Effects of Increased Intracranial Pressure on Cerebral Blood Flow and on Cerebral Venous pO₂, pCO₂, pH, Lactate and Pyruvate in Dogs

Abstract

Abstract The effects of increased cerebrospinal fluid (CSF) pressure on cerebral blood flow and on cerebral venous pO 2 , pCO 2 , pH, lactate, and pyruvate were studied in dogs by infusing an artificial CSF into the cisterna magna. With moderate and rapid increases in the CSF pressure, which did not lower cerebral perfusion pressure below 60–70 mm Hg, the cerebral blood flow was not measurably lowered, although there were sometimes detectable metabolic changes in cerebral venous blood suggestive of a transient reduction of the cerebral blood flow. That is, cerebral venous pO 2 and pH decreased slightly, and there were increases in the cerebral venous pCO 2 , in the lactate and pyruvate concentrations, and in the lactate/ pyruvate ratios, indicating an anaerobic glucolysis. When the pressure was released there was usually no reactive hyperemia, and no persisting metabolic changes in the cerebral venous blood. When the CSF pressure was markedly increased, and the cerebral perfusion pressure accordingly reduced to 30–50 mm Hg there were marked metabolic changes in cerebral venous blood, the pO 2 often approaching 10 mm Hg. In this case, a sudden reduction of the CSF pressure was almost invariably followed by a significant reactive hyperemia, which was paralleled by an arterialization of cerebral venous blood with a high pO 2 and a low pCO 2 . The changes in pO 2 usually expressed the changes in flow. During and after the reactive hyperemia there were no lactate/pyruvate changes to indicate the preceding period of anaerobic glucolysis.