Objective: To evaluate the pain-relieving effect of transcutaneous electrical nerve stimulation (TENS) during office-based hysteroscopy without sedation.
Methods: We conducted a randomized, double-blind, placebo-controlled trial. Participants were randomly assigned to the active TENS, placebo TENS, or control group. The active TENS intervention consisted of a varying high-frequency (80-100 Hz), 400-microseconds, individually adjusted, high-intensity TENS application with two self-adhesive electrodes placed parallel to the spinal cord at the T10-L1 and S2-S4 levels. In the placebo group, participants were connected to the TENS unit but delivering no electrical stimulation. The primary outcome was self-reported pain intensity (0-100 mm) measured on a visual analog scale at several stages (entry, contact, biopsy, and residual). The minimum clinically relevant difference for the visual analog scale has been previously reported as 10 mm. Sample size was calculated to provide 80% power to show a 10-mm difference (α=0.0125) in the primary outcome. Secondary outcomes included duration of the procedure, vital parameters, vasovagal symptoms, and participant satisfaction index (0-10 rating scale).
Results: A total of 138 women (46 per group) participated in the study between January 2016 and April 2016. No differences were found between groups regarding age, weight, body mass index, parity status, menopausal status, or previous hysteroscopy status. Visual analog scale scores highlighted a decrease in pain in the active TENS group compared with the placebo group (entry: -11 mm, 95% confidence interval [CI] -17 to -5; contact: -21.9 mm, 95% CI -30 to -13.9; biopsy: -30.5 mm, 95% CI -47.1 to -13.8, P<.001). Moreover, the reduction in pain reached the minimum clinically relevant difference. Regarding satisfaction, results also revealed differences between active TENS and placebo groups (1.3, 95% CI 0.5-2.2, P=.001).
Conclusion: Transcutaneous electrical nerve stimulation reduces pain and increases patient satisfaction during office hysteroscopy without sedation.
Clinical trial registration: ClinicalTrials.gov, www.clinicaltrials.gov, NCT02647008.