Just how does generalized anesthesia really work?

Factual Questions
1

I went in recently for a routine colonoscopy. This was the first one for me, and I believe I was medically sedated only once before as a teenager.

While the anesthesiologist was running through her pre-checks with me, I asked her what to expect. She used the word “twilight” which I interpreted as having some level of awareness, but being comfortable and not in discomfort or pain (I’ve thought general anesthetics not only knocked you out, but also blocked pain).

Of course, I have no recollection of the procedure, which got me thinking…what does this stuff (in this case, Propofol) do? I’m finding the google search results a bit horrifying:

“Anesthetics activate memory-loss receptors in the brain, ensuring that patients don’t remember traumatic events during surgery”

So…do patients actually feel pain/discomfort during surgery, but just can’t remember it? Are we paralyzed and not even reacting to it, even though we’re feeling it? I had no idea…and I guess the end result is the same, but this shocked me a bit (the source above is not the only one that described it this way).

2

Twilight anesthesia is different from general.

3

While patients are generally not completely out of it during colonoscopies, propofol does induce unconsciousness, though its main uses as I understand them are in rapid induction of and maintenance of anesthesia in concert with other drug(s). So you may be under completely for a time during the procedure.

It’s not like patients are screaming or writhing in pain during procedures utilizing propofol and just can’t remember it afterwards (this would be unpleasant and counterproductive as far as medical staff are concerned). There’s a lot to be said for feeling sleepy and transitioning seamlessly to awakening with everything done.

4

From what I recall having had conversations with the anesthesiologists when I had surgery, they do both- they give some sort of amnesia-inducing sedative beforehand, and then give you the actual anesthetic during the surgery itself.

First time around with knee surgery, they said “We’re going to give you Versed(midazolam) now”, and I was sitting up on the gurney outside the operating room. I said “I’ve heard of that- I won’t remember anything, will I? I read about it in a Tom Clancy novel where they were using it as part of an interrogation scheme.” They were surprised, but confirmed what I said. Then they injected it into my IV.

Next thing I was aware of, was being swaddled like a baby laying on my back with my knee and throat being vaguely sore. It was very strange, to put it mildly. From my perspective, one moment I was sitting up talking, and the next I was swaddled, on my back, and feeling entirely different sensations.

Next time around, it was less abrupt. I was in the OR, they were getting me ready, and the anesthesiologist gave me the sedative, and I fell asleep, fully aware that I’d wake up after surgery. So waking up wasn’t such a discontinuity.

My best friend/roommate had some kind of serious GERD, and had to have an upper GI endoscopy. For that, they just gave him the sedative by itself. The interesting part was that I took him to the endoscopy, waited around on him, picked him up, went to lunch afterward, and went back to the house, where he took a nap. Two hours later, he woke up and said “I assume you brought me home? I don’t remember anything after they gave me the sedative.” It was very strange- we’d had a great conversation over lunch and from my perspective, he was his normal self. But from his, there was a great big yawning gap in his memory, and I’m telling him that we had a conversation about these topics.

5

Thanks for this. My only other experience was when I had my wisdom teeth removed. Aside from NO2 and local anesthetic, I don’t know what I was given. I vaguely recall being awake - I still remember the feeling of pressure and the horrible sound of cracking teeth when they were pulling them out, but don’t remember pain. I was expecting something similar, but again I have no idea if they gave me anything else to sedate me.

6

Eg Halothane works via

As for sevoflurane,

Sevoflurane acts as a positive allosteric modulator of the GABAA receptor in electrophysiology studies of neurons and recombinant receptors. However, it also acts as an NMDA receptor antagonist, potentiates glycine receptor currents, and inhibits nAChR and 5-HT3 receptor currents.

With these kinds of drugs it is sleepy time pretty quickly, that is, you should be knocked out and not vaguely recall being awake.

7

This was better than 30 years ago, so I gather they have even better drugs now: I got food poisoning, started spitting up blood several hours later, went to the hospital where I was given an endoscopy (the camera down the throat, right?) to see if I really messed up something esophageal-wise. Small tear, nothing to write home about, take industrial strength antacid for the next month. End of story.

The procedure was actually FUN: they gave me some yellow pills to counteract the gag reflex, laid me on my side to avoid choking on saliva, pumped I-have-no-idea-what into my arm (like Mr. Sulu said, “With an armful of this stuff, I wouldn’t be afraid of a supernova!”) and went to work with the camera. I might have been actually asleep for about 5 minutes, but I was coherent the entire time. I asked to see my insides and they aimed the eyepiece for me, I joked with the nurses, and I drooled about four gallons of spit onto the table. A very informative experience. Except for the spit. :grinning:

8

I’ve had various types of drugs during surgery. The only one that keeps me awake but blocks the pain is nitrous oxide during dental work. The feeling is more buzzy and distant than normal, and it’s hard to understand the conversation going on around you.

