The effect of methoxyflurane on cerebrospinal fluid pressure in patients with and without intracranial space-occupying lesions.

The effect of methoxyflurane 0.5 per cent and 1.5 per cent on cerebrospinal fluid (c.si.) pressure has been studied in patients with normal c.s.f. pathways and in patients with intracranial space-occupying lesions. In patients with normal c.s.f. pathways, methoxyflurane 0.5 per cent produced variable responses, causing small increases in c.si. pressure in some and small decreases in others. On the other hand, methoxyflurane 1.5 per cent caused significant increases in c.s.f. pressure in all patients, increases that were not associated with any alteration in either carbon dioxide tension or central venous pressure. In those patients studied with intracranial space-occupying lesions, both 0.5 per cent and 1.5 per cent methoxyflurane produced increases in c.s.f. pressure which were markedly greater than those found in the patients without space-occupying lesions. The mean rise in c.s.f pressure was dependent on the concentration of the drug administered, being small with 0.5 per cent methoxyflurane, but much greater with the higher concentration. A possible hazard in such patients is that the administration of methoxyflurane may lead to gradients of intracranial pressure, thus aggravating brain shifts and mid-brain distortion and, if the skull is opened, lead to external brain herniation. 4