CERVICAL SYMPATHECTOMY REDUCES THE HETEROGENEITY OF OXYGEN-SATURATIONIN SMALL CEREBROCORTICAL VEINS

This study evaluated the hypothesis that the peripheral sympathetic ne rvous system is one of the factors increasing the heterogeneity of ven ous O2 saturation in selective brain regions. Regional cerebral blood flow and O2 saturation were determined in the anterior cortex, posteri or cortex, and medulla of either sham-operated or bilaterally sympathe ctomized Long-Evans rats. Cerebral venous O2 saturations, indicating t he balance between local O2 supply and consumption, were found to be s ignificantly more heterogeneous in the sham-operated group. In the ant erior cortex, the coefficient of variation [100(SD/mean)] for the sham -operated animals was 22.4%. Sympathectomy significantly reduced this heterogeneity in the anterior cortex through a reduction in the number of low O2 saturation veins (coefficient of variation 11.7%). Blood fl ow and O2 consumption in the anterior cortex were not different betwee n groups. The effects of sympathectomy in the posterior cortex were si milar to those in the anterior cortex. However, sympathectomy did not alter any measured variables in the medulla. Thus, bilateral superior cervical ganglionectomy reduced the heterogeneity of cerebrocortical v enous O2 saturation by reducing the number of low O2 saturation veins in the rostral part of the brain.