Dynamics of Cerebrovascular Responses to Oxygen
The generation of vasoactive metabolites (Siesjo et al, 1971; Kogure et al, 1977) and ions (Dora et al, 1979) or their release into the extracellular space provides an ample explanation for the accompanying cerebrovascular dilation when arterial PO2 (PaO2) is reduced below 40 torr (Borgstrom et al, 1975). However, changes in cerebral blood flow (CBF) with alterations in PaO2 between 50 torr and higher which may reduce local cortical CBF (1CBF) by 80% (Leniger-Follert et al, 1976) are unexplained by changes in brain lactate and other metabolites (Siesjo et al, 1971: Kogure et al, 1977; Dora et al, 1979). Changes in 1CBF, brain tissue PO2 (PtO2), and pH have not been systematically studied over PaO2s ranging tram hyperoxia to moderate hypoxia. Our aim in this study was to determine whether changes in brain hydrogen ion concentration ((H+)) could account for alterations in cerebrovascular tone when PaO2 is reduced from hyperoxic to moderately hypoxic levels. Local tissue steady-state measurements over a wide range of PaO2 may provide a higher resolution than whole brain or regional measurements and enable the detection of more subtle changes than abrupt, acute and severe hypoxic insults (Dora et al, 1979).
KeywordsCerebral Blood Flow Hypoxic Hypoxia Brain Lactate Cerebral Blood Flow Response Cerebrovascular Response
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- 2.Borgström L., Johannsson, H. and Siesjö, B. K., The relationship between arterial PO.,2 and cerebral blood flow in hypoxic hypoxia. Acta PFiysiol. Scand. 93: 423–432, 1975.Google Scholar
- 3.Dora, E., Zeuthen, T., Silver, I. A., Chance, B., and Kovach A. G. B., Effect of arterial hypoxia on the cerebrocortical redox state, vascular volume, oxygen tension, electrical activity and potassium ion concentration. Acta Physiol Aced Sci. Hung 54: 319–331, 1979.Google Scholar
- 4.Fencl, V., Vale, J. R. and Broch, J. A., Respiration and cerebral flow in metabolic acidosis and alkalosis in humans. J. Appt Physiol. 27: 67–76, 1969.Google Scholar
- 7.Kogure, K, Scheinbert, P., Utsunomiya, Y., Kishikawa, H. and Busto, R., Sequential cerebral biochemical and physiological events in controlled hypoxemia. Ann Neurol 2: 304310, 1977.Google Scholar
- 8.Leniger-Follert, E., Wrabetz, W., and Lubbers, D. W., Local tissue P02 and microflow of the brain cortex under varying arterial oxygen pressure. In Oxygen Transport to Tissue II, Edited by Grote, J., Reneau, D. and Thews, G., Plenum Press, New York, 1976, pp 361–367.Google Scholar
- 9.Siesjö, B. K., Nilsson, L. Rokeach, Energy Metabolism of the Brain at Reduced Cerebral Perfusion Pressures and in Arterial Hypoxaenia. In Brain Hypoxia, Chapter 8, edited by Brierley, J. B., and Meldrum, B. S., Laneham Press, Laneham, England, 1971, pp 79–93.Google Scholar