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Published on: May 26, 2023
Nitrous oxide versus lidocaine versus no analgesic for in-office hysteroscopy: a randomised clinical trial
J A Solano Calvo1, C Del Valle Rubido2, A Rodríguez-Miguel3,4
1Department of Obstetrics and Gynaecology, University Hospital 'Príncipe de Asturias', Alcalá de Henares, Madrid, Spain.
Objective:
To compare the effect of inhaled nitrous oxide (INO) on pain control during in-office hysteroscopy with 1% lidocaine paracervical infiltration and no analgesic.
Design:
Single-blind stratified randomised clinical trial with masked assessment by a third party.
Setting:
Department of Obstetrics and Gynaecology in a Spanish hospital.
Population:
Women who underwent hysteroscopy.
Methods:
Patients were stratified into three groups according to the purpose of the hysteroscopy (biopsy, polypectomy or tubal sterilisation) and then assigned to different treatment groups through a permuted-blocks randomisation within strata. Pain scale was provided by a gynaecologist totally blinded to procedures and treatments. Effects were assessed using a one-way analysis of variance following an intention-to-treat approach.
Main Outcome Measures:
Visual analogue scale (VAS) from 0 to 100 mm.
Results:
A total of 314 women were included: 105 to INO, 104 to 1% lidocaine and 105 to no analgesic. Baseline characteristics were comparable. Mean VAS score after the procedure was 34.7 ± 25.8 mm, 36.1 ± 22.9 mm (P = 1.0) and 47.3 ± 28.2 mm (P = 0.001) for INO, 1% lidocaine and no analgesic, respectively. No adverse events were reported in 91 (86.7%) patients in the INO group compared with 79 (76%) in the 1%-lidocaine group (P = 0.04) and 85 (81%) in the no-analgesic group (P = 0.26).
Conclusion:
INO was as effective as 1% lidocaine in pain control for in-office hysteroscopy and was better tolerated. The no-analgesic group presented the poorer results, so was the least recommended clinical option.
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