Fig. 4. Areas of greatest relative increases in regional cerebral blood flow (rCBF) and metabolic rate of oxygen (rCMRO²) caused by adding nitrous oxide (N²O) to sevoflurane or propofol. The colors indicate regions where the changes were statistically significant (P < 0.05, corrected for multiple comparisons). Red = subtle changes; yellow = peak effects (see the Materials and Methods section for details). Nitrous oxide increased flow (vs.  drug alone) with either drug in the occipital cortex (especially the medial surface) and the region of central sulcus but with sevoflurane also in the pons. The stereotactic coordinates for the voxel level findings are presented on the Anesthesiology Web site.