Do comatose patients dream?

November 9, 2004 11:41 AM

Do comatose patients dream? Do they remember those dreams when they wake up?

Additionally: do comatose patients ever have nightmares that they just can't wake up from (due to the coma)?

posted by cmonkey to health & fitness (33 comments total)

Three weeks ago I interviewed a guy who had been in a coma for two months. He says he remembers absolutely nothing of that period. Not even a dream. Sorry to be the bearer of boring news.
posted by Faze at 12:12 PM on November 9, 2004

I was told that general anesthesia is essentially an induced coma. I havent been in a coma but I've been under general anesthesia.

Not only did I not dream, there was no sense of the passage of time which you do have when you sleep even though its not obvious. I remember seeing the anaesthesiologists face as I was drifting away and then, in the next instant, I'm struggling to regain consciousness (its like swimming upwards in a deep well) and hearing the voices of my family standing next to my bed in the hospital. Really freaky experience.
posted by vacapinta at 12:20 PM on November 9, 2004

So all those movies where they say, "Keep talking to him. Encourage him. He can hear you." are bullshit?

If so: Cool! I literally blogged that that was the case 2 or 3 days ago in a fiction piece. My character doesn't look so stupid now, does she! Muahahaha!
posted by dobbs at 12:25 PM on November 9, 2004

A friend just spent a little more than a week in a coma. She remembers having horrible dreams that she couldn't escape. She could hear doctors talking to and about other patients in the intensive care unit and thought all those diseases/conditions/surgeries were happening to her.

My sister happened to be her attending physician and told me this was very common among coma patients.
posted by Monk at 12:27 PM on November 9, 2004

Monk - that is absolutely horrifying!!
posted by widdershins at 12:33 PM on November 9, 2004

I wonder if the difference between what Monk's friend experienced and others who don't remember anything has to do with why they are in the coma.

Interesting.
posted by evening at 12:35 PM on November 9, 2004

Hmm. Interesting, Monk. Horrifying but interesting.

Anyone have any good book recommendations on the medical side of comas (non-fiction)?
posted by dobbs at 12:41 PM on November 9, 2004

My mom was in a coma for two weeks last november, brought on by dehydration and infection from chemo / radiation therapy She remembers having several dreams that involved people and events from just before she slipped into the coma. The scary part is she has no recollection of the hours just before the coma began - during which she was especially lucid.
posted by adamkempa at 12:48 PM on November 9, 2004

I've was once unconscious for six hours or so and my experience was like vacapinta's. Basically close eyes, open them, and a half-day is gone. The weirder part of that was that people in the hospital swear I woke up and was agitated and fussing around and I don't remember any of it. In my mind, no time had passed. It's a weird jet lag-like experience; your brain thinks it's the morning, it's actually night time.
posted by jessamyn at 12:48 PM on November 9, 2004

Yeah, I had very similar experiences to jessamyn and vacapinta when I was under general anesthesia in May. My memories of the procedure go exactly like this, in sentence form:

"anesthesiologist placed mask on my facewaking up in post-op"

Not even a gap in time, it was literally like my memory just completely dropped out for an hour between the mask and me opening my eyes in the recovery room. Not sure if it's exactly like being in a coma, but probably close.
posted by 40 Watt at 12:55 PM on November 9, 2004

The confusion here may be from a lack of precise terms for all this. It looks like "coma" is used both to describe the initial state of unconsciousness and a deeper, vegetative state which follows it. It looks like the vegetative state is characterized by a shutdown of all major cognitive functions which would seem to imply no dreams.

I'm still not sure how that relates to anaesthesia or to unconsciousness like jessamyn. Any brain surgeons here? Or any outside reader that wants to email me at vacapinta at gmail?
posted by vacapinta at 12:55 PM on November 9, 2004

My sister's an anaesthesiologist. I'll give her a call tonight and see what she knows.

The "missing time" phenomena also happened to my friend. She didn't believe she'd been out for eight days. I don't know all the details, but the coma was due to complications from childbirth (the baby is fine) and a ruptured liver, if that makes a difference.

According to the Canadian Anesthesiologists' Society FAQ:

Will I dream?
No, the anesthetic state is more profound than the usual type of sleep in which dreams occur.

posted by Monk at 12:58 PM on November 9, 2004

Slate has an article about the different "kinds" of comas. It's essentially a very broad term to describe a variety of non-conscious states.

