Imagine going in for a low-risk operation that requires some general anesthesia, and everything seems to be going according to plan—when suddenly you wake up. The surgery must be over, right? Then you hear the words “scalpel, please,” and you realize you’re awake in the middle of the operation. It’s called accidental awareness during general anesthesia.
And it happened to Donna Penner.
Penner, then 44, went to the hospital for an exploratory laparoscopy in 2008. The procedure requires a few small incisions into the abdomen so that the surgeon can insert medical instruments and examine the organs for a diagnosis. 
The Canadian woman had been experiencing unusually heavy menstrual cycles and this operation was supposed to help doctors figure out the cause. But shortly after the anesthesiologist put Penner under, she awoke. That’s when she heard the doctor say, “Scalpel, please.”
Penner couldn’t breathe. She believed she was about to die.
She said she couldn’t alert anyone because of the paralytic they had given her, and so she heard the conversations and felt the pain of the surgery for an hour and a half. Penner was so paralyzed that she’s couldn’t even form tears. When she finally began to regain the slightest bit of movement, she mustered all her strength to twitch her foot. In response, a staff member laid a hand on the foot to calm it. Eventually she could move her tongue, so she tried to wiggle the breathing tube, hoping it would alert someone that she was awake. Instead, the anesthetist thought this meant the paralytic was wearing off and that she could breathe on her own, so he pulled the tube out. 
On the contrary, Penner couldn’t breathe. She believed she was about to die. A nurse was shouting at her to breathe when finally they placed a mask on her face and manually resuscitated her. Penner couldn’t talk about the incident for years because it left her with post-traumatic stress disorder. Now, she’s sharing her story, as in this horrifying essay she wrote for the BBC. Stories like Penner’s are uncommon, but tell that to the people who’ve lived through the nightmare. It’s not much comfort. Accidental awareness happens when you’re put on general anesthesia so that you’re unconscious during a surgery, but—for whatever reason—the anesthesia loses its effectiveness.
Then you wake up.
Some studies show that accidental awareness can happen to as many as one or two in 1,000 patients. These reports relied on patient interviews, where the patients were asked a few times over a period of two weeks about their experiences during and after the operation. The largest study of accidental awareness came out in 2014, and it relied solely on patients making independent reports. The study found about one in 19,000 patients experienced accidental awareness during general anesthesia.
What bothered patients more than pain was the inability to move and not understanding what is going on.
That’s quite a disparity from the other studies, which has led to a bit of controversy, but Professor Tim Cook, who co-wrote the 2014 report, says the newer report doesn’t necessarily discredit the older ones. Instead, it focuses on the population that made reports without being guided. 
Could there be patients who experienced accidental awareness and didn’t report it during the 2014 study? Absolutely. Could there also be patients from the older studies who were asked if they experienced awareness, and through groggy memories confused awareness with dreaming? Possibly. It’s hard to say. Either way, accidental awareness is so horrible that even once is too many times for it to happen. Because consider this: In an extreme case, the patient could be awake for the entire operation without the doctors realizing it.
So how long do episodes of accidental awareness really last?
According to a report by the Royal College of Anaesthetists (RCoA), most reported episodes of awareness are short. About three-fourths of those who experience it are only conscious for about five minutes or less. Cook, who is a consultant anesthetist at Royal United Hospitals Bath in England, says often it lasts even less than a minute. “In many cases it’s fleeting,” he tells HealthyWay. On top of that, about two-thirds of the incidents occur before the surgery begins or after it finishes. That means it’s not very likely that you will wake up as your surgeon is requesting a scalpel or some other tool with a similarly scary name. 
As far as pain goes, the report states that about 1 in 5 patients experience it during the episode, but Cook says that it actually doesn’t seem to be the most distressing aspect. “What bothered patients more than pain was the inability to move and not understanding what is going on,” he says. “The inability to communicate with those they wanted to.”
One type of medication causes more episodes of accidental awareness than any other: muscle relaxants.
