I was skeptical of the article's claims that anesthetized patients may continue to experience consciousness, but this has definitely shaken the foundations of that belief:
>At doses near the unconsciousness threshold, some anesthetics block working memory (20). Thus, patients may fail to respond because they immediately forget what to do. At much lower doses, anesthetics cause profound amnesia. Studies with the isolated forearm technique, in which a tourniquet is applied to the arm before paralysis is induced (to allow the hand to move while the rest of the body is paralyzed), show that patients under general anesthesia can sometimes carry on a conversation using hand signals, but post-operatively deny ever being awake (21). Thus, retrospective oblivion is no proof of unconsciousness.
Edit: there are some sections of this article that could prompt some interesting discussion from the crowd here. For example, from a subsection "Consciousness and integrated information":
>The evidence from anesthesia and sleep states (Fig. 2–3) converges to suggest that loss of consciousness is associated with a breakdown of cortical connectivity and thus of integration, or with a collapse of the repertoire of cortical activity patterns and thus of information (Fig. 2). Why should this be the case? A recent theory suggests a principled reason: information and integration may be the very essence of consciousness (52). Classically, information is the reduction of uncertainty among alternatives: when a coin falls on one of its two sides, it provides 1 bit of information, whereas a die falling on one of six faces provides ~2.6 bits. But then having any conscious experience, even one of pure darkness, must be extraordinarily informative, since we could have had countless other experiences instead (think of all the frames of every possible movie). Having any experience is like throwing a die with a trillion faces and identifying which number came up (Fig. 2). On the other hand, every experience is an integrated whole that cannot be subdivided into independent components. For example, with an intact brain you cannot experience the left half of the visual field independently of the right half, or visual shapes independently of their color. In other words, the die of experience is a single one throwing multiple dice and combining the numbers will not do.
Many years ago, I received a mild sedative while undergoing an endoscopy via my throat. Apparently, that's not a pleasant experience. I say apparently because I have no memory of it other than asking the nurse when they were going to start ... after the procedure was completed. I remember getting injected with the stuff and I remember me asking that question because I was getting bored just lying there. I don't remember losing consciousness, being asleep, or waking up, or anything like that. It's just a gap in my memory while they did their thing. Amazing stuff. I'm assuming I was conscious and responsive throughout.
I had proper surgery a few days later which involved being knocked out for two hours or so. That's a whole different situation. You start counting down and you are gone within a few seconds.
I've had an endoscopy with no sedatives/anesthetics etc. It was definitely not fun but doable. As soon as the scope went down my throat I went into panic mode. My heart rate was through the roof, and I couldn't stop retching. But after it passed that initial gag reflex point, it settled down. The nurse holding my hand holding my hand soothed me as well.
Then I got up, walked to my car and drove myself home with my brain at 100% (albeit with more adrenaline and cortisol than normal).
The drug they typically give to erase your memory is Midazolam.
You can give someone a small dose of Midazolam, they might report feeling a little dizzy, or say they feel like they’ve had a few drinks, but they will have absolutely no recall of the experience, despite interacting like a slightly tipsy “conscious person” - I like how they call it “conscious sedation” - most people end up believing they were unconscious.
Right, midazolam (aka versed) is a common one. So is propofol (colloquially known as "milk of amnesia").
I've read some horror stories online about people having postoperative nightmares about what they experienced while on the operating table while under versed, so I was really afraid to take it when I went under general anesthesia myself.. but I've had it a bunch of times now, and never experienced anything like that myself.
My postoperative amnesia has been complete, and I'm happy for that.
On the other hand, I still worry about what I might have experienced that I don't remember.
Falling asleep at night after an upper endoscopy, I had a vague recollection of the feeling of retching during the procedure. I know that they try to sedate as lightly as possible, so maybe they undershot slightly in my case. I think I had asked the anesthesiologist what they gave me when I was waking up, because I felt particularly hung over, and they said it was propofol.
At least for some anesthetics, the pain centers will be active while under anesthesia. Rather, interconnectivity between brain areas is disrupted, preventing your conscious experience of pain. Whether or not that is a case of amnesia regarding what you experienced, or a genuine lack of experience, is an open question. Although I firmly believe that brain wide integration is necessary for consciousness and so there is no experience of pain.
I wonder if the pain sensation in your brain , despite not being connected consciously to your experience, has some lingering after effects. Like the engine room of a ship springing a leak but the bridge is just fine and never noticed it when it happened.
I got a small dose of that for my colonoscopy. I was 100 % there, looking at the camera feed, complying with the doctor's orders, I even remember being a little surprised that I feel and remember everything. An hour later, sipping a milkshake at McDonald's I realized I didn't remember the procedure at all. Just these disjoint flashes of consciousness, the sound of the machine, the feeling of the tool moving around, but no real coherent story. Interesting experience.
Startup idea: video content moderation service for big social media
companies with moderators given medically supervised Midazolam; no
more high turnover due to PTSD and no counseling needed
Propofol is also common with endoscopy, and sometimes combinations of drugs, so it's hard to say what GP received.
There's also an interesting thing where the anesthesia you get is likely to be very different for the same procedure if you get the procedure at a hospital versus an outpatient clinic. Because anesthesia at a hospital is typically a department with influence, and turf wars happen.
