Background
Shock is a state of inadequate perfusion, which does not sustain the physiologic needs of organ tissues. Many conditions, including blood loss but also including nonhemorrhagic states such as dehydration, sepsis, impaired autoregulation, obstruction, decreased myocardial function, and loss of autonomic tone, may produce shock or shocklike states.
In hemorrhagic shock, reduced tissue perfusion results in inadequate delivery of oxygen and necessary for cellular function. The state of shock occurs when the cellular oxygen demand outweighs the supply. See the Medscape articles hemorrhagic shock and hypovolemic shock.