What's very freaky to me is the worst-case scenario of patients who get a bad mix of anaesthesia, and wind up immobile but mentally awake during surgery, and feel everything.
posted by mkultra at 1:21 PM on November 9, 2004

Anyone have any good book recommendations on the medical side of comas (non-fiction)?

there's an interesting chapter in one of daniel dennet's earlier books that discusses this kind of thing. he goes over a lot of medical info based on anaesthesia. i think the book was "brainstorms", but am not 100% sure.

one thing i remember from his discussion of patients that regain consciousness (to some extent) during an operation (not that unusual, because they're trying to give you as little drug as possible for safety) is that the anaesthetist may give them a drug that induces memory "just in case"...
posted by andrew cooke at 1:23 PM on November 9, 2004

...memory loss "just...
posted by andrew cooke at 1:24 PM on November 9, 2004

When I was unconscious, there was no time or space or anything.
posted by five fresh fish at 1:53 PM on November 9, 2004

I remember dreaming when I had my wisdom teeth extracted (under total anesthesia) years ago. After awakening I realized that some parts of the dreams corresponded to parts of the extraction procedure. It wasn't an unpleasant experience, though, not like mkultra's horror story. All the other times I've been under anesthetic, however, my experience has been like vacapinta and jessamyn's; I went from going under to waking up with no sense of elapsed time.

So if something happens to you yet you can't remember it (because you were unconcious or had taken andrew cooke's amnesia drug) does it still register subconciously and if so how would that manifest itself?
posted by TimeFactor at 1:55 PM on November 9, 2004

this is such a wonderfully freaky thread
posted by leotrotsky at 6:01 PM on November 9, 2004

What's very freaky to me is the worst-case scenario of patients who get a bad mix of anaesthesia, and wind up immobile but mentally awake during surgery, and feel everything.

I can personally testify to this, as it happened to me when I had minor elective laproscopic surgery. I couldn't move or speak from the anaesthesia, but I definitely had an awareness of pain and cutting and innards being moved around. The strangest thing to me is that I remember the sensations and I know I was horrified at the time, but don't really have any strong memory or impression of the terror itself.
posted by marsha56 at 9:01 PM on November 9, 2004

This is nothing more than idle speculation on my part, but I've wondered how doctors know that anesthetized patients are truly unconscious, or whether all general anesthesia is actually just immobility and amnesia.
posted by 4easypayments at 9:48 PM on November 9, 2004

I was told that general anesthesia is essentially an induced coma. I havent been in a coma but I've been under general anesthesia.

Very true. There is always a small chance that people will not wake up from anesthesia. My dad had to go under a few years ago for reconstructive knee surgery. He vividly remembers a struggle of sorts to wake up from the anesthesia, as if his body almost wasn't going to wake up from it.
posted by jmd82 at 10:00 PM on November 9, 2004

marsha56 - were you just "aware" of the pain, or did you "feel" it too? i ask because dennett also described the effect of a common pain killer - morphine, i think - as not deadening the pain, but rather making the pain "acceptable". people still know the pain is there, but it has no emotional impact. that might fit with your description... (which otherwise is the stuff my nightmares are made of!).
posted by andrew cooke at 4:15 AM on November 10, 2004

people still know the pain is there, but it has no emotional impact

I don't know what the local anasthetic I was given was, but when I was in my early double-digits I had a mole removed from the top of my head. The sensation was one of the most curious I've felt to this day. I could feel the extraction device (in my memory, which I strongly suspect is flawed, it was like one of those three-pronged "robot arm" extension toys) cut into my skull and pull the mole out.

Thankfully the anaesthesiologist warned me about the sensation before-hand, otherwise I'm quite certain I'd have freaked out.
posted by cCranium at 5:34 AM on November 10, 2004

The confusion in this thread is mostly definitional, I'd say.

As a neurologist, I recommend my students learn the best definition of coma, which takes about 200 pages - Plum and Posner's "Clinical Diagnosis of Stupor and Coma."

Dreaming is something that we know happens in REM sleep, which is defined by its typical EEG phenomenology. Vague emotional states, including night terrors, seem to occur in stage 4 sleep but they are not formed dreams.

"Coma" as I would use the term precludes dreaming. This could be verified with an EEG. Likewise, when surgical anesthesia is accomplished, with halothane-type inhaled anesthesia; barbiturates/benzodiazepines; or propofol; the EEG record would show profound changes indicating that the cerebrum is not functioning. Although such questions beg certain philosophical questions (and I'm really not interested in getting into that), we believe that dreaming is not possible in such states.

