Mm Chapter 7. Inhalation Anesthetics

Front 1

The study of the relationship between a drug's dose, tissue concentration, and elapsed time is called

Back 1

pharmacokinetics (how a body affects a drug).

Front 2

The study of drug action, including toxic responses, is called

Back 2

pharmacodynamics (how a drug affects a body).

Front 3

The greater the uptake of anesthetic agent, the greater the difference between inspired and alveolar concentrations, and the ....

Back 3

slower the rate of induction.

Front 4

Three factors affect anesthetic uptake:

Back 4

solubility in the blood, alveolar blood flow, and the difference in partial pressure between alveolar gas and venous blood.

Front 5

Low-output states predispose patients to

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overdosage with soluble agents, as the rate of rise in alveolar concentrations will be markedly increased.

Front 6

7 factors that speed induction also speed recovery:

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elimination of rebreathing, high fresh gas flows, low anesthetic-circuit volume, low absorption by the anesthetic circuit, decreased solubility, high cerebral blood flow, and increased ventilation.

Front 7

General anesthesia is 4 states

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reversible loss of consciousness,
analgesia of the entire body, amnesia, and some degree of muscle relaxation.

Front 8

The unitary hypothesis proposes that

Back 8

all inhalation agents share a common mechanism of action at the molecular level. This is supported by the observation that the anesthetic potency of inhalation agents correlates directly with their lipid solubility (Meyer–Overton rule).

Front 9

The minimum alveolar concentration (MAC) is

Back 9

is the alveolar concentration of an inhaled anesthetic that prevents movement in 50% of patients in response to a standardized stimulus (eg, surgical incision).

Front 10

Prolonged exposure to anesthetic concentrations of nitrous oxide can result in
2X

Back 10

bone marrow depression (megaloblastic anemia) and even neurological deficiencies (peripheral neuropathies and pernicious anemia).

Front 11

The course of general anesthesia can be divided into three phases:

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(1) induction, (2) maintenance, and (3) emergence.

Front 12

Although the mechanism of action of inhalation anesthetics remains unknown, it is assumed that their ultimate effect depends on attainment of a therapeutic tissue concentration in

Back 12

in the central nervous system

Front 13

The actual composition of the inspired gas mixture depends mainly on 3X

Back 13

the fresh gas flow rate, the volume of the breathing system, and any absorption by the machine or breathing circuit

Front 14

Tissues can be divided into four groups based on their solubility

Back 14

Vessel Rich
Muscle
Fat
Vessel Poor


The highly perfused vessel-rich group (brain, heart, liver, kidney, and endocrine organs) is the first to take up appreciable amounts of anesthetic.
Moderate solubility and small volume limit the capacity of this group, so it is also the first to fill (ie, arterial and tissue partial pressures are equal).

The muscle group (skin and muscle) is not as well perfused, so uptake is slower. In addition, it has a greater capacity due to a larger volume, and uptake will be sustained for hours. Perfusion of the fat group nearly equals that of the muscle group, but the tremendous solubility of anesthetic in fat leads to a total capacity (tissue/blood solubility x tissue volume) that would take days to fill. The minimal perfusion of the

vessel-poor group (bones, ligaments, teeth, hair, and cartilage) results in insignificant uptake.

Front 15

The concentration effect is more significant with___________ than with the volatile anesthetics, as the former can be used in much higher concentrations

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nitrous oxide

Front 16

Recovery from anesthesia depends on

Back 16

lowering the concentration of anesthetic in brain tissue

Front 17

Anesthetics can be eliminated 3 ways

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biotransformation, transcutaneous loss, or exhalation

Front 18

The most important route for elimination of inhalation anesthetics is

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alveolus

Front 19

diffusion hypoxia is prevented by

Back 19

prevented by administering 100% oxygen for 5–10 min after discontinuing nitrous oxide.

Front 20

MAC is a useful measure because it mirrors

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brain partial pressure, allows comparisons of potency between agents, and provides a standard for experimental evaluations

Front 21

The MAC values for different anesthetics are roughly _________.

Back 21

additive

Front 22

Roughly 1.3 MAC of any of the volatile anesthetics has been found to prevent movement in

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95% of patients

Front 23

One of the most striking is the ____% decrease in MAC per decade of age, regardless of volatile anesthetic.

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6%

Front 24

only inorganic anesthetic gas in clinical use

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Nitrous oxide (N2O; laughing gas)

Front 25

The circulatory effects of nitrous oxide are explained by

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its tendency to stimulate the sympathetic nervous system

Front 26

Hypoxic drive, the ventilatory response to arterial hypoxia that is mediated by

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peripheral chemoreceptors in the carotid bodies, is markedly depressed by even small amounts of nitrous oxide.

