Deficient adjustment of cerebral blood flow to cognitive activity due to chronically low blood pressure.

The present study aimed to investigate aberrances in the adjustment of cerebral blood flow to cognitive activity due to chronically low blood pressure. By means of transcranial Doppler sonography blood flow velocities in both middle cerebral arteries (MCA) were recorded during the execution of a serial subtraction task in 40 subjects with constitutional hypotension and 40 normotensive control persons. Additionally, blood pressure was continuously monitored. As a main result significant correlations between the task-induced changes in blood pressure and those in MCA blood flow velocities were found in hypotensives, but not in control subjects. The dependence of the regulation of cerebral blood flow on blood pressure points towards deficits in cerebral autoregulation in hypotension. Over the total sample the extent of the task-induced MCA flow velocity increase was positively related to cognitive performance. This underlines the importance of the adjustment of cerebral blood flow to current demands for optimal cognitive functioning.