The term anesthesia originally referred to the loss of sensation or perception, and subsequently to a state that allows the patient to undergo surgery or invasive procedures without pain or discomfort. It is generally accepted that anesthesia is a reversible functional depression of the central and peripheral nervous systems, produced by drugs or other methods, that is characterized by a loss of sensation, particularly nociception. The anesthetic drug is injected into the body by inhalation, intravenous or intramuscular injection or rectal instillation, so that the central nervous system is suppressed and the patient loses consciousness without pain sensation around the body is called general anesthesia; the local anesthetic drug is injected into the corresponding area so that the spinal nerve, nerve plexus or nerve trunk and finer peripheral nerve endings are blocked is called local anesthesia. In simple terms, anesthesia is a condition that enables the patient to complete the surgery without any pain sensation and without any unpleasant memories after the surgery, and this is the most basic role of anesthesia.