Isoflurane and cranial extradural pressure. A study in neurosurgical patients.

The effect of isoflurane on cranial extradural pressure (EDP) was studied in 10 patients. In eight patients with normal intracranial pressure, the addition of 1.0% isoflurane to nitrous oxide plus fentanyl in oxygen anaesthesia, at physiological carbon dioxide tensions, did not cause any significant change in EDP; 1.5% resulted in a small but significant increase. In two patients with clinical evidence of increased intracranial pressure isoflurane decreased EDP during the administration of isoflurane. In all patients, hyperventilation (3.2% carbon dioxide concentration) decreased EDP rapidly. Mean arterial pressure (MAP) was decreased significantly at the higher isoflurane concentration. It was concluded that use of isoflurane is not contraindicated in patients with mass lesions, either at normocapnic or hypocapnic concentrations of carbon dioxide and would appear to be suitable for use in neurosurgical anaesthesia.