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News

Ophthalmic Safety Alert – Do not use nitrous oxide when there is gas in an operated eye

There have been several case reports on the use of nitrous oxide in the presence of intraocular gas after vitreoretinal surgery with severe loss of vision due to central retinal artery occlusion.2-6 There have also been some cases identified via national incident reporting systems. Nitrous oxide leaves the bloodstream and vitreous cavity quickly once inhalation is terminated,7 restoring the position of the lens-iris diaphragm and reperfusion of the central artery can happen. However, irreparable damage to the retina is known to occur after 100 minutes of ischaemia.7 The extent of damage to the eye may therefore be dependent on the duration of general anaesthesia / use of Entonox and the size of intraocular gas bubble at that time. There is a theoretical risk of harm (raised intraocular pressure or hypoxic iris) in anterior chamber gas bubbles during keratoplasty in the same circumstances, that is flying, high altitude or nitrous oxide use. It is currently unclear whether this represents a significant risk, as there is little published, but some corneal surgeons are warning their patients not to fly postoperatively.