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Pharmacology > Volatile Anesthetics - Quiz 2 > Flashcards

Volatile Anesthetics - Quiz 2 Flashcards

1
Q

General anesthesia is a state in which the body is rendered insensible to pain or other stimuli. What are the 4 components?

A

amnesia
unconsciousness
analgesia
immobility

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2
Q

What is the goal of anesthesia?

A

produce and maintain a constant partial pressure of inhalational anesthetic in the brain

PA = Pa = Pbr

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3
Q

Uptake and distribution is divided into what 4 phases?

A
  1. Develop inspired concentration
  2. Develop alveolar concentration
  3. Develop blood concentration
  4. Distribute anesthetic agent from blood to tissues
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4
Q

What is the very first step in developing and inspired concentration?

A

introduction of an anesthetic agent into the delivery system of the anesthesia machine and circuitry

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5
Q

Ventilation introduces gas into the lungs called:

A

inspired gas (Fi)

Fi Sevo
Fi Iso

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6
Q

What is “wash in”

A

using high flow (5-10L) of delivery gases (O2/N2O) can precisely control the partial of the anesthetic inspired

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7
Q

If I use low flows during the induction phase, what will the effect be?

A

the concentration of anesthetic is not there and it decreases effect

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8
Q

What is the concentration effect?

A

The higher the concentration of inhaled anesthetic delivered to the alveolus = faster the onset.

(probably only clinically relevant with NO)

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9
Q

In the concentration effect, increased inspired volumes promotes an increase in alveolar partial pressure (PA) and allows what to happen?

A

helps to offset the decrease in partial pressure of the gases brought on by pulmonary capillary uptake = rapid induction

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10
Q

When using inhaled anesthetics in a spontaneously breathing patient, what happens to the RR when inhaled anesthetic introduced into the lungs?

A

RR increases

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11
Q

The rate at which the alveolar partial pressure of the anesthetic rises is determined by 2 factors:

A
  1. Inspired concentration (controlled by dial)

2. Alveolar ventilation (increased RR and high flows keeps anesthetic in the alveoli)

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12
Q

When alveolar ventilation is high, what happens to the partial pressure in the alveoli?

A

increases rapidly

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13
Q

What effect happens when there are 2 anesthetic gases in the lungs?

A

Second gas effect

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14
Q

What is the second gas effect?

A

N2O is picked up rapidly from the alveoli by the blood (temporarily shrinking the alveoli). The rapid crossing “pulls” the second gas with it = PP of second gas rising more rapidly.

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15
Q

To promote high alveolar ventilation in an anesthetized patient, what changes will we need to make?

A

Increased RR, increased concentration, increased flow rate

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16
Q

Three (3) factors determine how rapidly anesthetics pass from the inspired gases to the blood:

A
  1. Solubility of the agent (blood:gas)
  2. Rate of blood flow through the lungs
  3. PP of the agent in arterial/venous blood
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17
Q

How do you determine the solubility of an agent in the blood?

A

Anesthetic alveolar concentration (PA)

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18
Q

Why do more soluble agents (Sevo) have longer induction times?

A

The more soluble the agent is, the more of it must be dissolved in the blood in order to raise its partial pressure

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19
Q

What is the speed of induction for insoluble drugs (NO and Des)? and why

A

rapid induction because very little needs to be dissolved before the partial pressure needed is reached

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20
Q

Between Sevo, Iso and Des - which agent will take the longest to build up a Mac?

A

Iso (highest blood:gas solubility coefficient)

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21
Q

What happens with increased pulmonary blood flow (increased CO)

A

Higher blood flow = more blood exposed to agent = faster agent picked up from alveoli = faster delivered to tissues

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22
Q

High CO leads to a ______ onset

A

slower

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23
Q

Low CO leads to a ______ onset

A

faster

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24
Q

Initially, how what is the partial pressure in the venous system when returning to the right side of the heart?

A

Low - because the agent PP was delivered to the tissues

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25
Q

With each circulation time more anesthetic is delivered to the tissue and their partial pressure rises, what happened to the PP in the venous system retuning to the heart?

A

The returning venous blood will also begin to have higher partial pressure as it returns to the lungs.

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26
Q

As venous partial pressure rises, is there more or less picked up from the alveoli?

