Anaesthesia, 1979, Volume 34,pages 357-360
Forum Transcutaneous nerve stimulation for pain relief in labour
Jean E. Robson MA, MB, BChir, FFA RCS, Senior Registrar, Nufield Department of Anaesthetics, Radcliffe Infirmary, Oxford OX2 6HE*
Transcutaneous nerve stimulation (TNS) techniques have been developed over the past decade for the relief of chronic pain from a wide variety of conditions. In a recent review by Glynn,' sixty-four out of 100patients with a number of chronic pain conditions were relieved, and twenty-eight found permanent pain relief whilst TNS was in use. This compares well with a similar study of 197 patients by Long' where an overall 78% obtained relief when psychiatric factors were eliminated. The use of the technique in acute pain conditions is more recent and has been assessed for postoperative management in the USA by Hymes3 and Vander Ark.4 Shealy has also investigated its use in acute and chronic pain conditions in the USA and mentioned its use in l a b o ~ r and , ~ Augustinsson in Sweden has further reported on its use in labour.6 The aim of the present study was to assess whether TNS was useful as a method of pain relief in labour in a modern British obstetric hospital. Melzack and Wall's gate control theory of pain7 provides the theoretical foundation for TNS and the idea of stimulating large afferent fibres to prevent the smaller, pain-carrying C-fibres from transmitting to the brain has been pursued by many workers.8 Surprisingly, there is not universal agreement about the details of the sensory nerve supply to the uterus and birth canal. Most consider that visceral afferent fibres from the body and cervix of the uterus pass via the uterine, pelvic and hypogastic plexuses in the sympathetic nerves to the spinal cord at T11, 12 and L1. Pain from contraction of the uterine muscle and dilatation of the cervix is referred, therefore, to the areas supplied by the same nerves, i.e. the lower abdomen and back. Parasympathetic pelvic splanchnic nerves (S2,3 and 4) also run in the pelvic plexus to innervate the cervix but there is dispute as to their sensory function. Pain from
dilatation of the cervix, posterior occipital positions and inco-ordinate uterine activity can all be referred to the sacral area. Bonicag states that this is due to downward cutaneous spread from the posterior primary rami of T l l , 12 and L1, but S 2 4 may have to be blocked sometimes to give complete relief in the first stage of labour.I0 In the second stage of labour, pain from distension of the vulva and perineum is passed in somatic afferent nerves, mainly the pudendals, to the spinal cord at S2, 3 and 4. The visceral afferent nerve fibres are usually small diameter C-fibres, travelling at 0.5-2 m/s, whilst the pudendalnerve fibresaredeltaafferent fibres travelling at 10-40 m/s. Method and patient selection
Transcutaneous nerve stimulation was achieved by a specially adapted twin-channel nerve stimulator. Each channel has three controls-Level 1, Level 2 and Rate (Fig. 1). The pulse duration is fixed, but the amplitude and frequency can be altered to produce the required sensation. The electrical current is passed from the machine to the patient via four rubber electrodes, contact being made with electrode jelly. The whole electrode is firmly fixed to the skin with adhesive tape (OpSite3 was found to be very effective) (Fig. 2). In most cases where TNS is used, the electrodes are placed over the most painful area so that the cutaneous nerves in that area are stimulated. With the Travisens machine, the electrodes are placed on either side of the midline of the spine, and are designed to stimulate the posterior primary rami of the spinal segments receiving the painful stimuli during labour, i.e. T1 1-L1 and S2-4. ~
t Travisens, Sweden.
~~~
$ Smith & Nephew Ltd.
*Now Consultant Anaesthetist, Royal Surrey County Hospital, Guildford Surrey. 0003-2409/79/04o(M357$02.00 0 1978 Blackwell Scientilic Publications
3 57
358
Forum
Fig. 1. Twin-channel nerve stimulator control panel.
Fig. 2. Attachment of electrodes to patient.
