Is it incorrect terminology to say...

[SleepyTime]

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Let's say you have a pt with 2 of Sevo and 55% nitrous. Is it incorrect to say that the pt has a MAC of Sevo and a half-MAC of nitrous running? Should you just say it's one MAC sevo plus 55% nitrous?

 

[Noyac]

While MAC of N2O is 104 I find it hard to consider N2O having a MAC at all in some places. I practice at 6500ft in elevation and N2O just isn't potent enough at this elevation (partial pressure). Therefore, I would say the latter. 1MAC sevo with 55%N2O. Now remember, you are over 1 MAC at ET of 2.0 sevo with 55% N20 on board. But I guess its not incorrect tosay it the other way. So nevermind what I say.

 

[Adcadet]

As a student on an anesthesiology rotation, I might think that by "1 MAC sevo with 55% N2O" meant that the "total MAC" was 1 and was achieved with a mix of sevo and N2O, and that you were telling me the N2O percent so I would have an idea of what the FiO2 needs to be, and not the percent sevo since it's not so huge as to displace O2. But hey, I'm new at this and will need clarification either way.

So far in the OR when referring to summed MACs I'll specify the concentrations and give say "...for a total MAC of X" (and yes, I'll make the goofy finger quotation sign just to illustrate that this is a bit of a fuzzy concept, especially with N2O).

 

[VentdependenT]

Sevo end tidal of 2% = 1 mac
Nitrous of 55% = .5 mac
All that other stuff (fentanyl, versed, some propofol floating around)= additive mac

so pt is at least 1.5 mac.

Just add em up.

 

[DrDre']

The way Vent describes it is exactly the way we refer to N20 at our institution. If you use 55-65 N20, you can call it mac at sea lvl.

 

[jetproppilot]

Sevo end tidal of 2% = 1 mac

age dependent of course.

kids mac is higher

gray haired dudes are lower.

 

[VentdependenT]

Yeah. What Jet said.

 

[militarymd]

That's funny....I give some vec...and all it takes is 0.3 sevo for me to keep the patients from moving....but I can never figure out why they're so hypertensive and tachycardic. 😕

 

[militarymd]

While MAC of N2O is 104 I find it hard to consider N2O having a MAC at all in some places. I practice at 6500ft in elevation and N2O just isn't potent enough at this elevation (partial pressure). Therefore, I would say the latter. 1MAC sevo with 55%N2O. Now remember, you are over 1 MAC at ET of 2.0 sevo with 55% N20 on board. But I guess its not incorrect tosay it the other way. So nevermind what I say.

I talked to my partner....He tells me you have it pretty good up there 👍

 

[Noyac]

I talked to my partner....He tells me you have it pretty good up there 👍

Giddy up!!! 😉

 

[SleepyTime]

Somebody told me today that it is embarrassing to hear someone refer to N2O in terms of MAC even if one refers to 55% as about a half-MAC it was just weird to hear it said that way.

I want to understand why considering MAC is additive and we know that N2O has a MAC value that, albeit unattainable at sealevel, does allow us to ascertain a half-MAC.

Is N2O viewed more like Fentanyl and other IV drugs that contribute to anesthesia but are not quantifiable?

 

[jetproppilot]

That's funny....I give some vec...and all it takes is 0.3 sevo for me to keep the patients from moving....but I can never figure out why they're so hypertensive and tachycardic. 😕

uh, Dude, I hope you've got max attainable malpractice limits....

 

[jetproppilot]

Somebody told me today that it is embarrassing to hear someone refer to N2O in terms of MAC even if one refers to 55% as about a half-MAC it was just weird to hear it said that way.

I want to understand why considering MAC is additive and we know that N2O has a MAC value that, albeit unattainable at sealevel, does allow us to ascertain a half-MAC.

Is N2O viewed more like Fentanyl and other IV drugs that contribute to anesthesia but are not quantifiable?

N20's contribution to MAC has been proven to be linear AND quantifiable. So the answer to your question is no.

 

[SleepyTime]

Thanks for the input everybody. I continue to learn a little more each day.

 

[Noyac]

albeit unattainable at sealevel,

You might want ot check that one.

 

[VentdependenT]

That's funny....I give some vec...and all it takes is 0.3 sevo for me to keep the patients from moving....but I can never figure out why they're so hypertensive and tachycardic. 😕

I just use a vecuronium bolus followed by continuous infusion, metoprolol and labetolol bolus', plus a nitro drip and I've found that I don't even need the inhalational agents....or any sort of intravenous agents either.

The patients always cry though....must be sad to say goodbye to those gallbladders I guess? 😳