HOCK, a condition of decreased total body oxygen delivery, can be brought on by a number of mechanisms. These include failure of the heart to pump blood through the body (cardiogenic shock), loss of circulating fluid volume (hemorrhagic), decreased oxygen-carrying capacity (anemic), or loss of vascular tone (neurogenic). 1 Traumatic shock, shock brought on by an injury in an otherwise healthy patient, is best thought of as a combination of these factors. The initial phase is usually hemorrhagic: the patient bleeds, and perfusion decreases. This may be followed by an anemic phase as the patient is resuscitated with crystalloid solutions and simultaneously mobilizes interstitial fluid into the vasculature: A cardiogenic or neurogenic component may be present initially, caused by specific injuries to the heart or central nervous system, or may be the secondary result of hypoperfusion and the release of toxic factors. It is important to recognize that the traumatic shock observed clinically in severely injured patients may be quite different from the induced shock observed in laboratory animals hemorrhaged under controlled conditions.