Drifting off to sleep? The dis-analogy of sleep and general anaesthesia

Richard Armitage is a GP and Public Health Specialty Registrar, and Honorary Assistant Professor at the University of Nottingham’s Academic Unit of Population and Lifespan Sciences. He is on twitter: @drricharmitage

I recently had a general anaesthetic (GA). I was told beforehand on at least two occasions – during the pre-op assessment and while in the anaesthetic room – that the GA would make me “drift off to sleep” for the duration of the surgery, only for me to subsequently “wake up” later in the recovery room. “Going to sleep” is, of course, exactly how all doctors – including GPs when counselling their patients about surgical procedures – describe the nature of general anaesthetic and what patients should expect when they undergo their operations. However, upon close reflection of my experience of general anaesthesia – or, more accurately, the profound lack of experience that it entailed – it appears that general anaesthesia is in fact quite unlike sleep in its most fundamental components.

The key concept at work when contemplating both sleep and general anaesthesia is that of consciousness.  While the origin of conscious remains one of the central and enduring mysteries of neuroscience, philosophy of mind and evolutionary psychology, what is meant by consciousness is generally considered to consist of one’s subjective experience.¹  Qualia are individual instances of subjective experience – phenomenology such as perceiving the colour red and feeling the emotion of anger – which each necessitate consciousness for these states to be experienced by the agent in question.²  For Thomas Nagel, a being is conscious simply if there is “something that it is like” to be that creature – for example, what it is like to be a bat³ (Nagel held that each individual only knows, and can only know, what it is like to be that particular individual – the subjectivist’s perspective – and so the objective view – knowing what it is like to be another creature, so as another human or even a bat – is simply not feasible).  More recently, when describing his experiences of meditative practice, Sam Harris uses ‘consciousness and its contents’ as the framework of entities that collectively constitute the theatre of the mind.⁴  For Harris, there is simply consciousness – the capacity for experience – and its contents – the features of that experience.  I find Harris’ terminology useful, but prefer to use a more intuitive theatrical analogy – that consciousness is the necessary stage upon which its contents are acted out – meaning that consciousness is required for experience, but the stage remains present even while no actors are at work upon it (Harris similarly holds that, while in deep meditation, it is possible for all content to be discarded and for pure consciousness alone to remain).  I shall now use this theatrical analogy to illustrate two major states of consciousness – those of being awake and of being asleep – and to contrast these states with my own non-experience of general anaesthesia.

Awake

While I am awake, a great many actors are at work upon the stage of consciousness to produce a fascinatingly rich, dynamic, immersive tapestry of experiences that include visual, auditory, olfactory, tactile, instinctual and emotional qualia.  At each and every moment it is absolutely like something to be me, such as cold, elated, curious, hungry, or in pain.  Something definitely appears to be happening in my subjective experience – a totally compelling, practically useful (if not truly real),⁵ vista of fully integrated experiences in which I navigate and act in apparent real-time.  I am aware of time’s passage, and while it may subjectively speed up or slow down depending on what I do and do not find stimulating, time never seems stop in its entirety and certainly never runs backwards (I may be in a flow state, or bored out of my mind, and misinterpret the speed with which time subjectively elapses, but I am always aware that time is indeed passing, and its arrow is forward).⁶

Asleep

We commonly equate falling asleep with the loss of consciousness: at night time we climb into bed, become unconscious for 6-9 hours, then regain consciousness in the morning and get up to begin our day.  But, for this to be an accurate use of the word ‘consciousness,’ being asleep – or being ‘unconscious’ – must constitute the opposite of being awake – or being ‘conscious.’  Accordingly, being asleep must be synonymous with the absence of subjective experience.  However, we all have first-hand experience attesting to this not being at all the case: for example, dreams are high-resolution, deeply complex, intricate mental simulations consisting of a wide range of qualia including visual, auditory and emotional experiences (the characteristics of dreams are endlessly fascinating.  For me, the most astonishing is the brain’s ability to both create a joke in a dream and consider the punchline – which the same brain made up itself – to be genuinely unexpected and utterly hilarious – it seems the brain can withhold information from itself);⁷ as another example, when a loud noise begins to sound near a sleeping individual, that person both hears the sound and understands its meaning (if the word “Rich?” is spoken while I’m asleep, I both hear it and reply with “yes?”), and everyone has been awoken due the feeling of a full bladder or of an ‘unintentional’ elbow in return for stealing too much duvet; finally, even upon awaking from a dreamless, uninterrupted sleep I am aware of a sense that a significant amount time has certainly passed (indeed, I often wake up minutes before my alarm was due to sound, suggesting that I am aware of precisely how much time has elapsed since falling asleep).  These characteristics of sleep make a mockery of the suggestion it is synonymous with unconsciousness, which we have previously established amounts to an absence of experience.  In fact, a great breadth of detailed experiences reliably take place throughout our sleep.  As such, a more accurate depiction of the state of being asleep – to use the theatrical analogy – is that the actors are fewer and less active upon the stage during it, but at least some actors are at work there, and the stage itself is still well and truly present.  This hopefully reveals the awake-asleep dichotomy to be a false one, while a more useful construct may be the maximally awake–deeply asleep spectrum of subjective experience that we each navigate across during the circadian cycle.

