Shock is a critical condition brought on by a sudden drop in blood flow, oxygen, or glucose through the body. There is failure of the circulatory system to maintain adequate blood flow and oxygenation. This sharply cuts back the delivery of oxygen and nutrients to vital organs. It compromises the kidney and curtails the removal of wastes from the body. Shock can be due to a number of different mechanisms including not enough blood volume (hypovolemic shock) and not enough output of blood by the heart (cardiogenic shock). The signs and symptoms of shock include low blood pressure (hypotension), overbreathing (hyperventilation), a weak rapid pulse, cold clammy grayish-bluish (cyanotic) skin, decreased urine flow (oliguria), and mental changes (a sense of great anxiety and foreboding, confusion and, sometimes, combativeness). Shock is a major medical emergency. It is common after serious injury. Emergency care for shock involves giving fluids or blood intravenously and medications to help the heart. Intubation is usually required.