After fixing the electrodes on the patient’s back in these positions, the machine was switched on to Level 1 with all dials set at 0. The current to the thoraco-lumbar electrodes was gradually increased until the patient could feel a pleasant tingling sensation. As strong an impulse as was still pleasant was achieved and time allowed for the patient to adjust to the sensation. It was often found that, after 5
minutes or so, the amplitude could be increased without causing pain and the aim was to keep the amplitude maximal for a pleasant sensation. As labour proceeded, the level of stimulus required to be changed, relating not only to pain threshold but also to skin resistance changes and positioning of the patient. This Level 1 was maintained as a background stimulus between contractions. Level 2 was then set
Forum half-a-dial number ahead of Level 1 and, when a contraction occurred, the patient or her attendant switched over to the higher level to provide pain relief. When the contraction was over, the machine was switched back to Level 1. All patients were visited in the morning, in the delivery suite, immediately prior to induction or in early labour, when a rational discussion could take place and permission to try the new technique be obtained. Latterly, as the midwives became more aware of the method and its benefits, patients in established labour were also given the opportunity to try the machine. All patients who expressed a desire for epidural analgesia were excluded, as were those in whom epidural analgesia was considered advisable for obstetric reasons.
Results Transcutaneous nerve stimulation (TNS) was used on thirty-five patients, thirteen primiparae and twenty-two multiparae (Table 1). Five patients asked for it to be turned off within the first hour as they did not like the sensation-one saying that it made her backache worse. One patient developed severe fetal distress (evident before TNS was applied) and had an emergency Caesarean section. Ten patients obtained some relief from TNS at first, but, for a variety of reasons, abandoned it after between 1 to 4 hours' use and went on to other forms of pain relief-usually epidural analgesia (Table 2). Of the remaining nineteen patients, seven (one primipara, six multiparae) delivered spontaneously without any other form of pain relief, two used Entonox at the end of the first stage to help prevent them pushing before full dilatation, and nine received supplementary help in the form of reduced
Table 1. Pain relief in labour using TNS Total number of patients No help Some help (1-4 hours) Helped throughout
Painful Caesarean scar Sickle cell muscle pains
doses of pethidine in the accelerating phase of the first stage. All these patients wanted T N S to be kept on and found it a positive additional help. In fact, three of the above were in the second stage within 5 min of receiving the supplementary analgesia. The remaining patient had had Pethilorfan (150 mg) 4 h prior to T N S and then required n o further supplementary analgesia for the remaining 2&before dalivery-TNS being adequate. Twenty-one of the patients had complained of backache and eleven of these had confirmed posterior positions of the fetal head. Apart from the one who found that TNS made her backache worse, all others found great comfort when the electrodes were placed over the area of maximal backache. This did not necessarily correspond to the theoretically recommended positions of the electrodes. On two patients towards the end of the study, the thoraco-lumbar electrodes were moved to the suprapubic area where the pain was most intense towards the end of the first stage. Both patients derived great relief from this. Seven patients had fetal scalp electrodes applied to monitor the fetal heart-rate; in four the readings were affected by electrical interference from the sacral electrodes of the T N S machine. N o effect on the fetal heart-rate itself was noted but the sacral electrodes were turned off to ensure accurate monitoring. No detrimental effect to the babies occurred; the Apgar score of all those delivered with TNS in operation was seven or above at 1 and 5 minutes. Very few mothers found much benefit from TNS in the second stage, when the expulsive reflex was strong, and those requiring episiotomies were given local infiltration with lignocaine. No local complications relating to the electrodes and electrode jelly on the skin were recorded and no patient found the apparatus uncomfortable. No restriction to movement was necessary provided that care was taken to ensure the electrodes remained in good contact and the wires to the machine did not pull out.
