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doi:10.1111/jog.12345

J. Obstet. Gynaecol. Res. Vol. 40, No. 5: 1317–1323, May 2014

Transcutaneous electrical nerve stimulation for the relief of post-partum uterine contraction pain during breast-feeding: A randomized clinical trial Ligia de Sousa1, Flávia A. Gomes-Sponholz2 and Ana Márcia S. Nakano2 1 Federal University of Alfenas – UNIFAL, Alfenas, Minas Gerais, and 2College of Nursing, University of São Paulo, Ribeirão Preto, São Paulo, Brazil

Abstract Aim: To evaluate transcutaneous electrical nerve stimulation (TENS) used to relieve uterine contraction pain during breast-feeding in multiparous women. Methods: A controlled and randomized clinical trial was performed with 32 post-partum multiparous women who were breast-feeding. The participants were randomized into an experimental (EG, n = 16) and a control group (CG, n = 16). Pain was assessed using the Numerical Rating Scale and the descriptors of the Present Pain Intensity (PPI – McGill) during two sequential feeds. In the first assessment, the post-partum women in the EG and CG were monitored while breast-feeding and questioned regarding the degree of uterine contraction pain. In the second assessment, which was performed at the next feed, the EG used TENS while the CG was monitored, with pain being reassessed following. In the EG, the TENS electrodes were placed between T10–L1 and S2–S4, with a frequency of 100 Hz, a pulse duration of 75 μs and amplitude adjusted to produce a strong and tolerable sensation for 40 min. A descriptive analysis of the data and comparative intra- and intergroup analyses were performed by means of a non-parametrical test, with a significance level P ≤ 0.05. Results: The level of basal pain was 5.56 in the EG and 5.50 in the CG. In the intragroup analysis, the EG (P < 0.0001) and CG (P = 0.04) presented significant pain reduction. In the intergroup analysis, the EG had significant pain reduction (P < 0.01) in comparison to the CG. In the PPI analysis, a non-significant decrease in pain intensity was observed in the EG. Conclusion: TENS was found to be effective in reducing post-partum uterine contraction pain during breast-feeding. Key words: breast-feeding, pain, post-partum period, transcutaneous electrical nerve stimulation, uterine contraction.

Introduction The pain related to uterine contractions, experienced by post-partum women, is a frequent complaint that compromises the beginning of breast-feeding and its

effectiveness.1 Characterized as a type of colic, uterine contraction pain is acute2,3 and occurs due to the constant and rhythmic contractile activity of the uterus following cord clamping.4 These contractions are important to prevent post-partum hemorrhage and to

Received: June 25 2013. Accepted: November 1 2013. Reprint request to: Dr Ligia de Sousa, Curso de Fisioterapia, Universidade Federal de Alfenas, Unidade II – Av. Jovino Fernandes Sales, 2600 Santa Clara, Alfenas, MG 37130-000, Brazil. Email: [email protected] Scientific address where project was executed: College of Nursing, University of São Paulo, Ribeirão Preto, São Paulo, Brazil. Place where the study originated: College of Nursing, University of São Paulo, Ribeirão Preto, São Paulo, Brazil. Conflict of interest: None declared.

© 2014 The Authors Journal of Obstetrics and Gynaecology Research © 2014 Japan Society of Obstetrics and Gynecology

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maintain the homeostasis of the placental site, continuing for 5–7 days after childbirth.2 In the nursing mother, uterine involution is faster than in women who do not breast-feed, due to the stimulation of the nipples and galactophorous ducts. This stimulation results in uterine contractions, mediated by the release of oxytocin, a nonapeptide produced in the paraventricular and supraoptic hypothalamic nuclei and secreted into the circulation during labor and in response to suction during breastfeeding.5–7 Because oxytocin stimulates uterine contractile activity during the suction of the newborn or in response to nipple stimulation, this hormone exerts its action on the uterine fibers, which explains the relationship between lactation and uterine contraction pain.2,6,8 The use of non-pharmacological resources for pain relief in different post-partum situations has been the focus of several authors, including those who have evaluated the effects of transcutaneous electrical nerve stimulation (TENS). Transcutaneous electrical nerve stimulation is a simple, non-invasive, low-cost and easy-to-apply resource.3 It may be defined as a physiotherapeutic resource that utilizes small electrodes fixed onto the skin and placed in specific regions to produce electrical impulses, resulting in pain relief. According to Sluka and Walsh9 and Walsh et al.,10 TENS promotes immediate pain relief through the generation of a depolarized current, avoiding the formation of positive–negative ionic concentrations under each electrode or within the tissue. In addition, there are few adverse effects associated with TENS.9,11,12 Although other studies have already demonstrated the effectiveness of TENS in the relief of post-partum uterine contraction pain,3,13 there are no reports in the published work associating the use of TENS with reduction of pain during breast-feeding. Hence, the purpose of this study was to analyze the efficacy of TENS in the relief of uterine contraction pain in multiparous women during breast-feeding, in the immediate post-partum period.

