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29 Cards in this Set
- Front
- Back
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Some values of an ideal inhaled anesthetic |
inert, predictable onset and emergence, cardiovascular stability, doesn't trigger MH or PONV, is not flammable |
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What are iso, sevo and des? What about halothane? |
iso/sevo/des are all halogenated ethers
Halothane is an alkane |
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What is the MAC? |
it's the measure we use to estimate POTENCY of individual anesthetic gases. it's the alveolar concentration of the gas at which 50% of patients fail to respond to painful stimuli |
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What is the MAC of iso? |
1.15 |
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Des MAC |
6 |
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Sevo MAC |
1.7 |
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And what do we usually multiply the MAC by to figure out how much gas we need to give? |
1.3 * MAC
this is what is the effective concentration for 99% of patients |
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IF you're older, does it take more or less gas? |
less |
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What effect does body temp have on MAC? |
if you're hypothermic it decreaess the MAC |
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What effect do other medciations like opioids, barbiturates, a2 blockers etc. have on the MAC? |
they all decrease it |
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So basically age, body temp, metabolic state, other medications, etc. can all have a significant impact on MAC |
N2O added to a gas can POTENTIATE another gas |
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The partition coefficient is |
a number that states how much of the gas distributes between blood and the gas form |
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If a gas has a really high blood/gas partition coefficient then |
it can become extremely concentrated in the blood |
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The main thing that determines speed of onset for a gas is... |
the alveolar concentration. So if you turn up the MAC, turn up the flow rate, increase minute ventilation etc. youll put the patient down faster and deeper |
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Which gas is highly lipid soluble? |
sevo. The patient can keep falling asleep over and over because it continues to redistribute all the time |
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What is the second gas effect? |
it's the effect you see where one gas starts to drag other gases into the blood along with it because it's so soluble. Best example is N2O |
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What happens when N2O is suddenly turned off? |
you see a brief diffusion hypoxia as the N2O flows back out of the patient's system |
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What are the usual effects that a volatile anesthetic has on respiratory function? |
shallow breathing decreased TV increased resp rate |
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What determines the severity of these effects? |
they are dose dependent, and the physiologic mechanisms that respond to hypoxia/hypercarbia are blunted |
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so as a rule, most volatile anesthetics will start to worsen hypoxia if it's there |
and they also inhibit hypoxic vasoconstriction so the problem persists |
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What effect do inhaled anesthetics have on BP? |
they vasodilate |
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Why do we not use halothane anymore? |
it's highly associated with cardiac dysrhythmias- increases the myocardium's sensitivity to epi |
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What effect does halothane have on kids? |
it doesn't really affect them as much |
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What toxic compound is given off by methoxyflurane when metabolized int he P450 system? |
it gives off fluoride anions when metabolized |
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And what does fluoride do? |
highly nephrotoxic. Iso and Des do this too I believe |
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What is the renal downside of sevo? |
compound A- it's worse if the patient is a rapid metabolizer and the case is long it will start to build up to really high levels |
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What syndrome develops with nitrous oxide abuse? |
Subacute combined degeneration |
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What is a contraindication to nitrous oxide use? |
pneumothorax
Bowel gas, air emboli, and other disorders will also be expanded |
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Why is this? |
because nitrous is so tissue-soluble that it just goes in and expands the crap out of everything |
