Critical oxygen delivery levels during shock following normoxic and hyperoxic haemodilution with fluorocarbons or dextran.

Fluosol-DA 20% (FDA), an emulsion of fluorocarbons in a glucose electrolyte solution can deliver physiologically significant amounts of oxygen (O2) to the tissues and improve ischaemic hypoxia. To investigate its effect on critical oxygen delivery level (QO2c), four groups of six phenobarbitone anaesthetised air-ventilated splenic clamped mongrel dogs were haemodiluted to a haematocrit (Hct) of 25%; two groups with FDA and two with 6% dextran solution. Oxygen consumption (VO2) was derived from expired gas measurement and analysis, or by using a spirometer and carbon dioxide absorption. Whole body O2 flux (QO2) was calculated from mixed venous and arterial O2 contents and the Fick-derived cardiac output. QO2 was progressively decreased by haemorrhaging in steps of 1.5-2.5 ml per kg. Hct was kept at 25% using packed cells. VO2/QO2 pairs were calculated at each step and QO2c was determined for each animal by least squares fitting of data with 2 straight lines. Analyses of variance were performed. QO2c was significantly less in the FDA and O2 (F+O) group than either the dextran and O2 (D+O) or dextran and air (D+A) groups. Analysis of O2 extraction at QO2c, which effectively normalized results for differences in resting, VO2, had significantly better extraction in the FDA and air (F+A) than the D+A group. When fluorocarbon- and plasma-dissolved oxygen was subtracted, the O2 extraction in the F+A group was significantly better than in the D+A and F+O groups. The results imply that normoxic FDA haemodilution in animals respiring air can improve O2 delivery and that hyperoxia interferes with this process.