An emergency department (ED), also known as an accident & emergency department (A&E), emergency room (ER) or casualty department, is a medical treatment facility specializing in emergency medicine, the acute care of patients who present without prior appointment; either by their own means or by that of an ambulance. The emergency department is usually found in a hospital or other primary care center.
Due to the unplanned nature of patient attendance, the department must provide initial treatment for a broad spectrum of illnesses and injuries, some of which may be life-threatening and require immediate attention. In some countries, emergency departments have become important entry points for those without other means of access to medical care.
The emergency departments of most hospitals operate 24 hours a day, although staffing levels may be varied in an attempt to reflect patient volume.
Accident services were already provided by workmen's compensation plans, railway companies, and municipalities in Europe and the United States by the late mid-nineteenth century, but the first specialized trauma care center in the world was opened in 1911 in the United States at the University of Louisville Hospital in Louisville, Kentucky, and was developed by surgeon Arnold Griswold during the 1930s. Griswold also equipped police and fire vehicles with medical supplies and trained officers to give emergency care while en route to the hospital.
Today, a typical hospital has its emergency department in its own section of the ground floor of the grounds, with its own dedicated entrance. As patients can present at any time and with any complaint, a key part of the operation of an emergency department is the prioritization of cases based on clinical need. This process is called triage.
Triage is normally the first stage the patient passes through, and consists of a brief assessment, including a set of vital signs, and the assignment of a "chief complaint" (e.g. chest pain, abdominal pain, difficulty breathing, etc.). Most emergency departments have a dedicated area for this process to take place, and may have staff dedicated to performing nothing but a triage role. In most departments, this role is fulfilled by a triage nurse, although dependent on training levels in the country and area, other health care professionals may perform the triage sorting, including paramedics or physicians. Triage is typically conducted face-to-face when the patient presents, or a form of triage may be conducted via radio with an ambulance crew; in this method, the paramedics will call the hospital's triage center with a short update about an incoming patient, who will then be triaged to the appropriate level of care.