Module 4 Flashcards
Inhaled Anesthetics
1
Q
When discussing inhalational agents, what is the relationship between a higher blood/gas partition coefficient and its’ lipid solubility?
A
Higher lipophilicity
2
Q
Administered via lungs
Kinetics are the same as for any drug
Other factors may come into play
A
Inhalation agents
3
Q
Factors determining partial pressure gradiant necessary for establishment of anesthesia: Transfer of inhaled anesthetics from Anesthetic Machine to Alveoli
A
- Inspired partial pressure
- Alveolar ventilation
- Characteristics of anesthetic breathing system
4
Q
Factors determining partial pressure gradiant necessary for establishment of anesthesia: Transfer of inhaled anesthetics from Alveoli to Arterial Blood
A
- Blood-gas partition coefficient
- Cardiac output
- Alveolar-to–venous partial pressure difference
5
Q
Factors determining partial pressure gradiant necessary for establishment of anesthesia: Transfer of inhaled anesthetic from Arterial Blood to Brain
A
- Brain-blood partition coefficient
- Cerebral blood flow
- Arterial-to-venous partial pressure difference
6
Q
When a gradient is established between your machine and the patient via the lungs, the lungs in turn…..
A
Equilibrates with the blood, which in turn will equilibrate with brain causing the desired effect
7
Q
Most important factor in determining potency of inhalation agents
A
Blood-gas partition coefficient
8
Q
Function of solubility of the agent in blood and is a measure of how quickly the inhalation anesthetic equilibrates between the lungs and blood and ultimately the target site in the brain
A
Blood-gas partition coefficient
9
Q
Blood-gas partition coefficient is _________ proportional to induction rate, the higher the number the longer the induction and thus the longer the emergence
A
INVERSELY
10
Q
In the case of inhalational agents, what is the relationship between a higher lipophilicity and agent potency?
A
Higher potency
11
Q
With inhalational agents, the higher the blood/gas partition coefficient in the agent the _________ the solubility.
A
Higher
12
Q
Inhalational agents with high solubility have _________ uptake/onset of anesthetic effect
A
Slower onset/uptake
13
Q
A high blood/gas partition coefficient generally would mean a ________ MAC (Mean Alveolar Concentration).
A
Low MAC.
14
Q
When considering the effects of inhalational agents on induction it is helpful to consider that what is happening in the lungs/alveoli is likely happening in the _________.
A
Brain
15
Q
A mnemonic that identifies inhaled anesthetics in order of highest blood/gas partition-lipophilicity-solubility- and therefore slowest uptake.
A
“HI-SE” (H-alothane, I-soflurane, Se-voflurane) Not included are Desflurane and N20, in that order.
16
Q
Name inhaled anesthetics in order of fastest uptake.
A
N20, Desflurane, Sevoflurane, Isoflurane, Halothane (“HI-SE” in reverse)
17
Q
In reference to the elimination rate with inhaled anesthetic agents, the higher the plasma drug concentration the _________ the rate of elimination is.
A
Faster
18
Q
Inhaled anesthetic agents follow what type of pharmacokinetics?
A
First-order
19
Q
Order of recovery times from inhaled anesthetics from fastest to slowest.
A
N20-Desflurane-Sevoflurane-Isoflurane-Halothane. “HI-SE” in reverse. (inverse relationship between partition coefficient and uptake and recovery)
20
Q
Increased cardiac output does what to the speed of induction?
A
Slows it down with all inhaled anesthetics.
21
Q
How does hypothermia affect induction with inhaled anesthetics?
A
Slows induction.
22
Q
How does a high minute ventilation affect inhaled anesthesia induction?
A
Makes for a faster induction
23
Q
What is the MAC and blood:gas coefficient for N20?
A
104%, 0.47
24
Q
What is the MAC and blood:gas coefficient for Desflurane?
A
6.6%, 0.42
25
What is the MAC and blood:gas coefficient for Sevoflurane?
1.8%, 0.65
26
What is the MAC and blood:gas coefficient for Enflurane?
1.63%, 1.8
27
What is the MAC and blood:gas coefficient for Isoflurane?
1.17%, 1.4
28
What is the MAC and blood:gas coefficient for Halothane?
0.75%, 2.3
29
Factors which slow elimination of inhalational anesthetic agents
- High tissues solubility
- Longer anesthetic times
- Low gas flows
30
What causes diffusion hypoxia after an anesthetic case?
N2O elimination is so rapid that alveolar O2 and CO2 concentration is diluted.
31
How do you prevent diffusion hypoxia after an anesthetic case?
Administer 100% oxygen for 5-10 minutes after discontinuing N2O. Can be done through face mask or nasal cannula.
