Inhalation Anesthetics

Question 1

What can raise the apneic threshold?

Answer 1

Anesthetics (volatile agents, narcotics, propofol, versed, etc.) raise the apneic threshold

Question 2

How can you lower the apneic threshold?

Answer 2

Pain

Question 3

What is a normal hypoxic drive in a normal patient?

Answer 3

PaO2 of 60mmHg

Question 4

MAC?

Answer 4

The patient is 50% likely to move if they’re exhaling the MAC percentage of agent, MAC reflects potency

Question 5

Does it take more gas to prevent movement of awareness?

Answer 5

Movement

Question 6

A patient is inhaling 0.7 MAC of Des. What is the percentage they’re exhaling?

Answer 6

4.2%

Question 7

A patient is exhaling 1.2 MAC of Sevo. What is the percentage they’re exhaling?

Answer 7

2.4%

Question 8

0.6 MAC N20 + 1.2 MAC Sevo = _____MAC?

Answer 8

1.8 MAC

Question 9

1.2% Des + 20% N2O = _____ MAC

Answer 9

.4 MAC

Question 10

MAC Awake (assumes no stimulation)

Answer 10

0.4 MAC

Question 11

MAC Reliable awareness prevention (if narcotics are used)

Answer 11

0.8 MAC

Question 12

MAC Reliable awareness prevention (even without narcotics)

Answer 12

1.0 MAC

Question 13

50% chance of movement (without paralytics)

Answer 13

1.0 MAC

Question 14

5% chance of movement (without paralytics)

Answer 14

1.3 MAC

Question 15

What are two reasons why volatile agents are given

Answer 15

1. To prevent movement
2. To prevent awareness

Question 16

Factors that decrease MAC (5)

Answer 16

1. IV anesthetics
2. Old age (4-6% per decade over age of 40)
3. ACUTE alcohol intoxication
4. Pregnancy
5. Temperature related factors (Hypothermia, mild hyperthermia)
6. Blood related factors (Hypoxia, hypercarbia, hypotension, anemia)

Question 17

Factors that increase MAC (4)

Answer 17

“Young Hot Salty Alcoholics”

1. Young
2. Hot (extreme hyperthermia >42C, burn patients)
3. Salty (hypernatremia)
4. Alcoholics (chronic alcohol/drug abuse)

Question 18

What does the blood gas coeffecient tell you?

Answer 18

How well soluble the agent is in the blood

Question 19

Neurological effects of volatile agents

Answer 19

1. Dilates the cerebral vasculature, increases CBF, and increases ICP
2. Can cause emergence delerium in kids
3. Decreases the possibility of seizures
4. Decreases the cerebral metabolic rate of oxygen (CMRO2)

Question 20

Cardiac effects of volatile agents

Answer 20

1. Decreases cardiac contractility
2. Systemic vasodilation
3. Coronary vasodilation

Question 21

Respiratory effects of volatile agents

Answer 21

1. Rapid, shallow breathing, causes CO2 to increase
2. Increase a patient’s apneic threshold
3. Decreases a patient’s hypoxic drive
4. Cause bronchodilation

Question 22

Other effects of volatile agents

Answer 22

1. Decreases renal blood flow
2. Decreases hepatic blood flow
3. Prolongs muscle relaxants
4. Associated with PONV
5. All trigger malignant hyperthermia (MH)
6. Inhibits “non-shivering thermogenesis” in pediatric patients

Question 23

Nitrous oxide contraindications

Answer 23

1. Laryngeal/pharyngeal/facial surgery with a laser
2. Ophthalmic surgery
3. Patients with severe COPD
4. Cardiopulmonary bypass surgery
5. Abdominal surgeries
6. Inner ear surgeries
7. 1st trimester of pregnancy
8. Neurosurgery situations