Anesthesia or anaesthesia (see spelling differences; from Greek ??- an- ?without? + ???????? aisthesis ?sensation?) has traditionally meant the condition of having the feeling of pain and other sensations blocked. This allows patients to undergo surgery and other procedures without the distress and pain they would otherwise experience. The word was coined by Oliver Wendell Holmes, Sr. in 1846. Another definition is a "reversible lack of awareness", whether this is a total lack of awareness (e.g. a general anaesthestic) or a lack of awareness of a part of a the body such as a spinal anaesthetic or another nerve block would cause.Today, the term general anesthesia in its most general form can include:
Analgesia: blocking the conscious sensation of pain;
Hypnosis: produces unconsciousness without analgesia;
Amnesia: preventing memory formation;
Relaxation: preventing unwanted movement or muscle tone;
Obtundation of reflexes, preventing exaggerated autonomic reflexes.