Cardiorespiratory measurements were made in a severely anemic patient (hemoglobin concentration of 3.5 g/dl) who was preoperatively given the perfluorochemical blood substitute (Fluosol-DA, 20%). Hemodynamic and oxygen transport variables were monitored, including arterial and mixed venous oxygen content (Cao2and Cvo2) before, during, and after infusion of 1000 ml of Fluosol as well as throughout the intraoperative period. Blood samples revealed a maximum of 2.7% of the perfluorochemical. The Cao2increased 37% above the Cao2calculated without Fluosol; i.e., 5.8 ± 0.1 to 8.1 ± 0.6 ml/dl,p< 0.01. The cardiac index (CI) decreased from 7.2 ± 0.2 to 5.9 ± 0.8 L/min M2and the left ventricular stroke work decreased from 67 ± 6 to 58 ± 13 g M/M2, while the oxygen delivery increased, and the total body oxygen consumption (Vo2) remained essentially unchanged. Intraoperatively, 27% of the O2delivery and 51% of the Vo2were transported by Fluosol. No adverse effects of the Fluosol were noted.