New Research Shows How Brain ‘Wakes Up’ From Anesthesia

If you’ve ever had surgery that required anesthesia, you know the process of waking up can be a jarring one. Anesthesia induces a deep state of unconsciousness in a matter of seconds, but it can take several hours to return to normal after waking. Many people experience confusion, sleepiness, and even delirium-induced hallucinations as they awaken from surgery, but research on this waking process is limited. New research points to a complicated, meandering process through which the brain wakes up from anesthesia.

How Anesthesia Works

The state induced by anesthesia looks a lot like a deep sleep, but it’s actually quite different. Doctors rely on a variety of chemicals to induce unconsciousness, and each works slightly differently in the brain. What all general anesthesia recipes have in common is that they induce unconsciousness while preserving the body’s automatic functions, such as breathing and digestion. Anesthesia also reduces sensitivity to pain, which is why people don’t typically have dreams of being in surgery or experiencing pain when they’re under the knife.

Because a wiggly patient can quickly be injured, anesthesia also limits or eliminates your ability to move. For the one to two people out of 1,000 who briefly awaken during surgery, this paralysis can be terrifying. Fortunately, people who awake during surgery don’t typically experience pain.

Waking from Anesthesia

Doctors have traditionally theorized that, as anesthesia is eliminated from the body, the brain’s electrical activity steadily increases until the brain returns to normal. But new research at Rockefeller University has found that the process of waking up is much more complex.

Researchers knocked rats out using a popular anesthesia called Isoflurane. As the rats awakened from the anesthesia, researchers examined electrical activity in areas of the brain believed to be associated with wakefulness. In fully awake brains, the electrical activity in neurons oscillates, but in an anesthetized or sleeping brain, electrical activity is slower.

Instead of finding a gradual increase in oscillating neurons, researchers found that oscillations occurred suddenly. While every rat’s brain eventually had oscillations in the same “hubs,” the process through which neurons became more active in each hub varied from rat to rat. Researchers believe this indicates that there’s not a single path through which the brain awakens from anesthesia. Because every rat’s brain ultimately used the same hubs, though, the research suggests that certain brain activity is a necessary prerequisite to consciousness.

While research on rats isn’t always applicable to humans, rats and humans respond in similar ways to anesthesia. While anesthesia is extremely safe, a small number of people who undergo surgery don’t wake up. Among people over the age of 65, the risk is higher. By gaining a better understanding of how the brain wakes up from anesthesia, researchers may eventually find a way to reduce the risks of undergoing surgery.


  1. General anesthesia. (2013, January 19). Retrieved from
  2. To recover consciousness, brain activity passes through newly detected states. (2014, June 9). Retrieved from
  3. (2011, August 4). Under the knife: Study shows rising death rates from general anesthesia. Retrieved from

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  • Leave a Comment
  • Stacie

    June 11th, 2014 at 12:53 PM

    Finding answers to questions such as this would go a long way I believe in helping people be more comfortable when they have to have surgeyr of any kind. I think that alot of us are scared not because of what is being done to us but because there is this fear of never waking up and seeing family again. I think that if there was better understanding for the lay person about what really happens when you are out and the process of waking back up in general, this would lead most of us to a better understanding about what is going to happen and how it really is not that dangerous to undergo the procedure if we are otherwise on good health.

  • Linsey

    June 12th, 2014 at 4:26 AM

    If I don’t have to go to sleep for surgery, believe me, this is not something that I would ever choose!

  • morgan

    June 14th, 2014 at 5:35 AM

    I am not sure that this will change the way that anesthesiologists operate but it should definitely give them more insight and information about what they do.

  • Nan

    June 17th, 2014 at 3:43 PM

    I had that experience of waking up during surgery once but luckily they realized it right away and put me back under. It almost felt like a drean state but I could hear everything going on around me, but did feel no pain.

  • Cynthia

    April 12th, 2015 at 12:09 PM

    My uncle went in for a colonoscopy on friday afterwards they could not wake him up. It has been three days and he is not awake and has a tube breathing for him. Can anyone tell me what is next for him? His children, grandchildren,siblings etc are all at the hosptial so I don’t want to go up there or keep calling but I am so worried.

  • Marco

    January 10th, 2020 at 5:17 AM

    Any updates?

  • Alicia M

    October 3rd, 2018 at 12:14 PM

    I was woken up after a surgery and was instantly awake/alert. Was not groggy or confused at all. When I woke up the anesthetist and a nurse were there. They seemed just as surprised as me at how alert I was. I thought I would be out of it, but I also have sleep problems related to my PTSD and often wake up at night in a state of panic/hyper-alertness. This is how I felt coming out of anesthesia. I was able to completely understand questions and answer them & was fully aware of my surroundings. So, here I am looking up the waking up from anesthesia to try and figure out what that was all about, since other people report such different experiences.
    Thank you for the read, it was very interesting.

