A clinical condition caused by widespread impairment of blood flow resulting in an inadequate supply of oxygen to the body's tissues. Shock is a sudden and progressive condition that, if not reversed, can lead to death. Shock affects the entire body, as opposed to other conditions where blood flow is reduced to only a portion of a single organ, such as stroke or heart attack. It is typically, but not always, associated with a low blood pressure that can be felt as a weak pulse.