Effect of alterations in the arterial carbon dioxide tension on the blood flow through the cerebral cortex at normal and low arterial blood pressures.

Abstract

Using Lassen and Ingvar method and formula 302 measurements of blood flow through the cerebral cortex were made on 41 unselected mongrel dogs. Great care was taken to ensure no brain damage, steady state conditions and control of physiological variables. Therefore the investigators feel that the noted changes in blood flow reflect the induced alterations in PaCO2 [arterial CO2 tension] and blood pressure and are not due to extraneous factors such as hypoxia and variations in depth of anesthesia. The experiments were divided into normotensive, hypotensive with a mean arterial blood pressure of 100 mm Hg, and hypotensive with a mean arterial blood pressure of 50 mm Hg. In normotensive animals hypercapnia produced a marked increase and hypocapnia a decrease in blood flow. In hypotensive animals, however, this effect was reduced or absent. The clinical application of these findings is that there would be no advantage in administering CO2 in an attempt to restore cerebral blood flow in severe shock. In fact such procedure might raise the PCO2 to dangerously high levels.