Retinal venous oxygen saturation correlates with blood volume

Area of Science:

• Ophthalmology
• Physiology
• Medical Devices

Background:

• Early detection of blood loss is critical in managing trauma and surgical patients.
• Monitoring central venous O2 saturation (SvO2) is invasive and requires specialized equipment.
• Non-invasive methods for assessing hemodynamic changes are highly desirable.

Purpose of the Study:

• To assess the sensitivity of retinal venous O2 saturation (SrvO2) in detecting early blood loss and reinfusion.
• To determine the correlation between SrvO2 and mixed venous O2 saturation (SvO2) during hemorrhage and resuscitation.

Main Methods:

• Anesthetized swine underwent controlled blood withdrawal and reinfusion at varying rates (0.8, 1.6, and 2.4 mL/kg/min).
• Retinal venous O2 saturation (SrvO2) was measured using an eye oximeter (EOX).
• Mixed venous O2 saturation (SvO2) was measured using a fiber-optic catheter; blood pressure and pulse were also monitored.

Main Results:

• SrvO2 demonstrated strong correlations with the volume of blood removed (r = -0.88 to -0.97) and SvO2 (r = 0.87 to 0.98) during blood loss.
• SrvO2 also correlated well with blood re-infused (r = 0.63 to 0.82) and SvO2 (r = 0.80 to 0.96) during reinfusion.
• The rate of SrvO2 decrease per unit of blood removed was significantly higher at faster bleeding rates, unlike changes in blood pressure or pulse.

Conclusions:

• SrvO2 is a sensitive indicator of blood volume changes and correlates with SvO2.
• The rate of change in SrvO2 is more responsive to hemorrhage rate than traditional vital signs.
• The EOX shows promise for non-invasive monitoring of hemorrhage and resuscitation effectiveness.