Characterising the Features of 381 Clinical Studies Evaluating Transcutaneous Electrical Nerve Stimulation (TENS) for Pain Relief: A Secondary Analysis of the Meta-TENS Study to Improve Future Research

Background and Objectives: Characterising the features of methodologies, clinical attributes and intervention protocols, of studies is valuable to advise directions for research and practice. This article reports the findings of a secondary analysis of the features from studies screened as part of a large systematic review of TENS (the meta-TENS study). Materials and Methods: A descriptive analysis was performed on information associated with methodology, sample populations and intervention protocols from 381 randomised controlled trials (24,532 participants) evaluating TENS delivered at a strong comfortable intensity at the painful site in adults with pain, irrespective of diagnosis. Results: Studies were conducted in 43 countries commonly using parallel group design (n = 334) and one comparator group (n = 231). Mean ± standard deviation (SD) study sample size (64.05 ± 58.29 participants) and TENS group size (27.67 ± 21.90 participants) were small, with only 13 of 381 studies having 100 participants or more in the TENS group. Most TENS interventions were ‘high frequency’ (>10 pps, n = 276) and using 100 Hz (109/353 reports that stated a pulse frequency value). Of 476 comparator groups, 54.2% were active treatments (i.e., analgesic medication(s), exercise, manual therapies and electrophysical agents). Of 202 placebo comparator groups, 155 used a TENS device that did not deliver currents. At least 216 of 383 study groups were able to access other treatments whilst receiving TENS. Only 136 out of 381 reports included a statement about adverse events. Conclusions: Clinical studies on TENS are dominated by small parallel group evaluations of high frequency TENS that are often contaminated by concurrent treatment(s). Study reports tended focus on physiological and clinical implications rather than the veracity of methodology and findings. Previously published criteria for designing and reporting TENS studies were neglected and this should be corrected in future research using insights gleaned from this analysis.

The effects of interferential electrical stimulation current on labor pain and duration of active phase of labor in primiparous women: A randomized controlled trial

BACKGROUND

Labor pain is one of the most severe pains experienced by a woman during her life. Interferential current (IFC) is a type of transcutaneous electrical stimulation that can reduce pain, especially deep ones.

OBJECTIVE

This randomized controlled clinical trial (RCT) aimed to study the effects of quadripolar IFC on pain and the duration of the active phase of labor in primiparous women.

METHOD

In this RCT, 60 primiparous women were randomized into two groups of IFC and sham IFC. The IFC group received IFC in two periods. The sham group received sham IFC. Primary outcomes were labor pain in different times of active phase and duration of active phase, and secondary outcomes were delivery satisfaction; the number of infants transferred to neonatal intensive care units (NICUs), fetal heart rate (FHR) disorders, Apgar score, partograph variables, and adverse side effects were recorded.

RESULT

Between-group changes showed a significant decrease in labor pain during the active phase in the IFC group compared to the sham IFC group (mean difference (MD) = -0.95; 95% confidence interval (95% CI) = -1.35 to -0.55; P < .001). The mean of active phase duration was significantly shorter in the IFC group than in the sham IFC group (MD = -38.25; 95% CI = -62.84 to -13.67; P = .003).

CONCLUSION

This study showed the effectiveness of interferential electrical stimulation during labor to reduce pain and duration of the active phase, which can be valuable in improving the quality of care and encouraging natural childbirth.

Comparison of entonox and transcutaneous electrical nerve stimulation (TENS) in labor pain: a randomized clinical trial study

AIM

The aim of performing this study was comparison of Entonox and transcutaneous electrical nerve stimulation (TENS) in labor pain in Zanjan city, Iran.

MATERIALS AND METHODS

This clinical trial study was conducted on 120 pregnant women in Zanjan-Iran, 2016. The patients were randomly divided (by method of 1:1:1) into three groups (each group 40 patients): First group was TENS group; the second group was Entonox group and control group were choose from the patients that had a physiological delivery. They did not want to use analgesia. All the analyses were done using SPSS (version 23).

RESULTS

Before intervention the pain severity between three group was relatively same (p = .78). After intervention, pain score was significantly higher in control group compared to other two groups (p = .005), but the differences between mean Apgar score between three groups was not significant (p = .59). Also, both Entonox and TENS had significantly lower pain compared control group (p = .005), but there was no significant difference between Entonox and TENS in regard of pain score (p = .997).

CONCLUSIONS

Our findings reported that two groups of Entonox and TENS had similar effect on pain relief and decreased significantly pain scores. Therefore, TENS methods as a non-drug pain relief method can propose to women for relief of labor pain.

Transcutaneous Electrical Nerve Stimulation As A Pain-Relieving Approach in Labor Pain: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Transcutaneous electrical nerve stimulation (TENS) is a non-invasive electrophysical pain-relieving modality that also can be used in labor pain. Compared to other methods, TENS is not commonly practiced in intrapartum care due to a lack of knowledge about its clinical efficacy. Hence, a comprehensive overview of all types of randomized controlled trials (RCTs) on TENS can provide a better insight into this method and its efficacy in labor pain.

OBJECTIVES

To perform a systematic review to assess the efficacy of TENS for labor pain control compared to other treatments.

SEARCH STRATEGY

PubMed, Cochrane Library, Embase, and Web of Science databases were searched for studies using keywords "TENS" combined with "labor pain" and "labor."

SELECTION CRITERIA

Eligible criteria included RCTs, full-text studies, English, and Danish literature, whereas exclusion criteria included animal studies and abstracts.

DATA EXTRACTION AND ANALYSIS

The selection of eligible items and assessment of methodological quality were performed independently by two researchers (KT and PG). A meta-analysis was performed to analyze the treatment effects on pain intensity reduction, additional analgesia, and satisfaction of TENS.

MAIN RESULTS

Twenty-six RCTs were included in this review involving a total of 3348 parturients. TENS showed significant efficacy in the reduction of pain intensity (pooled RR 1.52, 95% CI [1.35; 1.70]). Most of the studies had a high risk of bias, and the average grade of the studies indicated low quality.

CONCLUSIONS

The forest plot showed a small, but statistically significant efficacy of TENS on the reduction of pain intensity. However, it is not clear if the results were affected by the poor quality of the studies. This systematic review is the first that shows the application of TENS has significant efficacy in lowering labor pain. Findings from this review encourage the application of qualified methods for future and prospective studies with TENS applied in labor pain.