Inhalational Anesthesia Flashcards
Can nitrous oxide alone be used as a general anesthetic?
No, but it can be when combined with things such as opioids.
How do isoflurane, desflurane, and sevoflurane relate molecular-ly to diethyl ether? One important functional property that sets them apart?
They are fluorinated / halogenated diethyl ether derivatives (or very similar structures, at least). Unlike ether, they aren’t flammable, which is important when using electrocautery in the OR.
What are 4 clinically relevant differences between inhaled anesthetic agents?
Potency
Solubility
Pungency
Cost
What are 5 things that you want your general anesthetic to do?
Hypnosis
Amnesia
Immobility / Muscle Relaxation / Akinesia
Blunting of Autonomic Responses
What kinetics for inhaled anesthetics are desirable?
Quickly induce anesthetic state, but be readily reversed when the gas is removed.
What effects do inhaled anesthetics have on brain metabolism? How about on synchrony?
Decreased metabolism. Increased synchrony (like sleeping?).
How do you achieve a controlled, constant dosage of inhaled drug being delivered to the patient?
By a vaporizer. (not an ether-soaked cloth)
What are the 3 compartments into which anesthetic will go? Which can hold the most drug?
Vessel Rich Group (Brain, liver, kidney)
Fat (biggest, lowest blood flow)
Muscle (intermediate blood flow)
How are anesthetic gases eliminated from the body?
By exhalation, mainly. Very little metabolic breakdown.
What variable that varies between tissue types greatly affects absorption?
Solubility. Inhaled drugs tend to be highly soluble in fat and less soluble in brain.
How does solubility in fat affect recovery time?
Less soluble in fat, less recovery time.
Three reasons why anesthetic gases that are less soluble perform better?
Less potent - (better? worse? unclear)
Faster onset / “offset”
Less accumulation in tissue / fat
How do inhaled anesthetic drugs affect cerebral blood flow?
They increase it.
Is the spinal cord affected by inhaled anesthetics?
Yes. Response to stimuli is blocked.
4 effects of inhaled anesthetics on respiration?
Bronchodilation
Increased respiratory rate
Decreased tidal volume
Decreased respiratory reflexes (i.e. RR won’t increase in response to low O2 / high CO2)
4 cardiovascular effects of inhaled anesthetics?
Decreased BP (vasodilation)
Blood redistributed from core to periphery (vasodilation)
Impairs autonomic reflexes to maintain BP (eg. carotid baroreceptor reflex)
Decreases contractile strength of heart muscle.
What’s the MAC? How is it used?
Minimum Alveolar Concentration: % of total gas that must be anesthetic in order to make 50% of patients not move in response to surgical incision.
Used as a starting point from which the dosage is adjusted for the patient.
3 factors other than MAC affecting the proper dose of inhaled anesthetic?
Intensity and type of surgical stimulus.
Age and medical condition of patient.
Concurrent use of other anesthetics (opioids, muscle relaxants).
What are 4 common problems with inhaled anesthesia?
Nausea and vomiting
Respiratory depression
Cardiovascular collapse
Inhibition of uterine contraction (post-delivery bleeding)
2 rare complications seen with inhaled anesthetics?
Malignant hyperthermia
Liver toxicity
1 controversial problem with anesthesia?
Neurotoxicity.
Are patients the only people who might be adversely affected by inhaled anesthetics?
No. They might harm the environment, esp. the ozone layer. (how about anesthesiologists, surgeons, nurses, and techs?)
What’s the mechanism of action of inhaled anesthetics?
Trick question. Nobody knows.
What’s the functional outcome of inhaled anesthetics, broadly speaking?
Disrupt normal patterns of neuronal transmission involved in consciousness, which we see on EEG.
What does the fact that that these gases work on flies, snakes, fish, and zebras tell us?
It works on evolutionarily ancient, conserved machinery.
What do we know about where, cellularly speaking, these drugs go?
They like membranes. It’s probably more about binding to proteins than altering membrane properties, though.
Is there just one receptor that inhaled anesthetics bind to?
No. They seem to bind to many.
Is there thought to be one receptor to which anesthetic gas binding is most important?
Yes. GABA-A appears to be pretty important.
Why are there suspicions that anesthetic gases pose cognitive risks?
Some animal models suggest reduced synapse formation after exposure.
Many anecdotal reports of “not feeling like self” after general anesthesia.
