The effect of desflurane and isoflurane on cerebrospinal fluid pressure in humans with supratentorial mass lesions

Desflurane, a new volatile anesthetic, produces cerebral vasodilation. The purpose of this study was to compare the effects of 1 MAC desflurane with those of isoflurane on cerebrospinal fluid pressure (CSFP) in patients with supratentorial mass lesions and a mass effect on computerized tomography (CT scan). Twenty adult patients undergoing craniotomy for removal of supratentorial mass lesions were studied. Ten patients received desflurane and 10 patients received isoflurane. Prior to induction of anesthesia, a radial artery catheter was inserted and a 19-G needle was inserted into the lumbar subarachanoid space to measure CSFP. Baseline arterial blood gases and CSFP were measured with the patient awake and unmedicated. Anesthesia was induced with thiopental (6-9 mg/kg) and muscle relaxation achieved with vecuronium (0.2 mg/kg). The lungs of all patients were hyperventilated to achieve an arterial CO₂ tension of 24-28 mmHg. Anesthesia was maintained with 1 MAC volatile anesthetic, either 7.0% desflurane or 1.2% isoflurane in an air:O₂ mixture to maintain an inspired O₂ fraction (FI(O₂)) of 0.50. Patients were not administered any other anesthetic until the dura was incised. Mean arterial pressure was kept within 20% of the patient's mean ward values with the use of esmolol or phenylephrine. CSFP, mean arterial pressure, end-tidal CO₂ concentration (PET(CO₂)), hemoglobin O₂ saturation, and cerebral perfusion pressure were recorded with the patient awake, immediately postinduction with thiopental, post-intubation, after institution of the volatile anesthetic, and every 5 min until the dura was incised. There was no difference in the mean (± SD) awake CSFP between the desflurane (11 ± 4 mmHg) and the isoflurane (10 ± 2 mmHg) groups. CSFP significantly decreased in all patients after administration of thiopental, followed by a variable increase with laryngoscopy and intubation. During administration of desflurane, the CSFP gradually increased (to 18 ± 6 mmHg) in all patients until the dura was incised. The CSFP was significantly greater than baseline measurement beginning 20 min after the institution of desflurane. There was no statistically significant change in the mean CSFP in the isoflurane group at any time during the study period after the volatile anesthetic was instituted. CSFP was 8 ± 2 mmHg at the time of dural incision in the isoflurane group. CSFP in the desflurane group became significantly greater than the CSFP in the isoflurane group beginning 10 min after institution of the volatile anesthetic. The results of this study indicate that, in hypocapnic neurosurgical patients with supratentorial mass lesions, the administration of 1 MAC desflurane resulted in an increase in CSFP. This is in contrast to 1 MAC isoflurane, which did not produce an increase in CSFP.