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Scientists know that anesthesia drugs are really good at knocking you out. What they don’t know is how.
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Sources:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1362956/
http://www.mayoclinic.org/tests-procedures/anesthesia/basics/definition/prc-20014786
http://io9.com/how-does-anesthesia-work-doctors-arent-sure-and-her-1592809615
https://www.newscientist.com/article/mg21228402.300-banishing-consciousness-the-mystery-of-anaesthesia/#.U6Ho-o1dVAE
http://www.scientificamerican.com/article/how-does-anesthesia-work/
http://www.scientificamerican.com/article/propofol-michael-jackson-doctor/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3162622/
http://www.nigms.nih.gov/education/pages/factsheet_anesthesia.aspx
http://neurowiki2013.wikidot.com/individual:neurotransmitter-system-and-neural-circuits-gover
http://pubs.acs.org/doi/abs/10.1021/jm010461a
http://jpet.aspetjournals.org/content/297/1/338.long
Special thanks to Joseph Praver!
I don’t mean to alarm anyone, but we don’t really know exactly how general anesthesia works. We do know THAT it works, and that it’s relatively safe. But scientists are still trying to figure out how all these different chemicals switch out the lights in your brain.

Anesthesia is a state where you’re insensitive to pain, and doctors use it so that when they need to get to your heart or kidneys or whatever, they can turn something invasive and traumatic into a peaceful nap. General anesthesia is the kind that knocks you out completely -- as opposed to local anesthesia, which just numbs a part of your body for a while, or twilight sedation, where you’re technically conscious but won’t remember anything that happened.

Usually, general anesthesia involves a combination of two drugs -- the first knocks you out fast, and the other one keeps you that way. The anesthesiologist can fine-tune the dosage of the second drug to make sure you don’t wake up too early, or go too far under. So we know that anesthetics knock you unconscious, and we know that they keep you from feeling pain, responding to your environment and -- almost always -- from remembering what happened. Which is a huge plus, because feeling -- and remembering -- being sliced up and stitched back together would not be pleasant.

But anesthesia’s not the same as going to sleep. Some parts of the brain are still active, but unlike when you’re fully conscious,
those active parts don’t really communicate with each other. The brain patterns of someone under anesthesia don’t look like sleep, either. There’s no rapid eye movement or dreaming under anesthesia. Anesthesia brainwaves actually look a lot like the brainwaves of a coma patient... which makes sense, because anesthesia is a lot like a coma. It’s just reversible under the doctor’s control.

The weird thing is, this same anesthetic state can be brought on by a whole bunch of different chemicals--from the noble gas xenon, to big molecules made up of rings of carbon. Since all these different anesthetics do similar things, scientists figured they must have something in common. And the most obvious one was that they almost all dissolve in oil... oils like the insides of your cell membranes.

For decades, researchers thought that anesthetics could dissolve in the membranes of your brain cells and disrupt them somehow. But some compounds that are similar to anesthetics and very oil-soluble don’t numb pain. And some anesthetics aren’t very oil-soluble at all. Instead, these days scientists think it has more to do with proteins, which have oily patches too. So anesthetics probably bond to proteins in your brain.

But it’s hard to study drugs that bond in an oily environment. Anesthetics bond very weakly to the proteins they act on, and it’s hard to get them to stick in place for long enough to know exactly where they’re stuck. The best understood anesthetic is also one of the most popular: propofol. Propofol binds the receptor for a chemical messenger called GABA, which is involved in controlling sleep and alertness, among other things. Propofol helps activate the brain’s receptors for GABA -- and researchers think it’s especially active in the part of the brain that handles sleep.

What we don’t know is exactly how that part of the brain controls consciousness, and how propofol switches it off, and then back on again as soon as it goes away. But, since studies have found that there’s also a bunch of other anesthetics that also bind to the GABA receptor, researchers think they’re on the right track.

There is one really strange thing we do know: Redheads need more anesthetic. Doctors have been reporting cases of this for a while, and at least one small study showed that redheads need 19% more anesthetic than people with dark hair. According to the authors of the study, the gene that produces red hair color seems to be related to resistance to anesthetic, especially since it’s also been linked to pain sensitivity.

So we don’t really know how general anesthesia works, but it’s a good thing that it does. And as we study it, we’re going to be learning more about how the brain is put together -- and maybe a little more about gingers.

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