Isoflurane and Cerebrospinal Fluid Pressure in Neurosurgery

Abstract

Isoflurane (Florane), a new inhalation anesthetic, resembles halothane in its physicochemical properties, even though its molecular structure (halogenated ether) resembles more that of methoxy-flurane. Studies to date of the cardiovascular and metabolic response to isoflurane indicate that it may offer several distinct advantages over other available volatile agents. Canine studies (1) have shown that, like halothane, isoflurane increases cerebral blood flow (CBF) in a dose response relationship. This CBF response to halothane is known to cause increases in intracranial pressure, particularly in patients with intracranial space-occupying lesions. In an earlier study (2), we demonstrated that this undesirable response to halothane could be consistently avoided by inducing significant levels of hypocapnia prior to the introduction of halothane. When hyperventilation and halothane were simultaneously initiated, significant increases in cerebrospinal fluid pressure (CSFP) were observed. The present study was designed to determine the extent of this relationship with isoflurane by measuring its effects on CSFP in the presence of hypocapnia and normocapnia.