Abstract
The changes in plasma electrolytes and blood pH and gases following the insufflation of air into the subarachnoid space for pneumoencephalography were investigated. The only significant change observed was a rapid fall of plasma potassium most evident at 60 minutes. A concomitant reduction of the urinary Na/K ratio supports the possibility that the change observed may be due to the stimulation of aldosterone secretion caused by this procedure, though its rapid occurrence and reversibility indicate that other influences might at least in part be responsible.