Transcutaneous Electrical Nerve Stimulation for Labour Analgesia

Objectives : To evaluate the efficacy of transcutaneous electrical nerve stimulation for analgesia during labour and delivery.

Methods : In a study group of 100 low risk full term patients, stimulation was given by a battery-operated generator producing biphasic pulses varying in frequency and amplitude. A low intensity stimulation was given continuously while high intensity stimulation was given during uterine contractions. The electrodes were taped at T10-L1 and S2-S3 during first and second stages of labour respectively.

Results : 48% of patients considered pain relief by TENS as very good; 26% as good; 24% as moderate while only 2% considered TENS was without any effect. There were no maternal or foetal complications.

Conclusion : Transcutaneous electrical nerve stimulation in labour is more effective in first stage of labour as compared to second stage of labour. There is no significant correlation between APGAR score and duration of TENS use.

Introduction

The pain associated with labour and delivery has been a challenge to modern medicine because little medication can be administered to the pregnant woman without affecting the newborn child. The conventional measures of pain relief during labour include analgesics, sedatives and epidural injection of local anaesthetics. All these pose varying degrees of potential risk both to mother and foetus. The most commonly used and effective amongst these is use of epidural analgesia. But it requires experience, qualified personnel, appropriate equipment and special constant supervision. All these factors make epidural analgesia more expensive and less frequently used method.

During the last 15 years an increasing number of reports concerning the pain reducing effect of transcutaneous electric nerve stimulation have been reported. Favourable experience with TENS prompted us to use the method during delivery in order to evaluate its pain reducing effect in labour.

Material and Methods

The study was conducted in a single unit at LTMG Hospital, Sion, Mumbai over a period of one year from January 2000 and December 2000. One hundred low risk pregnant patients were included in this study. All women were examined at the antenatal clinic during the pregnancy. Information about methods of pain relief available during labour including TENS was given to them. The method was again explained during early labour on admission. One hundred patients willing to use this method were included in this study and informed consent was taken. Only patients coming in early labour with less than three centimeters dilatation were included. Admission test on foetal monitor was done in all these patients. Only those with reactive admission test were included in this study.

The method of TENS was explained to each patient without suggesting that pain relief would necessarily accompany the feeling of stimulation. It was also made clear that whenever needed, conventional pain relief would be supplemented. Special efforts were made to keep aside cases with high risk factors such as heart disease, anaemia’s, toxaemias, previous caesarean sections, twins, cephalopelvic disproportion, malpresentations, etc. A few hours after delivery all patients answered a detailed questionnaire regarding the effect of TENS on pain relief.

Technique of stimulation

The stimulation system consisted of a stimulator and a pair of electrodes. The stimulator contains a pulse generator and two controls for amplitude, for amplitude and frequency. The pulse generator delivers biphasic pulses with a pulse length of 0.25 m/sec. The amplitude and frequency can be varied. The amplitude range is 0-200 volts and the frequency range is 10-150 hertz. The electrodes are made up of metal and have an active area of 30 mm x 80 mm. The electrodes are taped to the patients back symmetrically with respect to the spinal processes. During the first stage of labour, the electrodes were taped at T10-L1 and during second stage at S2-S3 because of difference in the level corresponding to the influx of pain into the spinal cord during the first and second stages of labour respectively. To obtain optimal analgesic effect, the stimulation amplitude was increased to a level where muscular fasciculations appeared in the vicinity of the electrodes. The high intensity stimulation was used during uterine contraction at the height of pain for about one minute. Otherwise, low intensity stimulation was used continuously during the first stage. Both the stimulation levels are experienced as tingling sensations of different intensity over the involved dermatomes of the back. Maternal and foetal condition was monitored clinically or by monitor if required during labour.

Observations and Results

Table 1 shows the age and parity distribution of the selected cases. There were 29 primigravidas and 71 multigravidas. Majority were in the age group of 20-30 years. Elderly primis and grand multis were not included in the study group. All patients were above 37 weeks period of gestation. The average cervical dilatation on admission was three centimeters. Tables 2 and 3 show the results of the questionnaire answered by the patient after delivery regarding subjective effect of TENS on pain relief during first and second stages of labour respectively. In the first stage of labour, 48% of patients rated the pain relief as very good while only 2% did not have any pain relief. In 29 patients oxytocin augmentation was required. In five patients caesarean section was done during first stage for foetal distress (3 patients) and failure to progress (2 patients). Out of remaining 95 patients who reached second stage of labour 30.52% had very good pain relief during second stage of labour. This indicated that the pain relief by TENS is more effective in the first stage of labour as compared to that in the second stage. Most of the patients who had very good pain relief with TENS were introduced and acquainted to TENS use during the antenatal clinic. Outcome of labour is shown in Tables 2 and 4. There were six caesarean sections, indications being foetal distress (3 patients), failure to progress (2 patients) and prolonged second stage (1 patient). Three patients had forceps delivery and in one patient vacuum was used. The APGAR scores of the newborns and its relation to the duration of TENS is shown in Table 5. There was no significant correlation between APGAR scores and the duration of TENS use.

