Inhalant Anesthesia

Question 1

what is vapor pressure?

Answer 1

partial pressure of gaseous phase when in equilibrium with liquid phase

Question 2

what is the vapor pressure of isoflurane?

Answer 2

240mmHg
32%

Question 3

what is the basic purpose of the anesthesia machine?

Answer 3

allow you to control the amount of vapor you deliver to the patient

Question 4

is there conservation of therapeutic dose (MAC) of inhalant anesthetics across species?

Answer 4

yes

Question 5

what is the definition of MAC?

Answer 5

minimum alveolar concentration required to prevent movement in 50% of the patients

Question 6

what is the MAC of isoflurane in a dog?

Answer 6

1.4

Question 7

what is the MAC of sevoflurane in a dog?

Answer 7

2.3

Question 8

what are some drugs that reduce MAC?

Answer 8

acepromazine
alpha 2 agonists
ketamine
opioids- not horses
benzodiazepines
lidocaine

Question 9

what does it mean that a drug is MAC sparing?

Answer 9

drug reduces MAC: lower vaporizer setting needed

Question 10

how does hypothermia impact MAC?

Answer 10

decreases MAC: 5% per degree of celsius

Question 11

how does age affect MAC?

Answer 11

increased age decreases MAC

Question 12

how does higher cardiac output affect MAC?

Answer 12

prevents drug from loading at high enough concentration in blood: slows onset of action

Question 13

what is the concentration of inhalant in inspired gas with a rebreather determined by?

Answer 13

vaporizer setting
how much anesthetic is left in exhaled gas
what percentage of total gas is fresh vs exhaled

Question 14

which gas is pungent and irritating to mucosa?

Answer 14

isoflurane

Question 15

what are the effects of inhalant anesthetics on the CNS?

Answer 15

increase intracranial pressure
CNS depressants

Question 16

if you spill less than 30ml of inhalant, what should you do?

Answer 16

wipe up and discard rag outside

Question 17

are volatile liquid anesthetic drugs flammable?

Answer 17

no

Question 18

what is sevoflurane vapor pressure?

Answer 18

180 mmHg
25%

Question 19

what are the positives of using inhalants instead of injectable anesthetics?

Answer 19

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

Question 20

at ________ MAC, cardiovascular depression becomes greater and greater

Answer 20

> 2x

Question 21

does 1.5xMAC of isoflurane result in the same depth of anesthesia as 1.5xMAC of sevoflurane?

Answer 21

yes

Question 22

what are the MACs for isoflurane and sevoflurane for a cat?

Answer 22

isoflurane: 1.6
sevoflurane: 2.6

Question 23

how does minute volume affect uptake of inhalants?

Answer 23

higher minute volume brings more inhalant into lungs

Question 24

what is the respiratory minute volume of a dog or cat?

Answer 24

180 ml/kg/min

Question 25

is sevoflurane or isoflurane faster onset?

Answer 25

sevoflurane: less soluble
also faster recovery

Question 26

what is compound A?

Answer 26

sevoflurane interacts with CO2 absorbent to produce
only relevant at fresh gas flow below 15 ml/kg/min

Question 27

which gas may be least impactful on intracranial pressure?

Answer 27

sevoflurane

Question 28

how do inhalants increase intracranial pressure?

Answer 28

impair autoregulation of blood flow
hypoventilation contributes to increases in intracranial blood flow

Question 29

how does the respiratory pattern change under inhalants?

Answer 29

changes from slow/deep to rapid/shallow

Question 30

what are the cardiovascular affects of inhalants?

Answer 30

cardiovascular depression- dose dependent
myocardial depression decreases cardiac output
vasodilation

Question 31

how much of the inhalants are metabolized by the liver?

Answer 31

isoflurane: 0.2%
sevoflurane: 5%

Question 32

how do inhalants mainly cause adverse effects on the liver?

Answer 32

causing low cardiac output

Question 33

what are the renal effects of inhalants?

Answer 33

reduce cardiac output which may reduce renal blood flow
autoregulation may be affected
nephrons may be damaged by reduced cardiac output