Nitrous oxide levels during retinal cryosurgery

D. F. Marcus and S. Gawecki

Nitrous oxide levels were monitored before, during, and after retinal cryotherapy. These units produced an average elevation of the nitrous oxide concentration in the operating room to the level of 963 ppm. Nitrous oxide levels in a control operating room using general endotracheal anesthesia with nitrous oxide ranged from 75 to 200 ppm. Nitrous oxide has been reported to be associated with various teratogenic effects in experimental animals and may be associated with other human ailments. The use of a scavenger system specifically designed to handle the exhaust from ophthalmic nitrous oxide units can reduce the nitrous oxide concentration by 50% or more and is, therefore, recommended.