Discussion

Pain is a complex phenomenon with various factors contributing to the degree of pain perceived. Separation of neurophysiological mechanisms through which pain relief is achieved from psychological mechanisms or placebo effect is difficult. From a practical standpoint, such a separation of neurophysiological mechanism is of little consequence or importance. One cannot have a control study of another person due to difference in the psychological make up. Hence we decided to do a self control study in which each participant judges the effectiveness of the unit by switching it off for some time and thus experiencing the contractions, with and without the unit. Although the sample of the study is not very large, 74% of mothers considered pain relief by TENS to be good or very good. 24% got moderate relief while 2% had no effect at all. Most of the patients expressed a desire to use TENS in subsequent deliveries. These results were comparable to those of the previous studies by other authors viz. Augustinsson1 88% pain relief; Robson2 - 82% pain relief; Andersson3 - 85% pain relief and Gandhi4 - 80% pain relief. In our study three patients developed foetal distress, two patients had failure to progress and one had prolonged second stage requiring caesarean section. The possibility of TENS induced irregularities in foetal heart sound cannot be excluded. The APGAR score of babies also did not show any change due to the use of TENS. A thorough neurobehavioural evaluation of infants in a study by Bunsden5 failed to show any significant difference between the study and control groups.

TENS may interfere with foetal monitoring especially recording because TENS interferes with signals to the foetal monitor. The TENS unit may be shut off periodically while monitoring. However, continuous foetal monitoring may be difficult. TENS has some advantage over other conventional methods of labour analgesia. It is safe to both mother and the foetus. It is non-invasive, cheap, easy to handle, easily administered and rapidly reversible. This is of particular importance to those with previous caesarean section and desiring subsequent vaginal delivery. The use of TENS allows pain to be used as a diagnostic symptom because it can be turned off at will with immediate effect of pain relief. It is clear from the results (Table 3) that the pain relief during second stage of labour was much less compared to that during first stage and may require supplementation by conventional analgesics. This might support the assumption that C-fiber mediated pain is more amenable to pain relief by TENS than is A-fiber mediated pain. TENS treatment does not influence the consciousness of the patient which implies that she can actively take part in the course of delivery and experience the joy of childbirth.

Conclusion

Though our study is small, the initial experience does suggest that TENS appears to be a simple, safe and effective method of labour analgesia, particularly in the first stage of labour.

Acknowledgement

We thank our Head of Department and Dean for allowing us to use and publish the Hospital data.

References

1. Augustinsson LE, Bohin P, Bunsden P. Pain 1977; 4 : 59.

2. Robson JF. Anaesthesia 1979; 34 : 35.

3. Anderson SA, Block E, Holmgreen E, Lakartidningan. Adv. Pain Res 1979; 3 : 577.

4. Gandhi AI. J Obst and Gynaec India 1993; 43 : 560.

5. Bunsden P, Ericson K, Patterson. Acta Obst Gynaecol Scurd 1982; 61 : 129.

SUICIDE IN INDIA

'The rates of suicide are several fold higher than those reported anywhere else in the world, specially in young women’.

Worldwide, self-inflicted injuries are the fourth leading cause of death in 15-19 year olds. Rita Aaron and colleagues measured the rates of suicide in 10-19 year olds in a rural region of southern India. They used the verbal autopsy method-establishing cause of death from relatives, neighbours, health workers, and village leaders of the deceased. From 1992 to 2001, suicides accounted for about a quarter of all deaths in young men, and between half and three quarters of all deaths in young women. The researchers conclude that these rates are much higher than those previously reported in India and the rest of the world, and require urgent intervention. Wun Jung Kin and Tanvir Singh put these findings in a national and international context, and consider possible causes of suicide and prevention strategies.

Lancet, 2004; 1090, 1117.