22 General Anesthesia I

Question 1

What is general anesthesia?

Answer 1

A pharmacologically-induced state of unconsciousness, amnesia, relaxation of skeletal muscles (immobility), and reduction in autonomic responses

Question 2

What is amnesia?

Answer 2

Lack of recall

Question 3

What is unconsciousness (hypnosis)?

Answer 3

Impaired perception and response to stimuli

Question 4

What is analgesia?

Answer 4

The absence of pain sensation without loss of consciousness

Question 5

What is premedication?

Answer 5

Sedation/anxiolysis before induction

Question 6

What is induction?

Answer 6

Initiation of unconsciousness

Question 7

What is maintenance?

Answer 7

The period during surgery

Question 8

What is emergence?

Answer 8

Regaining consciousness

Question 9

What is recovery?

Answer 9

Stabilization

Question 10

What are the uses of volatile anesthetics?

Answer 10

Used for maintenance of anesthesia and for induction in some cases

Question 11

What effects do volatile anesthetics produce (analgesia/amnesia/etc)?
Are they safe?

Answer 11

Amnesia
muscle relaxation
suppression of hemodynamic responses to surgical stimulus
Yes, safe

Question 12

What are the 6 necessary characteristics of volatile anesthetics?

Answer 12

Absence of flammability
vaporized at ambient temperature
potent (low inspired percentage required)
low solubility in blood
minimal tissue metabolism
produce skeletal muscle relaxation

Question 13

In what drug class will some drugs have these additional good characteristics?
suppress activation of sympathetic NS
non irritating to airway
low level of myocardial depression
absence of hepatic and renal toxicity

Answer 13

volatile anesthetics

Question 14

What is partial pressure?

What is the significance for a volatile anesthetic?

Answer 14

PP of a gas is expressed as a percent of all gases in a given volume
It is used to measure dosage

Question 15

Where is partial pressure of a volatile anesthetic measured? What is that measurement estimating

Answer 15

It is measured in the alveoli, which is estimating the level in the brain

Question 16

What does MAC stand for?

What is its significance?

Answer 16

MAC = minimum alveolar concentration
1 MAC = concentration of inhaled anesthetic that prevents skeletal muscle movements in response to a noxious stimulus in 50% of patients
It is a relative measure of depth of anesthesia and can be used to compare inhaled anesthetics
Useful index of potency

Question 17

What is the significance of ~1.3MAC?

Answer 17

It prevents skeletal muscle movement in nearly all patients during surgery

Question 18

How does the potency of NO compare to other inhaled anesthetics (-fluranes)?
Approximately what is its MAC?

Answer 18

Nitrous oxide is drastically less potent.

Its MAC is ~100 (105-110)

Question 19

Which -flurane has the lowest MAC?
Desflurane
Isoflurane
Sevoflurane

Answer 19

Isoflurane - MAC=1.15

Question 20

Which -flurane has the highest MAC?
Desflurane
Isoflurane
Sevoflurane

Answer 20

Desflurane - MAC=7.25

Question 21

How does the solubility of volatile anesthetics change its affects?
Which is more preferable for a short surgery? High or low solubility?

Answer 21

Solubility is critical for the onset and elimination
High solubility = slow onset and offset
Low solubility = fast onset and offset
Low solubility more preferable for short surgery

Question 22

How does solubility affect the partial pressure of an anesthetic gas in the blood? Why is this significant?

Answer 22

Anesthetic gases dissolved into the blood result in a decreased partial pressure in the blood. The partial pressure of the anesthetic gas in the brain produces general anesthesia
Anesthetic solubility = blood:gas partition coefficient

Question 23

T/F

A high solubility means a greater blood gas partition coefficient

Answer 23

True

Anesthetic solubility = blood:gas partition coefficient

Question 24

T/F

A high blood:gas partition coefficient means a greater effect on the brain than a low blood:gas partition coefficient.

Answer 24

False

High blood:gas partition coefficient -> high solubility -> lower concentration of gas having effect in brain

Question 25

Which -flurane has the highest blood-gas partition coefficient?
Desflurane
Isoflurane
Sevoflurane

Answer 25

Isoflurane - 1.4

Question 26

Which -flurane has the lowest blood-gas partition coefficient?
Desflurane
Isoflurane
Sevoflurane

Answer 26

Desflurane - 0.42

Question 27

Which -flurane does NO have the closest blood-gas partition coefficient to?

Answer 27

Desflurane - 0.42

NO - 0.46

Question 28

How is nitrous oxide often used because of its very high MAC?

Answer 28

as an adjunct to the potent volatile anesthetic agents

Question 29

What receptors do volatile anesthetics affect? Do they primarily affect CNS or PNS?

Answer 29

Facilitate inhibitory neurotransmission at GABA and glycine receptors. Reduce excitatory glutamate transmission
CNS

Question 30

How can the EEG be used with anesthesia?

Answer 30

It approximates anesthetic depth

Question 31

Drugs strongly affecting what CNS receptors are used for anesthesia?

Answer 31

GABA and glutamate receptors

Question 32

Drugs affecting what receptors have an effect on the properties of the administered anesthesia?

Answer 32

NE, ACh, and Hist

MAC sparing

Question 33

What are general side effects/complications of volatile anesthetics?

Answer 33

Side effects:
Respiratory depressants
Decrease arterial blood pressure (decrease HR, CO, and systemic vascular resistance) - good for tachycardia during surgery but problem with hemorrhage hypotension)
Complications:
Malignant hyperthermia

Question 34

What is malignant hyperthermia?

Answer 34

In susceptible individuals, anesthetics trigger increases in skeletal muscle metabolism, which overwhelms the body’s capacity to supply O2, remove CO2, and regulate body temp

Question 35

What drugs can cause malignant hyperthermia?

Answer 35

Volatile anesthetics and succinylcholine

Question 36

What drug treats malignant hyperthermia?

Answer 36

Dantrolene