EFFECTS OF ACETAZOLAMIDE ON CEREBRAL BLOOD FLOW OF DOGS DURING HYPERBARIC OXYGENATION

The effect of acetazolamide in improving cerebral blood flow and counteracting hyperoxic cerebral vasoconstriction was evaluated in 7 dogs breathing room air at ambient pressure and in 5 dogs breathing 100 per cent oxygen at 2.3 atmospheric pressure. Cerebral blood flow, measured with the radioactive xenon clearance method, was determined serially before and after administration of 5 mg. per kilogram of acetazolamide intravenously. Following the administration of acetazolamide at ambient environment, the mean fast flow increased from a base-line level of 60.8 to 112.4 ml. per 100 Gm. per minute and slow flow from 16.2 to 24.6 ml. per 100 Gm. per minute with the arterial pCO2 and arterial blood pressure remaining relatively constant. The cerebral blood flow was markedly increased at 10 minutes, it attained a peak at 30 minutes, and tended to remain elevated throughout the two hour observation period. Hyperbaric oxygenation (arterial pO2 = 1,548 mm. Hg) reduced the mean fast flow from 66.4 to 55.9 ml. per 100 Gm. per minute and mean slow flow from 17.2 to 15.3 ml. per 100 Gm. per minute. Administration of acetazolamide during hyperbaric oxygenation raised the mean fast flow to 134.8 and slow flow to 24.7 ml. per 100 Gm. per minute. This increase of cerebral blood flow was not observed in the 3 control animals which were subjected to only hyperbaric oxygenation without receiving acetazolamide. These studies demonstrate that acetazolamide in a small amount not only effectively counteracts the cerebral vasoconstricting effect of hyperoxia, but also significantly increases cerebral blood flow at both ambient and hyperbaric conditions. © 1969.