14 ms·

Consciousness and Anaesthesia (2009)

164 points by Quinzel 3y ago

Quinzel 3y ago
I think about consciousness a lot, and therefore, like to read about it.
dangitnotagain 3y ago
Is it worth noting that the term “consciousness” has multiple forms? Consciousness, having existential feedback and wakefulness are separate forms. We are existential feedback consciousness whether or not we have awareness (or memory), and we are awake conscious when we have continuity of awareness. The one word has two closely related functional contexts.
- dr_dshiv 3y ago
  Wakefulness is necessarily integrative at the level of the whole individual. Global Workspace Theory, and all that. Is the same true of existential feedback consciousness? I'm very interested in hierarchical models where low level consciousness might operate independently, but be bound together into an individual's conscious experience.
  - dangitnotagain 3y ago
    Existential feedback consciousness is happening in every neuron, every neural cluster, every brain region, and finally competing to produce the illusion of waking consciousness. Some, yet not all are perceptually aware of multiple scopes of awareness competing for coherence (“idea in the back of the mind”, “on the tip of the tongue”, intuition, etc.) Consciousness is actually so diverse we can train and automate outside of the scope of awareness (reflexive techniques such as learning language, martial arts, setting intentions, etc.) We often refer to this as “subconscious”, yet this is more truly the “consciousness” we are most interested in.
    - dr_dshiv 3y ago
      Any books to read or papers to suggest on this?
      - dangitnotagain 3y ago
        Every part of what I have described has been somewhere mentioned or eluded to by scientific exploration, yet not one single discussion or exposition likely exists which ties these topics together in a gratifying or coherent way. Leading trends incorrectly describe consciousness as an “emergent phenomenon” in “some region”, yet separately (and much earlier) the discussion of microtubules as a possible substrate for quantum interaction. I do not believe we possess the technology to observe or replicate how this might work, considering we cannot hypothesize or test how quantum interaction can be reliably maintained at body temperature (the answer I believe to be insulated layering, a properly of 2D crystallography, and mass aggregation.) that electrochemical perturbance occurs during neural firing is an inherent proposition of physics. Similarly on each other item I have mentioned such as what we call “subconscious” being key to understand underlying “consciousness”, or the programmability of neurological complexities, they seem almost self apparent yet cannot quite be conjectured by formalism. The luxury of citizen science/philosophy contends with the range of comfortably integrating speculations.
robobro 3y ago
I think the amnesiac effect of many anaesthestics also tricks us into thinking we go totally unconscious under their effects. I've been operated on several times and sustained near life threatening injuries in the past. I can't remember any of the most painful bits, despite occasionally making conversation / looking around with my eyes open. I'm thankful I can't remember.
- fzeroracer 3y ago
  There was some interesting studies and such I read around anesthetics + memory blockers that still lead to some subconscious exhibition of PTSD. I don't have them on hand but there was some interesting stuff on how potentially we may still remember traumatic surgeries even if we can't explicitly recall them. That's why there's been a push towards refining sedation techniques further both to reduce the odds of a patient being conscious during surgery and also to reduce the amount of stress it can put on the body.
  - Quinzel 3y ago
    I would absolutely love to read these studies!
    - fzeroracer 3y ago
      I found the first one I was talking about [1] which talks about possible memory encoding while unconscious. [1] https://pubmed.ncbi.nlm.nih.gov/17900016/ https://pubmed.ncbi.nlm.nih.gov/17900016/
      - Quinzel 3y ago
        Thank you! That is awesome :)
  - rcxdude 3y ago
    It would make sense if the mechanism for PTSD is unrelated to the mechanism for episodic memory which are disrupted by memory blockers
Defenestresque 3y ago
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.
- jillesvangurp 3y ago
  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.
lloydde 3y ago
