Isoflurane and Cerebrospinal Fluid Pressure in Neurosurgical Patients

Abstract

The effect of isoflurane on CSF pressure (CSFP) was determined in 20 patients undergoing craniotomy for intracranial supratentorial neoplasm or hematoma. In 15 of the patients, following endotracheal intubation, hyperventilation sufficient to cause PaCO2 [arterial CO2 partial pressure] 25-30 torr was begun simultaneously with the introduction of 1% isoflurane. In the remaining 5 patients ventilation was equivalent, but normocapnia was maintained by adding CO2 to the inspired gases. In the hypocapnic patients CSFP did not increase above awake values (range 5-45 torr) following isoflurane administration. In the normocapnic patients CSFP consistently increased. In 3 of these 5 patients the increases were precipitous, but were corrected rapidly by establishment of hypocapnia. The known cerebral vasodilator properties of isoflurane can be countered effectively by hypocapnia. Unlike the situation with halothane, it is not necessary to establish hypocapnia prior to introducing isoflurane to avoid CSFP increases.