Waking up in the middle of a surgery? It's the stuff horror stories are made of. Except the terror never ends, according to a study, citing long-term psychological effects.

It's called anesthetic awareness and it affects about one in every 1,000 patients undergoing surgery in the United States and one in every 19,600 in Ireland and the United Kingdom, according to a study published in the journal Anaesthesia. More than 3 million patients were surveyed for the study and most cases of anesthetic awareness developed when lighter anesthesia was used and/or paralytics were administered.

About 75 percent of cases are short-lived, lasting no more than five minutes. Unfortunately, that period is not brief enough because nearly half of all patients who experienced anesthetic awareness are now suffering from long-term psychological effects like depression and post-traumatic stress disorder.

Take Carol Weihrer, for example. The Reston, Va., resident underwent eye surgery in 1998, waking up in the middle of the procedure just in time to hear the doctor tell the trainee to "cut deeper into the eye."

"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," she recounted.

Since then, Weihrer has been struggling with PTSD, unable to sleep on a flat bed as it reminds her of the operating table. When she gets flashbacks, she starts thrashing violently. To get rest, she sleeps on a recliner. She's been doing that for the past 16 years.

Anesthetic awareness happens when the level of anesthesia in the body is not enough suppress consciousness. Given some procedures require lower doses of anesthesia, such as in emergency C-sections where not a lot of anesthesia can be used to prevent harming the baby, patients undergoing these procedures are at higher risk of experiencing the phenomena.

To combat anesthetic awareness, experts have suggested using nerve stimulators and brain monitors and watching heart rates and blood pressure levels. Educating patients about the possibility that they may wake up during surgery is also seen as helpful because when it does happen patients are not as distressed since they've been prepared.

Unfortunately, a consolidated measure to prevent anesthetic awareness has not been developed yet. When patients do experience waking up in the middle of surgery, doctors are urged not to dismiss their concerns. Immediate treatment is necessary if long-term psychological effects are to be avoided.