Inhalant Anesthesia

Question 1

Why is inhalant anesthesia used?

Answer 1

• predictable effects (narcosis, muscle relaxation, no analgesia)
• rapid adjustment of anesthetic depth
• minimal metabolism

Question 2

What is saturated vapor pressure?

Answer 2

the maximum administration percentage of vapor

Question 3

What is the blood-gas partition coefficient?

Answer 3

describes the amount of anesthetic in the blood vs. alveolar gas at equal partial pressure

Question 4

What are the features of low blood-gas PC?

Answer 4

• less anesthetic dissolved in blood at equal partial pressure (more in alveoli)
• affects brain faster
• short induction and recovery

Question 5

What are the features of a high blood-gas PC?

Answer 5

• more anesthetic dissolved in blood at equal partial pressure (less in alveoli)
• affects the brain slower
• long induction and recovery

Question 6

How can you increase gas delivery to alveoli?

Answer 6

increase inspired anesthetic concentration
- increase vaporizer setting
- increase fresh gas flow
increase alveolar ventilation
- increase minute ventilation
- decrease dead space ventilation

Question 7

How can you decrease removal of gas from alveoli?

Answer 7

• decrease blood solubility of anesthetic
• decrease cardiac output
• decrease alveolar-venous anesthetic gradient

Question 8

What is MAC?

Answer 8

minimum alveolar concentration of an anesthetic that prevents movement in 50% of patients exposed to a noxious stimulant

Question 9

What are the MAC values for Isoflurane and Sevoflurane in the dog?

Answer 9

Iso% 1.3

Sevo% 2.3

Question 10

What causes an increase in MAC?

Answer 10

• hyperthermia
• hypernatremia
• drugs causing CNS stimulation

Question 11

What causes a decrease in MAC?

Answer 11

• hypothermia
• hyponatremia
• drugs causing CNS depression
• MAP < 50 mmHg
• PaO2 < 40 mmHg
• PaCO2 > 95 mmHg
• pregnancy
• increased age

Question 12

What are the cardiovascular effects of volatile anesthetics?

Answer 12

• decreased CO, BP, systemic vascular resistance, and contractility
• no change/increased heart rate

Question 13

What are the respiratory effects of volatile anesthetics?

Answer 13

• decreased ventilation
• respiratory arrest at 1.5-3 MAC
• bronchodilation
• Des and Iso have irritating odor

Question 14

What are the neurologic effects of volatile anesthetics?

Answer 14

• increased ICP at > 1 MAC
• decreased cerebral metabolic rate
• immobility
• suppress seizure activity

Question 15

What are the renal effects of volatile anesthetics?

Answer 15

• decrease GFR and renal blood flow

- Sevo produces compound A

Question 16

What are the hepatic effects of volatile anesthetics?

Answer 16

• reduce liver blood flow and O2 delivery

- Halothane can cause hepatotoxicity

Question 17

What is malignant hyperthermia?

Answer 17

• myopathy occurring in genetically predisposed animals from exposure to inhalant anesthesia
• uncontrolled muscle contractions lead to hyperthermia, resulting in death

Question 18

What anesthetic-related complications can occur?

Answer 18

• hypotension
• hypoventilation
• hypothermia

Question 19

What values of MAP indicate hypotension in small and large animals?

Answer 19

Sm: <60 mmHg
Lg: <70 mmHg

Question 20

What problems can occur with a closed pop-off?

Answer 20

• increased pressure in lungs, decreased venous return, decreased CO
• clinical signs: apnea, bradycardia, fading Doppler signal leading to pulmonary arrest