The topic, but not this exception, is touched on in “Your Brain: Who's in Control? | Full Documentary | NOVA | PBS“ Episode 2 of a two-part series, premiered May 24, 2023. Both episodes are fascinating and eye opening. 08:36 Anesthesia and the Brain https://youtu.be/yQ6VOOd73MA https://youtu.be/yQ6VOOd73MA https://www.pbs.org/wgbh/nova/video/your-brain-whos-in-control/ https://www.pbs.org/wgbh/nova/video/your-brain-whos-in-contr...
amelius 3y ago
We're in the dark ages wrt consciousness. We might as well have multiple overlapping consciousnesses, some of which may experience pain during anaesthesia.
deepvibrations 3y ago
This is another nod to the non-duality philosophy, which I think deserves more attention. This conversation between Rupert Spira and Donald Hoffman talks about the unconscious in a way very relevant to this research. Very interesting to hear both sides and interesting that these revelations back Rupert's point that consciousness is always there on some level: https://www.youtube.com/watch?v=9rWqUBqprk8 https://www.youtube.com/watch?v=9rWqUBqprk8
lordnacho 3y ago
Have to say my experience of propofol was pretty interesting. It's this milky substance that is injected directly into your blood. The action seems to be super fast and super deep. I remember the anesthetist talking to me while doing it, I think it's standard practice, and I pretty much vanished mid-sentence. As in, not just "I feel like I'm sleeping" that you get each morning or evening in bed, more like "time just vanished" kind of way. Very hard to explain the speed with which you drop from awake to sort of sleeping to "there is no me". The way back is a bit slower but harder to pinpoint, but I knew something was different in the recovery room.
- apples_oranges 3y ago
  but during sleeping time also kind of vanishes? Seems like propofol skips the being-tired stage that precedes sleep but otherwise..
  - lordnacho 3y ago
    Yes, that is what felt so strange. It's like you're awake, you feel a bit of cold in your arm, then you're waking up. No in between, just snap fingers and you are elsewhere.
  - TacticalCoder 3y ago
    I often remember my dreams. My wife is always amazed that I remember so many of them (she hardly remembers any). But I never ever remembered a single "dream" I made under anaesthesia. I wonder if people who remember many of their dreams have different experience? To me it's pretty much like GP: mid sentence and then boom, gone.
    - 2-718-281-828 3y ago
      there is also retrograde amnesia. people live and feel. then suffer amnesia and can't remember having lived and felt. doesn't mean they didn't live and feel, though.
    - Sanzig 3y ago
danjc 3y ago
"...Thus, retrospective oblivion is no proof of unconsciousness". I have always found this prospect terrifying.
- retrac 3y ago
  In sleep, there is a state in which we have a inner mental narrative, with subjective sensations, thoughts, and emotions. And we usually forget it even if we remember at all; most of it never enters the awareness of our wake selves.
  - fyloraspit 3y ago
    Ok, Tyler Durden.
i_am_a_peasant 3y ago
When I was a kid I had my appendix removed and I woke up during operation. My vision was foggy but I could hear 20% of what was being said. I asked the surgeon "should I scream?". He shouted and waved his finger at me "Do not scream! Do not scream!" I went back to sleep and woke up in a hospital bed.
- op00to 3y ago
  Good god, that's horrifying. I hope you're ok now.
  - i_am_a_peasant 3y ago
    don't get me wrong nothing hurt. I was just counscious.
uoaei 3y ago
Steven Strogatz had Emery Brown of MIT on his Quanta-produced podcast to discuss anaesthesia and particularly its differences from typical sleep: https://www.quantamagazine.org/emery-brown-and-the-truth-about-anesthesia-20210426/ https://www.quantamagazine.org/emery-brown-and-the-truth-abo...
bbor 3y ago
WOW this is an amazing article, thanks for posting. As an aside, this popped out to me: the brain implements an algorithm not unsimilar to the TCP congestion window algo!! Perhaps I’m reading into it too much but that’s just terribly interesting. At intermediate anesthetic concentrations, neurons begin oscillating, roughly once a second, between a depolarized up-state and a hyperpolarized down-state (11). The up-state is similar to the sustained depolarization of wakefulness. The down-state shows complete cessation of synaptic activity for a tenth of a second or more, after which neurons revert to another up-state. As anesthetic doses increase, the up-state turns to a short burst and the down-state becomes progressively longer.
