RBC flow imaging and pO2 measurement in cerebral microcirculation:effect of hemodilution on oxygen supply to brain cortical arterioles

Hemodilution is still one of the taken therapy in stroke due to increase in cardiac output and decrease in blood viscosity. However, it is not clear the effect of a decrease in oxygen carrying capacity on oxygen supplying to the brain. The aim of this study is to seek the effect of isovolemic hemodilution on oxygen supply. We observed RBC flow rate and oxygen tension pO₂ on brain cortical arterioles by using closed cranial window, high-speed videomicroscopy and oxygen dependent quenching of phosphorescence technique. The result showed that RBC flow rate increased about four times from base line and pO2 values were kept within a arteliolar biological state (about a range from 70 to 90mmHg) until Hb was about l0g/dl, respectively. And more severe hemodilution made the both values decrease acutely. The results suggest the increase of RBC flow caused by isovolemic hemodilution keeps supplying oxygen to the brain cortex as low as Hb is l0g/dl.