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.[17] 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, emergency medicine, general

medicine, surgery or neurology.

Anesthesiologists have key roles in major trauma, resuscitation, airway management, and caring

for 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, as well as their expertise in regional anesthesia and nerve blocks, 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,

neuromodulatory technological methods such as transcutaneous electrical nerve stimulation or

implanted spinal cord stimulators, and specialized pharmacological regimens