N2O and intraocular gas

Entrance of nitrous oxide into cavities filled with gas (ex. bowel) can lead to an increase in pressure.After intravitreal injection of sulfur hexafluoride(colorless, odorless, non-flammable gas) or perfluoropropane(C3F8),nitrous oxide may increase intraocular pressure. This can be dangerous because ocular perfusion pressure (difference between arterial blood pressure and IOP) may be critically decreased. Regarding sulfur hexafluorideMiller states that “Nitrous oxide should be avoided for 15 minutes before the use of intraocular gas. Nitrous oxide must be avoided for 7 to 45 days after use, or until the gas bubble is resorbed.” Regarding,perfluoropropane, Miller states that “Perfluoropropane…can persist for weeks [and]nitrous oxide should be avoided for at least a month, or until the bubble is resorbed.“

With regards to IOP, keep in mind that volatile anesthetics reduce IOP (by contrast, ketamine and succinylcholine may can increase IOP)

N₂O and Eye Surgery

• Particularly dangerous with sulfur hexafluoride andperfluoropropane
• Avoid for 15 minutes before intraocular gas
• Avoid for 7-10 days after sulfur hexafluoride
• Avoid forat least a month after perfluoropropane

Finally, as noted by Miller “If a patient presenting for nonophthalmic surgery has a history of a recent retinal procedure, it is critical to establish whether the patient has an intravitreal gas bubble before using nitrous oxide. Otherwise, blindness can result.”