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Advanced Pharm Fall 24 > Inhalation Agents > Flashcards

Inhalation Agents Flashcards

1
Q

3 most common inhalation anesthetics

A
  1. Isoflurane
  2. Desflurane
  3. Sevoflurane
    (N2O, we give often… but not a true anesthetic)
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2
Q

Inhalation agents are direct…

A

Myocardial depressants

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3
Q

The primary objective of inhalation anesthesia is

A

To achieve a constant and optimal partial pressure of anesthetic administered in the brain

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4
Q

The target organ in inhalation anesthesia is the __

A

Brain

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5
Q

Equilibrium is referred to as ___

A

Steady state

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6
Q

At equilibrium (steady state)

A

Constant and optimal pressure is maintained

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7
Q

Partial pressure of a gas are…

A

Equal in both the blood and the gas phase (both sides of the partition)

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8
Q

Lambda coefficient is also called ___

A

Ostwald Coefficient/Partition Coefficient

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9
Q

Ostwald/partition coefficient refers to potentials of substances in (2 phases)

A

Blood and gas phases

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10
Q

The gas phase occurs in the ___

A

Alveoli

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11
Q

The blood phase occurs in the ___

A

Arterial/venous blood

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12
Q

At equilibrium…. the ___ = ___ = ____

A

Alveoli = arterial blood = brain

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13
Q

Partial alveolar is abbreviated as

A

PA

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14
Q

Partial arterial pressure is abbreviated as

A

Pa

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15
Q

Partial pressure is abbreviated as

A

P

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16
Q

Partial brain pressure is abbreviated as

A

Pbr

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17
Q

While partial pressures are equal… the anesthetic ___

A

Drug concentration is not equal

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18
Q

We determine equilibrium by

A

Input into alveoli - uptake of drug from alveoli into arterial blood

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19
Q

Input into alveoli, uptake of drug from alveoli into arterial blood occur during

A

Induction

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20
Q

Alveoli are the

A

“Windows to the brain”

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21
Q

Leaky bucket concept refers to

A

Drug absorption uptake

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22
Q

Drug concentration is (directly/inversely proportional) to partial pressure

A

Directly (but not equal)

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23
Q

Increased concentration =

A

Increased partial pressure

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24
Q

Decreased concentration =

A

Decreased partial pressure

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25
Q

Alveoli are window to the brain… we measure what is in alveoli by

A

End tidal CO2

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26
Q

At equilibrium, alveoli =

A

Blood partial pressure

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27
Q

Diseased lungs require

A

Increased concentration

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28
Q

Transfer from the machine to the alveoli is determined by

A

Vaporizer and flow meter settings, as well as type of equipment used

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29
Q

Never use oxygen <

A

30%

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30
Q

How to flush anesthesia machine for someone concerned with MH (option 1)

A

100% oxygen at 10L/min for at least 20 minutes
Replace breathing circuit and carbon dioxide canister
Inactivate/remove vaporizers
***newer anesthesia machines may require washout for 104 minutes

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31
Q

How to flush anesthesia machine for someone concerned with MH (option 2)

A

Adding commercially available activated charcoal filters to the circuit will remove anesthetic gases and remove need for purging system
***Anesthesia machine will still need to be flushed with high fresh gas flows >= 10L/min for 90 seconds

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32
Q

Higher fresh gas flow & lower absorption =

A

Faster induction

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33
Q

Pediatrics often only use…

A

Inhalation induction

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34
Q

Adults need IV induction as well, then you start inhalation. In theory you have ___

A

Two inductions

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35
Q

IV bypasses

A

Absorption

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36
Q

Inhalation must be ___

A

Absorbed

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37
Q

Alveoli to arterial blood (3 factors)

A
  1. B/Gλ (lipid solubility of agent)
    a. Drug you choose/solubility
  2. C.O. (pulmonary blood flow)
  3. Alveolar to venous partial pressure difference (diffusion gradient)
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38
Q

Goal in inhalation induction is to: (3)