There has been some muttering among the neurologic (and enlightened anesthesiologic) community about pushing for a limited EEG montage routinely during all anesthesia. Unfortunately, the current trend is instead in the direction of eliminating MD anesthesiologists in favor of the cheaper, less-well-trained nurse anesthetists.
posted by ikkyu2 at 7:34 AM on November 10, 2004

When I was 18, I had some minor sugery that required me to be placed under general anaesthesia. I also experienced the "going under-waking up-no sense of the passage of time" experience, although mine was slightly different.

The surgery I had was to correct a varicocele. I was alone in the city I went to school in (no family nearby, few friends) and was very nervous about all of this.

My anaesthesiologist was this crusty old bastard who needed a refresher course on bedside manner, and when he stuck me with that big needle, with no warning, it fucking HURT. In the second or so as I was fading out, all of my apprehension turned into instant rage at this guy. Then I was out.

When I woke up, I was just as angry as I had been when I went under. This meant that I had spent the entire (short) time I was unconscious tensed up and angry. My entire body was sore for a week afterward. My abs felt like I had done 10,000 crunches.
posted by Irontom at 7:43 AM on November 10, 2004

pushing for a limited EEG mon[itoring?] routinely during all anesthesia

a damn good idea!
posted by andrew cooke at 7:48 AM on November 10, 2004

Is it surprising that under anesthesia some people would have dreams or feel the passage of time and others not? Isn't that true of regular sleep? I've had times where I go to bed and suddenly it's morning; I've also had long, restless nights where I'm not really awake but I feel as if I can't fall asleep. And then most times, I have dreams and/or wake up feeling like I slept for a while.

I had minor surgery a while back and was offered general anesthesia or local + narcotic, and went with the latter, primarily because it was less dangerous, but boy was I glad I did :). I really didn't mind that they were cutting into my neck. Everything was so pleasant.

Weird, huh. It sort of freaks you out about what 'meaning' and 'emotion' and 'pain', etc, really are. There does seem to be something of a mind (brain)/ body split, after all...
posted by mdn at 9:43 AM on November 10, 2004

There does seem to be something of a mind (brain)/ body split, after all...

eh? those narcotics are chemicals that produce physical changes in your body. if your mind were a separate thing - fluffy etherical clouds - then you'd be unaffected by the anaesthetic...
posted by andrew cooke at 9:55 AM on November 10, 2004

I love Ask MetaFilter. When you have a question best answered by a neurologist, guess who drops by.

As promised, I asked my sister to contribute to this thread. In particular, I asked if she could clear up some definitions (which she agreed was the major source of confusion) and to comment on awareness and memory under anesthetic.

Coma is a state of profound, and usually, prolonged unconsciousness, meaning the patient cannot be aroused even by intense stimulation. The term, Coma, is usually reserved for unconsciousness caused by disease or injury, such as severe head injury or a metabolic disturbance such as very low blood glucose. I've got no idea if patients in a true coma can dream or not. This would be a question more fitting for a neurologist. The EEGs I've looked at (with a neurologist officially reading them) done on comatose patients are grossly abnormal and do not indicate the patient is in a state resembling natural sleep (they aren't in REM sleep, etc.).

Anesthesia is a loss of sensation, with or without unconsiousness (a common example of anesthesia without unconsciousness is a spinal anesthetic, where the patient has temporary loss of sensation below the level of the spinal anesthetic, but is completely awake and aware. Most people think of "general anesthesia," a reversible, induced state of unconsciousness along with loss of sensation, loss of awareness, an inability to move, and autonomic control (refers to control of heart rate, blood pressure, etc.). Dreaming definitely occurs for some patients under general anesthesia. Most patients I've talked with that tell me they had dreams report them to be pleasant. I always tell patients to think of something nice while they are drifting off to sleep so they will have good dreams and it seems to work—there is research suggesting you are able to influence patient behavior at this point (some studies show an improvement in smoking cessation in patients that listen to tapes with repetitive postitve statements about quitting smoking, etc.).

