Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

N524 Summer Pharm > Inhalational Agents > Flashcards

Inhalational Agents Flashcards

1
Q

Uptake of a volatile anesthetic into the blood = ____ x _____ x _____

A

Solubility x CO x A-v
Solubility: how anesthetic partitions between blood/reservoir and gas/alveoli (use partition coefficients aka “Oswaldt Solubility Coefficients”)
A-v is difference in partial pressures in alveolar and venous blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

At normal body temp (37C), list the blood/gas solubility coefficients (Des, N2O, Sevo, Iso, En, Halo)

A 
Des 0.42 (poorly soluble)
N2O 0.47
Sevo 0.69
Iso 1.4 
En 1.8
Halo 2.4
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The lower the solubility (Des), the ____ (faster/slower) induction and emergence

A

FASTER
Solubility determines how fast the concentration in the alveoli (FA) reaches the concentration inspired (FI), the faster these values, the faster uptake to the brain and induction (PA = Pa = Pbr), also the fastest rate of rise on FA/FI curves
It is faster bc very little anesthetic must dissolve in the blood before partial pressures equilibrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

An anemic patient will have a ____ (lower/higher) coefficient

A

Lower

Less soluble due to fewer binding sites for anesthetic in the blood, faster uptake of inhalational agent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does FA and FI represent? What are they determined by?

A

FA: partial pressure of anesthetic going to the brain. Determined by inhaled partial pressure, alveolar ventilation, breathing circuit (uptake into plastics/rubber), FRC.
FI: inspired %, can be controlled by flow rate and vaporizer setting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Change in FA (alveolar concentration) is ____ (faster/slower) with increase RR and decreased TV

A

FASTER
Except N2O bc it already has such a low solubility, inc in ventilation will not shift the curve significantly, especially compared to halothane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is uptake influence on FA/FI?

A

Uptake opposes the effect of ventilation (which increases FA), there is uptake at tubing, tissues, it all takes away from alveolar concentration
If uptake removes 2/3 of the anesthetic, FA would be 1/3 of FI
(Review slide 23)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is overpressure?

A

Use of high delivered concentrations
For example, halothane B/G of 2.4 would result in a slow induction, but using overpressure, increased concentration will speed up the induction
By increasing the PI above that required for maintenance of anesthesia, the high Pa (and slow induction) can be offset to some extent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Increased CO (seen in shock for example), will ____ (inc/dec) speed of induction

A

DECREASE

Increase CO will increase solubility, the higher solubility, the slower the induction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

For lean tissue (brain), coefficients are between __ and __

For fat, coefficients (except for N2O) are between ___ and ___

A

Lean tissue coeffiecients between 1-2

Fat coefficients are high, from 27-67, except N2O is 2.3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Vessel rich group is __% of body mass and ___ % of CO

Vessel poor group is __% of body mass and ___% of CO

A

VRG 9% of body mass and 75% of CO

VPG 22% of body mass and 0% of CO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Muscle group is __% of body mass and ___ % of CO

Fat group is __% of body mass and ___ % of CO

A

MG 50% body mass and 18% CO

FG 19% body mass and 7% CO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

In the FA/FI curve, what does the initial steep rise represent? First knee? Second rise? Second knee?

A

Initial rise: quick rise if low solubility
First knee: uptake by VRG
Second rise: uptake by MR group, uptake by VRG slows
second knee: uptake by MRG slows

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

____ influences knee height

____ influences tail

A

B-G solubility influences knee height

Tissue-Gas solubility influences tail

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is MAC

A

Minimum alveolar concentration, ED50 (effective dose in 50%)

The concentration that will produce absence of movement in 50% of patients to noxious stimuli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

To keep FA constant, how should FI be adjusted?

A

High at first, then decrease as VRG is equilibrated, decrease further when MRG is equilibrated.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The greater than alveolar ventilation/FRC ratio, the ___ (faster/slower) the induction

A

FASTER

Neonates have a very fast induction for example

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Inc ventilation and inc CO has what effect on FA/FI?

A

In theory no change, but slightly increases FA/FI

2x the ventilation and 2x the CO for example would double both input and removal

19
Q

What is the concentration effect?

A

Results when a large volume of gas in absorbed. The remaining residual gas is concentrated as the volume decreases and the inspired ventilation increases which adds more anesthetic (neg pressure created by uptake draws more gas into the lung), just think: alveoli shrink and agents become concentrated
Book definition: The higher the PI, the more rapidly the PA approaches the PI, speeds the rate PA increases

20
Q

What is the second gas effect?

