Total Brain Blood Flow Research Articles

The Significance of Cortical Extracellular pH for the Regulation of Blood Flow in the Cerebral Cortex

Since changes in vascular resistance within circumscribed regions of the brain cannot always be equated with changes of vascular resistance in the whole brain, the effects of variations in the acid-base balance in a small circumscribed region on the suprasylvian gyrus is measured. Local changes of the acid-base equilibrium do not affect the surrounding vessels in the same way as they do the region in which the local acid-base changes have taken place. Changes in total brain blood flow in most instances influence the local blood flow in a measurable way, whereas the reverse is not certain. The relations between pH and resistance demonstrate that a certain degree of acidosis is reached on the brain surface; the vessels have their maximal diameter and cannot dilate further. Blood flow, however, may increase during this phase. This depends then on the effective local blood pressure. Cortical blood flow reacts opposite to the cortical pH-changes, but only if the blood pressure remains constant. Increases of CO 2 concentrations in the air cause only very small changes of flow, but the normal relation between resistance and cortical pH is disturbed. The effects of hyperventilation may be different if the edema affects only a small and circumscribed area of the cortex, because of the -mentioned significance of the reactions of collateral vessels.

The Effect of Ether and Dial-Urethane Anesthesia on the Passage of Sulfathiazole into the Cerebrospinal Fluid

The passage of sulfathiazole from the blood to the csf was compared in dogs under ether and under dial-urethane anesthesia after intraduodenal and after intraperitoneal administration of sulfathiazole. Unanesthetized dogs were also studied after intraperitoneal injection. The transfer of sulfathiazole was indicated by the C/B ratios obtained by dividing the csf level by the blood level at the third hour after administration of the drug. It was found that there was an increased level of sulfathiazole in the csf during ether anesthesia. After intraduodenal injection, the C/B ratios were 29% higher with ether anesthesia than dial-urethane. After intraperitoneal injection the C/B ratios under dial-urethane were 20% higher than in unanesthetized animals and under ether they were 80% higher. It was also noted that higher blood sulfathiazole levels were obtained under ether anesthesia. These findings were discussed from the standpoint of the influence of changes in cerebral circulation. It is thought that the transfer of sulfathiazole to the csf may he regulated by the total brain blood flow.