35
Discussion
6 10 19
Table 2. Reasons for abandoning TNS after some help Slow progress in primiparae Slow progress in multiparae
359
7 1 1 1
It is evident that TNS is no alternative to effective epidural analgesia for quality of pain relief. However, even in a well-staffed obstetric unit, as in Oxford, only 40.6% of patients in 1976 received epidural analgesia. There are many other maternity units where, for various reasons, an epidural service is not in operation or is not freely available, where time-honoured methods of pain relief are still in operation.' ' It is against these alternative methods that T N S must be compared. A certain percentage of patients require no analgesia. In Oxford in 1975, 7% of patients with induced labours and 45% of patients with spontane-
3 60
Forum
ous labours were given no analgesia at all.'* Anderson et a / .in Sweden used a lo# frequency TNS on twenty-seven women in child-birth, with good relief in 48% and some relief in 37%.13 They considered that there was a clear relationship between the degree of hypnotisability and pain relief. Augustinsson and colleagues, using TNS in labour, reported that 47% of 109 mothers considered they had obtained good to very good pain relief and 40>; considered they had obtained some pain relief.6 However, these authors simply state that conventional pain relief methods were used where necessary, and so they themselves accept that it was difficult to evaluate the true effect of TNS on its own. Shealy studied fifty patients in the USA and concluded that 75% obtained good relief from their backache, whilst only 10% obtained good relief of perineal pain. In the present study of thirty-five patients, 20% required no other analgesia, 34% were considerably helped all through labour and 28% obtained some relief in early labour, a total of 82%. No attempt was made to assess a patient's degree of susceptibility to hypnosis but, in each case, the machine was switched off for at least two contractions in an attempt to assess whether the technique was providing pain relief. All asked for it to be switched on again as the contractions became more painful and their relief was evident. It was difficult to predict which patients would benefit from TNS. Those who were well prepared and keen on natural childbirth were not always the most enthusiastic and, in fact, two of the early failures were patients who had been to relaxation classes. The explanation could be that TNS acts as a diversion for some patients, but distracts from a method of relaxation, breathing and concentration provided by some courses. That more multiparae than primiparae were helped was not unexpectedthey had shorter, easier labours on the whole, were more aware of the nature of contraction pains and it was easier to explain the benefits of the TNS to them. A new method of pain relief will have no future unless it can be shown to be better than other methods, safe for the mother and the baby, noninvasive, require no additional nursing nor medical care and be reliable. TNS is non-invasive and believed to be safe for both mother and baby. It is easy to apply and can be operated by doctor, midwife, father or mother once realistic and enthusiastic explanation has been given. TNS is a great comforter to the majority of patients and, if effective, can be continued easily throughout labour. Supplementary analgesia can be given and, if TNS is still effective, the reduced doses of pethidine required must be of benefit to mother and baby. If TNS is not effective, no time is lost, no harm has been done and no drugs require to be eliminated.
The pain of labour is complex and analgesia is not the sole solution. TNS provides analgesia by neuro-physiological means, but it is obviously difficult to assess how much extra benefit the support and interest of the researcher and the distraction of the machine provides to the patient. There is no doubt that great help can be given by TNS, especially on backache, and this in itself could be useful. Summary
Transcutaneous nerve stimulation (TNS) was assessed for use on thirty-five patients in labour. It was of great benefit to 20% of patients and some benefit to a total of 82%. It was especially appreciated by those patients who complained of backache and further studies should be undertaken with the original idea of TNS in mind-stimulating those areas which feel most painful for the patient. If the method could be made more universally available and could be used by patients and midwives alone with the minimum of supervision and explanation, it would be a safe and useful addition to the present methods of pain relief in labour. Key words
ANAESTHESIA; obstetric. ANAESTHETIC TECHNIQUES ; regional, nerve stimulation, transcutaneous.
Acknowledgments
The Travisens machine was loaned by TNS Biomed Limited, 10 Bertram Road, Enfield, Middlesex EN1 ILT. The author wishes to thank Dr L.E.S. Carrie and Dr J. Edmonds-Seal, Consultant Anaesthetists to the John Radcliffe Hospital, for their help in setting up the trial, and Dr J. Lloyd and Dr C. Glynn of the Pain Relief Unit, Marcham Road Hospital, Abingdon, for their support and encouragement. Thanks are also due to the midwives and obstetricians of the delivery suite for their help and criticisms, and to Miss Sue Porter for her secretarial assistance.
References
GLYNN, C.J.(1977) Electrical stimulation for pain relief. British Journal of Clinical Equipment, 2, 184. 2. LONG,D.M.(1974) Cutaneous afferent stimulation for relief of chronic pain. Clinical Neurosurgery, 21, 1.
257.
3. HYMES,A.C., RAAB, D.E., YONEHIRO,E.G., NELSON, G.D. & PRINTY.A.L. (1974) Acute pain
control by electro-stimulation: a Preliminary report. Advances in Neurology, 4,761.
