Effect of cerebral extracellular fluid acidity on total and regional cerebral blood flow

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Abstract
Total and regional cerebral blood flow (CBF), and CSF, and arterial blood acid-base status were measured in 26 chloralose-urethan-anesthetized dogs before and after 30 and 60 min of ventriculocisternal perfusion with artificial CSF equilibrated with 7% CO2 and containing either low (8.7 or 9.1 meq/l), normal (19.6 meq/l), or high (34.7 meq/l) HCO3 concentration. An inverse linear relationship was observed between the CSF pH and total CBF. Regional blood flow changes were greater in structures that were closest to the ventricular system. Regional blood flow changes were greater in all tissues studied after 60 min of perfusion than after 30. Perfusion with the control [HCO3-] caused no significant changes in either acid-base status or CBF. The regional CBF changes are the result of changes in the H+ concentration gradient across the cerebral extracellular fluid (ECF) space due to the diffusional exchange of HCO3- between CSF and ECF. Cerebral ECF acidity is important in the local regulation of cerebral blood flow.