GenAne(Inhalants)-Gen Princ

Question 1

Which of the 5 effects of general anesthesia do the halogenated hydrocarbons lack?

Answer 1

Analgesia

Question 2

What are the two groups of inhaled anesthetics? Name them

Answer 2

Gases: nitrous oxide
Volatile liquids: MHIDES - "rane 
Methoxyflurane, 
Halothane, 
Isoflurane, 
Desflurane, 
Enflurane, 
Sevoflurane

Question 3

Which type of anesthetic is used in the maintanence of anesthesia after giving one IV?

Answer 3

Inhaled

Question 4

If an inhaled anesthetic is very soluble in blood, is it more likely to have a fast or slow rate of onset?

Answer 4

More soluble = slower onset

Less soluble = quicker onset

Question 5

If an inhaled anesthetic is highly liposoluble, is it likely to be more or less potent?

Answer 5

More liposolubility = more potent

Question 6

What effect do inhaled anesthetics have on the lungs?

Answer 6

Bronchodilation

Question 7

Inhaled anesthetics work by positive modulation of what two receptors?

Answer 7

GABAa and glycine - the two inhibitory ones

Question 8

Describe MAC for general anesthetics.

Answer 8

Concentration that results in immobility in 50% of patients when exposed to noxious stimuli like a surgical incision.
It is the standard comparison for potency of general anesthetics

Question 9

If the MAC of an anesthetic is low, what is that drugs potency like?

Answer 9

MAC is low for potent anestheticsHigh for less potent agents

Question 10

Increasing the MAC from 1.1 to 1.3 can change the percent of people immobilized from 50% to 95%. Explain how this is possible

Answer 10

Small changes in MAC make a large difference due to the steep dose response curve of inhalational anesthetics

Question 11

If you give 0.7 MAC of one drug and 0.3 MAC of another, how many total MAC effect do you see?

Answer 11

1.0 MAC - they are additive

Question 12

Which inhaled anesthic has the highest MAC? Lowest? What does this say about their potency?

Answer 12

Nitrous oxide has highest MAC - lowest potencyMethoxyflurane has lowest MAC - highest potency

Question 13

If a drug has a MAC of 104, what can you conclude about the uses of this drug in anesthesia? Which drug is it likely to be?

Answer 13

You’d need 104% of the drug to achieve anesthesia so it is not possible with this drug alone. It is likely nitrous oxide which is commonly combined in anesthesia

Question 14

What does the oil:gas partition coefficient tell you about a drug? If it goes up, how is potency affected? MAC?

Answer 14

It is a measure of liposolubility and because potency goes up with increasing liposolubility:
The higher the lambda(oil:gas) is, the more liposoluble, the more potent (also MAC decreases with increasing potency)

Question 15

What 5 parameters determine how quickly an anesthetic reaches the brain?

Answer 15

Solubility Concentration in inspired air
Pulmonary ventilation rate
Pulmonary blood flow
Concentration gradient of drug between arterial and venous blood

Question 16

What does the blood:gas partition coefficient tell you about an anesthetic? If it is low, what does that tell you about the speed of onset of action?

Answer 16

It tells you how soluble a drug is in the blood versus the air.
If the drug is not very soluble in blood, it will have a faster rate of onset (nitrous oxide is much faster than methoxyflurane in the inhalational anesthetics)

Question 17

How are the oil:gas and the blood:gas partition coefficients related to each other? To MAC?

Answer 17

Oil:gas = potency and
blood:gas = solubility/rate of onset
High potency correlates with slower onset
They are directly related to each other and both indirectly related to MAC.
As MAC decreases, both coefficients increase.Lower MAC = higher potency but slower onset (methoxyflurane)

Question 18

How does an increase in cardiac output affect the rate of rise of the anesthetic in arterial tension? Why?

Answer 18

Inc CO slows the rate of rise because a higher amount of blood is being exposed to the same amount of drug. It gets diluted

Question 19

If a drug distributes quickly into the tissues, how does this affect the rate of onset? Why?

Answer 19

Uptake by tissues slows the onset because less is making it to the brain

Question 20

How does the time of elimination change for an inhalational anesthetic that is not very soluble vs one that is very soluble?

Answer 20

If it has LOW solubility, elimination mirrors the rate of induction regardless of the duration of administration. If it has HIGH solubility, recovery depends on the duration of the administration of the drug. This is because it will have accumulated in fat and will be released slowly forms a depot

Question 21

What is the effect of most inhaled anesthetics on cardiac contractility? MAP?

Answer 21

Decreases both