Retinal venous oxygen saturation and cardiac output during controlled hemorrhage and resuscitation

The objective was to test calibration of an eye oximeter (EOX) in a vitiligo swine eye and correlate retinal venous oxygen saturation (Srv_O2), mixed venous oxygen saturation (Sv_O2), and cardiac output (CO) during robust changes in blood volume. Ten anesthetized adult Sinclair swine with retinal vitiligo were placed on stepwise decreasing amounts of oxygen. At each oxygen level, femoral artery oxygen saturation (Sa_O2) and retinal artery oxygen saturation (Sra_O2) were obtained. After equilibration on 100% O₂, subjects were bled at 1.4 ml·kg^-1·min^-1 for 20 min. Subsequently, anticoagulated shed blood was reinfused at the same rate. During graded hypoxia, exsanguination, and reinfusion, Sra_O2 and Srv_O2 were measured by using the EOX, and CO and Sv_O2 were measured by using a pulmonary artery catheter. During graded hypoxia, Sra_O2 correlated with Sa_O2 (r = 0.92). Srv_O2 correlated with Sv_O2 (r = 0.89) during exsanguination and reinfusion. SV_O2 and Srv_O2 correlated with CO during blood removal and resuscitation (r = 0.92). Use of vitiligo retinas improved the calibration of EOX measurements. In this robust hemorrhage model, Srv_O2 correlates with CO and Sv_O2 across the range of exsanguination and resuscitation.