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If you've had surgery,

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you might remember starting to count
backwards from ten,

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nine,

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eight,

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and then waking up with the surgery
already over before you even got to five.

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And it might seem like you were asleep,
but you weren't.

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You were under anesthesia,

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which is much more complicated.

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You were unconscious,

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but you also couldn't move,

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form memories,

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or, hopefully, feel pain.

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Without being able to block all those
processes at once,

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many surgeries would be 
way too traumatic to perform.

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Ancient medical texts from Egypt,
Asia and the Middle East

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all describe early anesthetics

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containing things like opium poppy,

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mandrake fruit,

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and alcohol.

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Today, anesthesiologists often combine

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regional, inhalational 
and intravenous agents

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to get the right balance for a surgery.

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Regional anesthesia blocks pain signals
from a specific part of the body

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from getting to the brain.

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Pain and other messages travel through
the nervous system as electrical impulses.

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Regional anesthetics work by setting up
an electrical barricade.

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They bind to the proteins 
in neurons' cell membranes

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that let charged particles in and out,

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and lock out positively charged particles.

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One compound that does this is cocaine,

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whose painkilling effects 
were discovered by accident

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when an ophthalmology intern
got some on his tongue.

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It's still occasionally used 
as an anesthetic,

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but many of the more common
regional anesthetics

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have a similar chemical structure
and work the same way.

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But for major surgeries where you need
to be unconscious,

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you'll want something that acts
on the entire nervous system,

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including the brain.

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That's what inhalational anesthetics do.

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In Western medicine, diethyl ether
was the first common one.

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It was best known as a recreational drug

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until doctors started to realize that
people sometimes didn't notice

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injuries they received 
under the influence.

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In the 1840s, they started sedating
patients with ether

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during dental extractions and surgeries.

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Nitrous oxide became popular
in the decades that followed

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and is still used today.

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although ether derivatives, 
like sevoflurane, are more common.

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Inhalational anesthesia is usually 
supplemented with intravenous anesthesia,

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which was developed in the 1870s.

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Common intravenous agents include
sedatives, like propofol,

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which induce unconsciousness,

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and opioids, like fentanyl, 
which reduce pain.

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These general anesthetics 
also seem to work

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by affecting electrical signals
in the nervous system.

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Normally, the brain's electrical signals
are a chaotic chorus

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as different parts of the brain
communicate with each other.

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That connectivity keeps you awake
and aware.

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But as someone becomes anesthetized,

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those signals become calmer
and more organized,

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suggesting that different 
parts of the brain

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aren't talking to each other anymore.

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There's a lot we still don't know
about exactly how this happens.

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Several common anesthetics bind to
the GABA-A receptor in the brain's neurons.

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They hold the gateway open,

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letting negatively charged particles
flow into the cell.

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Negative charge builds up
and acts like a log jam,

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keeping the neuron from transmitting
electrical signals.

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The nervous system has lots
of these gated channels,

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controlling pathways for movement,

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memory,

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and consciousness.

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Most anesthetics probably 
act on more than one,

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and they don't act on 
just the nervous system.

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Many anesthetics also affect the heart,

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lungs,

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and other vital organs.

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Just like early anesthetics,

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which included familiar poisons like
hemlock and aconite,

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modern drugs can 
have serious side effects.

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So an anesthesiologist has to mix
just the right balance of drugs

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to create all the features of anesthesia,

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while carefully monitoring
the patient's vital signs,

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and adjusting the drug mixture as needed.

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Anesthesia is complicated,

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but figuring out how to use it

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allowed for the development 
of new and better surgical techniques.

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Surgeons could learn how to routinely
and safely perform C-sections,

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reopen blocked arteries,

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replace damaged livers and kidneys,

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and many other life-saving operations.

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And each year, new anesthesia techniques
are developed

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that will ensure more and more patients
survive the trauma of surgery.