A
  1. Decrease gas solubility coefficient
  2. Decrease/maintain normal C.O.
  3. Increase arterial/venous partial pressure
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38
Q

Drug, ventilation and cardiac factors are determined by (2 things) with alveoli to arterial blood

A
  1. Agent chosen
  2. Patient’s heart and lungs
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39
Q

Tissue factors: (3) with arterial blood to brain

A
  1. Brain/blood λ
  2. Cerebral blood flow
  3. Arterial to venous partial pressure difference (diffusion gradient)
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40
Q

Arterial blood to brain tissue factors are determined by 2 things:

A
  1. Agent chosen
  2. Patient’s heart and lungs
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41
Q

Goal of inhalation absorption to tissue: (3)

A
  1. Decreased blood gas solubility coefficient
  2. Normal cerebral blood flow
  3. Increased arterial/venous partial pressure
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42
Q

Barriers that must be overcome to produce an effective anesthetic:

A
  1. Delivered
  2. Inspired
  3. Alveolar
  4. Arterial
  5. Tissue
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43
Q

MAC stands for

A

Minimum alveolar concentration

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44
Q

MAC compares

A

Potency of all inhalation agents

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45
Q

We breathe in…

A

78% Nitrogen
21% Oxygen
0.04% CO2 and other mixed gases

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46
Q

Pre-oxygenation is reallu

A

De-nitrogenation

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47
Q

At equilibrium, partial pressures are ___ and are reflective of

A

Equal
Total pressure exerted in alveoli

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48
Q

At equilibrium, concentrations are ___, so you must ___

A

Never equal
Dial the concentrations in

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49
Q

Pharmacodynamic effects of inhaled anesthetics must be ___

A

Based on a dose

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50
Q

Pharmacodynamic effects are based on

A

MAC

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51
Q

Each drug has a MAC, each MAC is different, but at that #….

A

It has equal potency at each MAC

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52
Q

Factors that reduce MAC

A

Increased age
Hypothermia
Admin of sedatives, co-administration of other anesthetics
Alpha 2 agonists
Opioids
Acute ethanol consumption
Hypoxemia
Hyponatremia
Hypermagnesemia
Anemia
Hypotension
Pregnancy
Lithium

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53
Q

Factors with no influence on MAC

A

Duration of anesthesia
Gender
Hypocapnia/hypercapnia
Metabolic alkalosis
Hypertension
Hyperkalemia/hypokalemia

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53
Q

Factors that increase MAC

A

Young age
Hyperthermia
Hyperthyroidism
Hypernatremia
Acute admin of CNS stimulant drugs
Red hair in females
Chronic alcohol abuse

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54
Q

1 MAC assesses…

A

Pt movement (aka ED50)

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55
Q

1MAC =

A

ED50 (no recall, LOC)

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56
Q

1.3MAC =

A

ED95

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57
Q

MAC value for N20

A

105

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58
Q

MAC value for Isoflurane

A

1.15
**1 in elderly

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59
Q

MAC value for Desflurane

A

5.8
**5.17 in elderly

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60
Q

MAC value for Sevoflurane

A

2.0
**1.45 in elderly

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61
Q

Pts < 1 year of age…

A

Have increased MAC

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62
Q

MAC decreases what percentage per each decade of life?

A

6-7% each decade

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63
Q

Do you use 105 of N2O?

A

No, you use 0.6MAC (60%)

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64
Q

If MAC is increased, you must give a(n) ____ dose

A

Increased

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65
Q

If MAC is decreased, you must give a(n) ___ dose

A

Decreased

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66
Q

Smaller the dose…

A

The more potent it is

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67
Q

MAC is highest between ____ of age

A

6-12 months

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68
Q

MAC-awake refers to

A

Approximately 1/3 of MAC
50% will open eyes when asked

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69
Q

MAC for loss of recall and awareness are

A

0.4-0.5 MAC

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70
Q

1-MAC

A

Derived value for agent that assesses movement on incision

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71
Q

Surgical-MAC

A

1.2-1.3x MAC
Anesthetic requirements > MAC by 20-30%
**Surgical MAC is where we operate

72
Q

MAC-BAR

A

1.6x MAC
**This is where you block adrenergic/stress response

73
Q

What MAC do you block adrenergic/stress response?

