A comparative study of transcutaneous electrical nerve stimulation (TENS), entonox, pethidine + promazine and lumbar epidural for pain relief in labor

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.

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.

A qualitative analysis of parturients' experiences using nitrous oxide for labor analgesia: It is not just about pain relief

BACKGROUND

A vast majority of women who choose nitrous oxide for labor report high satisfaction despite variable analgesic effectiveness. We analyzed comments provided by women who used nitrous oxide for labor, to identify determinants of satisfaction in this population, and to better understand reasons for continuing with nitrous oxide despite variable analgesic effectiveness.

METHODS

We conducted qualitative content analysis of comments in a quality improvement database of routine follow-up assessments of women who delivered vaginally, using nitrous oxide as the sole labor analgesic. An inductive grounded approach was used and emergent themes and subthemes were identified.

RESULTS

Of 6507 vaginal deliveries over 34 months in 2011-2014, 753 (12%) used nitrous oxide as their sole analgesic. Analysis of 264 clarifying comments yielded six emergent themes. Parturients cited nonanalgesic benefits of nitrous oxide use (relaxation, distraction, focus on breathing), as well as partial analgesic effects that they deemed to be sufficient, or consistent with their expectations. Numerous women described their nitrous oxide experience as consistent with their birth plan, including 14 who equated it with natural childbirth. Several comments described nitrous oxide as a vital component of the parturients' birth experience. Some described using nitrous oxide when neuraxial analgesia was not possible. Side effects were identified, as were difficulties using the apparatus/mask. Analysis highlighted importance of timely administration upon request and attention to technical aspects.

CONCLUSIONS

Among parturients who choose nitrous oxide as their sole labor analgesic, determinants of satisfaction are more variable than previously understood, and extend beyond analgesia.

Evaluation of association factors for labor episodic pain during epidural analgesia

Purpose

Epidural analgesia provides safe and effective labor pain relief. However, labor episodic pain can occur during epidural analgesia, requiring epidural top-ups, and may result in decreased patient satisfaction. The primary aim of our study was to investigate the factors associated with labor episodic pain during epidural analgesia.

Patients and methods

Electronic and hardcopy records of labor deliveries between January 2012 and December 2015 were reviewed at KK Women's and Children's Hospital, Singapore. The primary outcome was the prevalence of episodic pain. Demographic, clinical and anesthetic data were retrieved. Univariate and multivariate logistic regression analyses were used to identify associated risk factors for labor episodic pain experienced by parturients while receiving epidural analgesia. Model performance was assessed by area under the curve (AUC) from the receiver operating characteristic curve.

Results

The prevalence of labor episodic pain was 14.2% (2,951 of 20,798 parturients). The risk factors associated with labor episodic pain, which are given here as factor (OR, 95% CI), are the following: need for epidural resiting (11.4, 7.53-17.28), higher pain scores intrapartum (1.34, 1.32-1.36), higher Bromage scores (1.12, 1.02-1.22), the need for instrumental delivery (1.32, 1.16-1.52), the need for cesarean delivery (1.41, 1.26-1.59), the presence of venous puncture (1.29, 1.03-1.62), the presence of dural puncture (14.28, 5.92-34.43), the presence of high block (6.05, 1.39-26.35), the need for a urinary catheter (1.17, 1.17-1.34), larger volumes of local anesthetics used (1.01, 1.01-1.01) and higher body mass index (1.01, 1.01-1.02), and decreased maternal satisfaction (0.97, 0.97-0.98). The AUC was 0.80.

Conclusion

Knowledge of these factors may allow for future interventions in management to prevent labor episodic pain. Further research is needed to validate these association factors.

Should Nitrous Oxide Be Used for Laboring Patients?

Nitrous oxide, long used during labor in Europe, is gaining popularity in the United States. It offers many beneficial attributes, with few drawbacks. Cost, safety, and side effect profiles are favorable. Analgesic effectiveness is highly variable, yet maternal satisfaction is often high among the women who choose to use it. Despite being less effective in treating labor pain than neuraxial analgesic modalities, nitrous oxide serves the needs and preferences of a subset of laboring parturients. Nitrous oxide should, therefore, be considered for inclusion in the repertoire of modalities used to alleviate pain and facilitate effective coping during labor.

