Anesthesia and Consciousness

Since I work on anesthesia machines, I loved this fascinating piece by Devansh Malik on anesthestic agents and what exactly happens when anesthetized.

 

The story starts in the 1840’s, when a popular pastime (in the West) was to inhale ether or nitrous oxide at what was called the “laughing gas parties”:

“You’d inhale a bit, feel euphoric, do something embarrassing and everyone would laugh. Simple pleasures of life.”

 

Then people noticed something weird – people inhaling these gases didn’t experience pain (even when they hurt themselves badly). This led a dentist named Horace Wells to wonder if it might have the same effect on the tooth. He had a colleague extract his tooth under nitrous oxide and was happy he didn’t feel any pain. A public demonstration unfortunately didn’t work and the patient did experience pain. Another dentist named William Morton tried it again, with ether during a tooth extraction. It worked.

“Shortly after, a surgeon there removed a tumour from a patient’s neck using ether as an anaesthetic. The patient felt nothing throughout.”

 

Ether soon began to be used everywhere as the anesthetic. But ether came with some problems:

“It was irritating, it made patients nauseous and it was highly flammable. Which meant it was not ideal to use in an operating room!”

The hunt for a better anesthetic agent began. First, they found chloroform.

“It was easier to use, faster acting and not flammable! In 1853, Queen Victoria herself used it during childbirth, which did a lot for its public image.”

But chloroform had a critical risk:

“The difference between “enough to anaesthetise” and “enough to kill” was quite small.”

 

Today, the most common agents are propofol (injected into the blood) and sevoflurane (inhaled gas). The effect can be local (limited to a specific part e.g. tooth) or general (entire body). How does local anesthesia work?

“It works by blocking pain signals from travelling along your nerves to your brain. Like cutting a wire between a specific part of your body and your brain. Your brain never gets the “this hurts” message. You’re completely awake and present. Just numb in one specific area.”

And general anesthesia?

“It makes the different parts of your brain stop communicating with each other altogether. Brain scans of patients under general anaesthesia show that regions which normally talk to each other constantly just go quiet.”

~~

 

When under anesthesia, the sensory signals are still being sent to the brain.

“The information is still coming in. It’s just not being experienced.

Scientists describe this as ‘received but not perceived’.”

 

Which brings us to the topic of consciousness. After all:

“When that communication (between different parts of the brain) breaks down completely, you stop existing, in a sense. No awareness. No memory. You’re just gone.”

We enter a different realm:

“You need to understand what consciousness actually is. What is the ‘you’ that experiences things? And where does it come from?”

Nobody, not scientists, not philosophers, has the answer.

“We built an off-switch for ourselves before we understood what we were switching off.”

~~

 

Lastly, plants can be anesthetized too! How do we know/prove that? Take the Venus flytrap, a plant that folds its leaves when an insect lands on it. Expose it to an anesthetic, and it won’t fold its leaves anymore.

“These plants have no brain or nervous system. They almost certainly have no consciousness. And yet the same drugs work on them.”

 

And so we can end with more questions, not answers:

“So if anaesthesia is switching off consciousness, what exactly is it switching off in a Venus flytrap? And if it’s not targeting consciousness at all, then what exactly disappears when you go under?”