- op00to 3y ago
  I see it more like a NES system that has a bad connection to the cartridge - constantly rebooting, trying to get that signal from the copy protection chip.
ineedasername 3y ago
I had anesthesia once. Subjectively it’s about as close to being dead (or simply “not existing”) as I can imagine. One moment I was perfectly awake, and the next moment I was hearing the sounds of people talking around me and I groggily became aware of my doctor getting me to acknowledge him. There is still the question though, was my subjective experience post-surgery accurate? It’s conceivable that consciousness is suppressed to varying degrees, while the creation of memories is more significantly impacted. I may have had some degree of consciousness but my subjective post-surgery experience has no knowledge of it. And putting aside anesthesia altogether you have the phenomena of people that get blackout drunk. For some period of time they were up, senses receiving input and processing it even if their actions were high impaired, yet afterwards there is no memory. (There are of course degrees to this too, sometimes a person remembers the tiniest pieces, as if from a dream, sometimes not at all) The entire topic invites the question: Is consciousness required for intelligent behavior? Unless you include consciousness as part of the definition of intelligent, it is not an easy question. Somewhat on that topic I’d highly recommend the book Being no One by Thomas Metzinger
- ericmay 3y ago
  (Queue bar talk) Begs the question, what is intelligent behavior? Most of the time I see pretty anthropocentric interpretations of this (which are often well-reasoned) but there has to be some degree of definition that we can agree to as a starting point. My current view is one of consciousness operating on a spectrum, some animals/creatures/entities are "more aware"[1] than others but then you have to ask whether that just leads to consciousness being a useful phenomenon for interaction with other creatures or if it's something more meaningful. Were humans conscious before the invention of language? Another aspect of this is if "Chat-GPT" isn't conscious it kind of proves your dog is right? You're saying language/interaction isn't that big of a deal, and so it's based on biology. Not a lot different between a cat and a person if you really take a step back, let alone a chimpanzee and a person. Or maybe we're all not conscious at all in the sense that we mean it. I.e. it's just a useful illusion/delusion and evolutionary adaptation for cooperative behavior. Then we have to insert free will, determinism, etc. The whole thing is a mess. Most likely we're not conscious at all, nor do we have free will, as typically described. But we're conscious in that we're perceiving and our body as a whole has some amount of degrees of freedom to operate, but we're not special. Maybe that's scary idk. [1] Whatever that means
quercusa 3y ago
I've never liked Propofol and the hours of dopiness it induces post-op. I did my last colonoscopy with no anesthesia. It was only mildly uncomfortable and pretty interesting - the doctor acted as tour guide. The I got up and went home fully awake. I recommend it.
- luckman212 3y ago
  what do you do if your doctor refuses to do the procedure w/o anesthesia? find another doctor i guess?
  - quercusa 3y ago
    Probably - I'd wonder why they'd refuse. Most insurance (AFAIK) won't cover the anesthesia as 'not medically necessary'.
rybosworld 3y ago
I woke up during an endoscopy when I was young (4/5 years). I have a pretty vivid memory of that one single moment when I came too, and the doctors/nurses panicking a bit when they realized I was conscious. It ended pretty quickly when they gave me more of whatever the anesthesia was.
driggs 3y ago
Don't let all the physiology distract you from the HN-relevant information theory(?) in the `Consciousness and Integrated Information` section near the end: A recent theory suggests a principled reason: information and integration may be the very essence of consciousness. 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. On the other hand, every experience is an integrated whole that cannot be subdivided into independent components. Less metaphorically, the theory claims that the level of consciousness of a physical system is related to the repertoire of different states (information) that can be discriminated by the system as a whole (integration). A measure of integrated information, called phi (Φ), can be used to quantify the information generated when a system enters one particular state of its repertoire, above and beyond the information generated independently by its parts. In practice, Φ can only be measured rigorously for small, simulated systems. However, empirical measures could be devised to evaluate integrated information on the basis of EEG data, resting functional connectivity, or TMS-evoked responses.
