CO2 is the most potent cerebral [[vasodilator]].

[[Hyperventilation]] reduces [[PaCO2]] (hypocapnia), which decreases [[CBV]] but also [[CBF]]. The goal is generally end-tidal [[CO2]] ([[ETCO2]]) of 25–30 mm Hg with a correlating [[PaCO2]] of 30–35. Use with care for stereotactic procedures to minimize the shift of intracranial contents when using this method to control [[ICP]].