Inhaled anesthetics 2: pharmacodynamics 2 Flashcards
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. interact with stereoselective receptors
d. facilitate GABA transmission
The primary target of halogenated anesthetics in the brain is
the facilitation of the GABA-A receptor
The primary target of volatile anesthetics in the spinal cord is
stimulation of glycine channels and inhibition of NMDA receptors and sodium channels
Volatile anesthetics produce immobility in the ______ horn of the spinal cord.
ventral
As a general rule, volatile anesthetics either
stimulate inhibitory receptors or inhibit stimulatory receptors
The gaseous anesthetics (nitrous oxide and xenon) target
the NMDA receptor (antagonism) and the potassium 2P-channel (stimulation)
What inhibitory pathways do volatile anesthetics stimulate?
GABA-A receptor
potassium channels
Glycine channels
What stimulatory pathways do volatile anesthetics inhibit?
NMDA
nicotinic
sodium channels
dendritic spine function and motility
How do volatile anesthetics produce amnesia?
amygdala & hippocampus
Autonomic effects of volatile anesthetics are produced in the
pons & medulla
Analgesia is produced in the
spinothalamic tract
Immobility is produced in the
ventral horn of the spinal cord
Volatile anesthetics produce unconsciousness by interacting in the
cerebral cortex, thalamus, and reticular activating system
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. QT interval increases
Nitrous oxide __________MAP and ______________SVR by ____________
increases MAP & SVR by SNS activation
Current thinking disputes the theory of _______ steal. Volatile anesthetics precondition
coronary steal. precondition the myocardium and protect it against ischemia
Halogenated anesthetics ___ MAP in
reduce MAP in a dose-dependent fashion
(at equivalent doses, there’s little difference between agents)
Which halogenated agents increase heart rate?
isoflurane & desflurane (sevoflurane does not)
Which agent reduces SVR the least?
Sevoflurane
Halogenated decrease __________ in a dose-dependent fashion.
contractility & SVR
What are the cardiovascular effects of halogenated agents?
anesthetic preconditioning
vasodilation
cardiac dysrhythmias
myocardial depression
In cardiac muscle and vascular smooth muscle, volatile anesthetics reduce ______ influx in the sarcolemma
Calcium 2+ influx and decrease Ca2+ release from the SR
How do halogenated agents directly affect cardiac conduction?
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
Rapid increases in desflurane and to a lesser degree isoflurane cause
tachycardia
How can desflurane & isoflurane lead to tachycardia?
pulmonary irritation–> SNS activation–> increased norepinephrine release–> beta 1 stimulation
Volatile anesthetics increase ___________ blood flow in excess of
coronary; myocardial oxygen demand
Potency of coronary artery vasodilation from greatest to least
isoflurane>desflurane>sevoflurane
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
d. respiratory rate increases
The currently available halogenated anesthetics have the following effects on PaCO2:
hypercapnia
altered respiratory rate
increased apneic threshold
relaxation of the muscle leading to airway obstruction
bronchodilation
How does hypercapnia with halogenated anesthetics occur?
hypercapnia through depression of the central chemoreceptor and respiratory muscles
What altered respiratory pattern do halogenated agents produce?
decreased Vt and increased RR
How to volatile anesthetics contribute to hypercarbia?
altering the respiratory pattern
impairing the response to carbon dioxide
impairing motor neuron output and muscle tone to the upper airway and thoracic muscles
_______- can induce bronchoconstriction in asthmatics
Desflurane
How does a decrease in response to carbon dioxide effect the carbon dioxide response curve?
shifts the CO2 response curve down and the right
What is the apneic threshold?
the PaCO2 at which a patient is stimulated to breathe
What are causes of a left-shift to the carbon dioxide response curve?
stimulates ventilation!
anxiety
surgical stimulation
metabolic acidosis
increased ICP
salicylates
aminophlie
doxapram
What are the causes of right-shift to the carbon dioxide response curve?
depresses ventilation!
general anesthetics
opioids
metabolic alkalosis
denervation of peripheral chemoreceptors
A right shift of the carbon dioxide response curve produces
respiratory acidosis
A left shift of the carbon dioxide response curve produces
a respiratory alkalosis
How do volatile anesthetics contribute to upper airway obstruction?
they cause relaxation of the genioglossus or tensor palatine muscles
Which agent impairs the hypoxic ventilatory response the LEAST?
a. isoflurane
b. desflurane
c. sevoflurane
d. these drugs produce similar degrees of depression
b. desflurane
Impaired response to acute hypoxemia occurs at
0.1 MAC
Desflurane is the best volatile anesthetics choice for the patient who has
emphysema or sleep apnea because they rely on the hypoxic drive to breathe
In contrast to their effects on the ventilatory response to CO2, ____ & _________ do not reverse depression of the hypoxic ventilatory drive
pain & surgical stimulation
Volatile anesthetics impair the ________ for up to several hours after anesthesia
peripheral chemoreceptors
The _________ provides the sensory arm of the hypoxic drive
glomus type 1 cells in the carotid bodies
Because anesthetic metabolism is the source of reactive oxygen species, the patients that undergo the greatest amount of
biotransformation in the body inhibit the hypoxic drive the most (sevo>iso>des)
A PaO2 of ________ is a stimulus that increases minute ventilation to restore arterial oxygenation.
<60 mmHg
Where are the carotid baroreceptors located?
carotid sinus
Where are the carotid chemoreceptors located?
carotid body