- justinpombrio 3y ago
  An argument why IIT is nonsense: https://scottaaronson.blog/?p=1799 https://scottaaronson.blog/?p=1799
adasound 3y ago
I practice anesthesia. My most significant change so far has been to drastically reduce the amount of ketamine I give. It is a very interesting drug. Very stable re. cardiovascular concerns. Maintains blood pressure nicely. We use it to induce anesthesia and for pain, but others use it for depression, chronic pain, borderline personality disorder. It's fine for pediatrics. Adults not so much. We dose ketamine quite a bit higher as an induction agent at the start of operations than what would be considered a recreational or psychotherapeutic dose/"K hole". In opposition to kids, adult patients have frequently found themselves in a very bad place on emergence from anesthesia and in the recovery room. They sometimes endorse reliving trauma and confronting themselves in a dark region of their minds that they possibly have never known about. This is why it has promise as a therapeutic agent in psychotherapy, however it is often the case that patients are cared for by one recovery room nurse who is run off her feet/has more than one patient. I have learned that "K hole" context is everything. Kids are just fine with ketamine. I think it's because their brains are much more plastic & the variation of experience in their waking lives is higher than adults. I think that experiencing the moods and expressiveness and novel situations as a 3 year old for a day would be an incredible hallucinogen or psychedelic.
- basch 3y ago
  I have nothing to base this on, but I suspect kids do better because they lack experience, so there is nothing to resurface. Their lack of memories prevents any sort of introspective reevaluation of their life.
  - bbor 3y ago
    I think this is a little uncharitable to kids. Do you not remember the stressors and ruminating thoughts of childhood? To say nothing of children who have experienced trauma. Perhaps this could apply to pre-object-permanence infants, but by the time they're undergoing surgery (hopefully...) they've had years of conscious experience. Hopefully I'm not being too uncharitable, your idea is certainly plausible. I'm also just musing which feels disrespectful to the terribly interesting expert take in the ancestor comment, but I cringe whenever I hear arguments that I can reduce down to "being a child is not at all like what it is to be me", as it's been used for centuries to suppress their behavior and excuse abuses
hnu0847 3y ago
There's a very good Radiolab episode that discusses this: https://radiolab.org/podcast/anesthesia https://radiolab.org/podcast/anesthesia
calebm 3y ago
The book, "After: A Doctor Explores What Near-Death Experiences Reveal about Life and Beyond" (Bruce Greyson M.D.), explores this subject.
EMCymatics 3y ago
Anaesthesia is more dangerous and impactful than commonly realized. These chemicals and medicine need to be more strictly controlled.
trts 3y ago
Seeing the authors of this paper, I am reminded of some of my favorite conversations with Gulio Tononi on Closer to Truth, about the nature and constructs of consciousness. https://www.youtube.com/watch?v=uiS5i2d9zBA https://www.youtube.com/watch?v=uiS5i2d9zBA
NateEag 3y ago
I had surgery under general anesthesia for the first time in my life a year or two back, and it was very enlightening. Specifically, most people who have general anesthesia talk about how strangely different it was from sleeping. It was virtually identical to what my sleep has been like most of my life. I went out then I came back. I was groggy longer than usual waking up, but that was about the only difference. I almost never remember dreams, historically. I lay down, go out in < 5 minutes, then get up when something wakes me. That seems to be a rare experience, so I figure outta worth mentioning. Also interesting is that I've been taking atomoxetine for the past few months, and one of the effects has been that I don't sleep nearly as deeply and now remember dreams regularly. My nights are much longer and I don't like it.