In fact, muscle relaxants are one of the leading causes of accidental awareness during general anesthesia. Cook says in a typical operation that doesn’t use muscle relaxants, the patients will begin to move around in their sleep if the anesthesia is wearing off. That alerts the anesthetist to administer more before the patient regains consciousness. 
He says about half of operations use muscle relaxants, though, which paralyze the body. If the anesthesia starts to wear off, the patient can’t move, not even to open his or her eyes. The common response might be, “Why not just administer more anesthesia than necessary?”
The right dose of anesthesia is just enough.
Cook says that can do more damage than good. “Anesthesia is genuinely complex in that one is trying to run the gauntlet between giving too much of the [medication] and giving too little,” he says. If too much anesthesia is used, Cook says the person’s blood pressure will drop and they’ll take a longer time to recuperate after surgery. It’s also more likely that there will be complications after the surgery. “The right dose of anesthesia is just enough,” he says. The problem with just enough, though, is that if a minor interruption occurs, or if the patient is resistant to anesthesia, it could lead them to wake up.
There are a few other common causes of accidental awareness.
Your age and sex play a part, for example. According to the RCoA report, women and those between the ages of 25 and 45 are more likely to experience accidental awareness during general anesthesia.
There is a fine balance between too much and too little.
Cook says this is likely because those are the most common child-bearing ages, and accidental awareness is more likely to happen during a C-section. That’s because medical staff must minimize the amount of anesthesia given to reduce the effects on the baby. Obesity is another factor, because anesthesia is fat soluble. “The location the [medication] works in is the brain, of course,” Cook says. “If you give a [medication] that’s not fat soluble, it doesn’t get to the brain. A lot of the anesthesia will leak into the fat and sort of sit there.” Also, according to the report, if you are very ill, that could make your blood pressure low, and as anesthesia lowers blood pressure even more, “there is a fine balance between too much and too little.” For that reason, an anesthetist might administer a lower dose of anesthesia, leaving you more vulnerable to accidental awareness. 
Finally, the report states that if the equipment used to deliver anesthesia is malfunctioning, it could take the anesthetist a few minutes to figure out the cause. “During this time awareness can happen,” the report states. “So equipment failure is sometimes part of the cause of accidental awareness.”
Although it’s scary, you’re not in too terribly much danger.
“It’s undesirable from everybody’s point of view,” Cook says. “We’ve failed in that respect.” If one had a complete failure of anesthesia, he says, then it’s possible that there would be adverse cardiac responses, but the anesthetist would recognize that and address the problem. “Awareness in itself is not (physically) harmful,” Cook says. 
Psychological harm, on the other hand, is a reality. In the 2014 report, 65 percent of patients experiencing accidental awareness had “an acute emotional reaction” during the experience, including feelings of panic, helplessness, and/or fear. Other studies report varying numbers, “so how many [patients experience distress] is very hard to know,” Cook says. “But because you’ve got the paralysis, they feel they can’t breathe, can’t communicate,” he says. “Psychological harm is much more common.”
It’s often when patients aren’t prepared for the possibility of accidental awareness when the experience can leave them traumatized.
One way to lower the rate of post-traumatic stress disorder is to raise awareness of the phenomenon. “We made many recommendations in the report,” Cook says. “It’s really important that if people understand more about anesthesia itself and awareness, then it’s likely that when events happen then they may be less distressing.”
The recommendations we’ve made will undoubtedly make anesthesia safer.
Cook says all his patients receive information about anesthesia before going under. 
He also tries to keep them informed during the surgical process so that they remain calm. For example, after the operation is over, there might still be breathing tubes in the patient’s mouth as the paralyzing agent is wearing off. Some patients may experience awareness as the tubes are being pulled out. Cook says he will talk to the patient as he’s pulling them out, explaining that it only means the operation has come to an end. He says that anything that can be done to promote knowledge will be useful. The 2014 study happened, he says, because accidental awareness is a very important issue. Penner would most certainly agree. “I hope it will lead to improved information for patients,” Cook says. “And the recommendations we’ve made will undoubtedly make anesthesia safer.”