Front 27

nitrous oxide produces a mild elevation of intracranial pressure by...

Back 27

By increasing CBF and cerebral blood volume

Front 28

In fact, at high concentrations in hyperbaric chambers, nitrous oxide causes

Back 28

skeletal muscle rigidity

Front 29

Nitrous oxide appears to decrease renal blood flow by

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increasing renal vascular resistance. This leads to a drop in glomerular filtration rate and urinary output.

Front 30

Although nitrous oxide is insoluble in comparison with other inhalation agents, it is ____ times more soluble than nitrogen in blood.

Back 30

35

Front 31

Examples of conditions in which nitrous oxide might be hazardous include

Back 31

air embolism,
pneumothorax,
acute intestinal obstruction,
intracranial air (tension pneumocephalus following dural closure or pneumoencephalography),
pulmonary air cysts, intraocular air bubbles,
and tympanic membrane grafting.

Front 32

Because of the effect of nitrous oxide on the pulmonary vasculature, it should be avoided in patients with

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pulmonary hypertension.

Front 33

Halothane is a

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halogenated alkane

Front 34

Halothane

Cardiovascular

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Cardiac depression—from interference with sodium–calcium exchange and intracellular calcium utilization

Front 35

It is prudent to withhold halothane from patients 3X

Back 35

unexplained liver dysfunction

intracranial mass lesions because of the possibility of intracranial hypertension

Hypovolemic patients and some patients with severe cardiac disease

Front 36

Isoflurane

Cardiovascular

Back 36

Isoflurane causes minimal cardiac depression

Front 37

Cerebral
Isoflurane

Back 37

At concentrations greater than 1 MAC, isoflurane increases CBF and intracranial pressure

At concentrations greater than 1 MAC, isoflurane increases CBF and intracranial pressure

Front 38

Isoflurane is metabolized to

Back 38

trifluoroacetic acid

Front 39

Isoflurane

Contraindications

Back 39

Isoflurane presents no unique contraindications. Patients with severe hypovolemia may not tolerate its vasodilating effects.

Front 40

The structure of desflurane is very similar to that of isoflurane. In fact, the only difference is

Back 40

is the substitution of a fluorine atom for isoflurane's chlorine atom.

Front 41

Desflurane

blood/gas partition coefficient

Back 41

(0.42)

Front 42

Although desflurane is roughly ________ as potent as the other volatile agents, it is 17 times more potent than nitrous oxide.

Back 42

one-fourth

Front 43

MH Episodes

Treatment involves

Back 43

notifying the surgeon, discontinuing volatile agents or SCh,
giving 100% O2,
stopping anesthesia or continuing with nontriggers, dantrolene 2.5 mg/kg,
hyperventilation for respiratory acidosis,
bicarbonate for metabolic acidosis,
cooling for high temperatures,
diuresis for pigmenturia,
and calcium if there is dangerous hyperkalemia.

Front 44

how a body effects a drug

Back 44

-Pharmokinetics-

Front 45

how a drug affects a body

Back 45

Pharmacodynamics-

Front 46

4 Factors affecting inspiratory concentration

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fresh gas flow rate, volume of the breathing system, absorption by the machine or breathing circuit.

Front 47

Factors effecting alveolar concentration-

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The greater the uptake, the slower the rate of rise of alveolar concentration and the lower the FA:FI ratio. Avleolar partial pressure is important bc it determines the partial pressure of anesthetic in the blood and ultimately the brain. The greater the uptake of anesthetic agent, the greater the difference between inspired and alveolar concentrations, and the slower the rate of induction.

Front 48

3 factors that affect anesthetic uptake

Back 48

- solubility in the blood, alveolar blood flow, and the difference in partial pressure between alveolar gas and venous blood.

Front 49

Equilibrium is defined as

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equal partial pressure in two phases. For example, the blood/gas partition coefficient of N20 at 37 degress celsius is 0.47. At equilibrium, 1 ml of blood contains 0.47 as much N20 as does 1ml of alveolar gas even though partial pressures are same.

Front 50

Low output states predisposes patients to

Back 50

overdosage with soluble agents.

Front 51

The transfer of anesthetic from blood to tissue is determined by three factors:

Back 51

tissue solubility of the agent, tissue blood flow, and the difference in partial pressure between arterial blood and tissue.

