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What are the three different types of gas anesthesia?
- halothane
- isoflurane
- sevoflurane
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Which gas anesthesia do we not use anymore?
halothane
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When was isoflurane introduced?
1981
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Which gas anesthetic is the most widely used?
isoflurane
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What class of gas anestheic is isoflurane in?
halogenated ethers
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What are the physical properties of isoflurane?
- colorless
- ether-like odor
- non-irritating to mucous membrane (in debate)
- heavier than air
- non-flammable
- not corrosive to metals
- dose not react with soda lime
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What is the highest vapor pressure precentage isoflurane can get to?
30%
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What type of vaporizer do we need to use with isoflurane?
precision vaporizer
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What is solubility coefficient?
how easy gas gets into blood
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What kind of solubility coefficient does isoflurane have?
very low
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How long is induction and recovery using isoflurane?
rapid (1 - 2 minutes)
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What can we use for induction using isoflurane?
mask
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Can we change the depth of anesthesia using isoflurane?
yes - rapidly
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What is the rubber solubility of isoflurane?
very low - does not dissolve into rubber equipment
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What is it good to have low rubber solubility?
anesthesia is not prolonged after vaporizer is turned off
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What does MAC stand for?
minimum alveolar concentration
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What is the MAC of isoflurane?
- higher than halothane or methoxyflurane
- less potent
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At what temperature is isoflurane stable?
room temperature
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Does isoflurane have any preservatives?
no
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What is the margin of safety for isoflurane?
wider margin of safety than halothane or methoxyflurane
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Does isoflurane have a lot of side effects?
no - few
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What are the side effects of isoflurane?
- little or no: effect on HR, decrease in cardiac output, myocardial depression
- does not cause arrhythmias
- vasodilation in deep anesthesia
- low BP in deep anesthesia
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What inhalation anesthetic is the agent of choice for patients with heart problems?
isoflurane
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How is isoflurane eliminated?
through exhalation
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Is isoflurane metabolized by the liver or kidneys? Why?
very little because it has low fat solubility
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Because isoflurane is not excreted by the liver and kidneys, it has no what?
toxic metabolites
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Because isoflurane is excreted by exhalation, it is good to use with what kinds of patients?
- liver problems
- kidney problems
- neonates
- geriatric
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Does isoflurane produce good muscle relaxation?
yes
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Does isoflurane produce a good analgesic?
no
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What percent and how long do we use isoflurane for mask induction?
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What percent should we have isoflurane for the maintence period?
1.5 - 2.5%
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What are the physical properties of sevoflurane?
- clear and colorless
- sweet, non-pungent odor
- non-irritating to the respiratory system
- nonflammable
- does not corrode metals
- does react with soda lime and baralyme
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What is it called when sevoflurane reacts with soda lime or baralyme?
compound A
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What is the solubility coefficient of sevoflurane?
very low - lower than isoflurane
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What kind of induction does sevoflurane have?
rapid
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Can we change the depth of anesthesia using sevoflurane?
yes - rapidly
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What kind of recovery does sevoflurane have?
rapid
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Which anesthetic has a more rapid induction and recovery? Isoflurane or sevoflurane?
sevoflurane
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What kind of MAC does sevoflurane have?
higher than isoflurane (even less potent)
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What does it mean that sevoflurane is less potent than isoflurane?
it takes a higher % to maintain anesthesia
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What kind of rubber solubility does sevoflurane have?
low
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Does sevoflurane dissolve into rubber parts of the anesthetic equipment?
no
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Is sevoflurane stable?
yes
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Does sevoflurane contain any additives or chemical stabilizers?
no
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What effect does sevoflurane have on the cardiovascular system?
can increase or decrease HR
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What happens if we increase the concentration of sevoflurane during maintenance?
can produce a dose-dependent decrease in blood pressure
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What effect does sevolfurane have on the respiratory system?
depress respiration
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Sevoflurane has not been established for dogs with...
- renal, hepatic, or cardiac problems
- breeding
- pregnant
- lactating
- neonatals dogs
- dogs under 12 weeks of age
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Do we still use sevoflurane with dogs that have renal, hepatic, cardiac problems, or breeding, pregnant, lactating, neonatals, under 12 weeks of age? Why or why not?
yes because clinical experience suggests that it is still safe
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What can sevoflurane cause?
malignant hyperthermia (temperature goes up to really high level - 108)
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What is compound A?
produced by interaction of sevoflurane and soda lime or baralyme
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What animal does compound A cause nephrotoxicity? Do we still use sevoflurane with this animal? Why or why not?
- rats
- no
- not proven to be a problem in clinical practice
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When is compound A more likely to cause renal injury?
if used for long period at a low flow rate
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How do we minimize renal injury with compound A?
keep fresh gas flow rates (over 1 L/minute, preferable 2 L/minute)
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How is sevoflurane excreted?
- 95% exhaled
- 5% excreted in urine or taken up in bone
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What kind of O2 flow rates should we use for sevoflurane?
standard or slightly higher standard
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What kind of anesthesia circuit do we need to use for sevoflurane?
any kind
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What kind of drugs is sevoflurane compatible with?
- barbiturates
- propofol
- phenothiazines
- alpha 2 agonists
- opioids
- N2O
- benzodiazepams
- anticholinergics
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Are there any specific premedications we need to use for sevoflurane?
no
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What kind of induction does sevoflurane have?
very rapid (faster than isoflurane)
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For induction, what percent and how long for sevoflurane?
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For maintenance, what percent of sevoflurane do we use?
2.5 - 4 %
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Describe the recovery using sevoflurane.
- faster than isoflurane
- smooth and quiet (goes through stage ll excitement rapidly)
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