Shock is a life-threatening condition in which the blood pressure collapses and the blood circulation in the capillaries is reduced. As a result, the supply of oxygen in the tissues is insufficient. The causes of shock are acute blood loss (hypovolaemic shock), a failure of the circulatory regulation due to blood poisoning (septic shock) or an allergic reaction (anaphylactic shock), or if the heart’s pumping action is insufficient (cardiogenic shock). The brain is the most sensitive organ. An insufficient oxygen supply leads to unconsciousness.