Methods This was a controlled randomized clinical trial, developed in a maternity hospital in the state of São Paulo, Brazil. The research proposal was approved by the Research Ethics Committee of the University of São Paulo at Ribeirão Preto College of Nursing, under protocol number 1095/2009.

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Evaluated for eligibility Excluded (n=6) Did not meet inclusion criteria (n=5) Refused to participate in the study (n=1) Randomized (n=32)

Placed in EG (n=16) Subjects who received TENS (n=16)

Placed in CG (n=16) Subjects who not received TENS (n=16)

Losses or interrupted (n=0)

Losses or interrupted (n=0)

Analyzed (n=16)

Analyzed (n=16)

Figure 1 Trial design (CONSORT). CG, control group; EG, experimental group; TENS, transcutaneous electrical nerve stimulation.

Study participants were 32 multiparous women who had undergone natural childbirth, aged over 18 years, without post-partum complications, exclusively breastfeeding, who experienced uterine contraction pain while breast-feeding. The women were also literate and able to understand the pain rating scales used. Exclusion criteria were applied to post-partum women who presented intolerance to the stimulus generated by TENS and had complications requiring medical intervention, such as hemorrhage and infection. The volunteers were randomly divided, by means of a computer-based randomization, into an experimental group (EG) (n = 16), which received therapy with TENS and a control group (CG) (n = 16), which did not receive TENS. The study design is presented in Figure 1, as per CONSORT.

Device and treatment with TENS Transcutaneous electrical nerve stimulation was provided using a portable device (TENS KW Compact; KW Indústria Nacional de Tecnologia e Eletrônica, São Paulo, Brazil) that generated two-phase current and asymmetrical waves, with controllable variation of frequency and amplitude. Four silicon and carbon rubber electrodes (5 cm × 3 cm) were used, with pH-neutral conductive gel and hypoallergenic adhesive tape used for fixation. Two electrodes were placed in parallel in the T10–L1 region; the other two were placed in the

© 2014 The Authors Journal of Obstetrics and Gynaecology Research © 2014 Japan Society of Obstetrics and Gynecology

TENS for post-partum uterine pain

S2–S4 region,14 corresponding to the level of the spine that receives nociceptive information from the uterus and cervix.15 The TENS device was programmed to generate a 100-Hz current and 75 msec pulse for 40 min. Any increase in intensity was decided by the participants, after being instructed to keep a strong and tolerable stimulation without muscle contraction. The TENS device was calibrated before the beginning of data collection using a digital oscilloscope.

Procedures For the selection of the participants, the authors initially searched medical records of a rooming-in unit for multiparous women who had given birth within the past 48 h, who had not received pain medication for at least 6 h prior to data collection and who had no order for pain medication. The participants were informed that they could ask for pain medication at any time during the study without influencing the care received at the maternity hospital, but that this would result in their necessary exclusion from the study. The postpartum women were invited to participate in the study in the rooming-in unit of the maternity hospital, where they received information regarding the study procedures, and their signature on the Free and Informed Consent Form was obtained, after they read, understood and accepted it. Once the participant was included in the study, she was assigned to one of the groups, according to the randomization spreadsheet. Initially, a data collection form was filled out regarding sociodemographic, obstetric and breast-feedingrelated variables. The women in the EG and CG were assessed during two sequential feeds, the first without TENS and the second with the application of TENS in the EG. During the assessments, the participants were instructed to remain sitting up with their feet on the ground, and to hold their newborn in their arms, so as to standardize their body position while breastfeeding. In the first assessment, the participants in the two groups were monitored during breast-feeding and, following, rated their pain using the pain rating scale. The second assessment was performed during the following feed. This time, the EG had the TENS device applied, maintaining the standardized body position; the CG was monitored during breast-feeding and, following, the uterine contraction pain experienced during feeding was assessed. In the EG, TENS was applied during the whole breast-feeding from the beginning to the end of the feed. After its removal, the women were assessed again in terms of the uterine

contraction pain experienced during the feed. They also completed a questionnaire regarding their satisfaction with the treatment.

Pain measurement Uterine contraction pain was assessed by means of an 11-point Numerical Rating Scale (NRS), in which 0 means absence of pain and 10 represents extreme pain.16 Once they were provided the data regarding the scale, the participants were asked: ‘Which number would you assign for the strongest colic-like pain you felt while you were breast-feeding the baby?’ At the end of the study, the participants in the EG answered a questionnaire about their satisfaction with the treatment, comprising the following options: ‘very satisfied’, ‘poorly satisfied’ or ‘dissatisfied’ with the pain relief provided by TENS. The questionnaire also assessed the use of the device in future post-partum experiences for pain relief, requesting ‘yes’ or ‘no’ answers. The discomfort produced by the current stimulation was analyzed in the EG by the TENS discomfort questionnaire, a verbal scale of five options: ‘no discomfort’, ‘mild’, ‘moderate’, ‘severe’ and ‘worst possible discomfort’.3 Data analysis Sample size was calculated using a sample calculation based on a pilot study developed with six post-partum women, who received therapy with TENS. A clinically relevant reduction in pain scores after intervention was considered at 1.39 on the numerical rating scale;17 standard deviation ranged between 1.8 and 2.0 for the EG and CG, respectively (α = 0.01 and power = 90%; β = 0.1). Student’s t-test and the PASS 2008 (Power Analyses and Simple Size) program were used to determine a sample size of 16 subjects per group. Data were analyzed using the statistical SPSS (Statistical Package for the Social Sciences) program. In the statistical tests, a significance level of 5% was used (P ≤ 0.05). A descriptive analysis of sociodemographic and obstetric data were performed by χ2-test and Student’s t-test. The Mann–Whitney U-test was used for comparison of pain between the groups before and after application of TENS, and the Wilcoxon rank sum test for intragroup analysis.

