The Effect of Carbon Dioxide on Cerebral Blood Flow and Cerebral Metabolism in Dogs

Abstract

In 11 normally oxygenated, normotensive mongrel dogs, blood flow and oxidative metabolism of the brain was studied during normocapnia and during respiratory alkalosis and respiratory acidosis. During respiratory alkalosis (mean PaCO2 17.8 mm Hg) CBF decreased significantly from 61.0 to 33.9 ml/100 g/min (44%) while arteriovenous-substrate differences increased and the rates of oxygen and glucose metabolism remained constant. Cerebral venous-arterial difference of lactate was increased significantly as compared with the resting state. During hypercapnia CBF increased significantly from 61.0 (resting state) to 115.7 ml/100 g/min (89%) (mean PaCO2 64.7 mm Hg). The arteriovenous-substrate differences decreased while the cerebral metabolic rates remained constant. The data show that the relationship between PaCO2 and CBF in the range 20-65 mm Hg PaCO2 is expressed by a linear relationship: y = 2.88 + 1.69x; in this range, the oxidative metabolism of the brain is unchanged and the increased cerebral lactate production in respiratory alkalosis is not necessarily linked to tissue hypoxia.

Response of Cerebral Blood Volume to Changes in Arterial Carbon Dioxide Tension in Preterm and Term Infants

“…For quantification of CBVR, we have made the simplifying assumption that the relation between CBV and Paco2 is linear within the range of Paco2 observed. Linearity in CBF response over a wide range of Paco, has been found by a number of workers (3,4,8,9,12), but flattening of the response at extremes of Paco, has been observed (6, 7), suggesting a sigmoid relationship. It is likely that the relation between CBV and Paco2 will be broadly similar.…”

“…Quantitative data on the response of cerebral blood flow to changes in Pacer were initially obtained by Kety and Schmidt (2) using the nitrous oxide clearance method. Since then, numerous studies in adults (3,4), newborn infants (5,6), and experimental animals (7)(8)(9)(10) have confirmed the positive relationship between cerebral blood flow and Pacoz in normal individuals. Information on the response of CBV to changing Pacoz is more limited ( I 1-14), and only one report has been published involving newborn infants (1 5).…”

Mapping Cerebrovascular Reactivity Using Blood Oxygen Level-Dependent MRI in Patients With Arterial Steno-occlusive Disease

“…Similarly, hypercapnia does not affect cerebral metabolic rate of oxygen consumption. 24,25 Another potential confounder is the time delay between change in partial pressure of carbon dioxide in the pulmonary capillaries and arrival of this change in a given voxel in the …”

Monitoring of the Intracranial Hemodynamics and Oxygenation during and after Hyperventilation in Newborn Rabbits with Near-Infrared Spectroscopy

“…This evidence suggests that the decrease in CMR02 during respiratory alkalosis might be caused by a decrease in cerebral oxygen demand and an increase in anaerobic glycolysis against cerebral hypoxia. However, studies on both adult animals and human beings suggest that CMROz is maintained at a constant level during severe hypocarbia (4,5). Therefore, neonatal cerebral metabolism in hypocarbia may differ from that in adults.…”