  • Keith

    August 29th, 2019 at 7:52 AM

    You mention PTSD , is the impact of this on you the same as it was pre-anethesia.
    Like you I have undergone anethesia and am researching. Real peeps are the best research 👍

  • Fredrick K

    January 10th, 2020 at 11:18 AM

    Do I understand this correctly? People over 65 years old, there is a one in 10 chance of not waking up?

  • Dermott

    January 18th, 2020 at 5:29 AM

    I’l 73 and had a hernia repair. The operation took about ah hour
    After I was returned to the ward, I did not wake up until 4 days had passed. During that time they did many tests, so many that the costs of the unnecessary tests exceeded the cost of the operation 8 times. The medical plan declined to pay for the additional tests and I was taken to court by the hospital. I had to sell both houses to raise money to pay and my savings were wiped out

  • Marco

    January 19th, 2020 at 1:41 AM

    So you could not argue that because you were unconscious you won’t stand for the extra costs they made?
    I would not take any more anesthesia if I were you. But hey it was probably worth the money because they saved your life right?

  • Wendy

    February 29th, 2020 at 2:52 PM

    Shame on the author for making this statement. Read the article in the References. Do your homework right.
    “Among people over the age of 65, the risk is higher, with one study reporting an anesthesia death rate of 1 in 10. ” (Seriously?)

  • Christian

    July 12th, 2020 at 10:08 AM

    Im due to go in for back surgery for my prolapsed discs, and was wondering if I should follow through. I previously had surgery done on my wrist a few years back, but they found it very difficult to wake me up,to the point they had the crash cart out to revive me.
    My question is, should I continue with this surgery after having complications with my previous surgery. I am 35yrs old.

  • jim

    July 16th, 2020 at 4:10 PM

    Exactly! I now know at least one editor who can’t proof read…lol

  • Tristain

    September 16th, 2020 at 10:48 PM

    I had surgery for a perianal abscess, I believe I may have woke up during the procedure. While I couldn’t actually see them, I heard everything they were doing. The scary part started when I could feel my heart stop beating. For a simple procedure that started at 9am, I didn’t wake up until 2pm. I’m a 34 y/o male, recently diagnosed with CHF, discharged from the hospital last Thursday. Is it normal for CHF patients heart to stop under anesthesia?

  • Doug

    November 6th, 2020 at 9:26 AM

    The author is not only incorrect but irresponsible in publishing this opinion. I have copied more accurate data (about 1 person in a million dies from anesthesia) from a reliable source:
    The estimated rates from anesthesia-related deaths were 1.1 per million population per year (1.45 for males and 0.77 for females) and 8.2 per million hospital surgical discharges (11.7 for men and 6.5 for women). The highest death rates were found in persons aged 85 years and older. › pmc
    Epidemiology of Anesthesia-related Mortality in the United States, 1999 …

  • Ab

    January 6th, 2021 at 6:20 AM

    The author needs to reread the quoted reference, regarding the number of deaths while under general anesthetic and correct the error in the article. This is inaccurate and total incompetence. 1 in 10 people over the age of 65 die within a year of receiving general anesthesia. There are many reasons for this, such as older adults living into their 80’s and 90’s who receive general anesthesia for various illnesses and injuries. Their deaths are not caused by the general anesthesia.

  • LaurenGT

    January 7th, 2021 at 12:13 PM

    You’re right. Thanks for your help – I’ve updated the article.

  • cheryl b

    April 6th, 2021 at 8:49 AM

    I have a friend who had back surgery this past Tuesday and then the 2nd part was done on Thursday. She was in surgery for 7 hours this 2nd time. It’s been 5 days and she is not awake. She is diabetic. She is slow to awaken after surgery. She is breathing on her own and the dr. says the brain scan looks ok. We are so concerned.


    September 29th, 2021 at 2:25 PM

    Hi everyone my sister is still in hospital she was on surgery for (colon problem) but she still not awake for 8days now , Please Help

  • Carolina

    October 2nd, 2021 at 1:55 PM

    My husband didn’t wake up after surgery, his eyes where open, surgery went well all vitals were good he just didn’t wake up, he died a day after

  • MF

    December 5th, 2021 at 5:31 PM

    I woke up during MAC anesthesia, with a medical instrument in my body. I was held down, and talked through it. I hate doctors now and haven’t been to one in many years.

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