It’s not just that we don’t know how anaesthetics work – we don’t even know for sure that they work. Joshua Rothman’s review of a new book on the subject by Kate Cole-Adams quotes poignant stories of people on the operating table who may have been aware of what was going on. In some cases the chance remarks of medical staff seem to have worked almost like post-hypnotic suggestions: so perhaps all surgeons should loudly say that the patient is going to recover and feel better than ever, with new energy and confidence.

How is it that after all this time, we don’t know how anaesthetics work? As the piece aptly remarks, it’s about losing consciousness, and since we don’t know clearly what that is or how we come to have it, it’s no surprise that its suspension is also hard to understand. To add to the confusion, it seems that common anaesthetics paralyse plants, too. Surely it’s our nervous system anaesthetics mainly affect – but plants don’t even have a nervous system!

But come on, don’t we at least know that it really does work? Most of us have been through it, after all, and few have weird experiences; we just don’t feel the pain – or anything. The problem, as we’ve discussed before, is telling whether we don’t feel the pain, or whether we feel it but don’t remember it. This is an example of a philosophical problem that is far from being a purely academic matter.

It seems anaesthetics really do (at least) three different things. They paralyse the patient, making it easier to cut into them without adverse reactions, they remove conscious awareness or modulate it (it seems some drugs don’t stop you being aware of the pain, they just stop you caring about it somehow), and they stop the recording of memories, so you don’t recall the pain afterwards. Anaesthetists have a range of drugs to produce each of these effects. In many cases there is little doubt about their effectiveness. If a drug leaves you awake but feeling no pain, or if it simply leaves you with no memory, there’s not that much scope for argument. The problem arises when it comes to anaesthetics that are supposed to ‘knock you out’. The received wisdom is that they just blank out your awareness for a period, but as the review points out, there are some indications that instead they merely paralyse you and wipe your memory. The medical profession doesn’t have a good record of taking these issues very seriously; I’ve read that for years children were operated on after being given drugs that were known to do little more than paralyse them (hey, kids don’t feel pain, not really; next thing you’ll be telling me plants do…).

Actually, views about this are split; a considerable proportion of people take the view that if their memory is wiped, they don’t really care about having been in pain. It’s not a view I share (I’m an unashamed coward when it comes to pain), but it has some interesting implications. If we can make a painful operation OK by giving mnestics to remove all recollection, perhaps we should routinely do the same for victims of accidents. Or do doctors sometimes do that already…?


  1. 1. Scritch says:

    I was given IV ketamine once during an outpatient hernia repair surgery. I don’t remember the surgery itself, of course, but I *do* remember the process of waking up afterwards. The very first thing I remember after being put under was a slow return to the awareness that I existed – I remember being a little surprised that I was thinking again. I had absolutely no sensory contact with my physical body, and I found myself amused and incredibly peaceful. I remember trying to consider what I was experiencing, and in that time (the duration of which I don’t know) it felt to me as if I was a bubble of pure thought suspended in an infinite black abyss. *None* of my physical senses were available; none that I could discern, anyway/

    I waited like this for a while, fully aware of what was happening – I knew that either I was being operated on presently, or the operation had just recently finished, but I didn’t know which – but I felt no anxiety about this (there were other drugs in my anesthetic mix, including anxiolytics, I suspect). The very first sensory impression I felt was sound – I found I could hear talking from what sounded like an incredible distance away, and I couldn’t make out the words or identify the voices. As time went on, I slowly and without drama reconnected with my body, and began to hear the voices more distinctly – they belonged to my mother and my girlfriend at the time, who were chatting a bit while they waited for me to ‘wake up’.

    I think what I experienced is called a K-Hole wherein a ketamine user experiences total and complete dissociation from their body’s senses. This, it seems to me, is a very important factor in how anesthetics work, and is one you didn’t account for in this post.

    Incidentally, this has also gotten me interested in the recreational use of drugs like this – while I haven’t used ketamine recreationally (yet) I do think about this experience very, very often. It was probably the most peaceful experience of my entire life.

  2. 2. Michael Murden says:

    I’ve heard that a great many anesthesiologists are addicted to, or at least fond of ketamine.

  3. 3. Scritch says:

    That really, really doesn’t surprise me – at least not after my experience with it and other dissociatives.

  4. 4. David Duffy says:

    There is a nice linear relation between brain calibrated BOLD, PET, EEG 13C MR spectroscopy and depth of anesthesia. In deep anesthesia, the brain uses ~50% O2 of full consciousness.

    Anaesthetists have been keenly aware of “anaesthetic awareness” and medical malpractice claims regarding this for many years (I recall some anaesthetists talking reassuringly to their deeply unconscious patients, and shushing the surgeons in the 1980s). Intraoperative EEG is not uncommon in some settings to ensure adequacy of anaesthesia.

  5. 5. Hunt says:

    Seems to me that disregarding potential pain you may later not remember is like disregarding what may happen to your “twin” in the teleporter problem. It’s all good unless you’re the one who stays on Earth.

  6. 6. John Davey says:

    its somewhat unlikely that anaesthetics would not knock you out, but simply wipe your memories. We aren’t talking about computers here, but biological artefacts with graduated features. If you were left in pain there would be umpteen accounts of people experiencing pain and not quite forgetting it – millions of operations are performed each day, and such occurrences would be well documented.

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