A

When N2O is used with another gas, a reduction in volume and replacement of N2O will increase concentration and amount of any gas given with N2O, which was absorbed in large volume
The FA of a gas increases more rapidly when N2O is given as a second gas than when given alone

21
Q

As the duration of anesthesia lengthens, washout will take ___ (longer/shorter)

A

Longer, more anesthetic is in the reservoirs
Least soluble washout first
The higher the B/G solubility coefficient, the longer emergence will take
In general, emergence depends on length and depth of anesthesia, solubility of the agent, and MAC awake

22
Q

Which is more soluble, N2O or nitrogen? What is the implication (which surgeries are N2O avoided in)?

A

N2O is 34x more soluble.
Nitrogen=0.014, N2O=0.47
The bottom line with this difference is that when using N2O, increased pressure can build up in a closed space (bowel, pneumo, tympanic graft), and in these instances, N2O should be avoided

23
Q

What is diffusion hypoxia? How is it avoided?

A

Diffusion Hypoxia: when rapid transfer from blood and tissue to alveoli decreases arterial tension of oxygen
Avoided by washing out with oxygen instead of air for an adequate amount of time

24
Q

What is the Meyer-Overton Theory? (Critical volume theory)

A

Correlation between lipid solubility of inhaled anesthetics (oil:gas partition coefficient) and anesthetic potency shows that inhaled anesthetics act by disrupting the structure or dynamic properties of the lipid portions of nerve membranes.
Absorption of anesthetic molecules expands hydrophobic region of lipid bilayer which alters membrane function

25
Q

According to the Meyer-Overton Theory, increased affinity for lipid will ____ (inc/dec) potency
A decreased MAC means the inhaled agent is ____ (more/less) potent

A

Inc affinity for lipids will INCREASE potency

Dec MAC is MORE potent

26
Q

Which inhalational agents are cautioned with epi use?

A

Halothane

Enflurane

27
Q

CNS reflexes are mediated where?

A

Ventral horn of the spinal cord

28
Q

Compare stages 1 and 2 of Anesthesia according to Guedel (pupils, HR, BP)

A

Stage 1: amnesia/analgesia; pupils react normally to light; irregular pulse; normal BP
Stage 2: delirium/excitement: pupils pinpoint (reaction to light); irregular, fast HR, high BP, this stage can be disturbing to parents
Note: stage 3 “operative” pupils not reactive, stage 4 “danger/OD”

29
Q

T/F: N2O is safe to use as a sole anesthetic agent

A

FALSE. Use a balanced technique with other agents

MAC is 105%!

30
Q

As we increase altitude, we ___ barometric pressure

A

Decrease

31
Q

Boiling point occurs when what 2 values become equal?

A

When vapor pressure = barometric pressure

32
Q

List factors that decrease MAC

A 
Old age, pregnancy
Hypothermia, hyponatremia
Hypotension
Hypoxemia, anemia
Opioids, ketamine, benzos, clonidine, A2 agonists, LAs, ETOH
33
Q

List factors that increase MAC

A

Hyperthermia
CNS stimulants
Youth (under one year old)

34
Q

Which inhalational agent has the most potent bronchodilator effect?

A

Halothane

35
Q

What are the hepatic effects of halothane?

A

Oxidized metabolite: trifluroracetic acid
Hepatotoxicity
Halothane Hepatitis

36
Q

What are risk factors for volatile agent induced hepatitis?

A 
Fat
Female
Forty
Mexican
Prior exposure
37
Q

Which agent has 0 risk of halothane hepatitis, why?

A

Sevoflurane, it can’t be metabolized to trifluroacetylated liver proteins

38
Q

Which inhalational agents should you avoid in peds?

A

Isoflurane

Desflurane

39
Q

Which inhalational agents do not decrease hepatic blood flow?

A

Isoflurane
Desflurane
Sevoflurane

40
Q

Which inhalational agent is delivered through the tec 6 vaporizer?

A

Desflurane

41
Q

How can sevoflurane lead to renal toxicity? What is a good preventative measure?

A

Sevoflurane is not renal toxic, but if compound A is produced (when sevo interacts with soda-lyme) and goes through bioactivation, the conjugates that produce reactive thiol can be renal toxic
Prevent using at least 2 L/min FGF

42
Q

Which inhalational agent blunts the baroreceptor reflex, possibly leading to decreased HR? (All others increase or don’t change HR)

A

Halothane

43
Q

Which inhalational agent decreases seizure threshold?

A

Enflurane

44
Q

Which inhalational agent produces the highest level of carbon monoxide?

A

Desflurane

Then enflurane and isoflurane

N524 Summer Pharm (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions