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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
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?
The returning venous blood will also begin to have higher partial pressure as it returns to the lungs.
26
As venous partial pressure rises, is there more or less picked up from the alveoli?
less
27
The rise of PP in the tissues depends on 2 things:
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.)
28
What are the 4 categories of tissue groups?
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)
29
As uptake in the tissue begins to reach partial pressure in the blood, what happens to the uptake in the tissues?
It begins to slow
30
The rate of rise FA/Fi is the most rapid with which anesthetic agents?
the least soluble agents | NO, Des, Sevo
31
Which agents have a slower rate of rise
the more soluble agents | Iso, Halothane
32
What are the 4 stages of anesthesia?
1. Stage of analgesia 2. State of delirium or excitement 3. Stage of anesthesia 4. Stage of depression
33
When does stage 1 of anesthesia begin?
begins with the administration of anesthesia and ends with the loss of consciousness.
34
What is happening in stage 1 with the gas tension and dorsal horn activity?
Brain gas tension is very low. Dorsal horn activity decreases and there is decreased synaptic transmission in the spinothalamic tract.
35
What S/S would be seen in stage 1 of anesthesia?
``` Increased RR/Shallow breaths normal eye control and pupils Secretion of tears No laryngeal reflexes Normal muscle tone ```
36
When will you start to lose eyelid reflex?
End of stage 1
37
What happens to stage 1 with the addition of IV anesthetics?
jump past stage 1
38
When does stage 2 of anesthesia begin and end?
beings at loss of consciousness to beginning of surgical anesthesia
39
What happens in stage 2 with PP in the brain and inhibitory ions?
PP of brain rises | there is blockade of inhibitory neurons (why stage 2 is excitement phase)
40
What S/S would be seen in stage 2 of anesthesia?
``` Breathing erratic (rate & volume) Divergent of pupils/pupils dilated Secretion of tears - may cry Swallowing/retching/vomiting *pt would move during skin incision ```
41
What should you do to the patient during stage 2?
NOTHING - DO NOT MESS WITH THE PATIENT DURING THIS PHASE. Will have hyper reactions
42
What will happen if you try to extubatne during stage 2?
good chance pt will laryngospasm
43
What happens to HR and BP during stage 2?
both increase
44
What is movement into stage 3 characterized by?
return of regular respiration, excitement subsides, pupils become centered, cough, gag and eyelid reflex are absent.
45
What happens to PP in the brain that allows for suppression of spinal reflex activity or skeletal muscle relaxation.
PP in the brain further increases giving rise to progressive depression of the ascending (sensory) pathways of the reticular activating system
46
What happens to excitatory and inhibitory channels during stage 3?
Decreasing excitatory neurons Exciting inhibitory neurons
47
What happens in stage 4 of anesthesia?
PP in the brain continues to rise and there is depression of the vital medullary centers = profound respiratory and cardiac depression.
48
signs of stages of anesthesia will occur more slow with (higher or lower) soluble drugs
higher
49
Loss of reflexes and return of regular respiration means what?
surgical anesthesia is beginning (stage 3)
50
Signs of light anesthesia:
``` Increase respirations Increase BP, HR Increase muscle tone Swallowing, coughing returns Tear formation (abolished at surgical stage) ```
51
Signs of deep anesthesia:
Hypotension Bradycardia Diaphragmatic breathing (agonal) Pupils become dilated, lack luster
52
What is the definition for MAC
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
Where is MAC measured?
In the alveoli
54
True or False: High blood flow to the brain ensures a rapid equilibration between brain and alveoli.
True
55
True or False: MAC is a reliable indicator of dose and potency of an anesthetic.
True
56
The lower the MAC, the more _____ the agent and the higher the ______ partition coefficient.
potent oil : gas
57
What determining MAC, are we looking at the Fi or Fe?
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
What are some factors that decrease MAC? (don't need as much gas)
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
Factors that increase MAC: | increased agent needed
Age: infants, MAC usually greatest in newborn due to BMR Hyperthermia Drugs: alcohol, barbiturates, narcotics, etc., chronic use
60
How do these affect MAC? Hypothermia Hyperthermia
Hypothermia decreased MAC | Hyperthermia decreases MAC >42*C
61
How do these affect MAC? Young Eldery
Young increased MAC | Eldery decreased MAC
62
How do these affect MAC? Acute ETOH Chronic ETOH
Acute ETOH decreased MAC | Chronic ETOH increases MAC
63
How do these affect MAC? PaO2 < 40 mmHg    > 95 mm Hg
< 40 mmHg decrease MAC | > 95 mm Hg decreases MAC caused by
64
How does anemia affect MAC
HCT <10% decreases MAC
65
How does hyper/hypothyroid effect MAC?
No change
66
How does hypotension effect MAC?
MAP < 40 mm Hg decrease
67
Does hypercalcemia increase or decrease MAC?
Decreases MAC
68
What happens to MAC: Hypernatremia Hyponatremia
Hypernatremia increase Hyponatremia decrease (caused by altered CSF)  
69
Does pregnancy increase or decrease MAC?
