Local O₂ balance in cerebral ischemia-reperfusion improved during pentobarbital compared with isoflurane anesthesia

Background Most anesthetics affect cerebral blood flow and metabolism. We compared microregional O₂ balance in cerebral ischemia-reperfusion during pentobarbital and isoflurane anesthesia. Methods After 1 hour of middle cerebral artery occlusion and a 2-hour reperfusion under isoflurane (1.4%, n = 14) or pentobarbital (50 mg/kg, n = 14) anesthesia in rats, regional cerebral blood flow using ¹⁴C-iodoantipyrine autoradiography, microregional arterial and venous O₂ saturation (20-60 μm in diameter) using cryomicrospectrophotometry, and the size of cortical infarct were determined. Results Ischemia-reperfusion decreased the average cortical venous O₂ saturation in both pentobarbital and isoflurane groups (P <.0001), which was higher (P <.05) with pentobarbital despite a similar average regional cerebral blood flow and O₂ consumption. The heterogeneity of venous O₂ saturation reported as a coefficient of variation (100 × standard deviation/mean) was smaller (P <.005) with pentobarbital than that with isoflurane (7.5 versus 16.1). The number of veins with low venous O₂ saturation (<50%) was smaller (P <.005) with pentobarbital (5 of 80 versus 24 of 80). The percentage of cortical infarct in total cortex was smaller with pentobarbital (5.2 ± 2.5% versus 12.3 ± 2.6%, P <.001). Conclusions In the cerebral ischemic-reperfused cortex, the average venous O₂ saturation was higher, and its heterogeneity and the number of veins with low O₂ saturation were smaller under pentobarbital than isoflurane anesthesia. This improvement in microregional O₂ balance with pentobarbital was accompanied by the reduced cortical infarct. Our data suggest that the neurologic outcome could vary during cerebral ischemia-reperfusion depending on the anesthetics used.