Cerebral Venous Oxygen Research Articles

Blood P-CO2 and brain oxygenation at reduced ambient pressure.

Hyperventilation during breathing of 100% oxygen elevates the Po2 of alveolar gas by the same amount that it lowers its Pco2. Since the development of arterial hypocapnia causes cerebral vasoconstriction, brain oxygenation is drastically decreased even while arterial oxygenation is improved by hyperventilation. Administration of 30% CO2 with oxygen at an ambient pressure equivalent to that at 39,000-ft altitude prevented alkalemia and, in spite of hyperventilation, restored cerebral venous oxygenation to a level at least equivalent to that found when pure oxygen was breathed at rest at the same altitude. The respiratory minute volume during administration of CO2 with O2 was greater than when O2 alone was breathed at reduced ambient pressure. Since neither arterial Po2 nor cerebral venous Pco2 values differed in these two experimental situations, the respiratory stimulation may represent the quantitative demonstration in man of a respiratory effect of CO2 mediated by arterial chemoreceptor activation and unrelated to change in the level of central chemical stimulus. Submitted on March 16, 1962

The effect of hexamethonium upon cerebral blood flow and metabolism in patients with premalignant and malignant hypertension.

In 13 patients with grade III or grade IV hypertensive retinopathy the effect of intramuscular hexamethonium bromide on cerebral circulation and metabolism has been studied. The results have been compared with Dewar's study of hexamethonium in less severe hypertensive patients and with Kety's results following differential spinal sympathetic block. Sixty minutes after intramuscular hexamethonium, mean arterial blood pressure fell 39 per cent, cerebral vascular resistance was reduced 29 per cent, and cerebral blood flow decreased 16 per cent. Cerebral oxygen consumption was maintained at the expense of a reduction in cerebral venous oxygen saturation.

Cerebral Blood Flow and Metabolism in Pernicious Anemia

Abstract1. Cerebral blood flow and metabolism were measured in 16 patients with pernicious anemia. Seven of the patients were restudied in various stages of therapy.2. The patients fell into two equal groups, those with severe anemia and those with moderate or no anemia. In the first group, cerebral blood flow was increased and cerebral vascular resistance decreased; in the second group, cerebal blood flow was decreased and vascular resistance increased. In both groups, cerebral oxygen and glucose consumption was decreased, as was cerebral venous oxygen tension.3. There was a good correlation between the mental status defects and cerebral oxygen consumption and between severity of neurologic involvement and cerebral oxygen consumption. There was no correlation between cerebro-vascular resistance and cerebral oxygen consumption, nor between degree of anemia and cerebral oxygen consumption.4. Specific therapy resulted in a moderate increase in cerebral oxygen consumption and cerebro-vascular resistance. In no instance did cerebral oxygen consumption become normal.5. The disparity between the functional ability of the patients and the low values for cerebral metabolism is discussed.6. It is concluded that pernicious anemia results in specific nervous system involvement not related to the anemia, and that this damage is at least partially irreversible in many patients.