Occupational exposure to nitrous oxide during procedural pain control in children: a comparison of different inhalation techniques and scavenging systems

BACKGROUND

Nitrous oxide (N2 O 50% in oxygen) is commonly used for painful procedures in children. Potential negative health effects associated with chronic workplace exposure limit its use. Safe occupational N2 O exposure concentrations are below 25 ppm environmental concentration as a time-weighted average (TWA) and below 200 ppm as a short-time exposure level (STEL) of 15 min.

AIM

The aim was to assess occupational exposure of staff during nitrous oxide administration to children using different inhalation delivery devices and scavenging systems.

METHODS

Staff nitrous oxide exposure during use of a double face mask (DFM) with or without a demand valve (DV) was compared with a conventional single face mask (FM). We also compared exposure using the hospital central scavenging system with a portable evacuation system. N2 O concentrations, representing exposure values, were monitored within proximity to staff. Urine N2 O concentration was measured in staff administering the N2 O at the end of the procedural session.

RESULTS

The mean and median values of TWA and STEL within the working area were lower than recommended values in the DFM (10.8, 11.6 ppm for TWA; 13.9, 11.0 ppm for STEL) and DFM-DV groups (2.3, 2.8 ppm for TWA; 4.4, 3.5 ppm for STEL) using the portable evacuation system. The N2 O urine exposure in DFM-DV group was lower than DFM group: a mean difference of 9.56 ppm (95% CI 2.65-16.46). Staff N2 O urinary concentrations were within safe biological limits in both the DFM and DFM-DV groups. High exposure concentrations to N2 O were recorded in all FM and FM-DV environmental and biological samples.

CONCLUSIONS

The DFM system, with or without a DV, connected to a portable evacuation system during N2 O administration to children for painful procedures kept N2 O levels within the local environment below recommended limits.

Nitrous oxide for the management of labor pain: a systematic review

BACKGROUND

We systematically reviewed evidence addressing the effectiveness of nitrous oxide for the management of labor pain, the influence of nitrous oxide on women's satisfaction with their birth experience and labor pain management, and adverse effects associated with nitrous oxide for labor pain management.

METHODS

We searched the MEDLINE, EMBASE, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases for articles published in English. The study population included pregnant women in labor intending a vaginal birth, birth attendees or health care providers who may be exposed to nitrous oxide during labor, and the fetus/neonate.

RESULTS

We identified a total of 58 publications, representing 59 distinct study populations: 2 studies were of good quality, 11 fair, and 46 poor. Inhalation of nitrous oxide provided less effective pain relief than epidural analgesia, but the quality of studies was predominately poor. The heterogeneous outcomes used to assess women's satisfaction with their birth experience and labor pain management made synthesis of studies difficult. Most maternal adverse effects reported in the literature were unpleasant side effects that affect tolerability, such as nausea, vomiting, dizziness, and drowsiness. Apgar scores in newborns whose mothers used nitrous oxide were not significantly different from those of newborns whose mothers used other labor pain management methods or no analgesia. Evidence about occupational harms and exposure was limited.

CONCLUSIONS

The literature addressing nitrous oxide for the management of labor pain includes few studies of good or fair quality. Further research is needed across all of the areas examined: effectiveness, satisfaction, and adverse effects.

A newly developed scavenging system for administration of nitrous oxide during labour: safe occupational use

OBJECTIVE

Nitrous oxide (N(2) O) is routinely used as an analgesic in obstetrics during labour. Epidemiological studies have linked chronic occupational exposure to N(2) O to specific health problems, including reproductive risks. Occupational exposure limits (OELs) allow the use of N(2) O once appropriate preventive and safety measures have been taken. We assessed the effectiveness of a scavenger system (Anevac P-system®, Medicvent Heinen & Löwestein Benelux, Barneveld, the Netherlands) applied in N(2) O administration during labour in a midwifery-led birthing centre in the Netherlands.

METHODS

After informed consent, non-pregnant midwives were trained to administer N(2) O. N(2) O was delivered as a 50 : 50 mixture with oxygen and was self administered by the patient. The scavenging device, containing a double mask and a chin mask, was connected to the local evacuation system vented outside the building. Data on the 8-h time-weighted average (8-h TWA) as well as the 15-min TWA (15-min TWA) were obtained.

