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etomidator562 karma

I'm a practising Anaesthetist, and this is something I worry about every day. Luckily I've only ever seen it once, and that was someone else's patient. I'm curious as to what kind of anaesthetic they were using - was it gas, or a propofol infusion? And did you ever go to sleep and then wake up (so, for example, were you awake when they put the tube in?), or were there any parts where you drifted in or out or consciousness? Thanks for doing this AMA!

etomidator61 karma

Hope OP doesn't mind if I comment here. The procedure for going under a general anaesthetic (most of the time) is basically to get the patient onto the table, put on monitoring, and then fill their lungs with oxygen. This is important, because once the anaesthetic is given they stop breathing, and having large amounts of stored oxygen gives the anaesthetist more time to put them on the breathing machine before the oxygen levels in the blood get too low. The anaesthetic (usually propofol) is given to put them to sleep, and the muscle relaxant is given to make it easier to put the breathing tube in - it's not needed for all surgeries, because if you have enough anaesthetic on board you won't move during the procedure even without muscle relaxants. The problem with the muscle relaxant is that it takes several minutes to work, while the propofol takes about 20 seconds, so many anaesthetists give the relaxant at the same time as the propofol - you want the relaxant working properly before the oxygen stores run out, so you can put them on the breathing machine in time. This means that the relaxant is given before you know for sure the anaesthetic is working. This isn't normally a problem, because the doses we give to healthy people are generous enough to account for individual variation, but because we have to use less for sick, bleeding, elderly or pregnant people, and because drug users and alcoholics are more resistant, these people are more prone to being aware. For most healthy people, awareness occurs later in the surgery, due to inadequate depth of anaesthesia (if something really painful gets done to you unexpectedly, you may not have enough anaesthetic on board), inadequate monitoring, or equipment failure. The three ways there are of convincing yourself a patient is asleep are looking at their vitals (HR/BP sky high, patient is crying etc are bad signs) or movement (only if the relaxant has worn off/wasn't given), looking at the concentration of the anaesthetic gas they breathe out, and using a brainwave monitor. For most anaesthetics, the last two are equivalent, and even using these appropriately the rate of awareness is somewhere between 1 in 1000 - 15000. Retrospectively analysing these cases, most of the time there's a clear cause (i.e. The brainwave monitor said they weren't deep enough but no-one believed it - in practise, not too hard to imagine, because the monitors are often fiddly and get interference from everything), but there are very rare cases where we just don't know why

EDIT TL;DR Awareness is rare unless you're an alcoholic or dying. We have ways of making sure you're asleep. Sometimes they don't work

etomidator54 karma

I'm sorry you've gone through that. There's a large number of people with awareness who never tell their doctors because they are worried about not being believed, and it does make it much harder to get assistance and explanations and start the process of moving on. 2008 was around the time it was starting to get much more attention both in the media and from Anaesthetists in general, I'd be incredibly disappointed if you still had to fight huge battles getting medical professionals to take it seriously these days.

etomidator42 karma

So, I'll try to do the best I can without actually giving medical advice. Blah blah, disclaimer blah. Buprenorphine is tricky because it's quite controversial in Anaesthetics. Because it's a 'partial agonist' if it occupies a receptor then it will give pain relief, but theoretically less than a full agonist i.e. Morphine. Also it binds preferentially to receptors than say Morphine. So, classically Anaesthetists have thought that if someone's on Buprenorphine (Subutex) then they will need huge doses of morphine for pain relief, and so if there's a way to stop it before surgery then that would make things less confusing. Alternatively, keep people on whatever they usually take and then add in whatever we need on top of that. The problem, as you've pointed out, is that the amount of narcotic you need in this situation can be huge. This makes a lot of doctors and nurses uncomfortable, so there is a tendency to not give enough pain relief in these cases, which is suboptimal. The problem is systemic - i.e. even if I know you'll need heaps, it's difficult to explain this to every doctor/nurse that will look after you.

More recently though, some of us are coming around to the idea that it's actually more complicated than that. So, for example, I've started using Subutex in some patients for pain relief after surgery, and some places have started putting it in the PCA (buttons patients can push to give themselves a dose of pain relief). At these doses (up to 1.6mg/day, compared to like 16mg/day for drug treatment programs) it seems to work like a full agonist, but with less side effects.

Anyway, whatever happens, people on these medications ARE much more likely to have significant problems with pain relief after surgery, or pre-surgery in the case of say a fractured arm. The best way to get around this is to block the nerves themselves - so, having a brachial plexus block for arm surgery, a spinal or epidural for abdominal or leg surgery etc. When these techniques work, it doesn't matter how much pain relief people are on usually, because it's working by a different mechanism. But, this relies on you having an anaesthetist that has kept up their skill in these procedures. And a surgeon that allows them enough time pre-surgery to discuss and commence this.

In regards to awareness, chronic drug use (including OxyContin, Targin, Suboxone) is a risk factor. Put simply, the doses of anaesthesia (propofol/Sevoflurane etc) we use are about 0.5 - 0.7 of what you'd need to keep you asleep by itself. The reason we only need to use that 0.5 - 0.7 is because by adding in morphine/fentanyl we reduce the amount we need. So you can see that if someone is going to need huge doses of morphine, and we give them the usual dose, it won't have as much of an anaesthetic-sparing effect, and so they are more likely to be 'too light'.

How to discuss this with your Anaeesthetist? Most of us are professionals with a real interest in doing the best thing for the patient, and simply volunteering your medication history and specific concerns when they meet you pre-op should be enough for us to work out a plan. If they don't offer it, ask if a nerve block or epidural would be appropriate. And, quite frankly, if they come across as an uncaring pompous dick, mention that immediate family members have had awareness under anaesthesia - that should at least get their attention.

TL;DR Long-term medications for pain relief and drug withdrawal can predispose you to awareness and make post-operative analgesia much more different. There are ways to get around it if you have a professional Anaesthetist.