Forum 4. VANDERARK, G.D. & MCGRATH,K.A. (1975)
Transcutaneous electrical stimulation in treatment of postoperative pain. American Journal of Surgery, 130, 3 3 8 . 5. SHEALY, C.N. (1974) Transcutaneous electrical
stimulation for control of pain. Clinical Neuro-
361
Obstetric Analgesia and Anaesthesia, Volume 1, p. 107, Blackwell Scientific Publications, Oxford.
10. CARRIE, L.E.S.(1977) Conduction analgesia. In: Recent Advances in Obstetrics and Gynaecology, 12, (Ed. by S. Stallworthy and G . Bowne) p. 291.
Churchill-Livingstone, Edinburgh. 11. ROSEN,M. (1975) The management of labour:
surgery, 21, 269.
L.-E., BOHLIN, P.H., BUNDSEN, P., 6. AUGUSTINSSON, CARLSSON, C.A., FORSSMAN, L., SJOBERG,P. & TYREMAN, N.O. (1976) Smartlindring under forlossing med transkutan elektrisk newstimulering. Lakartidningen, 13, 4205. R. & WALL,P.D. (1965) Pain mechan7. MELZACK, isms: a new theory. Science, N.Y. 150, 971. 8 . NATHAN, P.W. & WALL,P.D. (1974) Treatment of
post-herpetic neuralgia by prolonged electric stimulation. British Medical Journal, 3, 645. 9. BONICA,J.J. (1967) Principles and Practice of
Proceedings of the Third Study Group of the Royal College of Obstetrics and Gynaecology, (Ed. by
R. Beard, M. Brudenell, P. Dunn and D. Fairweather) p. 140. Royal College of Obstetrics and Gynaecology, London. 12. FRUMAR, A.M. (1977) Personal communication, 13. ANDERSON,S.A., BLOCK,E. & HOLMCREN, E. (1 976) Lagfrekvent transkutan elektrisk stimulering for smartlindring vid forlossning. Lakartidningen, 13, 2421.
Anaesthesia, 1979, Volume 34, pages 361-364
Transcutaneous nerve stimulation as a method of analgesia in labour Peter Stewart M A , BMBCh, DRCOG, Obstetric Registrar, Nuneaton Maternity Hospital, Nuneaton, Warwickshire*
The relief of pain during labour continues to raise problems both for obstetricians and anaesthetists. Although extradural anaesthesia will give highly satisfactory control, the method is not without its complications and shortage of suitably trained staff may make it impossible for some units t o provide a full service. Consideration for the fetus may limit the use of parenteral or inhaled analgesic agents to a level below that required for optimum analgesia. In a recent study it was noted that patients with short labours (less than 4 hours) presented a particularly difficult problem.’ The search for a method of control which will have minimal deleterious effects on the mother and the fetus continues. This paper reports a trial of transcutaneous nerve stimulation (TNS) in labour. This method of pain control is already well established in patients with chronic pain, and its value in the postoperative situation has been shown by several authors (Hymes et Sheally and Maurer3 mention its use in labour without expanding on their experience, whilst Augustinsson et a14 give a more detailed account of this application. The use of T N S in the control of pain stems from the work of Melzack & Wall5 whose ‘gate theory’ of pain has aroused wide interest. Although later
authors6 have questioned the validity of the hypothesis, the empirical results of T N S are undeniable. Patients
Sixty-seven patients (34 primigravidae and 33 multigravidae) were studied. Fifty of these were given intravenous oxytocin either for induction with amniotomy or to augment uterine contractions. Patients admitted either for induction or already in early labour were offered the method if the stimulator was available a t the time. Patients in advanced labour and those who had already received other forms of analgesia prior to the stimulator being available were excluded. It was emphasised that acceptance of the method did not preclude other methods of pain relief should the patient so desire it. None of the patients had requested a n elective extradural anaesthetic nor had any received psychoprophylaxis. Method A ‘Travisens’ Stimulator (loaned by T N S Biomed, Enfield) was used. This is a dual-output device each output being independently variable for both amplitude and rate. In addition, a patient-operated
*Present address: Glasgow Royal Maternity Hospital, Rotten Row, Glasgow OOO3-2409/79/0400-0361$2.00
