Nitrous Oxide: CBF and CMRO2

N₂O increases CBF, CMR, and ICP. Mostly due to cerebral vasodilation, although partly due to sympathoadrenal stimulation. This effect is lessened by co-administration of IV anesthetics, but may be worsened by addition of volatile. CBF response to CO₂ is preserved w/ N₂O administration. According to Miller, “There is no uniform agreement about the effect of N₂O on CMR…” In a recent investigation in humans, administration of 70% N₂O on a background of either sevoflurane or propofol anesthesia resulted in modest increases in CMRO₂, thus indicating that N₂O does indeed increase cerebral metabolism.