Reply #91: Even surgical patients sometimes "wake up"...

[Bridget Burke]

In about 0.15% of patients undergoing general anesthesia, the anesthetic is inadequate to keep the patient unconscious during an operation. It may be inadequate from the beginning, or wear off during the operation. In this situation, a patient may feel the pain of surgery, pressure, hear conversations, and feel as if they cannot breathe. The patient may be unable to communicate any distress because they have been given a paralytic/muscle relaxant. Some patients become aware but do not feel pain or other unpleasant sensations.

http://en.wikipedia.org/wiki/Anesthesia_awareness

There's been speculation that some receiving "lethal injection" were, indeed, paralyzed from one of the drugs. But they felt the pain, fully.

There is really no clean & neat way to kill a human being.