Twelve years ago Carol Weihrer woke up in the middle of surgery, and her life has never been the same.

"It was the equivalent of being entombed in a corpse," said the 59-year-old flutist and vocalist. While having her diseased right eye removed, Weihrer woke in the midst of surgery. She recalls hearing disco music and remembers the surgeon commenting, "She's moving." While she didn't initially feel pain, Weihrer was aware of what was going on around her and even saw the room go black when her optic nerve was cut. The pain came when she was injected with a paralytic drug twice. "I thought I literally had to be flaming," she said of the sensation.

Yet there was nothing Weihrer could do to alert the surgery staff because she could not move. "I'm a person of great faith, so I was praying as well as yelling and screaming," Weihrer said. Of course, no one was aware she was awake, so nothing could be done to relieve the horror she was experiencing.

Weihrer says for a time she believed she had died and gone to hell, so traumatic was the experience.

What happened to Weihrer is known as "anesthesia awareness." While it's not an extremely common experience, the publicity that surrounded Weihrer's case has inspired many other patients to come forward with their own reports of what Dr. Lisa Marcucci, an academic surgeon and critical care physician in Kentucky as well as senior editor of "Avoiding Common Anesthesia Errors," calls "post-operative recall."

It's estimated that about 1 or 2 out of every 1,000 surgeries performed in this country each year results in anesthesia awareness, according to the American Society of Anesthesiologists.

Marcucci said there is no way to completely shut down awareness during surgery, and it's not uncommon for patients to have memories following surgery of hearing music in the operating room or to recall snippets of conversation among attending staff.

"You can't shut down implicit memory," Marcucci said.

The concern is not so much that a patient has some awareness during surgery but that he or she remembers it later. That memory, particularly if it was a traumatic one like Weihrer's, can lead to post-traumatic stress disorder.

While Weihrer has not experienced anesthesia awareness in any subsequent surgeries, the memory of that first experience has stayed with her, and she has been diagnosed with PTSD.

"I can't sleep flat," she said. "I have to sleep in a chair. I've been sleeping in a chair for 12 years."

She also reports being easily startled, she dislikes crowds and has triggers that will inspire a feeling of anxiety.

Weihrer's experience led her to start the Anesthesia Awareness Campaign Inc. with the goals of making patients aware of the risk factors for anesthesia awareness and supporting victims. Weihrer has spoken to audiences all over the world in the last 12 years, and she says nearly 5,000 other victims have contacted her with their stories.

One of the major initiatives Weihrer is lobbying for is the use of brain activity monitors in surgery to help alert surgery staff if a victim is experiencing consciousness. While Weihrer now refuses to undergo surgery without a brain activity monitor in the operating room, many medical experts feel the monitors are basically useless and provide no more data than what anesthesiologists are already collecting in the operating room.

"The literature does not support routine use of brain activity monitoring except in cases of high-risk patients or high-risk surgeries," Marcucci said. Those who are most at risk of experiencing anesthesia awareness or post-operative recall are those having trauma, upper abdominal or cardiac surgery. Having had a previous post-operative recall episode may also put a patient at risk, and children are more likely to have anesthesia awareness than adults.

So what do you do to avoid having a nightmare experience like Weihrer's if you're about to go under the knife?

Marcucci advises having a pre-operative interview with your anesthesiologist and expressing your concerns and fears. She says it's also essential that you provide the anesthesiologist with a full history of any drugs, controlled or uncontrolled, and supplements you are taking. If you have a glass of wine every day, be upfront about it. And don't forget to mention if you pop a St. John's Wort pill either. All of these things can impact the effectiveness of anesthesia. Interestingly enough, natural redheads tend to have higher risk of post-operative recall, too.

"You must be your own patient advocate," said Weihrer. "Doctors are not God. One case of awareness is one too many."