Inhalants

Question 1

What three inhalants are considered the “modern” anesthetic agents?

Answer 1

1) Sevoflurane
2) Desflurane
3) Isoflurane

Question 2

Do we know the molecular mechanism of action for inhalants?

Answer 2

not really, but we know some of the receptors they act on (GABAa, NMDA, glycine)

Question 3

Is inhalant anesthesia immobility brain or spinally mediated?

Answer 3

spinal

Question 4

gas

Answer 4

agent which exists in gaseous form at room temp and sea level

Question 5

vapor

Answer 5

agent which exists in liquid form at room temp and sea level

Question 6

Which undergoes a phase change - gas or vapor?

Answer 6

vapor

Question 7

What is the only inhalant anesthetic to NOT be considered a vapor?

Answer 7

nitrous oxide (N2O)

Question 8

blood:gas partition coefficient

Answer 8

ratio of the concentration of anesthetic in the blood vs. anesthetic in the alveoli

Question 9

solubility

Answer 9

measure of how soluble an anesthetic is in blood

Question 10

Are partition coefficient and solubility synonymous?

Answer 10

yes

Question 11

relationship between solubility and time to induce anesthesia

Answer 11

higher solubility = longer time to induce anesthesia

Question 12

Benefits of low solubility/blood:gas coefficient (3)

Answer 12

1) Faster induction
2) More control over depth
3) Faster recovery

Question 13

Minimum Alveolar Concentration (MAC)

Answer 13

MAC at 1atm that results in immobility in 50% of patients (the dose that keeps our patients under anesthesia)

Question 14

Relationship between solubility and MAC

Answer 14

Low solubility = high MAC

Question 15

Is MAC determined in sick or healthy animals?

Answer 15

healthy, with no other drugs!

keep this in mind because some conditions/drugs may affect (reduce) the MAC

Question 16

Isoflurane MAC in Cat & Dog & Horse

Answer 16

Cat = 1.63
Dog = 1.30
Horse = 1.31

Question 17

Sevoflurane MAC in Cat & Dog & Horse

Answer 17

Cat = 2.58
Dog = 2.36
Horse = 2.31

Question 18

Desflurane MAC in Cat & Dog & Horse

Answer 18

Cat = 9.79
Dog = 7.20
Horse = 8.06

Question 19

Vessel Reach Group (VRG)

Answer 19

organs which are highly vascularized (brain, lungs, heart, kidneys)

Question 20

What two tissues have the highest partition coefficients (therefore will suck up a lot of the anesthesia)?

Answer 20

muscle and fat

Question 21

relationship between cardiac output and induction time

Answer 21

higher cardiac output = longer induction time

Question 22

clearance

Answer 22

elimination of anesthetic from the CNS

Question 23

Fluoride-Associated Nephrotoxicity

Answer 23

previously seen with inhalant anesthetics but risk is minimal with modern inhalants

Question 24

effect of inhalants on cerebral blood flow

Answer 24

INCREASE (dose-dependent)

Question 25

Do inhalants cause vasoconstriction or vasodilation?

Answer 25

vasodilation

Question 26

effect of inhalants on intracranial pressure (ICP)

Answer 26

INCREASE

Question 27

apneic index

Answer 27

1.5-3 times the MAC indicates need for mechanical ventilation

Question 28

Do inhalants enhance or depress the respiratory system?

Answer 28

depress

Question 29

effect of inhalants on PaCO2

Answer 29

INCREASE

Question 30

Are inhalants bronchoconstrictors or bronchodilators?

Answer 30

bronchodilators!

Question 31

effect of inhalants on cardiac output

Answer 31

DECREASE (dose-dependent) due to decrease in stroke volume for decreased contractility

Question 32

effect of inhalants on arterial blood pressure

Answer 32

DECREASE (dose-dependent)

Question 33

Can inhalants cause renal effects?

Answer 33

YES but it is LIMITED to the time of anesthesia and is reversible

Question 34

Hepatic Effects of Inhalants

Answer 34

minimal (total flow maintained, some portal venous decrease)

Question 35

Malignant hyperthermia primarily affects what species?

Answer 35

pigs (halothane is the worst offender but all inhalants do it)

Question 36

Do inhalants cross the placenta?

Answer 36

yes

Question 37

Are inhalants safe to use in pregnant animals?

Answer 37

yes, but MAC should stay under 1.5 (dose dependent decreases in contractility and blood flow do occur starting at 0.5) inhalants exhaled by newborn upon birth