If you want some food for thought - it is this.
Run gas for 6 hours, then, turn it off, run a regular flow (like 1 liter), and see how long it takes for gas to come off. It takes forever for it to disappear from the system.
Of course it takes forever - at 1 lpm they'll rebreath ~80%+ of the volatile they exhale! You're about half a liter away from closed circuit anesthesia there.
Tissue offgassing, which is what I think you're trying to get at here, is heavily dependent on the oil:gas partition coefficient of the gas you choose (des 19, sevo 53, iso 97). This problem is solved by choosing the right gas for the patient and case.
I bet if you had a sensitive way to measure gas, a person would be off-gasing for a couple of days, and that low level of gas makes people feel like crap.
Maybe if the patient is obese and you're using methoxyflurane (oil:gas partition coefficient of 950
🙂) your couple of days speculation would pan out.
Use a modern volatile anesthetic, especially desflurane, and I'd take that bet.
(Side note, when I looked up those numbers I saw that cyclopropane has better numbers than desflurane. MAC of 9, smells nice, cheap. Too bad about the explosions and ventricular arrhythmmias and a boiling point of -34 C.)
Don't believe me eh? Start paying attention to people in the PACU how annoyed they are that they can't wake up..but the gas is making them super sleepy.
No ... have to disagree.
In almost every case, the thing that makes people sleepy in the PACU is the total dose of
opioid they got, not residual volatile. Unless you've got the obese / long case / isoflurane trifecta in play, in which case you clearly don't care about rapid emergence in the first place.
They hate that feeling. Now imagine that for 24 hours! That is the exact opposite with propofol. Propofol has teetered with being controlled substance because people feel awesome with it. People wake up feeling "happy, hungry, and horny:" as my attending would say. And I'm sure - like the gas - this sticks around for several hours...so this low level of feeling great can't be a bad thing.
Propofol wakeups are nice, I won't argue that. But so are desflurane wakeups. Or sevo/iso for short cases.
And more food.
We are all taught that anesthesia messes with sleep/wake cycle (as does surgery). But that is mostly with volatile anesthetic. In fact, if you have a sleep deficit, volitile anesthetic makes this worse. That isn't true with propofol. In fact, propofol REVERSES the sleep deficit!
I ... just don't care.
Someone comes in for outpatient surgery with a sleep deficit - so what? This person had a sleep deficit yesterday too. And last Thursday. And he's going to have one the day after tomorrow. He has a sleep deficit because he has lousy sleep hygiene. A couple hours of propofol isn't going to fix that.
Now, he goes home, and still has a sleep deficit. So what? He just had surgery and is going to spend at least a day or two doing what? Laying around and sleeping.
Now, if you could show me a meta-analysis that demonstrated propofol was more conducive to subliminal introp messaging to inspire weight loss and a reasonable bedtime, maybe ...
Here is the downside to using propofol. Gas prevents movement. Propofol is horrible at getting people to not move under surgical stimulus. You can paralyze them, but TIVA has classically been listed as a higher risk of recall. That may be why people love their gas. I have learned to deal with these two pesky things, so I love using it.
I'd like to think (nearly) everyone exits residency with the ability to run an anesthetic that involves amnesia, analgesia, and akinesia using a variety of techniques.
I feel like I am doing my patients a favor - even if I am not...I feel that way.
Heh. I guess there's no point in arguing that.
🙂