Just how does generalized anesthesia really work?

Factual Questions
21

I think they still induce you with Versed etc. though - since those are anesthetic GASES, which require that you’re intubated.

At least that’s how it was done for my septoplasty, back in 1989, and I think for my gallbladder surgery 12 years ago - and I think for my wrist surgery back in 2018. For the first, I actually had to move myself to the table in the OR; for the other two, they gave me something via IV while in the pre-op area, and the next thing I remember was being in the recovery area. I am guessing that I moved myself onto the operating table both times and simply don’t remember it.

I know for a fact that I was intubated for the nose surgery - I have a very, very faint memory of having the tube removed. Not unpleasant, just weird. I’m sure they also intubated me for the gallbladder surgery, but I don’t have even that memory; ditto the wrist surgery (though that may have been done with less-invasive airway management).

Interestingly, I’ve seen medical shows set in Canada and/or the UK where they have an awake-seeming patient in the OR and put a mask over the patient’s face to knock them out. As a lifelong asthmatic, who gets twitchy when something even SEEMS to be impairing my breathing (even when I know it does not - e.g. I cannot wear a turtleneck if the neck is too tight), that would freak me out.

:::shudder:::
When I had my wisdom teeth out, 40+ years ago, the dentist offered me the choice of a local, or IV sedation. He said “You won’t feel pain, but you may hear cracking” - to which I responded I’d like the IV please. In hindsight this was REALLY a good decision, given how much trouble I’ve had being numbed on other occasions. It would not have gone well. The only other “invasive” dentistry I’ve ever tried without sedation of any kind was my first root canal - which was sheer hell.

@Fear_Itself , sorry to hear about that unpleasant experience! I hope you let the facility know how badly they screwed up.

22

My only experience with fentanyl was after bruising my kidney (almost blacked out). It was 9/10 pain, and 10 is blacking out. IV fentanyl and I was just fine to talk to the doc. I almost had to go back to the ER, though–I couldn’t poop for a week. Seems like general has gotten pretty dialed in the last 15 years.

23

Just last week I had a routine colonoscopy and was given propofol. Because my insurance only pays for it after my deductible is met I did some research. It’s widely considered medically effective, but expensive so insurance companies don’t want to pay for it. Once they put it in my IV, it took barely seconds until I was out. When I came to, I wasn’t groggy at all. I was shocked when I found out I was out for about 20 minutes. No recollection at all of the procedure.

24

My dentist was well aware of my mom’s and my issues and frankly was not about to give me something stronger.

25

Before I went to pharmacy school, I dated a man who’d had knee surgery, and he said of the pre-op meds, “I was fully conscious, but they could have cut my leg off at the hip and I wouldn’t have cared.” Several years later, when the lecturer told us about Innovar (fentanyl and droperidol, a combination that is no longer commercially available), I knew instantly that this was what he got.

General anesthesia is divided into 4 stages, defined by the loss or regaining of certain behaviors and reflexes.

Stage 3, which is surgical anesthesia, and stage 4, which I’m pretty sure is to be avoided at all costs, are further subdivided into multiple planes.

26

Pre-medication and intravenous induction agents, like propofol and midazolam, are given to bypass Stage 2. I’ll never forget the elderly professor who, in describing stage 2, said, “You would never believe some of the words these proper little old ladies know, and use while passing through it.”

27

I’ve had general anesthesia for a few kidney stone procedures now. The weird thing for me is that, unlike many other (most?) people, who can remember right up to when they put the mask on and give you the anesthesia, my memory is knocked out sometime before then. For example, I will remember going into the operating room and transferring onto the table and then it just cuts out with no particular last event of note.

Also, this past time, my wife tells me that when I first came to, I was slurring my words so much that the nurses were concerned that I might have suffered a stroke (which leads me to believe that this was at least somewhat unusual). I have no memory of this, as my memory only cuts back in at a later point.

