anesthesia
"I also had Propofol (with Fentanyl) for a colonoscopy recently.  While a nurse was hooking up sensors, the surgeon explained the Fentanyl was for pain; Propofol for sedation.  Overall, he said I would be very drowsy during the procedure.  He pushed a pre-measured syringe of each with a warning that Propofol might burn a bit.  The Fentanyl produced an almost immediate light rush.  A few seconds later the nurse asked if I felt any burning.  I answered "No, but my wrist is a little sore."  My wrist immediately went numb and as I stared at it, my world went blank.  The next thing I knew, I was prying my eyes open, feeling pretty drowsy as well as half tipsy.  Someone said "All done!" and wheeled me to recovery.  No bad side effects; good stuff!"