A

less

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27
Q

The rise of PP in the tissues depends on 2 things:

A
  1. Solubility of gas in the tissues (tissue:blood coefficient) most tissues have similar coefficients
  2. Tissue blood flow (The higher the blood flow to a particular tissue, the faster the anesthetic is delivered and the faster the partial pressure and concentration will rise in that area.)
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28
Q

What are the 4 categories of tissue groups?

A
  1. Vessel rich (brain, heart, liver, kidney, endocrine)
  2. Muscle (skin and muscle)
  3. Fat (adipose tissue)
  4. Vessel poor (bone, ligament, teeth, hair, cartilage)
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29
Q

As uptake in the tissue begins to reach partial pressure in the blood, what happens to the uptake in the tissues?

A

It begins to slow

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30
Q

The rate of rise FA/Fi is the most rapid with which anesthetic agents?

A

the least soluble agents

NO, Des, Sevo

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31
Q

Which agents have a slower rate of rise

A

the more soluble agents

Iso, Halothane

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32
Q

What are the 4 stages of anesthesia?

A
  1. Stage of analgesia
  2. State of delirium or excitement
  3. Stage of anesthesia
  4. Stage of depression
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33
Q

When does stage 1 of anesthesia begin?

A

begins with the administration of anesthesia and ends with the loss of consciousness.

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34
Q

What is happening in stage 1 with the gas tension and dorsal horn activity?

A

Brain gas tension is very low.

Dorsal horn activity decreases and there is decreased synaptic transmission in the spinothalamic tract.

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35
Q

What S/S would be seen in stage 1 of anesthesia?

A 
Increased RR/Shallow breaths
normal eye control and pupils
Secretion of tears
No laryngeal reflexes
Normal muscle tone
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36
Q

When will you start to lose eyelid reflex?

A

End of stage 1

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37
Q

What happens to stage 1 with the addition of IV anesthetics?

A

jump past stage 1

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38
Q

When does stage 2 of anesthesia begin and end?

A

beings at loss of consciousness to beginning of surgical anesthesia

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39
Q

What happens in stage 2 with PP in the brain and inhibitory ions?

A

PP of brain rises

there is blockade of inhibitory neurons (why stage 2 is excitement phase)

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40
Q

What S/S would be seen in stage 2 of anesthesia?

A 
Breathing erratic (rate & volume)
Divergent of pupils/pupils dilated
Secretion of tears - may cry
Swallowing/retching/vomiting
*pt would move during skin incision
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41
Q

What should you do to the patient during stage 2?

A

NOTHING - DO NOT MESS WITH THE PATIENT DURING THIS PHASE.

Will have hyper reactions

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42
Q

What will happen if you try to extubatne during stage 2?

A

good chance pt will laryngospasm

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43
Q

What happens to HR and BP during stage 2?

A

both increase

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44
Q

What is movement into stage 3 characterized by?

A

return of regular respiration, excitement subsides, pupils become centered, cough, gag and eyelid reflex are absent.

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45
Q

What happens to PP in the brain that allows for suppression of spinal reflex activity or skeletal muscle relaxation.

A

PP in the brain further increases giving rise to progressive depression of the ascending (sensory) pathways of the reticular activating system

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46
Q

What happens to excitatory and inhibitory channels during stage 3?

A

Decreasing excitatory neurons

Exciting inhibitory neurons

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47
Q

What happens in stage 4 of anesthesia?

A

PP in the brain continues to rise and there is depression of the vital medullary centers = profound respiratory and cardiac depression.

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48
Q

signs of stages of anesthesia will occur more slow with (higher or lower) soluble drugs

A

higher

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49
Q

Loss of reflexes and return of regular respiration means what?

A

surgical anesthesia is beginning (stage 3)

50
Q

Signs of light anesthesia:

A 
Increase respirations
Increase BP, HR
Increase muscle tone
Swallowing, coughing returns
Tear formation (abolished at surgical stage)
51
Q

Signs of deep anesthesia:

A

Hypotension
Bradycardia
Diaphragmatic breathing (agonal)
Pupils become dilated, lack luster

52
Q

What is the definition for MAC

A

partial pressure of an inhalation anesthetic at 1 atmosphere that prevents skeletal muscle movement in response to a surgical skin incision in 50% of the patient population

53
Q

Where is MAC measured?

A

In the alveoli

54
Q

True or False: High blood flow to the brain ensures a rapid equilibration between brain and alveoli.

A

True

55
Q

True or False: MAC is a reliable indicator of dose and potency of an anesthetic.

