The Effect of Isoflurane on Cerebral Blood Flow and Metabolism in Humans during Craniotomy for Small Supratentorial Cerebral Tumors

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Abstract
Fourteen patients were studied during craniotomy for small supratentorial cerebral tumors. Cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) were measured twice by a modification of the Kety-Schmidt technique using 133Xe intravenously Anesthesia was induced with thiopental 5-7 mg .cntdot. kg-1, fentanyl 0.2 mg, and pancuronium, and maintained with 0.75% inspired isoflurane concentration in 67% nitrous oxide, and moderate hypocapnia. In one group of patients (n = 7), the inspired isoflurane concentration was maintained at 0.75% throughout anesthesia. One hour after induction of anesthesia, CBF and CMRO2 averaged 31 .+-. 3 ml .cntdot. 100 g-1 .cntdot. min-1 (X .+-. SEM), respectively. During repeat studies 1 h later, CBF and CMRO2 were unchanged. In a second group of patients (n = 7), an increase in the inspired isoflurane concentration from 0.75% to 1.5% was associated with a significant decrease in CMRO2 from 2.4 .+-. 0.1 to 1.9 .+-. 0.1 ml O2 .cntdot. min-1, and no change in CBF. It is concluded that this anesthetic regimen is safe to use in patients with small supratentorial tumors in whom only a small midline shift has occurred.