Shock is the medical condition in which the circulation of blood is so low that it cannot supply the metabolic needs of the tissue. It can be caused by: low blood volumes, e.g. due to dehydration or bleeding (hemorrhagic shock) heart cannot pump effectively (cardiogenic shock), e.g. after a heart attack obstruction to blood flow, e.g. occlusion of the blood vessels by amniotic fluid (amniotic fluid embolism)