Pupillary response to nitrous oxide administration in cataract surgery under general anesthesia

Despite recent innovations in cataract surgery, pupillary diameter is one of the most important affecting factors in outcome of this surgery. As cataract surgery is performed ideally when the pupil is sufficiently dilated, anesthesia may contribute significantly in success or failure of this operation. This study was performed to evaluate the effect of nitrous oxide on pupillary diameter in cataract surgery under general anesthesia.

Forty patients with cataract, scheduled for operation under general anesthesia, were randomly allocated into two groups. After induction of anesthesia, anesthesia was maintained with isoflurane and nitrous oxide - oxygen (60%-40%) in group 1 versus oxygen 100% in group 2. Pupillary diameter, heart rate and blood pressure were monitored and recorded, before induction of anesthesia, just before tracheal intubation, and one and 5 min after laryngoscopy and tracheal intubation.

Statistical analysis of the results using Mann-Whitney test showed no significant difference in pupillary diameter between two the groups.

According to the results of this study, nitrous oxide has no effect on pupillary diameter of patients under general anesthesia, so it could be safety used, in this regard, in ophthalmic operations.