Inhaled anesthetics 2: pharmacodynamics 2 Flashcards

1
Q

Modern theory of anesthetic action suggests inhaled anesthetics: (select 2)
a. interact with stereoselective receptors
b. stimulate the NMDA receptor
c. Produce immobility by binding in the dorsal horn of the spinal cord
d. facilitate GABA transmission

A

A. interact with stereoselective receptors
d. facilitate GABA transmission

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2
Q

The primary target of halogenated anesthetics in the brain is

A

the facilitation of the GABA-A receptor

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3
Q

The primary target of volatile anesthetics in the spinal cord is

A

stimulation of glycine channels and inhibition of NMDA receptors and sodium channels

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4
Q

Volatile anesthetics produce immobility in the ______ horn of the spinal cord.

A

ventral

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5
Q

As a general rule, volatile anesthetics either

A

stimulate inhibitory receptors or inhibit stimulatory receptors

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6
Q

The gaseous anesthetics (nitrous oxide and xenon) target

A

the NMDA receptor (antagonism) and the potassium 2P-channel (stimulation)

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7
Q

What inhibitory pathways do volatile anesthetics stimulate?

A

GABA-A receptor
potassium channels
Glycine channels

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8
Q

What stimulatory pathways do volatile anesthetics inhibit?

A

NMDA
nicotinic
sodium channels
dendritic spine function and motility

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9
Q

How do volatile anesthetics produce amnesia?

A

amygdala & hippocampus

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10
Q

Autonomic effects of volatile anesthetics are produced in the

A

pons & medulla

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11
Q

Analgesia is produced in the

A

spinothalamic tract

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12
Q

Immobility is produced in the

A

ventral horn of the spinal cord

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13
Q

Volatile anesthetics produce unconsciousness by interacting in the

A

cerebral cortex, thalamus, and reticular activating system

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14
Q

Regarding the modern halogenated anesthetics in the adult at 1 MAC:
a. QT interval increases
b. Heart rate decreases
c. systemic vascular resistance increases
d. mean arterial blood pressure increases

A

a. QT interval increases

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15
Q

Nitrous oxide __________MAP and ______________SVR by ____________

A

increases MAP & SVR by SNS activation

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16
Q

Current thinking disputes the theory of _______ steal. Volatile anesthetics precondition

A

coronary steal. precondition the myocardium and protect it against ischemia

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17
Q

Halogenated anesthetics ___ MAP in

A

reduce MAP in a dose-dependent fashion
(at equivalent doses, there’s little difference between agents)

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18
Q

Which halogenated agents increase heart rate?

A

isoflurane & desflurane (sevoflurane does not)

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19
Q

Which agent reduces SVR the least?

A

Sevoflurane

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20
Q

Halogenated decrease __________ in a dose-dependent fashion.

A

contractility & SVR

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21
Q

What are the cardiovascular effects of halogenated agents?

A

anesthetic preconditioning
vasodilation
cardiac dysrhythmias
myocardial depression

22
Q

In cardiac muscle and vascular smooth muscle, volatile anesthetics reduce ______ influx in the sarcolemma

A

Calcium 2+ influx and decrease Ca2+ release from the SR

23
Q

How do halogenated agents directly affect cardiac conduction?

A

decreased SA node automaticity
decreased conduction velocity through the AV node, His-Purkinje system, and ventricular conduction pathways
altered baroreceptor function
increased duration of myocardial repolarization by impairing the outward K+ current–> prolongs the QT interval

24
Q

Rapid increases in desflurane and to a lesser degree isoflurane cause

A

tachycardia

25
Q

How can desflurane & isoflurane lead to tachycardia?

A

pulmonary irritation–> SNS activation–> increased norepinephrine release–> beta 1 stimulation

26
Q

Volatile anesthetics increase ___________ blood flow in excess of

A

coronary; myocardial oxygen demand

27
Q

Potency of coronary artery vasodilation from greatest to least

A

isoflurane>desflurane>sevoflurane

28
Q

Regarding the modern halogenated anesthetics in the adult at 1 MAC:
a. minute ventilation increases
b. airway diameter decreases
c. dead space decreases
d. respiratory rate increases

A

d. respiratory rate increases

29
Q

The currently available halogenated anesthetics have the following effects on PaCO2:

A

hypercapnia
altered respiratory rate
increased apneic threshold
relaxation of the muscle leading to airway obstruction
bronchodilation

30
Q

How does hypercapnia with halogenated anesthetics occur?

A

hypercapnia through depression of the central chemoreceptor and respiratory muscles

31
Q

What altered respiratory pattern do halogenated agents produce?

A

decreased Vt and increased RR

32
Q

How to volatile anesthetics contribute to hypercarbia?

A

altering the respiratory pattern
impairing the response to carbon dioxide
impairing motor neuron output and muscle tone to the upper airway and thoracic muscles

33
Q

_______- can induce bronchoconstriction in asthmatics

A

Desflurane

34
Q

How does a decrease in response to carbon dioxide effect the carbon dioxide response curve?

A

shifts the CO2 response curve down and the right

35
Q

What is the apneic threshold?

A

the PaCO2 at which a patient is stimulated to breathe

36
Q

What are causes of a left-shift to the carbon dioxide response curve?

A

stimulates ventilation!
anxiety
surgical stimulation
metabolic acidosis
increased ICP
salicylates
aminophlie
doxapram

37
Q

What are the causes of right-shift to the carbon dioxide response curve?

A

depresses ventilation!
general anesthetics
opioids
metabolic alkalosis
denervation of peripheral chemoreceptors

38
Q

A right shift of the carbon dioxide response curve produces

A

respiratory acidosis

39
Q

A left shift of the carbon dioxide response curve produces

A

a respiratory alkalosis

40
Q

How do volatile anesthetics contribute to upper airway obstruction?

A

they cause relaxation of the genioglossus or tensor palatine muscles

41
Q

Which agent impairs the hypoxic ventilatory response the LEAST?
a. isoflurane
b. desflurane
c. sevoflurane
d. these drugs produce similar degrees of depression

A

b. desflurane

42
Q

Impaired response to acute hypoxemia occurs at

A

0.1 MAC

43
Q

Desflurane is the best volatile anesthetics choice for the patient who has

A

emphysema or sleep apnea because they rely on the hypoxic drive to breathe

44
Q

In contrast to their effects on the ventilatory response to CO2, ____ & _________ do not reverse depression of the hypoxic ventilatory drive

A

pain & surgical stimulation

45
Q

Volatile anesthetics impair the ________ for up to several hours after anesthesia

A

peripheral chemoreceptors

46
Q

The _________ provides the sensory arm of the hypoxic drive

A

glomus type 1 cells in the carotid bodies

47
Q

Because anesthetic metabolism is the source of reactive oxygen species, the patients that undergo the greatest amount of

A

biotransformation in the body inhibit the hypoxic drive the most (sevo>iso>des)

48
Q

A PaO2 of ________ is a stimulus that increases minute ventilation to restore arterial oxygenation.

A

<60 mmHg

49
Q

Where are the carotid baroreceptors located?

A

carotid sinus

50
Q

Where are the carotid chemoreceptors located?

A

carotid body