Anesthesia is a combination of medications that put you in a sleep-like state before a surgery or other medical procedure. Under general anesthesia, you don't feel pain because you're completely unconscious. General anesthesia usually uses a combination of intravenous drugs and inhaled gasses .Inhalational anesthetica are used for the induction and maintenance of general anesthesia as well as sedation. The mechanisms by which they act are still unknown. The most common inhalational anesthetics are sevoflurane, desflurane, and nitrous oxide. Of these, sevoflurane is the most common because of its rapid onset of action and the fact that patients recover quickly from it.