Xenon Inhalation on Whole-Brain Blood Flow and Metabolism in Awake and Fentanyl-Anesthetized Monkeys

Background and Purpose: Despite the documented diagnostic value of local cerebral blood flow maps by xenon-enhanced computed tomography, reports of cerebral blood flow activation by inhaled 33% Xe raised concerns about the method's safety and accuracy. We evaluated the effect of 33% Xe inhalation on cerebral blood flow and cerebral metabolic rates for oxygen and glucose in four awake and six fentanyl-anesthetized rhesus monkeys. Methods: Platinum microelectrodes and catheters in the torcular Herophili were used to measure cerebral blood flow by hydrogen clearance, and oxygen and glucose concentrations. Cerebral variables were measured after 5 and 35 minutes of exposure to room air followed randomly by 67% O2 in 33% N2 or Xe. Fiveand 35-minute measurements were combined because the duration of exposure had no effect Results: In awake monkeys, 33% Xe compared with 33% N2 reduced (p<0.05) cerebral blood flow from 75±12 to 66±9 (mean±SD) ml -100 g"' • min" and oxygen consumption from 6.1±0.7 to 5.1±0.6 ml • 100 g" • min". In fentanyl-anesthetized monkeys, cerebral variables during 33% N2 versus 33% Xe were cerebral blood flow, 84±26 versus 79±23 ml • 100 g" • min"; oxygen consumption, 5.0±0.7 versus 4.9±0.5 ml • 100 g" • min"; and glucose consumption, 8.4±1.9 versus 7.9±2.0 mg • 100 g" • min". Conclusions: In awake monkeys, 33% Xe reduced rather than activated cerebral blood flow and oxygen consumption by 12% and 16%, respectively; it had no effect in fentanyl-anesthetized monkeys. (Stroke 1992^3:69-74)