The dose-dependent effects of transcutaneous electrical nerve stimulation for pain relief in individuals with fibromyalgia: a systematic review and meta-analysis.

ABSTRACT: Transcutaneous electrical nerve stimulation (TENS) is a nonpharmacological modality widely used to manage pain; however, its effectiveness for individuals with fibromyalgia (FM) has been questioned. In previous studies and systematic reviews, variables related to dose of TENS application have not been considered. The objectives of this meta-analysis were (1) to determine the effect of TENS on pain in individuals with FM and (2) determine the dose-dependent effect of TENS dose parameters on pain relief in individuals with FM. We searched the PubMed, PEDro, Cochrane, and EMBASE databases for relevant manuscripts. Data were extracted from 11 of the 1575 studies. The quality of the studies was assessed using the PEDro scale and RoB-2 assessment. This meta-analysis was performed using a random-effects model that, when not considering the TENS dosage applied, showed that the treatment had no overall effect on pain (d+ = 0.51, P > 0.050, k = 14). However, the moderator analyses, which were performed assuming a mixed-effect model, revealed that 3 of the categorical variables were significantly associated with effect sizes: the number of sessions ( P = 0.005), the frequency ( P = 0.014), and the intensity ( P = 0.047). The electrode placement was not significantly associated with any effect sizes. Thus, there is evidence that TENS can effectively reduce pain in individuals with FM when applied at high or at mixed frequencies, a high intensity, or in long-term interventions involving 10 or more sessions. This review protocol was registered at PROSPERO (CRD42021252113).

Transcutaneous Nerve Stimulation for Pain Relief During Office Hysteroscopy: A Randomized Controlled Trial.

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.