Efficacy of low-concentration nitrous oxide gas anesthesia in routine cataract microsurgeries

To evaluate the sedative effects of low-concentration nitrous oxide (LCNO) anesthesia during cataract microsurgery (CMs) using bispectral index (BIS) monitoring. Thirty patients undergoing sequential CMs were randomized into the following three groups: Group A (LCNO for the first eye, oxygen for the second), Group B (oxygen for the first eye, LCNO for the second), and Group C (oxygen for both eyes) (n = 10 per group). BIS values, blood pressure, heart rate, and oxygen saturation were recorded at four time points: upon entering the operating room (T1), at the start of surgery (T2), at the conclusion of surgery (T3), and upon exiting the room (T4). A linear mixed model analysis was performed, with participants as the variable factor and group (LCNO-first, O2 first, both O2), duration (first and second eye), time (T1, T2, T3, and T4), interaction terms, and the initial values of each parameter (at entry) as fixed factors. BIS values at T2 and T3 were significantly lower in groups under LCNO compared to those under oxygen-only conditions (p < 0.001). No significant changes in heart rate, blood pressure, and oxygen saturation were observed in both groups. LCNO provided mild sedation during CMs, enhancing patient comfort without causing adverse effects. • Low-concentration nitrous oxide (LCNO) has been used in dentistry and some ophthalmic procedures and is believed to reduce anxiety and discomfort. • Evidence for its sedative effect in cataract microsurgery has largely relied on subjective patient reports rather than objective monitoring. • This study provides objective evidence, using bispectral index (BIS) monitoring, that LCNO induces mild sedation during routine cataract microsurgery. • LCNO significantly reduced the BIS values during surgery without causing clinically relevant changes in the vital signs or adverse events, supporting its safety and practicality for outpatient cataract surgery.