164 points by Quinzel 3y ago

I think about consciousness a lot, and therefore, like to read about it.

Is it worth noting that the term “consciousness” has multiple forms? Consciousness, having existential feedback and wakefulness are separate forms. We are existential feedback consciousness whether or not we have awareness (or memory), and we are awake conscious when we have continuity of awareness. The one word has two closely related functional contexts.

dr_dshiv 3y ago
Wakefulness is necessarily integrative at the level of the whole individual. Global Workspace Theory, and all that. Is the same true of existential feedback consciousness? I'm very interested in hierarchical models where low level consciousness might operate independently, but be bound together into an individual's conscious experience.
- dangitnotagain 3y ago
  Existential feedback consciousness is happening in every neuron, every neural cluster, every brain region, and finally competing to produce the illusion of waking consciousness. Some, yet not all are perceptually aware of multiple scopes of awareness competing for coherence (“idea in the back of the mind”, “on the tip of the tongue”, intuition, etc.) Consciousness is actually so diverse we can train and automate outside of the scope of awareness (reflexive techniques such as learning language, martial arts, setting intentions, etc.) We often refer to this as “subconscious”, yet this is more truly the “consciousness” we are most interested in.
  - dr_dshiv 3y ago
    Any books to read or papers to suggest on this?
    - dangitnotagain 3y ago
      Every part of what I have described has been somewhere mentioned or eluded to by scientific exploration, yet not one single discussion or exposition likely exists which ties these topics together in a gratifying or coherent way. Leading trends incorrectly describe consciousness as an “emergent phenomenon” in “some region”, yet separately (and much earlier) the discussion of microtubules as a possible substrate for quantum interaction. I do not believe we possess the technology to observe or replicate how this might work, considering we cannot hypothesize or test how quantum interaction can be reliably maintained at body temperature (the answer I believe to be insulated layering, a properly of 2D crystallography, and mass aggregation.) that electrochemical perturbance occurs during neural firing is an inherent proposition of physics. Similarly on each other item I have mentioned such as what we call “subconscious” being key to understand underlying “consciousness”, or the programmability of neurological complexities, they seem almost self apparent yet cannot quite be conjectured by formalism. The luxury of citizen science/philosophy contends with the range of comfortably integrating speculations.

robobro 3y ago

I think the amnesiac effect of many anaesthestics also tricks us into thinking we go totally unconscious under their effects. I've been operated on several times and sustained near life threatening injuries in the past. I can't remember any of the most painful bits, despite occasionally making conversation / looking around with my eyes open. I'm thankful I can't remember.

fzeroracer 3y ago
There was some interesting studies and such I read around anesthetics + memory blockers that still lead to some subconscious exhibition of PTSD. I don't have them on hand but there was some interesting stuff on how potentially we may still remember traumatic surgeries even if we can't explicitly recall them. That's why there's been a push towards refining sedation techniques further both to reduce the odds of a patient being conscious during surgery and also to reduce the amount of stress it can put on the body.
- Quinzel 3y ago
  I would absolutely love to read these studies!
  - fzeroracer 3y ago
    I found the first one I was talking about [1] which talks about possible memory encoding while unconscious. [1] https://pubmed.ncbi.nlm.nih.gov/17900016/ https://pubmed.ncbi.nlm.nih.gov/17900016/
    - Quinzel 3y ago
      Thank you! That is awesome :)
- rcxdude 3y ago
  It would make sense if the mechanism for PTSD is unrelated to the mechanism for episodic memory which are disrupted by memory blockers

Defenestresque 3y ago

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.

jillesvangurp 3y ago
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.

