

Increasing the FI of anesthetic causes an increase in the rate of rise (reach equilibrium faster)