A

True

56
Q

The lower the MAC, the more _____ the agent and the higher the ______ partition coefficient.

A

potent

oil : gas

57
Q

What determining MAC, are we looking at the Fi or Fe?

A

Fe - this shows what is in the brain

MAC of Sevo is 2.2 - when Fe reaching 2.2, the MAC will be 1

58
Q

What are some factors that decrease MAC? (don’t need as much gas)

A

Hypoxia: decreased PaO2 causes narcosis itself
Anemia: decreased PaO2, decreases MAC
Hypotension: decreased MAP decreases MAC
Drugs: lithium, narcotics, sedatives, calcium channel blockers, acute alcohol ingestion
Pregnancy: due partially to hormonal influences
Age: elderly, decreased CBF, CMRO2

59
Q

Factors that increase MAC:

increased agent needed

A

Age: infants, MAC usually greatest in newborn due to BMR
Hyperthermia
Drugs: alcohol, barbiturates, narcotics, etc., chronic use

60
Q

How do these affect MAC?
Hypothermia
Hyperthermia

A

Hypothermia decreased MAC

Hyperthermia decreases MAC >42*C

61
Q

How do these affect MAC?
Young
Eldery

A

Young increased MAC

Eldery decreased MAC

62
Q

How do these affect MAC?
Acute ETOH
Chronic ETOH

A

Acute ETOH decreased MAC

Chronic ETOH increases MAC

63
Q

How do these affect MAC? PaO2
< 40 mmHg
> 95 mm Hg

A

< 40 mmHg decrease MAC

> 95 mm Hg decreases MAC caused by

64
Q

How does anemia affect MAC

A

HCT <10% decreases MAC

65
Q

How does hyper/hypothyroid effect MAC?

A

No change

66
Q

How does hypotension effect MAC?

A

MAP < 40 mm Hg decrease

67
Q

Does hypercalcemia increase or decrease MAC?

A

Decreases MAC

68
Q

What happens to MAC:
Hypernatremia
Hyponatremia

A

Hypernatremia increase
Hyponatremia decrease

(caused by altered CSF)

69
Q

Does pregnancy increase or decrease MAC?

A

Decrease MAC

70
Q

What drugs decrease MAC?

A 
ALL LA except cocaine
Opioids
Ketamine
Barbiturates d
Benzodiazepines
Verapamil
Lithium 
Sympatholytics
           -Methyldopa decrease
           -Reserpine decrease
           -Clonidine 
Sympathomimetic
           -Amphetamine (Chronic)
71
Q

What drugs increase MAC?

A

Sympathomimetic

       - Amphetamine (acute)
       - Cocaine
       - Ephedrine
72
Q

MAC allows potency to be compared

A

among different anesthetics

73
Q

At a MAC of 1.2 - how many patient should not move with surgical incision?

A

95%

74
Q

At a MAC of 1.3 - how many patient should not move with surgical incision?

A

99%

75
Q

Define MAC-awake

A

the minimum alveolar concentration at which 50% of subjects will respond to the command “open your eyes”.

76
Q

End tidal concentration is usually associated with a loss of recall and is the equivalent of

A

1/3 MAC

77
Q

What would my MAC-awake be
Iso
Sevo
Des

A

Iso 0.1-0.2
Sevo 0.2-0.3
Des 1.5-2

78
Q

Define MAC-bar

A

MAC necessary to block adrenergic response to skin incision.

HR/BP/MAP

79
Q

Define MAC intubation

A

similar to MAC–BAR in that its values exceed the anesthetic requirements for surgical skin incision.

80
Q

MAC values for different anesthetics are

A

additive

0.5 MAC of Nitrous oxide plus 0.5 MAC of isoflurane has the same effect as 1 MAC of any inhaled anesthetic.

81
Q

One variable that restricts MACs application is the frequency at which surgical patient receive

A

NMB

Mac is still important because NMB don’t do anything other than stop them form moving

82
Q

How do I get to 50% MAC of NO if I want flow rates to be 2L

A

1L NO/ 1L O2

83
Q

How do I get to 70% MAC of NO if I want flow rates to be 2L

A

1.3L NO/ 0.7L O2

84
Q

What is the highest percent I can get NO to on the AGM?

A

70%

85
Q

What are some ways to estimate anesthetic depth?