RESULTS

Thirteen patients were included. Six patients were included in the first study period. In this period the 8-h TWA was not exceeded, however, in all patients, the 15-min TWA occasionally exceeded the OELs. After four additional measures, seven patients were included. After implementation of these measures, the 8-h TWA and 15-min TWA never exceeded the OELs. System leakage was not observed during both study periods.

CONCLUSION

The Anevac P-scavenging system during N(2) O analgesia in labour prevents exceeding OELs in professional workers. The scavenging system appeared acceptable and effective, and can be considered in hospital settings that use N(2) O as analgesic during labour.

A systematic review of the safety of analgesia with 50% nitrous oxide: can lay responders use analgesic gases in the prehospital setting?

A safe and effective form of pain relief would be an advantage in the prehospital treatment of patients experiencing extreme pain. Although used by many emergency medical services, 50% nitrous oxide (an inhaled analgesic known to have good pain relief properties) is not widely used by volunteer and semiprofessional organisations. This review aimed to determine whether 50% nitrous oxide is safe for use by first responders who are not trained as emergency medical technicians. A thorough search of the literature identified 12 randomised controlled trials investigating the use of 50% nitrous oxide (as compared with placebo or conventional analgesic regimens) in a range of conditions. The outcomes analysed for this review were: adverse events, recovery time, and need for additional medication. None of the studies compared the treatments in the prehospital setting; children were well represented. Adverse effects were rare and significant adverse outcomes such as hypotension and oxygen desaturation could not be attributed to nitrous oxide. Compared with patients receiving conventional analgesia, those receiving 50% nitrous oxide did not require additional medication any more frequently and had a faster recovery from sedative effects. The low incidence of significant adverse events from 50% nitrous oxide suggests that this agent could be used safely by lay responders.

Predictors of breakthrough pain during labor epidural analgesia

Parturients who receive labor epidural analgesia may experience breakthrough pain that requires supplemental medications. We investigated the factors associated with breakthrough pain. This prospective observational study included 1963 parturients who received epidural analgesia. Subjects were categorized into two groups on the basis of the number of episodes of breakthrough pain: the Recurrent Breakthrough Pain (RBP) group experienced three or more episodes. Univariate and multivariate regression analyses were used to evaluate factors associated with the RBP group. By multivariate analysis, nulliparity, heavier fetal weight, and epidural catheter placement at an earlier cervical dilation were found to be independently associated with the RBP group. These factors may predict which parturients' analgesia may be complicated by breakthrough pain. Parturients who received a combined spinal/epidural technique were less likely to be associated with the RBP group. The combined spinal/epidural technique may be superior to conventional epidural anesthesia, because breakthrough pain occurred less often. It is interesting to note that the characteristics that are associated with the RBP group are similar to those that have been associated with increased severity of maternal pain.

IMPLICATIONS

Nulliparity, heavier fetal weight, and epidural catheter placement at an early cervical dilation are predictors of breakthrough pain during epidural labor analgesia. The combined spinal/epidural technique may be associated with a decreased incidence of breakthrough pain.

[Prospective national survey on alternatives to obstetrical peridural analgesia]

OBJECTIVE

To assess the type of an alternative technique for epidural analgesia for pain relief during labour, the reason of its choice and its efficiency.

STUDY DESIGN

A one-year prospective survey in 34 french hospitals.

MATERIAL AND METHODS

A questionnaire was filled for each request for a non-epidural technique during labour. The data recorded the reason for this non-epidural method, the technique used, the repeated visual analog scale (VAS) pain scores before (T0) and during the treatment (T30, T60 T120,...), the maternal and foetal side effects of the method, and the maternal satisfaction.

