Inhalant Anesthesia Flashcards
what is vapor pressure?
partial pressure of gaseous phase when in equilibrium with liquid phase
what is the vapor pressure of isoflurane?
240mmHg
32%
what is the basic purpose of the anesthesia machine?
allow you to control the amount of vapor you deliver to the patient
is there conservation of therapeutic dose (MAC) of inhalant anesthetics across species?
yes
what is the definition of MAC?
minimum alveolar concentration required to prevent movement in 50% of the patients
what is the MAC of isoflurane in a dog?
1.4
what is the MAC of sevoflurane in a dog?
2.3
what are some drugs that reduce MAC?
acepromazine
alpha 2 agonists
ketamine
opioids- not horses
benzodiazepines
lidocaine
what does it mean that a drug is MAC sparing?
drug reduces MAC: lower vaporizer setting needed
how does hypothermia impact MAC?
decreases MAC: 5% per degree of celsius
how does age affect MAC?
increased age decreases MAC
how does higher cardiac output affect MAC?
prevents drug from loading at high enough concentration in blood: slows onset of action
what is the concentration of inhalant in inspired gas with a rebreather determined by?
vaporizer setting
how much anesthetic is left in exhaled gas
what percentage of total gas is fresh vs exhaled
which gas is pungent and irritating to mucosa?
isoflurane
what are the effects of inhalant anesthetics on the CNS?
increase intracranial pressure
CNS depressants
if you spill less than 30ml of inhalant, what should you do?
wipe up and discard rag outside
are volatile liquid anesthetic drugs flammable?
no
what is sevoflurane vapor pressure?
180 mmHg
25%
what are the positives of using inhalants instead of injectable anesthetics?
predictable, reliable, infinitely adjustable anesthesia
rapid onset and recovery- no metabolism
co-deliver with oxygen so generally good oxygenation
conservation of therapeutic dose across species
easier to create steady state of anesthesia
at ________ MAC, cardiovascular depression becomes greater and greater
> 2x
does 1.5xMAC of isoflurane result in the same depth of anesthesia as 1.5xMAC of sevoflurane?
yes
what are the MACs for isoflurane and sevoflurane for a cat?
isoflurane: 1.6
sevoflurane: 2.6
how does minute volume affect uptake of inhalants?
higher minute volume brings more inhalant into lungs
what is the respiratory minute volume of a dog or cat?
180 ml/kg/min
is sevoflurane or isoflurane faster onset?
sevoflurane: less soluble
also faster recovery
what is compound A?
sevoflurane interacts with CO2 absorbent to produce
only relevant at fresh gas flow below 15 ml/kg/min
which gas may be least impactful on intracranial pressure?
sevoflurane
how do inhalants increase intracranial pressure?
impair autoregulation of blood flow
hypoventilation contributes to increases in intracranial blood flow
how does the respiratory pattern change under inhalants?
changes from slow/deep to rapid/shallow
what are the cardiovascular affects of inhalants?
cardiovascular depression- dose dependent
myocardial depression decreases cardiac output
vasodilation
how much of the inhalants are metabolized by the liver?
isoflurane: 0.2%
sevoflurane: 5%
how do inhalants mainly cause adverse effects on the liver?
causing low cardiac output
what are the renal effects of inhalants?
reduce cardiac output which may reduce renal blood flow
autoregulation may be affected
nephrons may be damaged by reduced cardiac output