0 1979 Blackwell Scientific Publications
Forum Transcutaneous nerve stimulation for pain relief in labour
Jean E. Robson MA, MB, BChir, FFA RCS, Senior Registrar, Nufield Department of Anaesthetics, Radcliffe Infirmary, Oxford OX2 6HE*
Transcutaneous nerve stimulation (TNS) techniques have been developed over the past decade for the relief of chronic pain from a wide variety of conditions. In a recent review by Glynn,' sixty-four out of 100patients with a number of chronic pain conditions were relieved, and twenty-eight found permanent pain relief whilst TNS was in use. This compares well with a similar study of 197 patients by Long' where an overall 78% obtained relief when psychiatric factors were eliminated. The use of the technique in acute pain conditions is more recent and has been assessed for postoperative management in the USA by Hymes3 and Vander Ark.4 Shealy has also investigated its use in acute and chronic pain conditions in the USA and mentioned its use in l a b o ~ r and , ~ Augustinsson in Sweden has further reported on its use in labour.6 The aim of the present study was to assess whether TNS was useful as a method of pain relief in labour in a modern British obstetric hospital. Melzack and Wall's gate control theory of pain7 provides the theoretical foundation for TNS and the idea of stimulating large afferent fibres to prevent the smaller, pain-carrying C-fibres from transmitting to the brain has been pursued by many workers.8 Surprisingly, there is not universal agreement about the details of the sensory nerve supply to the uterus and birth canal. Most consider that visceral afferent fibres from the body and cervix of the uterus pass via the uterine, pelvic and hypogastic plexuses in the sympathetic nerves to the spinal cord at T11, 12 and L1. Pain from contraction of the uterine muscle and dilatation of the cervix is referred, therefore, to the areas supplied by the same nerves, i.e. the lower abdomen and back. Parasympathetic pelvic splanchnic nerves (S2,3 and 4) also run in the pelvic plexus to innervate the cervix but there is dispute as to their sensory function. Pain from
dilatation of the cervix, posterior occipital positions and inco-ordinate uterine activity can all be referred to the sacral area. Bonicag states that this is due to downward cutaneous spread from the posterior primary rami of T l l , 12 and L1, but S 2 4 may have to be blocked sometimes to give complete relief in the first stage of labour.I0 In the second stage of labour, pain from distension of the vulva and perineum is passed in somatic afferent nerves, mainly the pudendals, to the spinal cord at S2, 3 and 4. The visceral afferent nerve fibres are usually small diameter C-fibres, travelling at 0.5-2 m/s, whilst the pudendalnerve fibresaredeltaafferent fibres travelling at 10-40 m/s. Method and patient selection
Transcutaneous nerve stimulation was achieved by a specially adapted twin-channel nerve stimulator. Each channel has three controls-Level 1, Level 2 and Rate (Fig. 1). The pulse duration is fixed, but the amplitude and frequency can be altered to produce the required sensation. The electrical current is passed from the machine to the patient via four rubber electrodes, contact being made with electrode jelly. The whole electrode is firmly fixed to the skin with adhesive tape (OpSite3 was found to be very effective) (Fig. 2). In most cases where TNS is used, the electrodes are placed over the most painful area so that the cutaneous nerves in that area are stimulated. With the Travisens machine, the electrodes are placed on either side of the midline of the spine, and are designed to stimulate the posterior primary rami of the spinal segments receiving the painful stimuli during labour, i.e. T1 1-L1 and S2-4. ~
t Travisens, Sweden.
~~~
$ Smith & Nephew Ltd.
*Now Consultant Anaesthetist, Royal Surrey County Hospital, Guildford Surrey. 0003-2409/79/04o(M357$02.00 0 1978 Blackwell Scientilic Publications
3 57
358
Forum
Fig. 1. Twin-channel nerve stimulator control panel.
Fig. 2. Attachment of electrodes to patient.
