MECHANISMS AND EFFICACY OF FLUOROCHEMICAL OXYGEN-TRANSPORT AND DELIVERY

Fluorochemicals for medical use are metabolically inert liquids with a high solubility for gases, and can dissolve 50 percent or more of the ir own volume of oxygen (O-2) at ambient pressures. The solubility is directly proportional to the oxygen tension (PO2) and transport is thu s not saturable, unlike the O-2 saturation of hemoglobin (Hb) which fo llows the well known ''S'' shaped relationship with PO2. Intravenously -injected emulsions of fluorocarbons transport only about one seventh as much O-2 as Hb on a gram for gram basis, even when high concentrati ons of O-2 are respired. However, because of the high O-2 extraction f rom fluorocarbons in these circumstances, their contribution to O-2 co nsumption is more than 65% of that of Hb. O-2 delivery to the tissues depends on the product of the cardiac output and the arterial oxygen c ontent. When red cells are transfused, blood viscosity increases and c ardiac output decreases. This lessens the efficacy of blood in compari son to that of fluorocarbons, and increases the relative transport of O-2 in the metabolically readily-accessible plasma compartment. This p rovides an interesting application for low dose fluorocarbons during s urgery in combination with autologous blood use. The efficacy of fluor ocarbons in this setting can be predicted by computer modelling.