RESULTS

177 questionnaires were studied among the 270 collected. The lack of VAS measurements was the main reason for excluding questionnaires. Refusing the epidural by the obstetric patient was the most frequent reason for requesting a non-epidural method (39%). Five non-epidural methods were identified: nalbuphine (NAL, n = 75), sufentanil by patient-controlled analgesia (SUF, n = 44), nitrous oxide/oxygen inhalation (N2O, n = 22), pethidine (PET, n = 19), and spinal analgesia (SA, n = 17). The choice of the method was dependant on the prescribe (midwife or anaesthetist) and of the cervical dilation. The SA group exhibited the most pain relief compared to the other groups during the treatment. No difference in pain relief was noted between the 4 groups (SUF, NAL, PET, N2O). Only in the PET group did the VAS pain score remain unchanged at T30. There were 25 maternal side effects, with a significant maternal sedation in the NAL group, and pruritus in the SA group. There were 6 respiratory depressions in infants, unrelated with the analgesic method. Maternal satisfaction was higher in the SA, SUF and N2O groups than in the PET and NAL groups. Factors explaining lack of analgesic effect (i.e. no decrease in VAS pain score more than 10 mm during the treatment) were the use of pethidine, the VAS pain score at T0 and the induced labour.

CONCLUSION

Epidural and spinal analgesia are the most efficient methods for pain relief during labour. The analgesic effect of non-regional methods during labour is minimal, associated with some maternal side effects. Due to its lack of analgesic effect, pethidine should be avoided in this indication.

Study of the effects of various transcutaneous electrical nerve stimulation (TENS) parameters upon the RIII nociceptive and H-reflexes in humans

Despite over two decades of clinical use, the neurophysiological and anti-nociceptive effects of transcutaneous electrical nerve stimulation (TENS) have yet to be definitively described. The current study was designed to examine the effect of TENS on the RIII nociceptive reflex elicited in healthy human subjects; the H-reflex was measured concomitantly to monitor changes in alpha-motoneuron excitability. Following approval from the university's ethical committee, 50 healthy human volunteers (25 male and 25 female) participated in the study. The subjects ranged in age from 18 to 30 years (mean 22, SD 3). Subjects were randomly allocated equally to a control group or one of four TENS groups. In the TENS groups, stimulation was applied for a total of 15 min over the sural nerve in the left leg. Ipsilateral RIII and H-reflexes were recorded five times during the 45 min experimental period. In addition, subjects also rated pain associated with the RIII reflex using a computerized visual analogue scale (VAS). Statistical analysis using two-way repeated-measures ANOVA showed no differences between groups for H-reflex, RIII reflex nor VAS data. These results suggest that TENS does not significantly affect either of the two reflexes, at least using the parameters and application time in the current study.

Multicenter, randomized, controlled trial of delayed pushing for nulliparous women in the second stage of labor with continuous epidural analgesia. The PEOPLE (Pushing Early or Pushing Late with Epidural) Study Group

OBJECTIVE

This study was undertaken to determine whether a policy of delayed pushing for nulliparous women with continuous-infusion epidural analgesia reduces the risk of difficult delivery (cesarean delivery, operative delivery from a midpelvic position, low-pelvic procedures with rotation >45 degrees ).

STUDY DESIGN

In this multicenter, randomized, controlled trial women in the delayed pushing group (n = 936) were advised to wait > or =2 hours after full dilatation before commencement of pushing. Women in the early pushing group (n = 926) were advised to commence pushing as soon as they had been randomly assigned.

RESULTS

Difficult delivery was reduced with delayed pushing (relative risk, 0.79; 95% confidence interval, 0.66-0.95). The greatest effect was on midpelvic procedures (relative risk, 0.72; 95% confidence interval, 0.55-0.93). Although there was little evidence for an effect on low-pelvic procedures, spontaneous delivery was more frequent among women who practiced delayed pushing (relative risk, 1.09; 95% confidence interval, 1.00-1.18). Abnormal umbilical cord blood pH (<7.15 venous value or <7.10 arterial value) was more frequent in the delayed pushing group (relative risk, 2.45, 95% confidence interval, 1.35-4. 43). However, scores for a summary indicator, the Neonatal Morbidity Index, were similarly distributed in the 2 groups.

CONCLUSION

Delayed pushing is an effective strategy to reduce difficult deliveries among nulliparous women.

Transcutaneous electrical nerve stimulation (TENS) for adjuvant pain-relief during labor and delivery

OBJECTIVE

We examined the efficacy of transcutaneous electrical nerve stimulation (TENS) in general and the new Freemom TENS device (LifeCare, Israel) in particular, for pain relief during labor and delivery.

