Nitrous oxide increases intraocular pressure after intravitreal sulfur hexafluoride injection.

In anesthetized cats ventilated with oxygen, 0.5 ml of the inert gas sulfur hexafluoride (SF6) was substituted for vitreous. When the ventilating gas was changed to nitrous oxide (N2O) 66%, balance oxygen, intraocular pressure increased from 14.4 to 30.3 mmHg in 19.5 min. When the ventilating gas was changed back to oxygen, intraocular pressure decreased from 29.1 to 12.0 mmHg in 18.1 min. This intraocular pressure change secondary to gas volume alteration may adversely affect therapeutic outcome of ophthalmic surgery. Accordingly, N2O should be avoided in patients during and following intravitreal injection of SF6 for up to 10 days.