Can you tell me how anesthesia prevent pain?

Several Ways: Anesthesia means "not to feel" and is commonly meant "no pain". Local and Spinal anesthesia is a chemical that turns off the nerve to an area. Narcotics( morphine, fentanyl,etc) prevent normal perception of pain, making it more tolerable. General Anesthetics interfere with all nervous functions, the deeper the anesthetic, the more complete the disturbance. If you are expecting surgery ask, ask!!