lloydde 3y ago

The topic, but not this exception, is touched on in “Your Brain: Who's in Control? | Full Documentary | NOVA | PBS“ Episode 2 of a two-part series, premiered May 24, 2023. Both episodes are fascinating and eye opening. 08:36 Anesthesia and the Brain https://youtu.be/yQ6VOOd73MA https://youtu.be/yQ6VOOd73MA https://www.pbs.org/wgbh/nova/video/your-brain-whos-in-control/ https://www.pbs.org/wgbh/nova/video/your-brain-whos-in-contr...

amelius 3y ago

We're in the dark ages wrt consciousness. We might as well have multiple overlapping consciousnesses, some of which may experience pain during anaesthesia.

deepvibrations 3y ago

This is another nod to the non-duality philosophy, which I think deserves more attention. This conversation between Rupert Spira and Donald Hoffman talks about the unconscious in a way very relevant to this research. Very interesting to hear both sides and interesting that these revelations back Rupert's point that consciousness is always there on some level: https://www.youtube.com/watch?v=9rWqUBqprk8 https://www.youtube.com/watch?v=9rWqUBqprk8

lordnacho 3y ago

Have to say my experience of propofol was pretty interesting. It's this milky substance that is injected directly into your blood. The action seems to be super fast and super deep. I remember the anesthetist talking to me while doing it, I think it's standard practice, and I pretty much vanished mid-sentence. As in, not just "I feel like I'm sleeping" that you get each morning or evening in bed, more like "time just vanished" kind of way. Very hard to explain the speed with which you drop from awake to sort of sleeping to "there is no me". The way back is a bit slower but harder to pinpoint, but I knew something was different in the recovery room.

apples_oranges 3y ago
but during sleeping time also kind of vanishes? Seems like propofol skips the being-tired stage that precedes sleep but otherwise..
- lordnacho 3y ago
  Yes, that is what felt so strange. It's like you're awake, you feel a bit of cold in your arm, then you're waking up. No in between, just snap fingers and you are elsewhere.
- TacticalCoder 3y ago
  I often remember my dreams. My wife is always amazed that I remember so many of them (she hardly remembers any). But I never ever remembered a single "dream" I made under anaesthesia. I wonder if people who remember many of their dreams have different experience? To me it's pretty much like GP: mid sentence and then boom, gone.
  - 2-718-281-828 3y ago
    there is also retrograde amnesia. people live and feel. then suffer amnesia and can't remember having lived and felt. doesn't mean they didn't live and feel, though.
  - Sanzig 3y ago

danjc 3y ago

"...Thus, retrospective oblivion is no proof of unconsciousness". I have always found this prospect terrifying.

retrac 3y ago
In sleep, there is a state in which we have a inner mental narrative, with subjective sensations, thoughts, and emotions. And we usually forget it even if we remember at all; most of it never enters the awareness of our wake selves.
- fyloraspit 3y ago
  Ok, Tyler Durden.

i_am_a_peasant 3y ago

When I was a kid I had my appendix removed and I woke up during operation. My vision was foggy but I could hear 20% of what was being said. I asked the surgeon "should I scream?". He shouted and waved his finger at me "Do not scream! Do not scream!" I went back to sleep and woke up in a hospital bed.

op00to 3y ago
Good god, that's horrifying. I hope you're ok now.
- i_am_a_peasant 3y ago
  don't get me wrong nothing hurt. I was just counscious.

uoaei 3y ago

Steven Strogatz had Emery Brown of MIT on his Quanta-produced podcast to discuss anaesthesia and particularly its differences from typical sleep: https://www.quantamagazine.org/emery-brown-and-the-truth-about-anesthesia-20210426/ https://www.quantamagazine.org/emery-brown-and-the-truth-abo...

bbor 3y ago

WOW this is an amazing article, thanks for posting. As an aside, this popped out to me: the brain implements an algorithm not unsimilar to the TCP congestion window algo!! Perhaps I’m reading into it too much but that’s just terribly interesting. At intermediate anesthetic concentrations, neurons begin oscillating, roughly once a second, between a depolarized up-state and a hyperpolarized down-state (11). The up-state is similar to the sustained depolarization of wakefulness. The down-state shows complete cessation of synaptic activity for a tenth of a second or more, after which neurons revert to another up-state. As anesthetic doses increase, the up-state turns to a short burst and the down-state becomes progressively longer.