I started using versed a few decades ago when I had my wisdom teeth pulled. Not only did I not remember a thing until I was in the after room, but my wife told me I had woken up earlier, talked to the dentist, and wanted to leave. That’s why you are told you cannot drive yourself home afterward. Today, however, my understanding is that the amount of versed is lowered and cut with other drugs like propofol. Some people stay awake during colonoscopies, but I ask not to.

I don’t believe you are in active pain but simply not remembering it when such drugs are used. In fact, during carpal tunnel surgery I woke up and lifted my head to see what was going on. I felt no pain at all and they simply gave me a boost to put me back under.

9

When I had surgery on my foot back in ‘99 (man that makes me sound like an old guy) I was brought around to some state of consciousness about half way through. It seems this is or was standard practice to make sure the patient hadn’t suffered something unfortunate while anesthesized. The thing that sorta puzzled me was that I remember being “woken” and then the surgeon telling the anaesthesiologist to put me back under after my responses to whatever were good. I was told that wasn’t uncommon and that we don’t entirely know why the drugs work but that they do with some variation between individuals.

10

Every time I’ve undergone a general (maybe 5x) I found it very curious. And I’ve been surprised at the frequency of adverse reactions - including death, and the uncertainty as to the exact manner in which it works.

The weirdest one was when I shattered my ankle and then walked on it, causing the bones to slip over each other. (You know - trying to convince myself it was just a sprain! :roll_eyes:). At the ER they wanted to yank it out before I had surgery a couple of days later. As I recall, they gave me an injection that lasted no longer than 10 minutes or so, with no loss of consciousness, allowing the doc to yank away at my foot.

11

Man, I wish I could have had that shot when they set the bones in my broken arm as a kid. That was, traumatic, to say the least.

12

Yeah, well - then there was the time they stapled my head after a martial arts injury. Had had stitches many times, but never staples. Thought it would be something other than basically just pounding on a heavy duty Swingline…

After the first 7 or so, I asked if they could possibly use something to numb it at least, and they said something along the lies of, “Oh, did you want that? Oh well, we’re almost done.” :grimacing:

13

I took my brother for his vasectomy, and we had a similar experience. When I picked him up afterwards he was pretty loopy in a way similar to if he were drunk. I was hungry so we drove through Taco Bell and talked on the ride back, but from his perspective he went from being at the appointment to being at home in his recliner covered in cheese and lettuce and taco wrappers.

When I got my vasectomy all they did was load me up with Valium and administer a local anesthetic. I felt extremely chill for a while but never lost consciousness, and acted disappointingly normal for my wife when she picked me up afterwards.

14

I didn’t even get valium; just the local, and I drove myself home. I had the no-scalpel kind, so maybe that’s why.

15

Same here. They sent me home with a script for Vicodin, but I just took a couple of Tylenol and some frozen peas to keep me company. One of the easiest procedures I have had.

On the other hand, I had propofol with my colonoscopy and from “you are going to feel the anesthesia going in now” to “we are all done” seemed to me to be about 5 seconds with nothing in between.

16

Best thing I did was get some fairly tight jockey shorts beforehand and wore those and my old softball jock-strap (not at the same time). Support was the key to comfort.

17

Wow, sounds like you’ve had a rougher time than most patients. :grimacing:

18

When I had my wisdom teeth removed, they just loaded me up with a lot of novocaine. (The teeth had one big root each instead of the usual number – 4? 3?. This made them a lot easier to remove.) I drove myself home after the procedure.

When I had outpatient kidney surgery, I got uncontrollable tremors in bed at night. Not just little shivers, but big shakes that disturbed the cats. My urologist said I had probably been a little overmedicated with the anesthetic.

I mentioned this at my last colonoscopy. The anesthesiologist decided to cut back on the amount they gave. I was awake for the whole procedure. At times it hurt a little, and at times it was just uncomfortable. But somehow I didn’t have the ability to make the doctors aware that I was awake. I remember laying there thinking, “I really ought to say something,” but not quite knowing how to talk. It was very weird.

19

I’ve had two colonoscopies this year (one to remove a 4cm sessile polyp, and one to make sure it wasn’t growing back). Both times I received midazolam and fentanyl. The first time I received 250mcg of fentanyl, and felt no pain, but was able to watch the procedure on the monitor and talk to the doctor and nurse. The second time, they only gave me 150mcg of fentanyl, and I experienced significant discomfort. I don’t know why I got more the first time, but the second nurse commented she thought it was too much. She was mistaken.

20

I only got novocaine when I got my wisdom teeth out. It took between 9 and 12 shots to keep me numb enough to yank them all, thanks to having inherited my mother’s tendency to not have painkillers always work. Yay! The Tylenol #4? #1? I took afterwards - Whichever is least potent - didn’t work on me at all.

To my surprise, then, when I got my port in May whatever they used to sedate me worked like a charm. But I refuse to let them use lidocaine when they access my port - I have them use the cold spray.

Needless to say, I worry about anesthesia and painkillers after when I get surgery hopefully later this year.