A

MAC-BAR (1.6x MAC)

74
Q

Blood/gas λ of N2O

A

0.47 (in blood) and 1 in gas

75
Q

Blood/gas λ of Isoflurane

A

1.4 (in blood) and 1 in gas

76
Q

Blood/gas λ of Desflurane

A

0.42 (in blood) and 1 in gas

77
Q

Blood/gas λ of Sevoflurane

A

0.6 (in blood) and 1 in gas

78
Q

Fat/blood λ of N2O

A

2.3:1

79
Q

Fat/blood λ of Isoflurane

A

45:1

80
Q

Fat/blood λ of Desflurane

A

27:1

81
Q

Fat/blood λ of Sevoflurane

A

48:1

82
Q

What is the preferred inhalation agent in bariatric patients?

A

Desflurane because fat/blood is lowest true anesthetic of 27

83
Q

FA/FI = 1 = ___

A

Equilibrium

84
Q

The speed of anesthetic induction (with inhalation) is determined by ___

A

The rate at which alveolar partial pressure approaches inspired partial pressure

85
Q

FA/FI is

A

Alveolar: Inspired

85
Q

The key is to look at what is in alveoli (lung) to ___

A

To determine how fast they will go to sleep

86
Q

FA/FI (interchangeable with FA:FI) is the degree ___

A

To which alveolar concentration is becoming closer to inspired concentration of anesthetic

86
Q

If alveolar concentration equals the inspired concentration….

A

The ratio will be 1/1 or 1:1 or simply 1

87
Q

FA/FI = 1 is the same as saying ___

A

Rate at which alveolar concentration of anesthetic equals inspired concentration of anesthetic
**AKA equilibrium

88
Q

3 factors determining uptake from lung (absorption) alveoli–arterial blood

A
  1. B/G λ solubility of the agent
  2. C.O.
  3. Alveolar to venous anesthetic partial pressure difference between lung and blood (diffusion gradient)
89
Q

Blood is a pharmacologically ____

A

Inactive reservoir

90
Q

Blood (inactive reservoir) size is determined by ___

A

Solubility of anesthetic agent in blood

91
Q

If the B/G λ is high, a ___ amount of anesthetic must be dissolved in blood before the Pa (arterial) equilibrates with alveoli (PA)

A

LARGE

92
Q

If the B/G λ is low, ___ of the anesthetic must be dissolved in blood before the Pa (arterial) equilibrates with PA (alveoli)

A

Less

93
Q

An increase in anesthetic uptake (absorption) results in…

A

A slower induction— a SLOWING of anesthetic induction (or increase in induction time)

94
Q

The B/G λ (Ostwald) is a distribution ratio describing ___

A

Itself between two phases: blood and gas

95
Q

Equilibrium is equal to

A

Partial pressure on both sides

96
Q

B/G λ =

A

Anesthetic blood concentration/anesthetic alveolar gas concentration

97
Q

Isoflurane’s B/G λ is…

A

1.4

98
Q

With isoflurane:
At equilibrium, the concentration in blood will be ___x the concentration in the alveoli but the partial pressures will be ___

A

1.4 and equal
1.4:1 or 1.4/1

99
Q

In predicting MAC from O/G λ, what is the formula?

A

MAC = 150 / (O/G λ)

100
Q

MAC = 150 / (O/G λ is good at determining

A

Anesthetic potency

100
Q

The correlation between lipid solubility and potency follows which rule?

A

Meyer-Overton rule

101
Q

What type of oil was used to determine oil/gas solubility?

