Pain, 4 (1977) 59-65 0 Elsevier/North-Holland







(L.-E.A. and C.-A.C.) Department of Neurosurgery, Sahlgrenska Sjukhuset, Giiteborg, (P.Bo.) Department of Anesthesiology, (N.O.T.) Department of Obstetrics and Gynecology, Lasarettet, Uddevalla, (P.Bu. and L. F.) Department of Obstetrics and Gynecology, &tra Sjukhuset, Giiteborg, and (P.S.) Dansjii Elektronik AB, Sundyberg (Sweden)






The degree of pain alleviation achieved by transcutaneous electrical nerve stimulation (TNS) during delivery has been evaluated. The usual technique of TNS was modified to suit the requirements of pain relief during delivery. Two pairs of electrodes were taped on the parturient’s back at levels ThloL, and S,-S,. These segments correspond to the pathway of pain afferents into the spinal cord during the first and second stages, respectively. Stimulation was delivered by a two-channel generator producing biphasic pulses which were variable in frequency and amplitude. A low-intensity stimulation was given continuously and a high-intensity stimulation could be initiated by the parturient herself whenever pain increased. Stimulation was provided via the thoracic electrodes throughout the delivery, whereas sacral stimulation was added from the later part of the first stage. No complications with respect to mother or child have occurred. One hundred and forty-seven women have been treated, 65 (44%) of whom considered the pain relief by TNS to be good to very good, 65 (44%) experienced moderate effect, while 17 (12%) women considered that TNS was without effect. In view of the relatively good results and since no complications have occurred, we consider the method recommendable as a primary pain relieving measure to which conventional methods can be added according to need.


During the last years an increasing number reducing effect of transcutaneous electrical

of reports concerning the painstimulation (TNS) have been


published. The results are relatively uniform. TNS is found to give temporal alleviation of pain in about lialf of the cases in unselected series of severe pain conditions. Even if the pain-reducing effect varies considerably betlveen different diagnostic groups, there are at present no reliable criteria for patient, selection. No complications of significance have been reported. Favorable experience with TNS prompted us to use the method during delivery in order to evaluate its pain-reducing effect. The stimulation tecshnique was modified on a theoretical and empirical basis to suit the demands of pain control during the whole course of delivery. DELIVERY


This subject is extensively covered by Bonica [6,7]. During the first stage it is assumed that pain receptors are activated by contractions of the uterus and dilatation of the cervix. The evoked impulses are mediated in afferents which run in the hypogastric nerves and reach the spinal cord via the dorsal roots Th ,,,-L, The pain is referred to large areas of the abdomen and the back. During the second stage, pain is also caused by distension and stretching of the delivery canal, the pelvic floor, the vulva and the perineum. During this stage the pain is localized to the place for pain activation. The impulses reach the spinal cord mainly via the pudendal nerves and the dorsal roots S,-S,. During the first stage, the pain is characterized as an ache i+,hich in other pain conditions has been considered to be mediated in C fibers [3]. The pain during the second stage has the distinct localized and intensive nature which is usually identified with A6 fiber pain to which the C fiber mediated pain adds its more diffuse effect. PATIENTS



The study includes 147 patients, 90 primiparae and 57 multiparae. The method of TNS was explained to each patient without suggesting that pain relief would necessarily accompany the feeling of stimulation. It was also made clear that conventional pain relief would be supplemented whenever needed. The participation was quite voluntary. Otherwise no particular criteria for patient selection were used. In 55 cases the fetal heart rate and uterine activity were monitored using a scalp electrode and an intrauterine catheter. In 42 cases, delivery was induced by amniotomy and intravenous oxytocin depending on conventional obstetrical indications, e.g., toxemia, Rh-immunization, post-term pregnancy. A few hours after delivery all patients answered a questionnaire concerning the effect of the pain relief given.



The stimulation system consists and one hand switch. The stimulator

of a stimulator, two pairs of electrodes has two channels with separate sockets


for the two pairs of electrodes. Each channel contains two parallel-coupled pulse generators with separate controls. By means of the hand switch, rapid changes between two different, prefixed stimulation levels can be accomplished. The pulse generators deliver biphasic pulses with a pulse length of 0.25 msec. The amplitude and frequency can be varied. The amplitude range is O-220 V (O-40 mA at 4.7 kS1) and the frequency range is 40-150 Hz. The electrodes are made of carbon rubber and have an active area of 30 mm X 120 mm for the thoracic and 30 mm X 80 mm for the sacral application. Technique of stimulation The two pairs of electrodes were taped to the patients’ back symmetrically with respect to the spinal processes (Fig. 1). One pair levels with the spinal processes Th,*- L, and the other with Sz-Se. These segments correspond to the levels for the influx of pain into the spinal cord during the first and second stages of delivery, respectively. If possible, stimulation should be initiated during the transition between the latent and active phases of the first stage. Two levels of stimulation intensity were used. To obtain optimal analgetic effect the stimulation amplitude was increased to a level where muscular fasciculations appeared in the vicinity of the electrodes. The other stimulation level was approximately 25 V lower. Both stimulation levels were experienced as tingling sensations of different intensity over the involved dermatomes of the back.

Fig. 1. Electrode sites.

