Background: Venous oxygen saturation (SvO2) reflects the residual oxygen after tissue oxygen extraction and represents the relation between tissue oxygen supply and demand. We studied SvO2 and arterial lactate during progressive isovolemic anemia to assess the relation between SvO2 and tissue hypoxia.

Subjects: Ten 8-10 day old anesthetized ventilated piglets.

Intervention: We induced progressive anemia by exchange of blood with plasma. SaO2 and SvO2 were measured continuously by a fiberoptic catheter (Oximetrix, Abbott Lab.) in the carotid and pulmonary artery. Aorta flow (Qt), arterial and venous bloodgases, hemoglobin and lactate (â–µ lact) were measured. O2 delivery (DO2) and consumption (VO2) were calculated.

Results: Table Linear regression analysis comparing SaO2 and ScvO2 with DO2 yielded a r2 of 0.12 and 0.54, respectively. Tissue hypoxia was confirmed by a reduced VO2 and an increase in lactate.

Table 1

Conclusion: SvO2 reflects better a reduced DO2 obtained by progressive anemia than SaO2.