General anaesthesia

However, my encounter with a general anaesthetic reveals general anaesthesia to not be locatable on either the awake-asleep dichotomy or on the maximally awake–deeply asleep spectrum.  In fact, the key characteristics of general anaesthesia appear to be of a different kind entirely.

What was it like to be me under general anaesthesia?  Well, it certainly wasn’t like what it is to be me now – awake – while I write this article.  I didn’t have the urge for coffee, feel an ache across my shoulders, or repetitively worry that what I’m writing is nonsense.  Nor was it like what it was like to be me last night – asleep.  I wasn’t dreaming that I could fly, noticing that my bladder was distended, or flinching at the pain of sharp surgical instruments.  There was simply a complete absence of any subjective experience.  Even the sense of the passage of time – which is generally preserved in even the deepest of sleeps – was distinctly lacking once I woke up in recovery.  There was no – and I mean truly no – fragment of any subjective experience throughout the entire 2.5 hour surgery.  From the point of view of my consciousness, I had simply not existed throughout the passage of that time.  Not only had the actors left the stage entirely empty, there was simply no stage in existence whatsoever – nor even the capacity for actors, stages, or anything else, to exist.  Could it be described as a ‘nothing’ akin to an infinite black void?  No it could not, because such a description would require the capacity for the dimensions of time (infinite) and space (void), and the potential for the existence of photons and an observer to recognise their absence (darkness).  But there were simply none of these things, and not even the potential for anything at all.

So, what was it like to be me under general anaesthesia?  The question simply doesn’t make sense.  Since it is not possible to experience an absence of consciousness – because consciousness is necessary for even the experience of itself – asking what it was like to experience general anaesthesia is akin to asking what happened before the Big Bang (which itself started time, meaning there was no ‘before’ it) or what was your experience before you came into existence (there was no ‘you’ to have such an experience)?  To say it was like anything at all to be under general anaesthetic would therefore be meaningless.  It is the statement’s antithesis that in fact turns out to be true – that the experience of general anaesthesia is in fact a non-experience.

So what?

For me, general anaesthesia is so unlike sleep that “just drifting off” before surgery is a marked disanalogy.  The closest analogy I can arrive at – assuming that analogies could be both useful and desired – is to that of a turntable that is skipping over the vinyl: the lyrics that were bypassed went simply unsounded, there was no experience of those lyrics being played in even their distorted forms, and there is no recognition of time having passed between the wavering of the needle and its return to the groove.  It is like the information contained within the skipped section of record simply does not exist and was never truly actualised.

So, if “drifting off to sleep” is profoundly inaccurate, what should we tell patients to expect when it comes to their general anaesthetic?  Upon brief reflection, it appears that “you should expect the complete annihilation of your capacity for subjective experience and even your first-person conceptualisation of what it means to be ‘you’” might not be exactly reassuring for our patients or particularly kind of their doctors.

Perhaps the dis-analogy is best left alone after all.

References

1. R van Gulick. Consciousness. Stanford Encyclopedia of Philosophy 2014 https://plato.stanford.edu/entries/consciousness/ [accessed 28 November 2022]
2. M Tye. Qualia. Stanford Encyclopedia of Philosophy 2014 https://plato.stanford.edu/entries/qualia/ [accessed 28 November 2022]
3. T Nagel. What Is It Like to Be a Bat? The Philosophical Review 1974; 83(4): 435-450
4. S Harris. The mystery of consciousness. 11 October 2011. https://www.samharris.org/blog/the-mystery-of-consciousness [accessed 28 November 2022]
5. DD Hoffman. The Case Against Reality: How Evolution Hid the Truth from Our Eyes. Allen Lane 2019.
6. SM Carroll and J Chen. Spontaneous Inflation and the Origin of the Arrow of Time. arXiv 24 October 2004. DOI: 10.48550/arXiv.hep-th/0410270
7. LJ Volz and MS Gazzaniga. Interaction in isolation: 50 years of insights from split-brain research. Brain 2017; 140(7): 2051-2060. DOI: 10.1093/brain/awx139

Featured photo by Wolf Zimmermann on Unsplash