Over time, Campbell’s most severe symptoms subsided, and she learned how to cope with those that remained. She managed to move on, become an accountant, and start a family of her own, but she wasn’t cured. Her nightmares continued, and nearly anything could trigger a panic attack: car horns, sudden bright lights, wearing tight-fitting pants or snug collars, even lying flat in a bed. She explored the possibility of post-traumatic stress disorder with her therapists, but could not identify a triggering event. One clue that did eventually surface, though, hinted at a possibly traumatic experience. During a session with a hypnotherapist, Campbell remembered an image, accompanied by an acute feeling of fear, of a man looming over her.

Then, one fall afternoon in 2006, four decades after her symptoms began, Campbell met an anesthesiologist at a hypnotherapy workshop. Over lunch, she found herself telling the anesthesiologist about her condition. She mentioned the appendectomy she’d had not long before everything changed.

The anesthesiologist was intrigued. He told her about a phenomenon that had sometimes accompanied early gas anesthetics, particularly ether, in which patients reacted to the gas by coughing and choking, as if they were suffocating.

The comment sparked something in Campbell. “I started having all these flashes,” she remembers. “The flashes were me being on the table. The flashes were of the room. The flashes were of the bright lights over me.” A man—the same one from her memory?—was there. At some point, the room went black. “And then I got to the place where I was on the table, and I just remember feeling terror,” she says. “That’s all I remember. I don’t see anything. I don’t feel anything. It’s absolute, abject terror. And the feeling that I am dying.” At that moment, Campbell realized that something had happened to her during her appendectomy, something that changed her forever. After several years of investigation, she figured it out: she had woken up on the table.

This experience is called “intraoperative recall” or “anesthesia awareness,” and it’s more common than you might think. Although studies diverge, most experts estimate that for every 1,000 patients who undergo general anesthesia each year in the United States, one to two will experience awareness. Patients who awake hear surgeons’ small talk, the swish and stretch of organs, the suctioning of blood; they feel the probing of fingers, the yanks and tugs on innards; they smell cauterized flesh and singed hair. But because one of the first steps of surgery is to tape patients’ eyes shut, they can’t see. And because another common step is to paralyze patients to prevent muscle twitching, they have no way to alert doctors that they are awake.

Many of these cases are benign: vague, hazy flashbacks. But up to 70 percent of patients who experience awareness suffer long-term psychological distress, including PTSD—a rate five times higher than that of soldiers returning from Iraq and Afghanistan. Campbell now understands that this is what happened to her, although she didn’t believe it at first. “The whole idea of anesthesia awareness seemed over-the-top,” she told me. “It took years to begin to say, ‘I think this is what happened to me.’ ” She describes her memories of the surgery like those from a car accident: the moments before and after are clear, but the actual event is a shadowy blur of emotion. She searched online for people with similar experiences, found a coalition of victims, and eventually traveled up the East Coast to speak with some of them. They all shared a constellation of symptoms: nightmares, fear of confinement, the inability to lie flat (many sleep in chairs), and a sense of having died and returned to life. Campbell (whose name and certain other identifying details have been changed) struggles especially with the knowledge that there is no way for her to prove that she woke up, and that many, if not most, people might not believe her. “Anesthesia awareness is an intrapersonal event,” she says. “No one else sees it. No one else knows it. You’re the only one.”