• Napas Lohtrakul, Chanane Wanapirak, and Theera Tongsong.
• Department of Obstetrics and Gynecology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
• Medicina (Kaunas). 2023 Mar 20; 59 (3).

AbstractAim and Objective: To compare the analgesic effectiveness of the patient-controlled inhaled nitrous oxide (Entonox®) with intravenous opioids (pethidine/midazolam) in reducing pain during minor gynecological operative procedures, including manual vacuum aspiration (MVA), fractional curettage and dilatation and curettage. Materials and Methods: Patients undergoing minor gynecological procedures from August 2021 to December 2022 were randomized to receive nitrous oxide or intravenous pethidine (50-75 micrograms) plus midazolam (2 mg). Pain scores during and post-procedure, satisfaction level, and side effects were assessed and compared. Results: A total of 106 patients met the inclusion criteria, including 53 in the pethidine/midazolam group and 53 in the nitrous oxide group. Baseline characteristics were comparable (p-value > 0.05). Pain scores during, immediately and 30 min after procedures were not significantly different in two groups (4.94 ± 3.15, 2.74 ± 2.57, 1.58 ± 2.13 vs. 5.47 ± 2.80, 2.98 ± 2.70, 1.64 ± 2.70; p-value: 0.174, 0.634, 0.889, for pethidine/midazolam vs. nitrous oxide group, respectively. Satisfaction scores were comparable in both groups (p-value > 0.05). However, the rate of side effects was significantly lower in the nitrous oxide group (3.8% vs. 28.3%; p-value 0.001). Additionally, the discharge scores showed a significantly faster recovery time in the nitrous oxide group at 60 and 90 min after the procedure; median (IQR): 10 (9-10) vs. 9 (8-10) and 10 (10-10) vs. 10 (8.5-10); p-value 0.002 and 0.029, respectively). Conclusions: Nitrous oxide is as effective as pethidine/midazolam for pain relief in minor gynecological operative procedures but associated with significantly lower side effects and significantly faster recovery time.

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