(CNN) — “I was awake but paralyzed,” says Carol Weihrer as she recalls undergoing eye surgery in 1998.

“I could hear the surgeon telling his trainee to ‘cut deeper into the eye,'” she says. “I was screaming, but no one could hear me. I felt no pain, just a tugging sensation. I tried to move my toes or even push myself off the operating table, but I couldn’t move. I thought I was dying.”

The Reston, Virginia, resident inadvertently woke up during surgery, an infrequent phenomenon called “accidental awareness during general anesthesia.” She’s been struggling with post-traumatic stress disorder ever since.

“I’ve had to sleep in a recliner for the last 16 years,” Weihrer says. “If I lie flat, I get flashbacks of the operating table and I start violently thrashing.”

Fortunately, anesthetic awareness is rare. But new research is shedding light onto risk factors and the devastating psychological effects the phenomenon can have on patients who experience it, especially those who are awake and paralyzed.

The numbers

According to the largest study of its kind recently published in the journal Anaesthesia — in which researchers surveyed more than 3 million patients who received general anesthesia in the United Kingdom and Ireland — roughly one in 19,600 patients “accidentally” wakes up during surgery.

Previous studies in the United States reported a far higher rate of one in 1,000 surgical patients. However, cases of anesthetic awareness in the new study were reported voluntarily by patients, which could misrepresent the true number. Researchers did find that certain surgeries requiring “lighter” anesthesia, like emergency C-sections, carried a higher risk — a rate of one in 670.

Most incidents of anesthetic awareness occurred among patients who had received paralytics as part of their anesthetic cocktail — presumably since they couldn’t move to alert doctors to the fact they were regaining consciousness.

Contrary to folklore, awareness was most likely to occur when patients were being put to sleep before surgery started or after the surgery had ended — not when the surgeon was actually operating.

Patients described a range of sensations, including choking, paralysis, pain, hallucinations, and near-death experiences. Most episodes were short-lived, with 75% of them lasting under five minutes.

Despite this, nearly half of all patients who were conscious during surgery had long-term psychological consequences such as PTSD and depression.

Among the symptoms experienced during the event, paralysis was the most distressing to patients — more so than pain, says professor Jaideep Pandit, consultant anesthetist at Oxford University Hospitals and lead author of the study.

“Paralysis is terrifying and has never been experienced by most people,” Pandit says.

In the United States, more than 21 million patients receive general anesthesia. Experts estimate that roughly 26,000 of these patients experience anesthetic awareness. Even if we applied the relatively low rate found in this new study, at least 1,000 Americans each year would still wake up during surgery.

And “even one is too many,” says Dr. Daniel Cole, vice president of the American Society of Anesthesiologists.

Anesthetic awareness

General anesthesia involves a drug concoction that renders you unconscious, takes away your pain, and induces amnesia. A paralytic is often added to ease the insertion of a breathing tube, prevent patients from moving, and allow surgeons to operate in areas that are inaccessible when muscles are tense.

Anesthetic awareness occurs when the amount of anesthesia is insufficient to suppress human consciousness, Cole says. And certain surgeries — where lower doses of anesthesia are required — carry a higher risk.

Emergency C-sections, for instance, necessitate lower doses of anesthetic to prevent harm to the baby. Lower doses are required, also, during cardiac and emergency trauma surgeries, since large doses could push these medically fragile patients over the edge, Cole says.

But anesthetic awareness really becomes an issue when paralytics are used, Pandit says, since patients can’t move to let doctors know they’re regaining consciousness. Doctors must instead rely on subtle, often unreliable, methods of monitoring consciousness.

For instance, increases in heart rate and blood pressure may signal to doctors that a patient is stressed and possibly awake. But drugs given before or during the operation could block the body’s stress response. Also, though doctors continuously measure the level of anesthetic gas in patient’s lungs to ensure appropriate dosage, the gas may affect each person differently, Pandit says.

Brain monitors, which track electrical activity in the brain, have been touted as a potential solution to the problem. Doctors can use the monitors to keep brain activity below a certain threshold during surgery. But some studies have shown a benefit, while others have shown no reduction in the rate of anesthetic awareness when brain monitors are used, Pandit says.

This uncertainty has prevented the widespread implementation of brain monitors across the United States and has led the ASA to recommend that the monitors only be used on a case-by-case basis in high-risk patients.

Without foolproof methods of assessing consciousness in paralyzed patients, it’s inevitable that some cases of anesthetic awareness are only recognized after surgery — once the patient can communicate what happened.

Still, more can be done to prevent anesthetic awareness, says Pandit.

Nerve stimulators, which measure the extent of paralysis, should be used throughout surgery to ensure that doctors only use the minimum amount of paralytic required, Pandit says. This would still give patients the ability to move if they started to wake up.

Also, educating patients about anesthetic awareness prior to surgery is crucial, says Pandit.

“Patients who were told about awareness before surgery were prepared and not distressed when they experienced it,” he says.

Cole recommends that doctors discuss the possibility of awareness only with patients who are at high risk or when patients themselves raise questions about the topic.

There’s a concerted effort to educate doctors as well. Education about anesthetic awareness is a mandatory part of residency training, board certification, and annual meetings, Cole says. The ASA also maintains a database of all awareness cases to allow doctors to better understand what went wrong.

The aftermath

When anesthetic awareness does occur, doctors need to be more proactive in supporting patients, Pandit says.

“We can’t dismiss the concerns of these patients. We need to offer immediate treatment to avoid long-term psychological harm.”

Parents like Kristen — whose 6-year-old son experienced anesthetic awareness when he underwent tonsil surgery four years ago — couldn’t agree more. Kristen lives in New York but didn’t want to disclose the family’s last name to protect her son’s privacy.

“The surgery went as planned,” Kristen says. But after leaving hospital it became clear that something was wrong. “Our son’s behavior was very odd. He had severe separation anxiety.”

Kristen took her son to multiple therapists, all of who attributed her son’s behavior to being a “difficult child.” It was a year later when Kristen and her husband, a neurosurgeon, got to the bottom of what had happened.

“Our son began to speak about his experience of being awake during surgery. He remembered what the surgeon looked like and the sensation of the surgery itself,” Kristen says.

Her son was particularly distressed by the memory of being unable to move.

Therapists were bewildered that Kristen’s son, who now suffers from PTSD, had such vivid memories of the surgery. He has nightmares, flashbacks, and extreme anxiety from triggers in everyday life, Kristen says. “This has been a life-altering event for us.”

Anesthetic awareness isn’t a myth, Kristen says. “If it weren’t for the fact that my husband was a doctor, I’m not sure we’d have realized what happened to our son or received the support that we did,” she says.

For Weihrer, the eye surgery patient, early support could have made all the difference.

“None of the doctors thought it was a big deal. My anesthetist told me, ‘At least you weren’t hurt, don’t worry,'” she says.

“We place so much emphasis on PTSD among our veterans, who witness death on the battle field. But many patients with anesthetic awareness have near-death experiences and feel like they died over and over again. Where’s their support?”