Local cerebral blood flow measured by stable xenon CT during fentanyl-diazepam anesthesia

We assessed the local cerebral blood flow (LCBF) in 40 patients under fentanyl-diazepam anesthesia. The measurement of LCBF was made using 50%–70% stable xenon with 20 min of inhalation interval and a shuttle method for computed tomography imaging. All patients were anesthetized with 5.95±1.76 μg·kg⁻¹ fentanyl and 0.22±0.07 mg·kg⁻¹ diazepam under mechanical ventilation during CBF measurement. The values and distribution of LCBF on non-affected hemisphere appeared to be unaltered by fentanyldiazepam anesthesia. We also assessed the cerebral carbon dioxide reactivity in 6 patients. The cerebral carbon dioxide reactivity, expressed as percentage change in LCBF per unit change in arterial carbon dioxide partial pressure, was 5.39±1.07, and there were no significant differences of reactivity among regions studied. In conclusion, we showed reference values of LCBF and carbon dioxide reactivity, measured by stable xenon-enhanced computed tomography, in patients under fentanyl-diazepam anesthesia. Carbon dioxide reactivity was preserved in all regions including gray matter, white matter, and basal ganglia.