Critical care evolved from an historical recognition that the needs of patients with acute, life-threatening illness or injury could be better treated if they were grouped into specific areas of the hospital. Thus evolved the ICU, Intensive Care Units.

Care in these ICU's is provided by multidisciplinary teams of health care professionals who are organized by a qualified critical care physician. These physicians (intensivists) specialize in total patient care and understand the effects of treatments on each organ system in the body.