It does seem bizarre to me that I had experiences that I just have absolutely no memory of. I kind of wonder, “If the memory isn’t there, did it really even happen to me in any sense?” Another question that nags at me is why I react in this way to the general anesthesia. In particular, it seems very out-of-character in the sense that I am quite resistant in general to sedating medications. At best, medications that are supposed to have a strong sedative effect (Vicodin, Benedryl, sedating anti-depressants, even intravenous morphine for kidney stone pain) might help me to get to sleep a bit better; at worst, they don’t even seem to do that.

So, I have come up with this “theory” that I am actually quite resistant to anesthesia and the memory issues / slurring issues come about because they end up having to give me so much of it to overcome my resistance. The only problem with this theory is that it is completely devoid of any evidence because anesthesiologists don’t seem to come around afterwards once you are awake so that you can ask them questions about how the administration of the anesthesia went. So, at this point, it still remains somewhat of a burning mystery for me.

In an unrelated note, I have also had several kidney stone lithotripsies and getting my wisdom teeth out under just sedation (e.g., nitrous oxide) and an epidural or numbing medication. For these, I do have a pretty full memory of the event although I can realize afterwards that the sedation did mess with my sense of time and also did really relax me: For example, for the wisdom teeth, I remember the oral surgeon saying something like, “Oh boy, this one is deeply embedded and upside-down” and I remember thinking at the time, “Cool!” and then afterwards thinking, "That’s pretty great stuff to change my normal reaction from worry and “Oh shit” to “Cool”!

Finally, I have also had twilight anesthesia for both kidney stone procedures and colonoscopies. For me, they are pretty similar to general anesthesia in the memory just totally cutting out (although, unlike general, I think I may remember all the way up to when they say they are injecting the anesthesa…I will have to check next time I have a colonoscopy to verify if that is so).

28

I’m going to add that scientists and doctors do not fully understand how general anesthesia works, just that it does, and for that, humanity is grateful. I rank its discovery on an equal par with the invention of the printing press as the greatest advances of the years 1000 to 2000.

29

Anaesthesia is close to witchcraft IMHO. As much as there are hand-waving mechanistic justifications, there are few ideas as to why anaesthetics work so well, and provide pretty close to exactly what is needed.

One thing that has always puzzled me is our memory creation process and its disablement. For every general I have had I can remember the conversation with the anaesthetist right up to the near second of losing consciousness. This would suggest an interesting question about memory processing. Somehow my brain either processed the memory into long term in the gap between induction and establishing full anaesthesia, or it was held in stasis and processed into memory after. I would guess the former, but I have always been intrigued by the phenomenon. It isn’t as if a typical anaesthetist waits around long before sending you properly under, so the gap in time needed to process the memory is short.

The distressing phenomenon of patients that become awake and aware, but remain paralysed, during surgery is another mystery.

30

There is a theory that at least with alcohol blackouts, the memories never form at all.

Which is unfortunate, as the anaesthetic effect - passing out - usually appears some time after the user has blacked out and making a fool of himself.

31

UGH!!!

Obviously you only need that particular procedure once, but definitely find a different person next time you need anything major.

I’d gone well over a year between dental visits - we’d quit seeing the dentist we’d been using for years, after he botched a decay issue with my daughter (hygienist saw the beginnings; dentist said “it’s nothing”…4 months later she was hysterical with pain; the tooth had decayed further and abscessed and needed to be extracted - luckily it was a baby tooth). We took the daughter to a different dentist after that, but I avoided seeing anyone despite a tooth getting more and more painful.

I finally broke down and went to my daughter’s dentist, and was very up front about my history of painful dental work including that horrifying root canal. I suggested a horse tranquilizer and a hammer to the side of the head might help. She suggested a more controlled approach: an oral sedative and nitrous. While it didn’t work QUITE as advertised - she said I wouldn’t even really be aware of time passing, and I was - it did the trick in that I felt no pain, and was very relaxed during the 5 and a half hours I was in the chair.