32
True/False High fresh gas flows will increase elimination of inhalational anesthetic agents.
True
33
What CNS effects are decreased with inhaled anesthetics?
- Mental function and awareness
- Cerebral metabolic oxygen requirements
- Seizure Threshold (specifically Enflurane)
34
What CNS effects are increased with inhaled anesthetics?
- Cerebral blood flow
- Intracranial pressure
- Cerebrospinal fluid production (can be increased or not changed)
35
Other CNS effects caused by inhaled anesthetics.
- Electroencephalogram (EEG)
- Evoked potentials (Don't want agents too high during a neuro case)
- Cerebral protection
36
The concentration of an agent at 1 atmosphere of pressure that prevents skeletal muscle movement in response to supramaximal painful stimulus in 50% of patients.
Mean Alveolar Concentration (MAC)
37
What are the physiological factors that can alter MAC levels?
- Hyperthermia
- True Redheads
- Catecholamines
- Increased cardiac ouput
38
Flow delivered (FD) of volatile agents is dependent on what two factors?
- Type of vaporizer
| - Flowmeter settings
39
Inspired gas concentration (FI) is dependent on what three factors?
- Fresh gas flow rate (vaporizer, flowmeter)
- Breathing circuit volume
- Absorption by machine or breathing circuit
40
Alveolar concentration (FA) is dependent on what two factors?
- Uptake
| - Second gas effect (theoretically)
41
Uptake is determined by what five factors?
- Pulmonary circulation (whisking away)
- Minute volume
- Inspired anesthetic concentration
- Volume delivered
- Cardiac output
42
How is the minute volume determined?
RR x TV (Respiratory Rate x Tidal Volume)
43
How is cardiac output determined?
PR X SV (Pule Rate x Stroke Volume)
44
What concept is assumed to be explained by the reaching equilibrium between the alveoli-arterial circulation-and target tissue in the CNS
The mechanism of action of inhalational anesthetics
45
A higher delivery of flow (FD), leads to a higher inspired concentration of gas (FI), leads to an increased rate of rise in alveolar concentration (FA), ultimately leading to??
- Faster induction
| - Faster induction/recovery
46
Why can alveolar concentration (FA) never approach inspired concentration (FI) (FA/FI<1.0)?
- Uptake, pulmonary circulation ("whisking away effect")
47
Three factors that affect anesthetic uptake?
- Solubility in blood
- Alveolar blood flow
- Partial pressure difference between alveolar gas and venous blood
48
Alveolar partial pressure determines partial pressure of anesthetic in the blood and ultimately...
Partial pressure of anesthetic in the brain/CNS, creates clinical effect.
49
Anesthetic gases need to pas through what three pressure gradient to enact their clinical effect?
Alveoli-Blood-Brain
50
What attribute of volatile agents determines their solubility?
Blood/gas partition coefficient
51
Because they are less readily taken up by blood, insoluble agents have ______ inductions?
- Faster
| - Alveolar concentration builds
52
What is the relative solubility of anesthetic agents in air, blood, and tissues?
Blood/gas partition coefficient
53
The higher the blood/gas partition coefficient the greater the _______ by pulmonary circulation.
Uptake
54
What inhaled anesthetics produce similar and dose-dependent decreases in mean arterial pressure when administered to healthy human volunteers?
Halothane, isoflurane, desflurane, and sevoflurane
55
In contrast with volatile anesthetics, nitrous oxide produces what changes to systemic blood pressure?
Either no change or modest increases in systemic blood pressure
56
What three specific inhaled agents cause decrease in systemic blood pressure due to a decrease in systemic vascular resistance?
isoflurane, desflurane, and sevoflurane
57
The decrease in blood pressure produced by halothane is due to?
A consequence of decreases in myocardial contractility and cardiac output.
58
What effect does Isoflurane, desflurane, and sevoflurane have on the HR?
Increases Heart Rate.
59
What inhaled agent causes decrease in cardiac output?
Halothane
60
What type of effect do all volatile anesthetic cause to patient’s left ventricular stroke volume?
The calculated left ventricular stroke volume was similarly decreased by 15% to 30% for all the volatile anesthetics
61
Which inhaled agents increase CVP?
Halothane, isoflurane, and desflurane increase right atrial pressure (central venous pressure)
62
Which volatile anesthetics decrease blood pressure principally by decreasing systemic vascular resistance?
Isoflurane, desflurane, and sevoflurane
63
Which volatile anesthetic decreases systemic blood pressure by decreasing CO?
Halothane
64
Does Nitrous oxide have any effect in systemic vascular resistance?
Nitrous oxide does not change systemic vascular resistance.
