[[The two major medical ways to control pain during surgery are: 1) general anesthesia (deactivate the brain¹s ability to interpret pain stimuli); or, 2) local anesthesia (deactivate the pain receptors in the surgical area). In any case, the residual pain will return when the effect of the general or local anesthesia wears off. Then the patient can be given drugs which will interfere with the brain¹s ability to detect pain stimuli. ]]
Not really related to the snake question, but related to the above statement, Cecil wrote a fascinating - if creepy - column about this: “Do some people remain alert – but paralyzed – under anesthesia?” Apparently sometimes anesthetized people can feel the pain but are knocked out enough that they can’t complain about it!
http://www.straightdope.com/columns/990226.html