The regulation of cerebrospinal fluid pH

Abstract

The past ten years have witnessed an increasing interest in the regulation of the cerebrospinal fluid (CSF) pH.Part of this interest stems from the fact that the extracellular fluid (ECF) pH in the brain serves as an important regulator of pulmonary ventilation [1–4] and a major determinant of cerebral blood flow [5–10].Furthermore, since the CSF pH has been shown to be subject to a considerable degree of homeostatic control in a variety of conditions which change the acid-base status of blood, many attempts have been made to unravel the physiological mechanisms which are responsible for this control [2, 3, 11, 12].Finally, since the acid-base metabolism of the cerebral compartments (including the ECF) may influence cerebral function to a significant degree [13, 14], the CSF pH and the mechanisms which regulate it have become of concern to neurologists and neurosurgeons. Available evidence shows beyond doubt that there are efficient mechanisms which guard the constancy of the CSF pH in non-respiratory and, to some extent, in respiratory acid-base disturbances as well.However, the changes in CSF pH are often so small that controversy exists as to their directional change in non-respiratory acidosis and alkalosis.Moreover, despite many efforts to define the regulatory mechanisms, they still remain largely unknown.In the following review, we will therefore try to distinguish between established fact and unproven hypothesis; the different possible regulatory mechanisms will be described and examined without any serious attempt to establish their quantitative importance.