After fixing the electrodes on the patient’s back in these positions, the machine was switched on to Level 1 with all dials set at 0. The current to the thoraco-lumbar electrodes was gradually increased until the patient could feel a pleasant tingling sensation. As strong an impulse as was still pleasant was achieved and time allowed for the patient to adjust to the sensation. It was often found that, after 5
minutes or so, the amplitude could be increased without causing pain and the aim was to keep the amplitude maximal for a pleasant sensation. As labour proceeded, the level of stimulus required to be changed, relating not only to pain threshold but also to skin resistance changes and positioning of the patient. This Level 1 was maintained as a background stimulus between contractions. Level 2 was then set
Forum half-a-dial number ahead of Level 1 and, when a contraction occurred, the patient or her attendant switched over to the higher level to provide pain relief. When the contraction was over, the machine was switched back to Level 1. All patients were visited in the morning, in the delivery suite, immediately prior to induction or in early labour, when a rational discussion could take place and permission to try the new technique be obtained. Latterly, as the midwives became more aware of the method and its benefits, patients in established labour were also given the opportunity to try the machine. All patients who expressed a desire for epidural analgesia were excluded, as were those in whom epidural analgesia was considered advisable for obstetric reasons.
Results Transcutaneous nerve stimulation (TNS) was used on thirty-five patients, thirteen primiparae and twenty-two multiparae (Table 1). Five patients asked for it to be turned off within the first hour as they did not like the sensation-one saying that it made her backache worse. One patient developed severe fetal distress (evident before TNS was applied) and had an emergency Caesarean section. Ten patients obtained some relief from TNS at first, but, for a variety of reasons, abandoned it after between 1 to 4 hours' use and went on to other forms of pain relief-usually epidural analgesia (Table 2). Of the remaining nineteen patients, seven (one primipara, six multiparae) delivered spontaneously without any other form of pain relief, two used Entonox at the end of the first stage to help prevent them pushing before full dilatation, and nine received supplementary help in the form of reduced
Table 1. Pain relief in labour using TNS Total number of patients No help Some help (1-4 hours) Helped throughout
Painful Caesarean scar Sickle cell muscle pains
doses of pethidine in the accelerating phase of the first stage. All these patients wanted T N S to be kept on and found it a positive additional help. In fact, three of the above were in the second stage within 5 min of receiving the supplementary analgesia. The remaining patient had had Pethilorfan (150 mg) 4 h prior to T N S and then required n o further supplementary analgesia for the remaining 2&before dalivery-TNS being adequate. Twenty-one of the patients had complained of backache and eleven of these had confirmed posterior positions of the fetal head. Apart from the one who found that TNS made her backache worse, all others found great comfort when the electrodes were placed over the area of maximal backache. This did not necessarily correspond to the theoretically recommended positions of the electrodes. On two patients towards the end of the study, the thoraco-lumbar electrodes were moved to the suprapubic area where the pain was most intense towards the end of the first stage. Both patients derived great relief from this. Seven patients had fetal scalp electrodes applied to monitor the fetal heart-rate; in four the readings were affected by electrical interference from the sacral electrodes of the T N S machine. N o effect on the fetal heart-rate itself was noted but the sacral electrodes were turned off to ensure accurate monitoring. No detrimental effect to the babies occurred; the Apgar score of all those delivered with TNS in operation was seven or above at 1 and 5 minutes. Very few mothers found much benefit from TNS in the second stage, when the expulsive reflex was strong, and those requiring episiotomies were given local infiltration with lignocaine. No local complications relating to the electrodes and electrode jelly on the skin were recorded and no patient found the apparatus uncomfortable. No restriction to movement was necessary provided that care was taken to ensure the electrodes remained in good contact and the wires to the machine did not pull out.