A

Olive oil

102
Q

Oil/gas partition coefficient of N20

A

1.4

103
Q

Oil/gas partition coefficient of Isoflurane

A

99

104
Q

Oil/gas partition coefficient of Desflurane

A

18.7

105
Q

Oil/gas partition coefficient of Sevoflurane

A

50

106
Q

If lipid solubility is increased…

A

So does anesthetic potency

107
Q

If you know oil/gas…

A

You can figure out MAC

108
Q

Meyer-Overton rule:

A

Anesthetic potency of inhalation agents correlates directly with lipid solubility

109
Q

Meyer-Overton rule implies that ___

A

Anesthesia results from molecules dissolving at specific lipophilic sites

110
Q

Problem with Meyer-Overton rule:

A

All lipid-soluble molecules are not anesthetic and some are convulsants (correlation between anesthetic potency & lipid solubility is only approximate)

111
Q

O/G λ

A

How efficiently drug can access the sites of action (potency)

112
Q

B/G λ

A

How fast drug is delivered to tissue (solubility)

113
Q

Inhalation anesthetics are…
a. potentiaters
b. additive
c. syngergistic
d. antagonists

A

Additive

114
Q

0.5 MAC of one agent + 0.5 MAC of 2nd agent =

A

1.0 MAC

115
Q

What gas is the only gas you can add?

A

Nitrous oxide

116
Q

General rule of thumb using N2O…

A

1% reduction in MAC for each 1% N2O

117
Q

Uptake (absorption) is ___ proportional to C.O.

A

Directly

118
Q

Increased C.O. =

A

Increased uptake (slower induction)A

119
Q

An increased cardiac output means a slower/faster induction

A

Slower

120
Q

Decreased C.O. = ___ uptake

A

Decreased uptake (more rapid induction)

121
Q

A decreased cardiac output means a slower/faster induction

A

Faster

122
Q

Increased C.O. = ___ lung perfusion

A

Increased

123
Q

Increased lung perfusion =___

A

Increased drug absorption (increased uptake)

124
Q

Increased drug absorption (uptake) =

A

Decreased rate of rise in alveolar drug (slower induction)

125
Q

Drug absorption (uptake) is also known as the…

A

Leaky bucket

126
Q

Decreased C.O. = ___ lung perfusion

A

Decreased

127
Q

Decreased lung perfusion = ___ drug absorption (uptake)

A

Decreased

128
Q

Decreased drug absorption (uptake) =

A

Increased rate of rise in alveolar drug (more rapid induction)

129
Q

The leaky bucket (lung) theory correlates with

A

Drug absorption

130
Q

The greater the difference in partial pressure between the agent in the alveoli and the ___ the greater the uptake

Will the induction be slower or faster

A

Venous blood

Slower

131
Q

High pressure in lung is required to get __

A

Rise

132
Q

If there is no uptake (absorption) of anesthetic gas from alveoli, FA would…

A

Rapidly equal the concentration of anesthetic gas in inspired gas FI

133
Q

No uptake =

A

Faster response

134
Q

FA (alveolar) lags behind FI because…

A

Pulmonary circuit takes up anesthetic gas and lowers concentration in alveoli

135
Q

The greater the amount of uptake (absorption)…

A

The slower the FA/FI ratio rise toward 1

136
Q

Uptake delays, but it happens to ___ people

A

ALL

137
Q

Uptake is ____ related to rate of rise of the FA/FI ratio

A

Inversely

138
Q

There are 3 phenomena influencing uptake & distribution of inhaled agents

A
  1. Concentration (overpressure)
  2. Second gas effect
  3. Diffusion hypoxia
139
Q

Overpressurization is analogous to…

A

An upfront IV loading bolus of a drug

140
Q

Overpressurization definition:

A

The admin of a higher partial pressure of anesthetic than the alveolar concentration actually desired for the patient

141
Q

When you reach equilibrium with overpressurization… what should you do immediately after and why?

