Brainscape's Knowledge GenomeTM

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


See full index

Pharmacology > Inhalant Anesthetics: Pharmacokinetics/Dynamics > Flashcards

Inhalant Anesthetics: Pharmacokinetics/Dynamics Flashcards

1
Q

To creat anesthesia, inhalants must go from the vaporizer to _____

A

The brain

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

________, not concentration, of anesthetic in the _____ produces anesthesia

A

Partial pressure; brain

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

Brain partial pressure equilibrates quickly or slowly with alveolar partial pressure?

A

Quickly -cardiac output to brain is high -brain partial pressure ALWAYS moves towards alveolar partial pressure

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

Alveolar partial pressure is a balance between what two things?

A
  1. input to the alveoli - Delivery
  2. Loss from the alveoli - Uptake
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Factors that affect delivery

A
  • inspired anesthetic concentration
  • Vaporizer setting
  • Fresh gas flow
  • Volume of breathing circuit
  • alveolar ventilation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Inhalants are removed from alveoli by _____

A

Pulmonary blood (this is uptake)

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

Factors that influence uptake

A
  • solubility of anesthetic
  • patient’s cardiac output
  • alveolar-venous anesthetic partial pressure difference
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How can we make an animal anesthetize quickly?

A
  1. Fast rise in alveolar concentration
  2. Increase delivery
  • turn up vaporizer output
  • turn up carrier gas flow rate
  • minimize volume of breathing circuit
  • increase ventilation
  1. Slow down uptake
  • inhalant w/ low solubility
  • slow down cardiac output
  • minimize partial pressure gradient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the effects of solubility on the uptake and distribution of inhalants?

A

Less soluble = readily leaves blood to reach equilibrium with gas and tissues More soluble = greater tendency to stay in the blood

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

A low blood:gas partition coefficient will have what 3 effects on uptake and distribution?

A
  1. Rapid induction 2. Precise control of anesthetic depth 3. Rapid elimination and recovery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why does decreased solubility result in rapid rise of anesthesia?

A

Decr solubility > faster alveolar rate of rise > faster brain rate of rise > rapid anesthesia

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

How does the amount of cardiac output affect uptake and distribution?

A

Amount of blood flow to lungs and tissues influences uptake

  • high CO = greater amount of blood carrying inhalant away from alveoli to tissue
  • low CO = less blood flow through lungs with less anesthetic removed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

With lower cardiac output states, such as colic or sepsis, it is easier/harder to overdose on inhalants?

A

Easier

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

What is the effect of arterial to venous partial pressure gradient on uptake and distribution?

A
  • venous blood returning to the lungs for re-oxygenation will retain some inhalant
  • Pa - Pv gradient must exist fro uptake to occur
  • as anesthetic duration progresses, alveolar rate of rise slows due to narrowing of the Pa-Pv gradient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is uptake into muscle and fat slower than the brain?

A

Due to lower tissue perfusion and higher tissue:blood partition coefficients

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

Recovery from anesthesia is due to _____

A

Removal of inhalants from the CNS - Gradient: CNS > blood > alveoli > outside - decr partial pressure in alveoli & anesthesia circuit

17
Q

4 factors that affect elimination of inhalants

A
  1. Alveolar ventilation 2. Inhalant solubility 3. Cardiac output 4. Duration of anesthesia
18
Q

If a drug has a lower solubility, it will have a faster/slower recovery?

A

Faster

19
Q

Other factors affecting inhalant recovery include:

A
  • decr inhalant delivery > faster elimination - incr alveolar ventilation > faster elimination - incr CO > faster elimination -body temperature Decr temp > incr solubility > longer recovery -metabolism of inhalants (minimal)
20
Q

Describe the role of inhalant metabolism on removal from the body?

A

-minimal role in removal - toxic metabolites can be produces E.g. Sevo > Compound A Iso, desflurane, enflurane > carbon monoxide

21
Q

Which of these is incorrect? A. MAC is a measure of potency B. MAC is a measure of speed of induction C. MAC is additive among multiple inhalants

A

B

22
Q

Name some desirable effects of inhalants

A
  • reversible, dose-dependent general anesthesia -non-addictive -decrease cerebral metabolic rate -elimination not dependent on hepatic and renal function
23
Q

What effects do inhalants have on the cardiovascular system?

A

-Major effect -all REDUCE cardiac output - decreased myocardial contractility Decr stroke volume and CO -decrease peripheral vascular resistance Hypotension -dose-dependent effects

24
Q

What effects do inhalants have on the pulmonary system?

A

As inhalant dose is increased:

  • decr spontaneous ventilation
  • depressed tidal volume & resp frequency
  • incr arterial CO2
  • medically stimulation of respiration due to hypercapnia is reduced
  • respiratory arrest occurs at 1.5-3 MAC
25
Q

How the dose-related decrease in ventilation and blunting the response to increased CO2 act as a safety mechanism?

A

Incr partial pressure in brain > decr ventilation > decr uptake > decrease partial pressure of brain

26
Q

What are the effects of inhalants on the CNS?

A
  1. Immobility and unconsciousness
  2. increase cerebral blood flow
  • Cerebral vasodilation
  • Hypoventilation > incr CO2 > vasodilation
  • Leads to an incr in ICP (dose related)
  1. high doses of inhalants (>1 MAC) > loss of cerebral blood flow autoregulation
    * these are often avoided with increased intracranial pressure b/c brain is within a fixed space and contains CSF, blood/vasculature, brain tissue
27
Q

What are the effects of inhalants on the liver?

A
  1. Minimal hepatic metabolism of inhalants
  2. Possible prolongation of drug metabolism
  • decr CO > decr hepatic blood flow
    • decr hepatic metabolism co-administered drugs
  1. Isoflurane most likely to maintain hepatic blood flow
28
Q

What are the effects of inhalants on the kidneys?

A
  1. Mild, reversible, dose-related decrease in renal blood flow & GFR - Related to overall decr CO 2. Nephrotoxicity - Rarely documented in domestic spp. - Breakdown of sevoflurane > free fluoride ions & Compound A
29
Q

What is malignant hyperthermia?

A
  1. Reported in horses, dogs, pigs
  2. Myopathy secondary to inhalant exposure
  • Genetic mutation of ryanodine receptor (in mm cells, important in mm contraction)
    • massive incr in cytosolic Ca2+
    • incr sk mm oxidative metabolism
    • decr O2 supply and incr CO2
    • eventually causes cric collapse & death
  1. Treatment:
  • discontinue inhalant administration
  • Dantrolene sodium - muscle relaxant
30
Q

Isoflurane

A

High potency -MAC = 1.2-1.6% Intermediate solubility -Blood:gas partition coefficient = 1.4 Minimal liver metabolism -Best at maintaining liver perfusion Most common modern inhalant used (cheap)

31
Q

Sevoflurane

A

Intermediate potency - MAC = 2.2-3% Low solubility - Blood:gas partition coefficient Small amount of liver metabolism (-5%) Compound A production - no real clinical significance

32
Q

Desflurane

A
  • Low potency (MAC 8%)
  • Low boiling point (22 degrees C)
  • High vapor pressure (700mmHg)
  • Rapid induction/recovery
  • VERY low solubility
  • NO liver metabolism
  • Needs a specialized heated & pressurized vaporizer

Pharmacology (33 decks)

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