Anaesthesiology, anesthesiology, anaesthesia or anaesthetics is the medical speciality 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.
An anesthesiologist controlling a patient's airway while inducing anesthesia.
|Focus||Anesthesia, perioperative medicine|
Intensive care medicine|
Critical emergency medicine
Various names are used for the specialty, and those who practise it, in different parts of the world:
- In North America and China, the medical study and application of anesthetics is called anesthesiology,, and a physician in the specialty is called an anesthesiologist. The word "anesthetist" is used to refer to non-physician providers of anesthesia services such as nurse anesthetists.
- In several countries that are current or former members of the Commonwealth of Nations–namely, United Kingdom, Australia, New Zealand, Ireland and South Africa–the medical specialty is instead referred to as anaesthesia or anaesthetics, with an extra "a". As such, in these countries the same term may be used to refer to the overall medical specialty, the medications and techniques that are used, and the resulting state of loss of sensation. The term anaesthetist is used only to refer to a physician practising in the field; non-physicians involved in anaesthesia provision use other titles in these countries, such as "physician assistant".
- In most other parts of the world, the spelling anaesthesiology is most commonly used when writing in English, and a physician practising it is termed an anaesthesiologist. This is the spelling adopted by the World Federation of Societies of Anaesthesiologists and most of its most of its member societies, as well as the European Society of Anaesthesiology, and it is the most commonly used term found in the titles of medical journals.
As a specialty, the core element of anesthesiology is the practice of anesthesia. This comprises the use of various injected and inhaled medications to produce a loss of sensation in patients, making it possible to carry out procedures that would otherwise cause intolerable pain or be technically unfeasible. Safe anesthesia requires in-depth knowledge of various invasive and non-invasive organ support techniques that are used to control patients' vital functions while under the effects of anaesthetic drugs; these include advanced airway management, invasive and non-invasive hemodynamic monitors, and diagnostic techniques like ultrasonography and echocardiography. Anesthesiologists are expected to have expert knowledge of human physiology, medical physics, and pharmacology, as well as a broad general knowledge of all areas of medicine and surgery in all ages of patients, with a particular focus on those aspects which may impact on a surgical procedure. In recent decades, the role of anesthesiologists has broadened to focus not just on administering anesthetics during the surgical procedure itself, but also beforehand in order to identify high-risk patients and optimize their fitness, during the procedure to maintain situational awareness of the surgery itself so as to improve safety, as well as afterwards in order to promote and enhance recovery. This has been termed "perioperative medicine".
The concept of intensive care medicine arose in the 1950s and 1960s, with anesthesiologists taking organ support techniques that had traditionally been used only for short periods during surgical procedures (such as positive pressure ventilation), and applying these therapies to patients with organ failure, who might require vital function support for extended periods until the effects of the illness could be reversed. The first intensive care unit was opened by Bjørn Aage Ibsen in Copenhagen in 1953, prompted by a polio epidemic during which many patients required prolonged artificial ventilation. In many countries, intensive care medicine is considered to be a subspecialty of anesthesiology, and anesthesiologists often rotate between duties in the operating room and the intensive care unit. This allows continuity of care when patients are admitted to the ICU after their surgery, and it also means that anesthesiologists can maintain their expertise at invasive procedures and vital function support in the controlled setting of the operating room, while then applying those skills in the more dangerous setting of the critically ill patient. In other countries, intensive care medicine has evolved further to become a separate medical specialty in its own right, or has become a "supra-specialty" which may be practiced by doctors from various base specialties such as anesthesiology, general medicine, surgery or neurology.
Anesthesiologists have key roles in major trauma, resuscitation, airway management, and caring other patients outside the operating theatre who have critical emergencies that pose an immediate threat to life, again reflecting transferable skills from the operating room, and allowing continuity of care when patients are brought for surgery or intensive care. This branch of anesthesiology is collectively termed critical emergency medicine, and includes provision of pre-hospital emergency medicine as part of air ambulance or emergency medical services, as well as safe transfer of critically ill patients from one part of a hospital to another, or between healthcare facilities. Anesthesiologists commonly form part of cardiac arrest teams and rapid response teams composed of senior clinicians that are immediately summoned when a patient's heart stops beating, or when they deteriorate acutely while in hospital. Different models for emergency medicine exist internationally: in the Anglo-American model, the patient is rapidly transported by non-physician providers to definitive care such as an emergency department in a hospital. Conversely, the Franco-German approach has a physician, often an anesthesiologist, come to the patient and provide stabilizing care in the field. The patient is then triaged directly to the appropriate department of a hospital.
The role of anesthesiologists in ensuring adequate pain relief for patients in the immediate postoperative period has led to the development of pain medicine as a subspecialty in its own right. The field comprises individualized strategies for all forms of analgesia, including pain management during childbirth, technological methods such as transcutaneous electrical nerve stimulation or implanted spinal cord stimulators, and specialized pharmacological regimens.
Over the past 100 years, the study and administration of anesthesia has become more complex. Historically anesthesia providers were almost solely utilized during surgery to administer general anesthesia in which a person is placed in a pharmacologic coma. This is performed to permit surgery without the individual responding to pain (analgesia) during surgery or remembering (amnesia) the surgery.
Many procedures or diagnostic tests do not require "general anesthesia" and can be performed using various forms of sedation or regional anesthesia, which can be performed to induce analgesia in a region of the body. For example, epidural administration of a local anesthetic is commonly performed on the mother during childbirth to reduce labor pain while permitting the mother to be awake and active in labor & delivery.
In the United States, anesthesiologists attend four years of medical school to earn either a Doctor of Medicine (MD) degree or a Doctor of Osteopathic Medicine (DO) degree and then follow it with four years of residency. Certified Registered Nurse Anesthetists or CRNAs are advanced practice registered nurses with additional post-graduate training in anesthesia. By 2025, all CRNA programs will require a doctorate degree. In the United States, the most common anesthesia care model is where an anesthesiologist and Certified Registered Nurse Anesthetist work as a team (termed medical direction or medical supervision). In 17 states, CRNAs can practice without the supervision of a physician (though physician does not dictate it be an anesthesiologist). 
Effective practice of anesthesiology requires several areas of knowledge by the practitioner, some of which are:
- Pharmacology of commonly used drugs including inhalational anaesthetics, topical anesthetics, & vasopressors as well as numerous other drugs used in association with anesthetics (e.g., ondansetron, glycopyrrolate)
- Monitors: electrocardiography, electroencephalography, electromyography, entropy monitoring, neuromuscular monitoring, cortical stimulation mapping and neuromorphology
- Mechanical ventilation
- Anatomical knowledge of the nervous system for nerve blocks, etc.
- Other areas of medicine (e.g., cardiology, pulmonology, obstetrics) to assess the risk of anesthesia to adequately have informed consent, and knowledge of anesthesia regarding how it affects certain age groups (neonates, pediatrics, geriatrics)
- "What is Anesthesiology". Retrieved 5 December 2016.
- "Helsinki Declaration on Patient Safety in Anaesthesiology". European Society of Anaesthesiology. 12 June 2010. Retrieved 1 September 2018.
- American Heritage Dictionary
- "What's in a name?". Australian and New Zealand College of Anaesthetists. 2017. Retrieved 1 September 2018.
- "Anaesthetics National Recruitment Office". Health Education England. Retrieved 1 September 2018.
- "Physicians' Assistant (Anaesthesia)". Royal College of Anaesthetists. Retrieved 1 September 2018.
- "Archived copy". Archived from the original on 2016-08-16. Retrieved 2016-06-08.