35
Discussion
6 10 19
Table 2. Reasons for abandoning TNS after some help Slow progress in primiparae Slow progress in multiparae
359
7 1 1 1
It is evident that TNS is no alternative to effective epidural analgesia for quality of pain relief. However, even in a well-staffed obstetric unit, as in Oxford, only 40.6% of patients in 1976 received epidural analgesia. There are many other maternity units where, for various reasons, an epidural service is not in operation or is not freely available, where time-honoured methods of pain relief are still in operation.' ' It is against these alternative methods that T N S must be compared. A certain percentage of patients require no analgesia. In Oxford in 1975, 7% of patients with induced labours and 45% of patients with spontane-
3 60
Forum
ous labours were given no analgesia at all.'* Anderson et a / .in Sweden used a lo# frequency TNS on twenty-seven women in child-birth, with good relief in 48% and some relief in 37%.13 They considered that there was a clear relationship between the degree of hypnotisability and pain relief. Augustinsson and colleagues, using TNS in labour, reported that 47% of 109 mothers considered they had obtained good to very good pain relief and 40>; considered they had obtained some pain relief.6 However, these authors simply state that conventional pain relief methods were used where necessary, and so they themselves accept that it was difficult to evaluate the true effect of TNS on its own. Shealy studied fifty patients in the USA and concluded that 75% obtained good relief from their backache, whilst only 10% obtained good relief of perineal pain. In the present study of thirty-five patients, 20% required no other analgesia, 34% were considerably helped all through labour and 28% obtained some relief in early labour, a total of 82%. No attempt was made to assess a patient's degree of susceptibility to hypnosis but, in each case, the machine was switched off for at least two contractions in an attempt to assess whether the technique was providing pain relief. All asked for it to be switched on again as the contractions became more painful and their relief was evident. It was difficult to predict which patients would benefit from TNS. Those who were well prepared and keen on natural childbirth were not always the most enthusiastic and, in fact, two of the early failures were patients who had been to relaxation classes. The explanation could be that TNS acts as a diversion for some patients, but distracts from a method of relaxation, breathing and concentration provided by some courses. That more multiparae than primiparae were helped was not unexpectedthey had shorter, easier labours on the whole, were more aware of the nature of contraction pains and it was easier to explain the benefits of the TNS to them. A new method of pain relief will have no future unless it can be shown to be better than other methods, safe for the mother and the baby, noninvasive, require no additional nursing nor medical care and be reliable. TNS is non-invasive and believed to be safe for both mother and baby. It is easy to apply and can be operated by doctor, midwife, father or mother once realistic and enthusiastic explanation has been given. TNS is a great comforter to the majority of patients and, if effective, can be continued easily throughout labour. Supplementary analgesia can be given and, if TNS is still effective, the reduced doses of pethidine required must be of benefit to mother and baby. If TNS is not effective, no time is lost, no harm has been done and no drugs require to be eliminated.
The pain of labour is complex and analgesia is not the sole solution. TNS provides analgesia by neuro-physiological means, but it is obviously difficult to assess how much extra benefit the support and interest of the researcher and the distraction of the machine provides to the patient. There is no doubt that great help can be given by TNS, especially on backache, and this in itself could be useful. Summary
Transcutaneous nerve stimulation (TNS) was assessed for use on thirty-five patients in labour. It was of great benefit to 20% of patients and some benefit to a total of 82%. It was especially appreciated by those patients who complained of backache and further studies should be undertaken with the original idea of TNS in mind-stimulating those areas which feel most painful for the patient. If the method could be made more universally available and could be used by patients and midwives alone with the minimum of supervision and explanation, it would be a safe and useful addition to the present methods of pain relief in labour. Key words
ANAESTHESIA; obstetric. ANAESTHETIC TECHNIQUES ; regional, nerve stimulation, transcutaneous.
Acknowledgments
The Travisens machine was loaned by TNS Biomed Limited, 10 Bertram Road, Enfield, Middlesex EN1 ILT. The author wishes to thank Dr L.E.S. Carrie and Dr J. Edmonds-Seal, Consultant Anaesthetists to the John Radcliffe Hospital, for their help in setting up the trial, and Dr J. Lloyd and Dr C. Glynn of the Pain Relief Unit, Marcham Road Hospital, Abingdon, for their support and encouragement. Thanks are also due to the midwives and obstetricians of the delivery suite for their help and criticisms, and to Miss Sue Porter for her secretarial assistance.
References
GLYNN, C.J.(1977) Electrical stimulation for pain relief. British Journal of Clinical Equipment, 2, 184. 2. LONG,D.M.(1974) Cutaneous afferent stimulation for relief of chronic pain. Clinical Neurosurgery, 21, 1.
257.
3. HYMES,A.C., RAAB, D.E., YONEHIRO,E.G., NELSON, G.D. & PRINTY.A.L. (1974) Acute pain
control by electro-stimulation: a Preliminary report. Advances in Neurology, 4,761.
