Oxygent is a stable concentrated perfluorochemical (PFC) emulsion being developed for use as a temporary oxygen carrier. In this application, PFC emulsions can be used to augment oxygen delivery during acute blood loss and thereby provide a margin of safety during hemodilution and surgical anemia. PFCs simply dissolve oxygen in direct proportion to its partial pressure. The oxygen transported by a PFC emulsion is present in the plasma compartment and is therefore easily extracted and consumed by the tissues. Preclinical and clinical studies have demonstrated that a relatively low dose (1.35 g PFC/kg) of Oxygent can support oxygen delivery despite ongoing blood loss. Clinical safety studies in 57 healthy, conscious volunteers and in 30 anesthetized surgical patients have been completed. In these studies, there were no hemodynamic changes or vasoconstriction and cardiac output increased normally in response to hemodilution. Two transient side effects were observed, but only in the high dose (1.8 g PFC/kg) group: a 1-1.5 degrees C increase in body temperature (at 4-6 hours), and a moderate decrease in platelet count (mean nadir approximately 130,000/microL by 2-3 days) without any bleeding complications. Oxygent is presently being evaluated as an alternative to allogeneic blood transfusion in patients undergoing medium- to high-blood-loss surgical procedures.