65
Which agent decreases the dose of epinephrine necessary to evoke ventricular cardiac dysrhythmias?
Alkane derivative Halothane
66
Effect on coronary blood flow caused by Volatile anesthetics?
Volatile anesthetics induce coronary vasodilation
67
Peripheral vasodilation produced by isoflurane, desflurane and sevoflurane is undesirable in patients with?
Aortic Stenosis
68
Brief exposure to a volatile anesthetic (isoflurane, sevoflurane, desflurane) can activate KATP channels resulting in?
Cardioprotection (anesthetic preconditioning) against subsequent prolonged ischemia and myocardial reperfusion injury.
69
How do inhaled anesthetics affect the frequency of breathing?
Inhaled anesthetics, except for isoflurane, produce dose-dependent increases in the frequency of breathing.
**(Isoflurane doesn’t increase frequency at a concentration of >1 MAC).**
70
How do Volatile anesthetics affect ventilatory response to CO2?
Volatile anesthetics produce dose-dependent depression of ventilation characterized by decreases in the ventilatory response to carbon dioxide and increases in the PaCO2.
71
How is the ventilatory response to hypoxemia affected by inhaled anesthetics?
All inhaled anesthetics, including nitrous oxide, profoundly depress the ventilatory response to hypoxemia.
72
Risk factors for developing bronchospasm during anesthesia?
Young age (<10 years), perioperative respiratory infection, endotracheal intubation, and the presence of COPD.
73
Isoflurane and sevoflurane produce bronchodilation in patients with?
COPD
74
Vasoconstrictor on the hepatic circulation?
Halothane
75
Hepatic blood flow and hepatic artery blood flow is maintained while portal vein blood flow is increased by using which agents?
Sevoflurane, isoflurane and desflurane.
76
How do inhaled anesthetics affect intrinsic clearance by hepatic metabolism of drugs such as propranolol?
Intrinsic clearance by hepatic metabolism of drugs such as propranolol is decreased by 54% to 68% by inhaled anesthetics
77
How do volatile anesthetics affect hepatotoxicity?
Postoperative liver dysfunction has been associated with most volatile anesthetics, with halothane receiving the most attention.
78
Risk factors commonly associated with halothane hepatitis?
Include female gender, middle age, obesity, and multiple exposures to halothane
79
Clinical manifestations of halothane hepatitis?
Eosinophilia, fever, rash, arthralgia, and prior exposure to halothane
80
What factors slow elimination of inhalational anesthetic agents?
Exhalation
Bio-transformation
Transcutaneous loss
81
Recovery from anesthesia depends on
Lowering the anesthetic concentration in the brain
82
True or False
| Factors that increase induction also increase recovery
True
83
In regards to concentration:
| Effects of uptake can be lessened by
Increasing the inspired concentration
Stoelting ch 4, pg 104 5ed
84
In regards to concentration:
| A higher inspired concentration results in
A disproportionately concentration higher alveolar concentration
85
Does Higher FD and thus higher FI increase or decrease the rate of rise of FA
Increases
86
True or False
| The higher the FI, the more rapidly the FA approaches the FI.
True
Stoelting ch 4, pg 104 5ed
87
True or False
| The higher FI provides anesthetic molecule input to offset uptake and thus speeds the rate at which the FA increases
True
Stoelting ch 4, pg 104 5ed.
88
What is Alveolar blood flow essentially equal to?
Cardiac Output
89
Perfusion but no ventilation
Shunting
90
Ventilation but no perfusion
Dead Space
91
As CO increases, how is anesthetic uptake, alveolar pressure, and induction affected?
Anesthetic uptake Increases, the rise in alveolar pressure slows, and induction is prolonged
92
Patients with a low cardiac output are at risk for?
Overdosage with more soluble agents
93
The transfer of anesthetic agent from blood to tissues is determined by:
- Tissue solubility of anesthetic agent
- Tissue blood flow – brain will perfuse and uptake more than the bone
- Partial pressure difference between arterial blood and tissue – facilitate from blood to tissue
94
Alveolar (gas) to venous (blood) partial pressure differences depend on what gradient?
Tissue uptake
95
Due to what effect can higher than anticipated levels of volatile anesthestic do to CO?
Lower CO due to its myocardial depressant effect
96
Name the four tissues groups based on their solubility and blood flow
Vessel-rich group
Muscle group
Fat group
Vessel-poor group
97
Which organs make up the vessel-rich group.
Brain, heart, liver, kidneys, and endocrine organs
98
Which organs make up the muscle group.
Skin and muscle
99
what makes up the fat group.
adipose tissue
100
Which organs make up the Vessel-poor group.
Bone, ligaments, teeth, hair, and cartilage.