op00to 3y ago
I see it more like a NES system that has a bad connection to the cartridge - constantly rebooting, trying to get that signal from the copy protection chip.

ineedasername 3y ago

I had anesthesia once. Subjectively it’s about as close to being dead (or simply “not existing”) as I can imagine. One moment I was perfectly awake, and the next moment I was hearing the sounds of people talking around me and I groggily became aware of my doctor getting me to acknowledge him. There is still the question though, was my subjective experience post-surgery accurate? It’s conceivable that consciousness is suppressed to varying degrees, while the creation of memories is more significantly impacted. I may have had some degree of consciousness but my subjective post-surgery experience has no knowledge of it. And putting aside anesthesia altogether you have the phenomena of people that get blackout drunk. For some period of time they were up, senses receiving input and processing it even if their actions were high impaired, yet afterwards there is no memory. (There are of course degrees to this too, sometimes a person remembers the tiniest pieces, as if from a dream, sometimes not at all) The entire topic invites the question: Is consciousness required for intelligent behavior? Unless you include consciousness as part of the definition of intelligent, it is not an easy question. Somewhat on that topic I’d highly recommend the book Being no One by Thomas Metzinger

ericmay 3y ago
(Queue bar talk) Begs the question, what is intelligent behavior? Most of the time I see pretty anthropocentric interpretations of this (which are often well-reasoned) but there has to be some degree of definition that we can agree to as a starting point. My current view is one of consciousness operating on a spectrum, some animals/creatures/entities are "more aware"[1] than others but then you have to ask whether that just leads to consciousness being a useful phenomenon for interaction with other creatures or if it's something more meaningful. Were humans conscious before the invention of language? Another aspect of this is if "Chat-GPT" isn't conscious it kind of proves your dog is right? You're saying language/interaction isn't that big of a deal, and so it's based on biology. Not a lot different between a cat and a person if you really take a step back, let alone a chimpanzee and a person. Or maybe we're all not conscious at all in the sense that we mean it. I.e. it's just a useful illusion/delusion and evolutionary adaptation for cooperative behavior. Then we have to insert free will, determinism, etc. The whole thing is a mess. Most likely we're not conscious at all, nor do we have free will, as typically described. But we're conscious in that we're perceiving and our body as a whole has some amount of degrees of freedom to operate, but we're not special. Maybe that's scary idk. [1] Whatever that means

quercusa 3y ago

I've never liked Propofol and the hours of dopiness it induces post-op. I did my last colonoscopy with no anesthesia. It was only mildly uncomfortable and pretty interesting - the doctor acted as tour guide. The I got up and went home fully awake. I recommend it.

luckman212 3y ago
what do you do if your doctor refuses to do the procedure w/o anesthesia? find another doctor i guess?
- quercusa 3y ago
  Probably - I'd wonder why they'd refuse. Most insurance (AFAIK) won't cover the anesthesia as 'not medically necessary'.

rybosworld 3y ago

I woke up during an endoscopy when I was young (4/5 years). I have a pretty vivid memory of that one single moment when I came too, and the doctors/nurses panicking a bit when they realized I was conscious. It ended pretty quickly when they gave me more of whatever the anesthesia was.

driggs 3y ago

Don't let all the physiology distract you from the HN-relevant information theory(?) in the `Consciousness and Integrated Information` section near the end: A recent theory suggests a principled reason: information and integration may be the very essence of consciousness. 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. On the other hand, every experience is an integrated whole that cannot be subdivided into independent components. Less metaphorically, the theory claims that the level of consciousness of a physical system is related to the repertoire of different states (information) that can be discriminated by the system as a whole (integration). A measure of integrated information, called phi (Φ), can be used to quantify the information generated when a system enters one particular state of its repertoire, above and beyond the information generated independently by its parts. In practice, Φ can only be measured rigorously for small, simulated systems. However, empirical measures could be devised to evaluate integrated information on the basis of EEG data, resting functional connectivity, or TMS-evoked responses.

