RETINAL VENOUS OXYGEN-SATURATION CORRELATES WITH BLOOD-VOLUME

Objectives: To evaluate the sensitivity of retinal venous O-2 saturati on (SrvO(2)) for early blood loss and reinfusion. A secondary objectiv e was to measure the correlation between SrvO(2) and mixed venous O-2 saturation (SvO(2)) during blood loss and reinfusion. Methods: Seven a nesthetized swine were bled at 0.8 ml/kg/min to 16 mL/kg. Shed blood w as re-infused at the same rate and the swine were allowed to equilibra te. After equilibration, repeat hemorrhages were performed at 1.6 ml/k g/min and 2.4 ml/kg/min. SrvO(2) was measured using an eye oximeter (E OX) and SvO(2) was measured using a fiber-optic catheter. Results: Dur ing blood loss, SrvO(2) correlated with blood removed (r = -0.88, -0.9 7, -0.96) and SvO(2) (r = 0.87, 0.98, 0.92). During reinfusion, SrvO(2 ) correlated with blood re-infused (r = 0.63, 0.76, 0.82) and SvO(2) ( r = 0.80, 0.93, 0.96). SrvO(2) decreased 1.22 +/- 0.60%/mL/kg of blood removed. The rate of decrease in SrvO(2) per minute (Delta SrvO(2)) w hen blood was removed at 2.4 ml/kg/min was significantly greater than Delta SrvO(2) when blood was removed at 0.8 mL/kg/min (p < 0.007). The rates of change in blood pressure (BP) and pulse were not significant ly different at any rate of blood removal. Conclusions: In this model, retinal venous O-2 saturation correlated with blood volume and centra l venous O-2 saturation. Unlike the rate of change in BP and heart rat e, Delta SrvO(2) values were significantly different at different rate s of blood removal. Use of an EOX to monitor for blood loss, estimate the rate of hemorrhage, and evaluate the response to therapy during re suscitation warrants further study.