A

Turn gas down because it causes major cardiac depression

142
Q

Concentration effect is d/t: (2)

A
  1. Concentrating effect
  2. Hyperventilation effect
143
Q

Concentrating effect definition:

A

Total volume of lung is decreased by amount of uptake of inhalation agent by the blood (concentrates remaining gas in lung)

144
Q

Hyperventilation Effect/Increased tracheal inflow…

A

When a large volume of gas is taken up by the blood a negative pressure is created and fresh gas inflow augments alveolar ventilation

145
Q

Concentration effect’s biggest difference occurs in how many breaths?

A

2-3

146
Q

Concentration effect speeds up induction by the concentrating effect and the ___

A

Hyperventilation effect

147
Q

Net effect means

A

You are delivering a greater concentration of agent than is actually being administered

148
Q

Second gas effect is the uptake of large volumes of a ___

A

1st primary gas (N2O) that accelerates alveolar rate of rise of a 2nd gas (isoflurane) administered at the same time

149
Q

Second gas effect theory:

A

Rapid uptake of primary gas concentrates the second gas because of the decrease in total lung volume

150
Q

To tell the difference between concentration vs. second gas… ask yourself…

A

Are you giving 1 or 2 gases?

151
Q

Concentration and second gas effects do what to induction and emergence?

A

Hasten (speed up)

152
Q

Concentration and second gas occur during ___ for approximately ___

A

InductionF
First 5-15 minutes (most dramatic and significant within first few breaths)
***Occurs during emergence for first 5 min

153
Q

Diffusion hypoxia (anoxia) occurs during what phase… induction, maintenance, or emergence?

A

Emergence

154
Q

Diffusion hypoxia ONLY occurs with the use of ___

A

N2O
**Postop first 5 min

155
Q

To avoid diffusion hypoxia you should….

A

Wake the patient up with oxygen

156
Q

Why does diffusion hypoxia occur?

A

Nitrogen comes in/out and crowds the lungs and causes hypoxia

157
Q

SHUNTS:
Examples of right-to-left shunt (2)

A

Intra-cardiac shunt
Intra-pulmonary shunt (bronchial intubation)

158
Q

SHUNTS:
Example of left-to-right shunt (1)

A

Tissue shunt

159
Q

Which type of shunt can cause de-oxygenation?

A

Right-to-left (they are cyanotic)

160
Q

Examples of tissue shunts (not significant in de-oxygenation)

A

AV fistula
Volatile anesthetic induced in increase in cutaneous blood flow)

161
Q

Right-to-left shunts could slow the rate of induction d/t a ____

A

Dilutional effect

162
Q

Right-to-left shunts have greater impact on:

A

poorly soluble agents like:
Desflurane
Sevoflurane
N2O

163
Q

Right-to-left shunt compensation for deficits: (2)

A

Increased concentration of insoluble agents
Increased ventilation w/ soluble agents

164
Q

Right-to-left shunt = decreased or increased PA

A

Decreased

165
Q

Left-to-right shunts result in delivery to ___

A

Lungs of venous blood with a higher partial pressure of anesthetic than that present in blood (that has passed through tissue)

166
Q

Left-to-right shunts increase or decrease PA tension

A

Increase

167
Q

Is a left-to-right shunt alone detectable?

A

No

168
Q

What type of shunt is detectable?

A

Right-to-left

169
Q

In the presence of a right-to-left shunt, a left-to-right shunt will ____

A

Offset dilution effects (could prolong IV induction)

170
Q

Three stages of anesthesia:

A

Induction
Maintenance
Recovery

171
Q

Induction has three:

A

Excitement (see in children mostly)
Rigidity (set their jaw)
Relaxation

172
Q

Maintenance has two:

A

Constant (set anesthesia machine)
Variable (we adjust w/ variable)

173
Q

Recovery has two:

A

Crisis (very rapid wake up)
Lysis (smooth even w/ wake up)

174
Q

We want patients in the ____ phase of recovery

A

Lysis

175
Q

What gas is preferred in bariatric?

A

Desflurane

176
Q

Three factor equation for uptake from lung:

A

UL = λB Q(PA - PV) / BP

Advanced Pharm Fall 24 (3 decks)

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