Results Characteristics of the participants The study participants presented a mean age of 26.84 ± 5.14 years, with no statistical difference

© 2014 The Authors Journal of Obstetrics and Gynaecology Research © 2014 Japan Society of Obstetrics and Gynecology

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between the groups (P = 0.06). The variables regarding education (P = 0.95), marital status (P = 0.65), occupation (P = 1.00) and race (P = 0.99) did not present any statistical difference between the groups either, assuring the homogeneity of the sample. All women in the study breast-fed their babies on demand; that is, there was no predetermined time scheduled for breast-feeding, which was provided as per the newborn’s signs/cues of hunger. However, all newborns were breast-fed within 30 min after delivery. The mean duration of the feed in the first assessment of the studied women was 28.43 ± 11.65 and 25.31 ± 6.18 min in the EG and CG, respectively (P = 0.35). In the second assessment, the mean feeding time was 29.68 ± 10.24 min in the EG and 25.33 ± 7.89 min in the CG (P = 0.21). Table 1 presents characteristics of the patients and the main variables related to labor, childbirth and the post-partum period.

Results related to pain Numerical pain rating scale None of the participants made use of medication for pain relief 6 h before or during of the study. The studied groups presented a similar score for basal pain levels (considering the first feed assessed), with 5.56 in the EG and 5.50 in the CG. Table 2 presents the results obtained with TENS, comparing the studied groups.

Questions regarding TENS Regarding the satisfaction with the TENS treatment in the EG, among the 16 participants in this group, 10 (62.5%) felt ‘very satisfied’ and six (37.5%) women claimed to be ‘satisfied’ with the treatment. None of the women felt ‘poorly satisfied’ or ‘dissatisfied’ after the use of conventional TENS. As for the discomfort produced by the current of the device, all women (100%)

Table 1 Distribution of the frequency (n) and percentage (%) of the characteristics and variables related to labor, childbirth and the post-partum period EG, n

Variable Body mass index Underweight Appropriate Overweight Previous pregnancies 1–3 4–6 ≥7 Correct latch Correct Incorrect Correct position of the newborn Correct Incorrect Use of analgesia for labor Yes No Oxytocin – labor Yes No Perineum Intact RMLE First degree laceration Oxytocin – post-partum Yes No Skin-to-skin contact Yes No

6 7 3

% 37.5 43.75 18.75

CG, n

%

Total, n

%

P

1 10 5

6.25 62.5 31.25

7 17 8

21.875 53.125 25

0.99

9 5 2

56.25 30.25 12.5

23 7 2

71.875 21.875 6.25

0.99

14 2 —

87.5 12.5 —

16 —

100 —

15 1

93.75 6.25

31 1

96.875 3.125

0.30

16 —

100 —

14 2

87.5 12.5

30 2

93.75 6.25

0.46

10 6

62.5 37.5

14 2

87.5 12.5

24 8

75 25

0.22

12 4

75 25

12 4

75 25

24 8

75 25

1.00

6 6 4

37.5 37.5 25

9 2 5

56.25 12.5 31.25

15 8 9

46.875 25 28.125

14 2

87.5 12.5

13 3

81.25 18.75

27 5

84.375 15.625

0.62

7 9

43.75 56.25

8 8

50 50

15 17

46.875 53.125

0.72

0.65

CG, control group; EG, experimental group; RMLE, right mediolateral episiotomy.

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© 2014 The Authors Journal of Obstetrics and Gynaecology Research © 2014 Japan Society of Obstetrics and Gynecology

TENS for post-partum uterine pain

Table 2 Analysis of the mean difference of the NRS scores in the first and second assessments NRS EG 1st assessment – 1st feed 2nd assessment – 2nd feed Dif. 1st – 2nd P-value

Mean ± standard deviation CG

5.56 ± 1.99 3.56 ± 1.78 2.00 ± 0.96

Transcutaneous electrical nerve stimulation for the relief of post-partum uterine contraction pain during breast-feeding: a randomized clinical trial.

To evaluate transcutaneous electrical nerve stimulation (TENS) used to relieve uterine contraction pain during breast-feeding in multiparous women...
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