The Effects of Hyperbaric Oxygen at 2 and 3 Atmospheres Absolute and Intravenous Mannitol on Experimentally Increased Intracranial Pressure

Hyperbaric oxygen at 2 atmospheres absolute, which increased arterial Po2 to 1,227 mm Hg, caused a 30-percent reduction in intracranial pressure, which had been artificially increased in anaesthetised dogs by cerebral cold injury. The accompanying changes in cerebral venous blood gases were consistent with a reduction of cerebral blood flow. Hyperbaric oxygen at 3 atmospheres absolute increased arterial Po2 to 1,891 mm Hg, but failed to reduce intracranial pressure. The cerebral venous blood gas measurements suggested that there was now no cerebral vasoconstriction. Intravenous mannitol solution, administered at the end of the experiments, produced a 37-percent reduction of intracranial pressure.