justinpombrio 3y ago
An argument why IIT is nonsense: https://scottaaronson.blog/?p=1799 https://scottaaronson.blog/?p=1799

adasound 3y ago

I practice anesthesia. My most significant change so far has been to drastically reduce the amount of ketamine I give. It is a very interesting drug. Very stable re. cardiovascular concerns. Maintains blood pressure nicely. We use it to induce anesthesia and for pain, but others use it for depression, chronic pain, borderline personality disorder. It's fine for pediatrics. Adults not so much. We dose ketamine quite a bit higher as an induction agent at the start of operations than what would be considered a recreational or psychotherapeutic dose/"K hole". In opposition to kids, adult patients have frequently found themselves in a very bad place on emergence from anesthesia and in the recovery room. They sometimes endorse reliving trauma and confronting themselves in a dark region of their minds that they possibly have never known about. This is why it has promise as a therapeutic agent in psychotherapy, however it is often the case that patients are cared for by one recovery room nurse who is run off her feet/has more than one patient. I have learned that "K hole" context is everything. Kids are just fine with ketamine. I think it's because their brains are much more plastic & the variation of experience in their waking lives is higher than adults. I think that experiencing the moods and expressiveness and novel situations as a 3 year old for a day would be an incredible hallucinogen or psychedelic.

basch 3y ago
I have nothing to base this on, but I suspect kids do better because they lack experience, so there is nothing to resurface. Their lack of memories prevents any sort of introspective reevaluation of their life.
- bbor 3y ago
  I think this is a little uncharitable to kids. Do you not remember the stressors and ruminating thoughts of childhood? To say nothing of children who have experienced trauma. Perhaps this could apply to pre-object-permanence infants, but by the time they're undergoing surgery (hopefully...) they've had years of conscious experience. Hopefully I'm not being too uncharitable, your idea is certainly plausible. I'm also just musing which feels disrespectful to the terribly interesting expert take in the ancestor comment, but I cringe whenever I hear arguments that I can reduce down to "being a child is not at all like what it is to be me", as it's been used for centuries to suppress their behavior and excuse abuses

hnu0847 3y ago

There's a very good Radiolab episode that discusses this: https://radiolab.org/podcast/anesthesia https://radiolab.org/podcast/anesthesia

calebm 3y ago

The book, "After: A Doctor Explores What Near-Death Experiences Reveal about Life and Beyond" (Bruce Greyson M.D.), explores this subject.

EMCymatics 3y ago

Anaesthesia is more dangerous and impactful than commonly realized. These chemicals and medicine need to be more strictly controlled.

trts 3y ago

Seeing the authors of this paper, I am reminded of some of my favorite conversations with Gulio Tononi on Closer to Truth, about the nature and constructs of consciousness. https://www.youtube.com/watch?v=uiS5i2d9zBA https://www.youtube.com/watch?v=uiS5i2d9zBA

NateEag 3y ago

I had surgery under general anesthesia for the first time in my life a year or two back, and it was very enlightening. Specifically, most people who have general anesthesia talk about how strangely different it was from sleeping. It was virtually identical to what my sleep has been like most of my life. I went out then I came back. I was groggy longer than usual waking up, but that was about the only difference. I almost never remember dreams, historically. I lay down, go out in < 5 minutes, then get up when something wakes me. That seems to be a rare experience, so I figure outta worth mentioning. Also interesting is that I've been taking atomoxetine for the past few months, and one of the effects has been that I don't sleep nearly as deeply and now remember dreams regularly. My nights are much longer and I don't like it.