Critical Care Medicine: a branch of medicine concerned with the diagnosis and management of life-threatening conditions that may require sophisticated organ support and invasive monitoring. Critical care medicine encompasses the diagnosis and treatment of a wide variety of clinical problems representing the extreme of human disease. Critically ill patients require intensive care by a coordinated team. The care of critically ill patients also raises many complicated ethical and social issues, and the intensivist must be competent in areas such as end-of-life decisions, advance directives, estimating prognosis, and counseling of patients and their families.