Local cortical blood flow and oxygen consumption during isoflurane-induced hypotension. Results in patients undergoing intracranial aneurysm clipping.

Abstract

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 micrograms/kg and 70% nitrous oxide combined with 30% oxygen. Hypotension was induced with isoflurane. A thermal diffusion probe was used to measure lCoBF, 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 lCoBF decreased from 69 +/- 20 mL/100 g/min at normotension to 59 +/- 13 mL/100 g/min during hypotension (P less than .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 less than .03, NS) for normotension upsilon 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.