anesthesia
"Just had propofol administered today after a colonoscopy.  There was a slight burning sensation once given but I fell asleep and didn't feel a thing during the procedure which was good.  I woke up laughing and had what seemed like a slight cold (sneezing and watery eyes for a little bit).  The laughing didn't stop  for about an hour.. it was not an unpleasant experience, but some people who have this reaction may feel a bit embarrassed!"