Forum 4. VANDERARK, G.D. & MCGRATH,K.A. (1975)
Transcutaneous electrical stimulation in treatment of postoperative pain. American Journal of Surgery, 130, 3 3 8 . 5. SHEALY, C.N. (1974) Transcutaneous electrical
stimulation for control of pain. Clinical Neuro-
361
Obstetric Analgesia and Anaesthesia, Volume 1, p. 107, Blackwell Scientific Publications, Oxford.
10. CARRIE, L.E.S.(1977) Conduction analgesia. In: Recent Advances in Obstetrics and Gynaecology, 12, (Ed. by S. Stallworthy and G . Bowne) p. 291.
Churchill-Livingstone, Edinburgh. 11. ROSEN,M. (1975) The management of labour:
surgery, 21, 269.
L.-E., BOHLIN, P.H., BUNDSEN, P., 6. AUGUSTINSSON, CARLSSON, C.A., FORSSMAN, L., SJOBERG,P. & TYREMAN, N.O. (1976) Smartlindring under forlossing med transkutan elektrisk newstimulering. Lakartidningen, 13, 4205. R. & WALL,P.D. (1965) Pain mechan7. MELZACK, isms: a new theory. Science, N.Y. 150, 971. 8 . NATHAN, P.W. & WALL,P.D. (1974) Treatment of
post-herpetic neuralgia by prolonged electric stimulation. British Medical Journal, 3, 645. 9. BONICA,J.J. (1967) Principles and Practice of
Proceedings of the Third Study Group of the Royal College of Obstetrics and Gynaecology, (Ed. by
R. Beard, M. Brudenell, P. Dunn and D. Fairweather) p. 140. Royal College of Obstetrics and Gynaecology, London. 12. FRUMAR, A.M. (1977) Personal communication, 13. ANDERSON,S.A., BLOCK,E. & HOLMCREN, E. (1 976) Lagfrekvent transkutan elektrisk stimulering for smartlindring vid forlossning. Lakartidningen, 13, 2421.
Anaesthesia, 1979, Volume 34, pages 361-364
Transcutaneous nerve stimulation as a method of analgesia in labour Peter Stewart M A , BMBCh, DRCOG, Obstetric Registrar, Nuneaton Maternity Hospital, Nuneaton, Warwickshire*
The relief of pain during labour continues to raise problems both for obstetricians and anaesthetists. Although extradural anaesthesia will give highly satisfactory control, the method is not without its complications and shortage of suitably trained staff may make it impossible for some units t o provide a full service. Consideration for the fetus may limit the use of parenteral or inhaled analgesic agents to a level below that required for optimum analgesia. In a recent study it was noted that patients with short labours (less than 4 hours) presented a particularly difficult problem.’ The search for a method of control which will have minimal deleterious effects on the mother and the fetus continues. This paper reports a trial of transcutaneous nerve stimulation (TNS) in labour. This method of pain control is already well established in patients with chronic pain, and its value in the postoperative situation has been shown by several authors (Hymes et Sheally and Maurer3 mention its use in labour without expanding on their experience, whilst Augustinsson et a14 give a more detailed account of this application. The use of T N S in the control of pain stems from the work of Melzack & Wall5 whose ‘gate theory’ of pain has aroused wide interest. Although later
authors6 have questioned the validity of the hypothesis, the empirical results of T N S are undeniable. Patients
Sixty-seven patients (34 primigravidae and 33 multigravidae) were studied. Fifty of these were given intravenous oxytocin either for induction with amniotomy or to augment uterine contractions. Patients admitted either for induction or already in early labour were offered the method if the stimulator was available a t the time. Patients in advanced labour and those who had already received other forms of analgesia prior to the stimulator being available were excluded. It was emphasised that acceptance of the method did not preclude other methods of pain relief should the patient so desire it. None of the patients had requested a n elective extradural anaesthetic nor had any received psychoprophylaxis. Method A ‘Travisens’ Stimulator (loaned by T N S Biomed, Enfield) was used. This is a dual-output device each output being independently variable for both amplitude and rate. In addition, a patient-operated
*Present address: Glasgow Royal Maternity Hospital, Rotten Row, Glasgow OOO3-2409/79/0400-0361$2.00
0 1979 Blackwell Scientific Publications