A

VS
End-tidal gas
Immobility

86
Q

What phase of pharmokokinetics is: absorption from alveoli into the systemic circulation

A

Uptake

87
Q

What phase of pharmokokinetics is: cardiac output and blood flow

A

Distribution

88
Q

What phase of pharmokokinetics is exhaled unchanged by lungs or minimally metabolized in the liver

A

Elimination

89
Q

What does variable bypass mean?

A

Some air/oxygen bypasses the vaporizer, some goes down into vaporizer to pick up gas

90
Q

how is PA (Alveolar) determined?

A

determined by input (delivery) into the alveoli minus uptake (loss) of the drug from the alveoli into the pulmonary arterial blood.

91
Q

What 3 things control input to the Alveoli

A
  1. Inspired partial pressure
  2. Alveolar ventilation
  3. Characteristics of the breathing system
92
Q

How does alveolar ventilation change input into the Alveoli?

A

Ventilate too slow - not keeping a high concentration of gas in the alveoli for the blood to take to the brain. (slow induction)

Ventilate “quicker” - keeps the concentration in the alveoli higher (speeds up induction)

93
Q

What 3 things control uptake into pulmonary arterial blood

A
  1. blood:gas solubility
  2. CO
  3. Alveolar - venous partial pressure
94
Q

True or False: All gases have similar quick onset

A

True

rate of rise graph

95
Q

Which gas has the quickest onset

A

Nitrous oxide

96
Q

What 3 thins control uptake from arterial blood to brain

A
  1. brain:blood coefficient
  2. CBF
  3. Arterial venous partial pressure difference
97
Q

explain concentration effect

A

A high PI during induction is necessary to increased anesthetic delivered to alveoli to speed up induction

98
Q

What is concentration effect aka

A

over-pressurization

99
Q

Using the concentration effect, what would we turn Des up to on induction

A

normal MAC 6 - turn up to 12 to get quick effect

100
Q

What is the second gas effect?

A

The ability of the first gas to accelerate the that rate of PA increase of a concurrently administered 2nd gas

101
Q

Does the second gas effect occur in conjunction or independently with the concentration effect?

A

independently

102
Q

Can an anesthetic gas dissolve into tubing?

A

yes - the rubber/plastic has some solubility

103
Q

Does a low vapor pressure change fast or slow to a gas state

A

slow to change from liquid to gas

104
Q

Why does des have to be heated and use a Tec6 vaporizor

A

Des is so close to ATM pressure that they had a hard time maintaining a certain concentration

(doubled to 1400 PP) and now there is a bigger difference from atmospheric pressure

105
Q

True or False: High blood solubility means that a large amount of inhaled anesthetic must be dissolved (undergo uptake) in the blood before equilibrium with the gas phase is reached.

A

True

106
Q

High CO ______ induction

A

slows

107
Q

Slow CO ________ induction

A

speeds up

108
Q

How does a right to left shunt effect induction?

A

Slows it down because the blood is bypassing the lungs

109
Q

How does a left to right shunt effect induction?

A

not clinically significant

110
Q

Alveolar:venous and Tissue blood take how many time constants to reach equillibrium?

A

3 time constants

111
Q

Why do rich vessels equilibrate quicker?

A

Vessel right groups are only 10% of body mass but they receive 75% CO and 75% perfusion

112
Q

During emergence, what will lead to a slow wake up and anesthetic transferring back into tissues from the blood?

A

hypoventilation and low FGF

not getting pulled out quick enough so it recirculates

113
Q

What is diffusion hypoxia

A

When NO is rapidly discontinued at the end of a case, it is still in the body. It diffuses across the alveoli/capillary membrane diluting O2 concentration

114
Q

How can diffusion hypoxia be avoided?

A

Can be is easily avoided by administering 100% O2 for 5-10 minutes after the N2O has been discontinued.

115
Q

How does the duration of a procedure effect emergence?

A

Gas build up in fat, muscle, bone

Now we have to get it out of all these areas

116
Q

How does temperature effect emergence?

A

cold – anesthetic dissolved more in blood

117
Q

How does obesity effect emergence?

A

Adipose tissue not highly perfused so it takes even longer to get off

can reanesthetized when it moves out of adipose tissue

118
Q

What is deep extubation?

A

Extubating in stage 3 when the patient has no protective reflexes

119
Q

What is an awake extubation?

A

Extubating when the patient is awake and can protect their own airway

120
Q

What is contest sensitive half time?

A

elimination of inhaled anesthetics depends on the length of administration AND the solubility in the blood and tissues

Pharmacology (8 decks)

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