Front 52

-Tissues can be divided into 4 groups based on their solubility and blood flow:

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1. Highly perfused vessel rich group ( brain, heart, liver, kidney, and endocrine organ.) this group is first to fill.
2. muscle group (skin and muscle)-not as well perfused, so uptake slower. Larger volume as well.
3. fat
4. vessel poor group which is minmial perfusion (ie bones, ligaments, teeth, hair, cartilage).

Front 53

Second gas effect-

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a high concentration of N20 will augment not only its own uptake but theoretically that of a concurrent administered volatile anesthetic. M and M states second gas effect is probably insignificant.

Front 54

3 Factors effecting elimination

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biotransformation, transcutaneous loss, or exhalation.

Front 55

7 -Factors that speed recovery

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elimination of rebreathing,
high fresh gas flows,
low anesthetic-circuit volume,
low absorption by the anesthetic circuit,
decreased solubilty,
high cerebral blood flow,
and increased ventilation

Front 56

Diffusion hypoxia-

Back 56

Elimination of N20 is so rapid that alveolar O2 and Co2 are diluted. You can prevent it by giving 100% O2 for 5-10 min after discontinuing N20.

Front 57

-The MAC

Back 57

(minimum alveolar concentration) of an inhaled agent is the alveolar concentration that prevents 50% of patients to move with a standard stimulus. MAC mirrors brain partial pressure, which makes it a good tool. 1.3 MAC reduces movement with 95% of patients.

Front 58

-MAC decreases____ per decade of age, regardless what volatile anesthetic is used.

Back 58

6%

Front 59

N20 tends to stimulate

Back 59

sympathetic nervous system. Because N2) increases endogenous catecholamine levels, it may be associated with higher incidence of epinephrine induced arrhythmias

Front 60

Do not give N20 to
__________ due to tetragenic effects

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pregnant people

Front 61

-N20 decreases MAC by aprox. _____%

Back 61

50%

Front 62

Do not give these 6 patients N20

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air embolism,
pneumothorax,
acute intestinal obstruction,
intracranial air (tension pneuocephalus following closure or pneumoenephalography,
pulmonary air cysts,
intraocular air bubbles, tympanic membrane grafting.

Front 63

halothane sesnitizes the heart to

Back 63

to the arrhythmogenic effects of epinephrine, so that doses of epinephrine above 1.5 mcg/kg should be avoided.

Front 64

Apnic threshold

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PACO2 at which a patient remains apnic.

Front 65

Halothane Hepatitis

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is extremely rare (1 in 35,000 cases). Risks include multiplie exposures, middle aged obese women, familial predisposition to halothane toxicity. Hold halothane with anyone that has unexplained liver dysfunction

Front 66

Isolurane- FYI

Back 66

Cardiac output is maintained by a rise in hear rate due to partial preservation of carotid baroflexes. Conflicting reports on coronary steal sydnrome. (which may cause myocardial ischemia during episodes of tachycardia or drops in perfusion pressure. Some Anesthesia providers avoid iso with patients that have CAD due to this theory.
-At 2 MAC Iso produces an electrically silent EEG.

Front 67

Desflurane- FYI

Back 67

-low solubility of desflurane causes a rapid wash in and washout of the drug. Wake-up time is 50% less longer than ISO wake-up time. Desflurane is roughly ¼ as potent as the other volatile agents, it is 17 times more potent than N20. High vapor pressure (681 mm hg) and short duration, moderate potency are all characteristics of Des.
-Rapid increase in desflurane can cause elevated catecholamines and increased HR. Unlike Isoflurane, Desflurane does not increase coraonary artery blood flow.
-Desflurand (more than other agents) can be degraded by desiccated CO2 absorbent into potentially significant levels of carbon monoxide.
-Desflurane emergence is associated with delerium in some pediatric patients

Front 68

Rapid increase in desflurane can cause

Back 68

elevated catecholamines and increased HR

Front 69

Desflurand (more than other agents) can be degraded by desiccated CO2 absorbent into potentially significant levels

Back 69

levels of carbon monoxide.

Front 70

Sevoflurane FYI

Back 70

- nonpungent, good for inhalational induction. Also can be associated with delerium with pediatric patients.
-Sevo may prolong QT interval
-Sevo is not associated with increased HR (like des and iso)
-Barium hydroxide can degrade SEVO, producing nephrotoxic compound A (proven in rat studies) keep fresh gas flow a 2l, and do not administer to patients with kidney insufficiency.

Front 71

anatomic dead space=

Back 71

1ml/kg. Which is aprox 70 ml pre breath for normal person

Front 72

Equipment dead space=

Back 72

Compliance X pressure
= approx 200ml/breath