Pharmacology-General Anesthetics

Question 1

4 A’s of General Anesthesia

Answer 1

Amnesia, Analgesia, Akinesia, Autonomic & sensory reflex blockade

Question 2

What is defined as the concentration of an inhalant required for immobility of 50% of subjects exposed to a noxious stimulus?

Answer 2

Minimum alveolar concentration (MAC)

Question 3

Are the MAC values of different drugs additive?

Answer 3

Yes

Question 4

What does 1 MAC do? 1.3 MAC? 1.5-2 MAC?

Answer 4

50% of patients won’t move at surgical incision. 95% of patients will not move at surgical incision. Blocks 50% of patient autonomic responses.

Question 5

Stage I of anesthesia

Answer 5

Analgesia w/o amnesia

Question 6

Stage II of anesthesia

Answer 6

Delirious excitement

Question 7

Stage III of anesthesia

Answer 7

Surgical anesthesia

Question 8

Stage IV of anesthesia

Answer 8

Medullary depression

Question 9

What is the goal in delivering inhaled anesthetics?

Answer 9

The partial pressure in the alveolar gas (FA) = partial pressure in inspired gas (FI). When this ratio gets close to 1, you’ve reached steady state because the tissue can no longer take up more gas.

Question 10

What happens to speed of induction as minute ventilation is increased?

Answer 10

It also increases

Question 11

What is the blood:gas partition coefficient?

Answer 11

The difference in concentration between the inspired gas and blood at steady state.

Question 12

Why do you need very little nitrous oxide to put someone out? Why do you need lots of halothane?

Answer 12

It has low solubility. The blood does not absorb any of it, so most of what is delivered through the ventilator goes to the target tissue. Halothane needs lots of gas because it is very soluble.

Question 13

How does decreased cardiac output affect reaching your target blood concentration?

Answer 13

It increased the induction rate because most blood is going to your target tissue, the brain.

Question 14

How are most general anesthetic eliminated? How does solubility affect elimination.

Answer 14

Lungs. The lower the solubility the better it is eliminated. The liver gets rid of some

Question 15

Why would you never give a patient 2 MAC of volatile anesthetic?

Answer 15

You can drop their mean arterial pressure to 50.

Question 16

How does halothane affect SVR and CO?

Answer 16

It has a huge CO depression and little effect on SVR.

Question 17

Why are patients at higher risk for arrhythmias when given volatile anesthetics?

Answer 17

They sensitize the heart to the effects of NE

Question 18

How do volatile anesthetics affect respiration?

Answer 18

Increased RR, decreased ventilatory response to hypoxemia and decreased minute ventilation

Question 19

How to volatile anesthetic affect the brain?

Answer 19

Decreased metabolic O2 requirement, increased cerebral blood flow (may increase intracranial pressure)

Question 20

How do volatile anesthetics affect the kidneys and liver?

Answer 20

Blood flow to these organs is decreased.

Question 21

Inhalation of what anesthetic can cause malignant hyperthermia? How do you treat a patient with this?

Answer 21

Succinyl choline and other anesthetics. It is treated by giving dantrolene (Ca2+ channel blocker)

Question 22

What are the four classes of sedative hypnotics? What are these used for?

Answer 22

Barbituates, Etomidate, Propofol, Benzodiazepines (used to induce unconsciousness)

Question 23

What is the idea that the longer you infuse a drug, the longer it will take to eliminate it due to increased uptake by other tissues during infusion?

Answer 23

Context sensitive half time

Question 24

What is them most commonly used induction agent?

Answer 24

Propofol (works at GABA receptors)

Question 25

Why would you use etomidate over propofol?

Answer 25

It has minimal CV effects

Question 26

What induction agent might you use if someone is in shock?

Answer 26

Ketamine. It maintains blood pressure and heart rate.