While under general anesthesia during an emergency Caesarean section, Angela DeLessio's eyes were closed and her body was unable to move, but she remained fully conscious.
"It was like a searing pain," DeLessio told ABC News recently. "I felt like I was being burned. … I was awake as I am right now and having surgery - both with feeling and sensation and mental awareness, exactly the way I am now except I was paralyzed. It was terrifying."
Her doctors had no way of knowing that DeLessio was experiencing anesthesia awareness and was feeling everything.
But a new approach that could monitor consciousness may provide a breakthrough.
Dr. Giulio Tononi, a neuroscientist and psychiatrist at the University of Wisconsin, Madison, believes that the electrical signals - sight, sound and pain -spreading across the brain create consciousness. During surgery, anesthesia stops the signals from spreading, making a person completely unconscious.
Tononi's new awareness monitor stimulates the brain with an electrical current and then looks to see whether the signal has spread. In a truly unconscious brain, the signal would not spread; in a brain aware during surgery, the signal would.
"You don't want the patient to move, to feel any pain, to have any memory [during a surgical operation]," Tononi said. "You're actually injecting current to the brain and finding out whether the various parts of the brain are talking to each other or not."
Experts say anesthesia awareness occurs because anesthesia is more of an art than a science. It's more common in women and runs in families. According to the International Anesthesia Research Foundation, for every 1,000 patients under general anesthesia, one or two will be aware.
"It's a frightening experience," DeLessio said. "It really does affect somebody's life a great deal."
Details of Tononi's work are available in the Atlantic magazine currently on newsstands.