Awareness under general anesthesia is very rare—estimated from large studies to be 0.05-0.2% of healthy patients undergoing elective surgery. Most patients that experience recall do not report unpleasant experiences. Awareness is more common in emergency surgery such as that needed in severe trauma, or emergency Caesarean section under general anesthesia. This is when, in order to save a life, a decision is made to risk awareness to optimize the patient's chances. (You're too sick to tolerate any more medications, etc.) This is rare, and in this situation, a drug that blocks memory formation may be given as much as the patient can tolerate it. I don't know of any anesthesiologist routinely giving such a medication at the end of a case as such a drug is not known to produce what is called "retrograde amnesia," or erase previously formed memory. The benzodiazepines (valium, midazolam, lorazepam etc) certainly produce antegrade amnesia reliably and may be given as part of an anesthetic for many reasons, one of which might be to aid in preventing recall or awareness.

(BTW most patients "put under" for a tooth extraction are not receiving a general anesthetic, but are given sedation which would make it very likely that they would be aware, but not unpleasantly so, during the procedure.)

Critically ill patients in intensive care units frequently require sedation drugs for anxiolysis, and pain medications, and anti-psychotics or other such medications for agitation and delerium. As you can imagine, when you are seriously ill, your mind can play tricks on you and the most calm, mild mannered patient can exhibit atypical agitation, confusion, or delirium (a sudden reversible state of mental confusion). Many different drugs are used in an attempt to safely sedate patients so that they are comfortable, relaxed, and pain free. This is easier said than done. Some patients are in a coma because of their illness, others are deeply sedated and could be described as being in a coma due to the sedation required to provide care, but most patients are somewhere in between. This is because putting everyone into a deeply sedated state prolongs care unnecessarily and exposes the patients to additional risks associated with being ill in an ICU (hospital-acquired infection being the most common). It is recommended that every patient have their sedation stopped daily to allow them to awaken and be fully assessed neurologically. This is easier said than done but is a goal we are working towards.

I can't comment on your friend's experience due to patient confidentiality, but I can say that it is not uncommon for patients to recall negative experiences while critically ill. I would think being so sick is a negative experience in itself so it would unfortunately make sense that bad dreams or experiences occur. I would imagine most are misinterpretations of actual or perceived events, such as a bad dream you might have while ill with a fever, etc. We try our best to make the environment calm, quiet, gentle, and provide gentle compassionate care, and use drugs as needed to keep a patient safe, calm, and anxiety and pain free. This is an area of critical care that is incredibly challenging for a multitude of reasons.

posted by Monk at 1:12 PM on November 10, 2004

the figure given in schwender et al is 0.5-2% not 0.05-0.2%. see first paragraph of main text, just before Patients [...] are awake, in agony, intensely fearful but completely helpless
posted by andrew cooke at 2:09 PM on November 10, 2004

Note that of the nine studies used to come to Schwender's figure, seven were at least 30 years old. I wouldn't be surprised if a 10-fold reduction were possible in the last three decades. But you are right to question any numbers thrown about. I'll see if I can get a cite from my sister.

I'm surprised at how few studies there are about awareness. The only recent studies I could find (Feb 2000) put the incidences of awareness at 0.15% (18 out of 11,785) with 11 experiencing pain or anxiety (0.093%)

An earlier article by Schwender et al (Nov '95) also uses the higher estimation but goes into more detail (emphasis mine):

The incidence of conscious awareness with explicit recall and severe pain has been estimated at less frequent than 1/3000 general anaesthetics [<0.03%]. Conscious awareness with explicit recall but no complaints of pain has been reported in the literature with an incidence of 05-2%.

Still, I wouldn't want any amount of awareness, pain-free or not. Reading some of the testimonials in Andrew's link (pages two and three) are awful.
posted by Monk at 5:42 PM on November 10, 2004

ah, thanks (and thanks for posting after this has gone off the front page).
posted by andrew cooke at 4:11 AM on November 11, 2004

eh? those narcotics are chemicals that produce physical changes in your body. if your mind were a separate thing - fluffy etherical clouds - then you'd be unaffected by the anaesthetic...

oh, I'm sorry I missed this - woulda been an interesting conversation. Yes, of course it's physical, but what I mean is the difference between what something means to you mentally and physically - the fact that under anesthetic you can experience pain that doesn't hurt. It's just a bizarre feeling - you can feel that it's painful, but you don't mind. It feels as if your body is undergoing pain, but not your brain. I am not suggesting there's anything non-empirical about it - I'm assuming a material causation, etc - but I think we've often drawn a conclusion that if the mind is not "ethereal" then it must be equivalent to the body, and it seems that actually consciousness isn't identical with physical experiences, but somehow overlays them, and can "observe" or "undergo". Consciousness is a weird phenomenon, basically...
posted by mdn at 2:32 PM on December 7, 2004