If you think the tourniquet technique sounds interesting you should read up on “awake craniotomies” - another very interesting area of anaesthesia and consciousness.
Ultimately in anaesthesia, the mind may not recall the experience but the body still feels it. You see this in unparalysed body’s that flinch when they’re cut, or in fully paralysed bodies that signal pain in an observable increase in heart rate and blood pressure.
However, most the time, people are also given substantial analgesics to reduce their likelihood of experiencing pain, but the point I’m trying to make is an unconscious person is still able to feel pain of they have not been given adequate pain relief.
What if the experience of pain is separate to the experience of heart rate rising and blood pressure rising?
Like, you get a cut, and the trigger is the "damage" that then triggers pain and the heart rate rising. It's not the pain itself that triggers the heart rate but the damage. Maybe? Idk
I've read about something similar called split brain where there can be separate consciousness in the brain and maybe elsewhere. Interesting experiments have been done on it and it just all seems so weird. Very tricky figuring out this consciousness thing from the inside.
"But then having any conscious experience, even one of pure darkness, must be extraordinarily informative, since we could have had countless other experiences instead (think of all the frames of every possible movie)."
It is worth asking why this argument does not also apply events like the die-rolling case, and it is because the state of the world immediately after the event is strongly constrained by its state immediately before.
The argument quoted above tacitly assumes there are no such prior constraints in the case of consciousness, but this does not seem to be supportable. If it were so, it would seem that our minds would be constantly taking a random walk through a vast number of possibilities, and it seems inconceivable that there could be consciousness in that case.
As '(52)' in the longer passage is a reference to an early paper by Tononi on his Integrated Information Theory (IIT), I think it is worth pointing out that this argument does not support IIT specifically, or more strongly than any other theory consistent with the premise that the current state of one's mind strongly constrains what happens next.
A childhood fear of mine was that every time I lost consciousness my mind could be going through the worst torture imaginable and I just don't remember it. I still wonder if I'm having horrific nightmares every time I wake up sweaty.
I had the same fear too growing up. I found peace with it and stopped thinking about for many years until now, when I realized that practically it wouldn't affect my waking life if it actually did happen, if I had no memory of it at all, so there would be no use worrying about it.
Being an oldie, I have occasional colonoscopies in which I've always been anesthetized. My most recent one was a couple of years back. I'm not sure what happened, but during the procedure (after evidently going under), I was fully conscious of everything that was going on. I couldn't move and had no feeling for what was happening, but I could hear the doctors talk and could tell what was happening. It was much like a dream, but the most vivid dream one could imagine.
And I'm not an expert in this area, but my understanding is that during a colonoscopy they use a level of anesthesia called "conscious sedation", and the drugs they use also tend to have strong amnesia-inducing properties.
Anesthesia for surgery is more complicated and involves a cocktail of different drugs, administered in a particular sequence, tending to include paralytic drugs as well as special inhaled drugs that we don't even really know how they work (eg sevoflurane). It amounts to a much deeper state of anesthesia than the conscious sedation used in things like GI endoscopy and wisdom tooth extraction.
IANAA (I Am Not An Anesthesiologist) but I like to read about stuff like this and ask my doctors about it whenever it comes up for me.
I had a somewhat similar experience when I got my wisdom teeth out recently.
I consciously remember saying "Wow, this is working way faster than I thought it would" right before the dental assistant told me to go to sleep if I felt like it.
I have some memories of the surgery happening, like my head being jerked around when they pulled teeth out, but it was painless. Immediately after the surgery after I "woke up" I felt like I could remember quite a bit of the procedure but that feeling faded after some time and it all felt like a dream.
>At doses near the unconsciousness threshold, some anesthetics block working memory (20). Thus, patients may fail to respond because they immediately forget what to do. At much lower doses, anesthetics cause profound amnesia. Studies with the isolated forearm technique, in which a tourniquet is applied to the arm before paralysis is induced (to allow the hand to move while the rest of the body is paralyzed), show that patients under general anesthesia can sometimes carry on a conversation using hand signals, but post-operatively deny ever being awake (21). Thus, retrospective oblivion is no proof of unconsciousness.
Edit: there are some sections of this article that could prompt some interesting discussion from the crowd here. For example, from a subsection "Consciousness and integrated information":
>The evidence from anesthesia and sleep states (Fig. 2–3) converges to suggest that loss of consciousness is associated with a breakdown of cortical connectivity and thus of integration, or with a collapse of the repertoire of cortical activity patterns and thus of information (Fig. 2). Why should this be the case? A recent theory suggests a principled reason: information and integration may be the very essence of consciousness (52). Classically, information is the reduction of uncertainty among alternatives: when a coin falls on one of its two sides, it provides 1 bit of information, whereas a die falling on one of six faces provides ~2.6 bits. But then having any conscious experience, even one of pure darkness, must be extraordinarily informative, since we could have had countless other experiences instead (think of all the frames of every possible movie). Having any experience is like throwing a die with a trillion faces and identifying which number came up (Fig. 2). On the other hand, every experience is an integrated whole that cannot be subdivided into independent components. For example, with an intact brain you cannot experience the left half of the visual field independently of the right half, or visual shapes independently of their color. In other words, the die of experience is a single one throwing multiple dice and combining the numbers will not do.