Effects of Low-Concentration Nitrous Oxide Anesthesia on Patient Anxiety During Cataract Surgery: A Retrospective Cohort Study

PURPOSE: We investigated the effects of 30% low-concentration nitrous oxide (N(2)O) anesthesia on anxiety, pain, and vital signs and the patient population that would benefit from low-concentration N(2)O anesthesia during cataract surgery. PATIENTS AND METHODS: Sixty-three patients who underwent cataract surgery due to visual impairment from cataracts were included in this single-center retrospective cohort study conducted at the Ophthalmology Department of Shinseikai Toyama Hospital, Japan. Fifty eyes of 39 patients received a combination of local and N(2)O anesthesia (N(2)O group), and 30 eyes of 24 patients received local anesthesia without N(2)O anesthesia (Air group). The primary outcome measures were visual analogue scale (VAS) scores for patient anxiety, pain, and vital signs. The secondary outcome measures were the patient population. RESULTS: The change in the VAS scores for anxiety and pain decreased significantly (p = 0.002 and p = 0.014, respectively) in the N(2)O group (−15.6 ± 22.9 and 12.4 ± 14.9, respectively) compared with that in the Air group (1.2 ± 20.6 and 24.2 ± 22.4, respectively). The systolic and diastolic blood pressure changes did not significantly differ between both groups (p = 0.093 and p = 0.23, respectively). The change in heart rate decreased significantly (p = 0.001) in the N(2)O group (−4.8 ± 4.8 bpm) compared with that in the Air group (−0.6 ± 5.8 bpm). Multivariate analyses demonstrated that the change in anxiety level in the N(2)O group correlated significantly with patient age (p = 0.045) and preoperative VAS score for anxiety (p = 0.0001), whereas the change in anxiety level in the Air group did not correlate with any factor. CONCLUSION: Low-concentration N(2)O anesthesia showed beneficial effects on intraoperative anxiety and pain during cataract surgery; this may aid the stabilization of intraoperative vital signs. Moreover, low-concentration N(2)O anesthesia during cataract surgery could benefit young patients and patients with high levels of preoperative anxiety.