The effect of nitrous oxide on the cerebrospinal fluid pressure during encephalography.

Cerebrospinal fluid pressure was measured in twenty-three patients undergoing encephalography. Three different programmes were followed to determine the effect of nitrous oxide on intracranial pressure with and without injection of air and nitrous oxide into the theca. In every case the initial c.s.f. pressure remained unchanged when nitrous oxide was used for encephalography, while it increased significantly after the inhalation of nitrous oxide with air encephalography. However, this increase always remained within the normal range of c.s.f. pressure and therefore the conclusion is drawn that the use of nitrous oxide in the anaesthetic mixture during encephalography could be followed without any risk in cases of normal intracranial pressure. In cases of high intracranial pressure, and in the presence of nitrous oxide in the anaesthetic gas mixture, the intrathecal use of nitrous oxide instead of air is probably a safer method.