New Research Shows How Brain ‘Wakes Up’ From Anesthesia

Surgical Team Working In Operating roomIf 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, with one study reporting an anesthesia death rate of 1 in 10. 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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  • 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

    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

    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?)

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