Anesthesiology, anaesthesiology, or anaesthesia is the medical specialty concerned with the total perioperative care of patients before, during and after surgery.
It encompasses anesthesia, intensive care medicine, critical emergency medicine, and pain medicine.
A physician specialized in anesthesiology is called an anesthesiologist or anaesthetist, depending on the country. (In some countries the terms are effectively synonymous, but in other countries they refer to different positions and the term "anesthetist" is only used for non-physicians, such as nurse anesthetists.)
The core element of the specialty is the study and use of anesthesia to safely support a patient's vital functions through the perioperative period.
Since the 19th century, anesthesiology has developed from an experimental area with non-specialist practitioners using novel, untested drugs and techniques into what is now a highly refined, safe and effective field of medicine.