Decrease MAC
70
What drugs decrease MAC?
``` ALL LA except cocaine Opioids Ketamine Barbiturates d Benzodiazepines Verapamil Lithium Sympatholytics -Methyldopa decrease -Reserpine decrease -Clonidine Sympathomimetic -Amphetamine (Chronic) ```
71
What drugs increase MAC?
Sympathomimetic - Amphetamine (acute) - Cocaine - Ephedrine
72
MAC allows potency to be compared
among different anesthetics
73
At a MAC of 1.2 - how many patient should not move with surgical incision?
95%
74
At a MAC of 1.3 - how many patient should not move with surgical incision?
99%
75
Define MAC-awake
the minimum alveolar concentration at which 50% of subjects will respond to the command “open your eyes”.
76
End tidal concentration is usually associated with a loss of recall and is the equivalent of
1/3 MAC
77
What would my MAC-awake be Iso Sevo Des
Iso 0.1-0.2 Sevo 0.2-0.3 Des 1.5-2
78
Define MAC-bar
MAC necessary to block adrenergic response to skin incision. HR/BP/MAP
79
Define MAC intubation
similar to MAC–BAR in that its values exceed the anesthetic requirements for surgical skin incision.
80
MAC values for different anesthetics are
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
One variable that restricts MACs application is the frequency at which surgical patient receive
NMB Mac is still important because NMB don’t do anything other than stop them form moving
82
How do I get to 50% MAC of NO if I want flow rates to be 2L
1L NO/ 1L O2
83
How do I get to 70% MAC of NO if I want flow rates to be 2L
1.3L NO/ 0.7L O2
84
What is the highest percent I can get NO to on the AGM?
70%
85
What are some ways to estimate anesthetic depth?
VS End-tidal gas Immobility
86
What phase of pharmokokinetics is: absorption from alveoli into the systemic circulation
Uptake
87
What phase of pharmokokinetics is: cardiac output and blood flow
Distribution
88
What phase of pharmokokinetics is exhaled unchanged by lungs or minimally metabolized in the liver
Elimination
89
What does variable bypass mean?
Some air/oxygen bypasses the vaporizer, some goes down into vaporizer to pick up gas
90
how is PA (Alveolar) determined?
determined by input (delivery) into the alveoli minus uptake (loss) of the drug from the alveoli into the pulmonary arterial blood.
91
What 3 things control input to the Alveoli
1. Inspired partial pressure 2. Alveolar ventilation 3. Characteristics of the breathing system
92
How does alveolar ventilation change input into the Alveoli?
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
What 3 things control uptake into pulmonary arterial blood
1. blood:gas solubility 2. CO 3. Alveolar - venous partial pressure
94
True or False: All gases have similar quick onset
True | rate of rise graph
95
Which gas has the quickest onset
Nitrous oxide
96
What 3 thins control uptake from arterial blood to brain
1. brain:blood coefficient 2. CBF 3. Arterial venous partial pressure difference
97
explain concentration effect
A high PI during induction is necessary to increased anesthetic delivered to alveoli to speed up induction
98
What is concentration effect aka
over-pressurization
99
Using the concentration effect, what would we turn Des up to on induction
normal MAC 6 - turn up to 12 to get quick effect
100
What is the second gas effect?
The ability of the first gas to accelerate the that rate of PA increase of a concurrently administered 2nd gas
101
Does the second gas effect occur in conjunction or independently with the concentration effect?
independently
102
Can an anesthetic gas dissolve into tubing?
yes - the rubber/plastic has some solubility
103
Does a low vapor pressure change fast or slow to a gas state
slow to change from liquid to gas
104
Why does des have to be heated and use a Tec6 vaporizor
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
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.
True
106
High CO ______ induction
slows
107
Slow CO ________ induction
speeds up
108
How does a right to left shunt effect induction?
Slows it down because the blood is bypassing the lungs
109
How does a left to right shunt effect induction?
not clinically significant
110
Alveolar:venous and Tissue blood take how many time constants to reach equillibrium?
3 time constants
111
Why do rich vessels equilibrate quicker?
Vessel right groups are only 10% of body mass but they receive 75% CO and 75% perfusion
112
During emergence, what will lead to a slow wake up and anesthetic transferring back into tissues from the blood?
hypoventilation and low FGF not getting pulled out quick enough so it recirculates
113
What is diffusion hypoxia
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
How can diffusion hypoxia be avoided?
Can be is easily avoided by administering 100% O2 for 5-10 minutes after the N2O has been discontinued.
115
How does the duration of a procedure effect emergence?
Gas build up in fat, muscle, bone | Now we have to get it out of all these areas
116
How does temperature effect emergence?
cold – anesthetic dissolved more in blood
117
How does obesity effect emergence?
Adipose tissue not highly perfused so it takes even longer to get off can reanesthetized when it moves out of adipose tissue
118
What is deep extubation?
Extubating in stage 3 when the patient has no protective reflexes
119
What is an awake extubation?
Extubating when the patient is awake and can protect their own airway
120
What is contest sensitive half time?
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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