Local cortical blood flow and oxygen consumption during isoflurane-induced hypotension
Steven Roth, MD
Stephen C. Jones, PhD
Zeyd Y. Ebrahim, MDAddress reprint requests to Z.Y.E., Department of General Anesthesia, Cleveland Clinic Foundation, One Clinic Center, 9500 Euclid Avenue, Cleveland, Ohio 44195.
Harry Friel, MS
John R. Little, MD
Cerebral cortical blood flow (lCoBF) and metabolic rate for oxygen (lCoMRO2) were studied in eight patients undergoing intracranial aneurysm clipping. The patients were anesthetized with fentanyl 10 μg/kg and 70% nitrous oxide combined with 30% oxygen. Hypotension was induced with isoflurane. A thermal diffusion probe was used to measure ICoBF, and arterial and cerebral venous blood samples were obtained for measurement of arterio-cerebral venous O2 content difference. Measurements were made prior to hypotension, during hypotension (to mean arterial pressure approximately 50 mmHg), and posthypotension. Mean ICoBF decreased from 69 ± 20 mL/100 g/min at normotension to 59 ± 13 mL/100 g/min during hypotension (P <.03, NS) and was 61 ± 18 mL/100 g/min upon return to normotension (all values mean ± 1 SD). The lCoMRO2 averaged 3.9 ± 1.6 mL/100 g/min and 3.1 ± 1.5 mL/100 g/min, respectively (P <.03, NS) for normotension v hypotension. Values for cerebral venous PO2 and O2 saturation also did not differ significantly between study periods. These results indicate that isoflurane-induced hypotension during fentanyl-nitrous oxide anesthesia allows maintenance of a constant lCoBF and oxygen delivery.