32

This was 1982…

33

A neighbor of mine - or rather, her husband, tells the hilarious tale of the wife behaving in… an imappropriate way with him after the sedation kicked in but before he left the pre-op room where he’d been waiting with her.

She has zero memory of it, just laughs and says “What can I say? I love my husband!”.

They kicked my husband out before they sedated me, for my wrist surgery, so we never had a chance to find out how I’d behave!

34

I’ve been under general anesthesia once or twice, twilight sedation three or four times, and have administered twilight sedation probably a hundred times.

The terms twilight sedation, conscious sedation, and moderate procedural sedation are synonyms. Moderate procedural sedation is the official term where I work now. Although I’ve heard the term twilight, it’s never been used in my hospitals.

There are several indicators for which is which, but the main bright line separating the two is maintining your protective airway reflexes. Generally speaking, losing your gag reflex for whatever reason will indicate the need for intubation, this can be from anesthetics, or a brain injury. We try hard to avoid that level of sedation in the ER (sometimes GI will do procedures there), but have the preparations to do so if needed.

Occasionally we’ll have to hold someone’s airway for a minute or so, but drugs are chosen for procedural sedation because they are potent and short acting, I’ve never had to intubate someone.

You can be sure that the individual cells being damaged are sending out a pain signal, but different pain control methods work in different ways. A nerve block, like the dentist uses, temporarily ‘cuts’ the line and the signal doesn’t get past it. Propofol and Versed impair long term memory formation and you may be able to answer questions that you don’t remember later. Propofol will also render you unconscious, but Versed, a benzodiazepine, doesn’t have analgesic properties, so we usually combine it with Fentanyl.

Having a patient yelling or flailing is dangerous whether they remember it later or not, so although you might verbalize some pain, we’ll stop and re-dose you if you do.

Propofol and Versed can be a bit of a truth serum, in my experience. Not that they compel you to honesty, but that they remove inhibitions, I’ve heard some interesting things. When I was coming out of Versed I recognized my recovery nurse, she’d worked in the ER before. She’d also brought her daughter in when she was having a mental health crisis. I started asking questions about the girl and offering advice which was not, necessarily, bad advice, but, yeah, inappropriate.

35

Just a quick question: when I was a kid in the '60s, I had adenoids and tonsils taken out several times (yes, tonsils three times) and each time, I got the mask over the nose and mouth with the foul tasting gas, count backwards from 100, wake up with a headache and my mouth and throat tasting like I fellated the Goodyear Blimp. What was that gas, do they still use it and since I was out like a light, I figure that was general anesthesia. Comments?

36

That was probably ether, or some other agent, like chloroform or cyclopropane, that isn’t used any more.

True “twilight sleep” did not alter consciousness, but it did cause amnesia, which was why it was used during labor for many, many years. I’ve heard that it was actually NURSES who lobbied for its abolition, because women still experienced pain but didn’t remember it, and they could get really violent too. It also frequently made the babies dopey and they would have respiratory distress until it wore off for them.

37

Maybe back in the day, but hard disagree for modern procedures.

38

The old twilight sleep used morphine and scopolamine, or sometimes paraldehyde when that was still available. Modern twilight sleep, which is still occasionally used on the battlefield or by EMS, is done with ketamine and diazepam.

Anyone remember this story? (Reader discretion advised.) Yep, ketamine and diazepam; I was a year out of school and wondered what they did. The first story is sanitized quite a bit.

39

-shrug- I never see diazepam used for procedures, Versed (midazolam) is much better.

40

Yeah - not any kind of medico here, but I’ve always heard of Versed (and when I’ve had anything, it was Versed). I’ve had diazepam (Valium) or trialozam (Halcion) for things like dental procedures and MRI anxiety, but that’s a pill, not IV, and just made me loopy and a bit drowsy.

Why is Versed preferred, anyway? Does it have to do with its fast action? speed of reversal? something else? I expect that the Valium or Halcion would have also hit me quite fast if given via IV.