METHODS

The study group consisted of 104 women. Forty-six nulliparas (44.2%) and 58 multiparas (55.8%), all of whom used the TENS device for pain relief during labor. All participants completed a questionnaire on the degree of pain relief afforded them by TENS during the delivery and related questions. The objective evaluation was based on the documented labor and delivery parameters including medical interventions during delivery.

RESULTS

The majority of subjects (72% of the nulliparas and 69% of the multiparas) considered TENS effective for the relief of pain during labor. Most of them (67% of the nulliparas and 60% of the multiparas) responded positively to the use of TENS in future deliveries. Sixty-five percent of the multiparas considered TENS at least as effective as the other pain relief methods they had used before. TENS significantly reduced the duration of the first stage of labor P < 0.001 for nulliparas, P < 0.005 for multiparas and it significantly decreased the amount of analgesics administered to individual patients. No significant difference was found in fetal heart rate tracings, Apgar scores and cord blood pH between the study group and an equal number of matched controls who used other forms of pain management.

CONCLUSIONS

TENS is an effective non-pharmacological, non-invasive adjuvant pain relief modality for use in labor and delivery. TENS application reduced the duration of the first stage of labor and the amount of analgesic drug administered. There were no adverse effects on mothers or newborns.

Transcutaneous electrical nerve stimulation (TENS): a technology assessment

The scientific evidence for clinical effectiveness of transcutaneous electrical nerve stimulation (TENS) for treatment of acute, chronic, and labor and delivery pain is assessed in this paper, and it is concluded that there is little evidence for other than a limited use of TENS. The utilization of TENS in Canadian hospitals and payments for TENS services are addressed. Some practicalities regarding the use and assessment of health technologies are discussed.

Obstetrical anaesthesia in Ontario

The purpose of this study was to determine the availability of regional anaesthesia for Caesarean section, of epidural opioids and patient-controlled analgesia after Caesarean section, and of epidural and other forms of analgesia in labour. A mail survey was sent to the "Head Nurse, Department of Obstetrics" at each of the 142 hospitals in Ontario with designated obstetric beds. Responses were obtained from 100% of hospitals. For Caesarean Section, general anaesthesia was used in all hospitals, and was the only option in seven. Epidural anaesthesia was used in 93% of hospitals, and spinal anaesthesia in 48%. Postoperatively, patient-controlled analgesia was used in 31% of hospitals and spinal opioids in 28%. In 66 hospitals, im or iv opioids were the only types of analgesia available. For analgesia in labour, im or iv opioids were used in 96% of hospitals, nitrous oxide was used in 75%, epidural analgesia in 75%, transcutaneous electrical nerve stimulation in 52% and patient-controlled analgesia in 10%. The overall epidural rate was 38%. Although the average rate in the 73 hospitals with fewer than 500 births per year was only 6%, 14 large hospitals had an epidural rate of 60% or higher. It is concluded that regional techniques for peripartum analgesia have been widely accepted. Analgesia after Caesarean section could be improved. Epidural analgesia should be more widely available, especially in the many small hospitals in Ontario.

The King Edward Memorial Hospital 1,000 mother survey of methods of pain relief in labour

A survey of one thousand women having a vaginal delivery in an obstetric teaching hospital was conducted in order to ascertain maternal opinions of various methods of pain relief in labour. Women were questioned on the day following delivery as to their pain experience, the degree of analgesia obtained, their satisfaction with and criticisms of the analgesic method or methods used, and their overall satisfaction with their childbirth experience. More pain than expected was reported significantly more often by primiparous women (P less than 0.001) and those having induced or augmented labour (P less than 0.04). Epidural analgesia was significantly more effective and resulted in greater satisfaction than other methods alone, or when used in combination (P less than 0.0001). 'Inadequate analgesia' was also reported less frequently by women using non-pharmacological methods alone (P less than 0.0001). Dissatisfaction with their experience was reported by 5% of women and was most frequently related to inadequate pain relief. Although uncommonly cited as a reason, instrumental delivery was statistically associated with dissatisfaction (P less than 0.003). The incidence of dissatisfaction did not significantly differ with respect to the analgesic method or methods used.