101
How can lowering of alveolar partial pressure by uptake can be countered?
Lowering of alveolar partial pressure by uptake can be countered by increasing alveolar ventilation
102
When will the effect of increasing ventilation be most obvious?
The effect of increasing ventilation will be most obvious in raising the FA/FI ratio for soluble anesthetics
103
How does increasing ventilation affect insoluble agents?
For insoluble agents, increasing ventilation has minimal effect (consider the FA/FI ratio…)
104
How does hyperventilation affect FA?
Hyperventilation increases the rate of rise of FA
105
How does hypoventilation affect FA?
Hypoventilation decreases the rate of rise of FA
106
Which Bronchus is more vertical, shorter, and wider? Left or right?
Right
107
What replaces cartilage as you move down the trachea into the bronchial tubes?
Smooth muscle [ think asthma]
108
What is the function of the tracheobronchial tree?
Conduct gas flow to and from the alveoli
109
Where does the tracheobronchial tree start and end?
It starts in the trachea and ends in the alveoli sacs
110
What I'd the function of the upper airway?
Humidify and filter inspired air
111
What generation does gas exchange begin in?
Generation 17-19
112
What is the alveoli surface area in the lungs?
Approx 750 square ft
300 million alveoli
113
Which inhaled anesthetic is a halogenated methyl ethyl ether with intermediate solubility in blood, high potency, and is an isomer of enflurane?
Isoflurane
114
Which inhaled anesthetic has a MAC of 1.17?
Isoflurane
115
Which inhaled anesthetic is a fluorinated methyl ethyl ether with a pungent odor?
Desflurane
116
Desflurane has ____ blood gas solubility, _______ induction and ________ recovery.
Low; prompt; rapid
117
What type of vaporizer does desflurane require?
A heated and pressurized one (Injector type- Tech 6).
118
What is the MAC of desflurane?
6.6
119
Which inhaled anesthetic is a fluorinated methyl isopropyl ether with minimal, non-pungent odor?
Sevoflurane
120
Which inhaled anesthetic produces compound A, bronchodilation, and the least amount of airway irritation?
Sevoflurane
121
What is sevoflurane’s MAC?
1.8
122
Which inhaled anesthetic is non-pungent, odorless, nonexplosive, and a chemically inert gas?
Xenon
123
Xenon is ______ __________, meaning the MAC levels differ depending on whether the patient is male or female.
Gender dependent; female MAC= 63, Male= 70s.
124
What are the advantages and disadvantages of xenon?
Advantages: Does NOT trigger malignant hyperthermia in susceptible swine, quick emergence, potent hypnotic and analgesic, no hemodynamic suppression (no decrease in HR or MAP)
Disadvantages: cost, availability, FDA guidelines for approval take a long time.
125
What are some characteristics of nitrous oxide?
Low molecular weight, Odorless, Nonflammable (but supports combustion)
126
What are possible adverse effects of nitrous oxide administration?
High-volume absorption in gas-containing spaces, Increase risk of PONV (especially if opioids are used), Ability to inactivate vitamin B12
127
In which types of patient cases should nitrous oxide NOT be used?
Closed eye injury cases and ear cases
128
What is the MAC of nitrous oxide?
104
129
Characteristics of halothane
Halogenated alkane derivative, sweet, nonpungent odor, and intermediate solubility in blood, high potency
130
How does enflurane affect the seizure threshold?
Decreases the threshold for seizures
131
Enflurane usage should be avoided in patients with a history of ______ and/or _______
Renal failure / seizures
132
Characteristics of enflurane
Halogenated methyl ethyl ether, intermediate solubility in blood (high potency), decreases the threshold for seizures and inorganic fluoride ions ---> nephrotoxic
133
Inhaled Anesthetics
| Functions of the Respiratory system?
- Gas Exchange
- Acid-base balance
- Phonation
- Pulmonary defence
- Metabolism
134
The most commonly administered anesthetics depend on the lungs for (___) and (____)
The most commonly administered anesthetics depend on the lungs for (UPTAKE) and (DISTRIBUTION)
135
anesthetic gases enter the Lung and alveoli then pass through what
Through the alveolar membrane into the blood, to the left side of the heart, and distributed to the tissue of the body
136
How do you children a very young age respond to the PharmaKinetics of inhaled anesthetics
They have an increase requirement of the drug
137
What is the order that the tissues are perfused for when anesthetics gas mixtures when they are administered
the brain, vital organs, muscles, skin, fat, and then connective tissues
138
What is the goal for inhaled anesthetics
To achieve brain concentration of inhaled anesthetic agents that promote amnesia and analgesia
139
What can influence PharmaKinetics of volatile anesthetics
Aging
