Large trials have demonstrated that around 1 to 2 per 1000 patients experience some form of awareness. The majority of these do not feel pain although around one third did. The most traumatic case of anesthesia awareness is full consciousness during surgery with pain and explicit recall of intra-operative events. The patient may feel the pain or pressure of surgery, hear conversations, or feel as if they cannot breathe. The patient may be unable to communicate any distress because they have been given a paralytic/muscle relaxant. A fully paralyzed patient is unable to move, speak, blink the eyes, or otherwise respond to the pain. If anesthesia awareness does occur, about 42% feel the pain of the operation, 94% experience panic/anxiety (sometimes because they cannot breathe), and 70% experience lasting psychological symptoms. Currently, the anesthesia provider community accepts that anesthesia awareness occurs yet is in denial about its frequency. Most studies show its incidence is 1–2%.
From: http://en.wikipedia.org/wiki/Anesthesia_awareness