The low-intensity stimulation was used ,continuously during the first stage. The patient was instructed to initiate the high-intensity stimulation by the hand switch when a uterine contraction started. The high-intensity stimulation was kept on during the contraction and for at least 1 min duration. The high and low levels of stimulation were increased when the patient reported fading effect. During the later part of the first stage and during t,he second stage sacral stimulation was used in addition to thoracic stimulation. RESULTS

The types of delivery are given in Table 1. The state of the children as judged from the Apgar score was satisfactory. One child scored below 5, four between 5 and 7 and all the others between 8 and 10 at the age of 1 min. The patients’ subjective experiences of this type of pain relief as judged from the questionnaires are given in Table II. It appears that the pain relief was considered fairly equal by primi- and multiparae. The back pain as a rule responded well. In the later part of the first stage the patients often got an intensive pain suprapubically. This pain could be reduced by sacral stimulation. During the second stage, sacral stimulation was usually given at high intensity all the time. This might give satisfactory pain relief but it was especially during the second stage that complementary pain-reducing methods had to be supplemented. Thus, pudendal blocks were given to 68 of the 90 primiparae and to 30 of the 57 multiparae. Four patients had epidural block anesthesia. The most suitable parameters for stimulation were determined individually. A frequency of 60-80 Hz was found to be most appropriate. The stimulation voltage (amplitude) showed a greater spread ranging between 60 and 120 V for the high-intensity stimulation level. No serious side effects have been seen. Thus no labor abnormalities occurred. The sacral stimulation interfered with the signal of the fetal heart rate monitoring in isolated cases. The disturbances occurred as a totally irregular recording or as a zero or maximal recording. Auscultation revealed that in no case was there any real effect on the fetal heart rate. However, the







Occipito-posterior Vacuum Sectio

extraction caesarea

* Also included

Primiparae _-_~___...~~-81

Multiparae ~~ -56

Total 137






12 *

2 in the occipito-anterior

2 vertex






OF TNS Primiparae

















cardiotacographic disturbances often necessitated other forms of pain relief in the second stage, e.g., pudendal block, in order to continue cardiotacographic monitoring. DISCUSSION

In the present study, 44% of the mothers considered the pain reduction by TNS to be good or very good; 44% got moderate alleviation while in 12% the treatment had no effect at all. These results are comparable with the overall results of TNS treatment in other pain conditions. To the best of our knowledge there are only two other reports about TNS during delivery. Shealy and Maurer [14] have reported that TNS gave excellent control of back pain in almost all patients, while the relief of the anterior pain was satisfactory in only 3 of 50 patients. Andersson et al. [2] have in a current report used low-frequency (2 Hz) TNS applied on the back and legs in 27 parturients. They reported good or very good pain relief in 48% and some relief in 37% of the women. The authors considered that the effect showed a positive correlation to hypnotizability. From a practical clinical point of view it might seem irrelevant if electrical stimulation has a suggestive effect or not. The question is, however, important with respect to the future development of the method. Most investigations indicate that the pain-reducing effect of TNS is achieved by real neurophysiological mechanisms and that a suggestive effect, if it occurs, has a minor significance [1,10,11,16]. The mere fact that in the present study the positions of the electrodes were essential for an optimal response might be taken as an indication that neurophysiological mechanisms are operating on a segmental spinal level [12]. It has to be emphasized, however, that the interaction between neurophysiological and psychological phenomena in the pain process is enigmatic. It is well known that variations of the psychological state of the patient highly influence the intensity of perceived pain [5,12,15]. This is particularly obvious during delivery [13] where the pain-stimulating factors can be supposed to be fairly equal in different patients, but pain experience differs considerably from patient to patient, representing the whole scale from no pain at all to unbearable pain. The method of TNS which was used in the present study differs from TNS on other pain conditions. This concerns both the position of the electrodes

and the stimulation pattern. The usual technique for TNS implies that stimulation is applied over painful skin areas or along the route of associated peripheral nerves. This technique was considered not practically possible during delivery. Not only were the painful areas too extended but the sites of the electrodes would interfere with other activities. The stimulating electrodes were therefore placed over the dermatomes on the back, the afferents of which belong to the same spinal cord segments as the pain afferents during the course of delivery. This technique has previously been used with good results in isolated cases with referred, projected and directly evoked pain. Thus stimulation over the upper thoracic dorsal segments has alleviated precordial pain in angina pectoris and stimulation over the sacrum has been effective against extended pain in sacral segments from pelvic tumors. The same technique has also been used in some patients to control severe itching 181. The stimulation pattern had also to be modified. _r\ continuous lowintensity stimulation, which was intensified when the pain increased, was found to be the most satisfactory. The low-intensity stimulation was sufficient to eliminate the dull low-graded backache. It also made the intensification of stimulation less uncomfortable. The increased stimulation level may be more effective by activating not only a greater amount of superficial afferents, but also by reaching afferents in deeper structures. There is some evidence that activation of muscle afferents is significant for pain inhibition [lo]. If, however, high-intensity stimulation was used during too long periods of time, its pain-relieving effect faded. Apart from the fact that stimulation had to be replaced by other methods during the second stage due to disturbances of the fetal heart monitoring signal, it appeared that the pain relief was less effective during this stage than during the first stage. This might support the assumption that C fiber mediated pain is more amenable to blocking by electrical stimulation than is the A6 mediated pain [ 3,4]. The suprapubic pain appears in the transition between the first and second stages. The genesis of this pain is unclear but it coincides with the accelerated cervical dilatation. Its suppression by sacral stimulation might therefore indicate that the pain from the cervix is mediated to sacral levels. This is also claimed by some authors on the basis of clinical and experimental observations [9,17]. The most significant fact about the method is that no complications have occurred. The conventional methods used for pain alleviation during delivery including ana,lgetic and sedative drugs, N,O inhalation, epidural anesthesia and local blockades, all possess a varying degree of potential risks. Another factor is that the choice of analgesia cannot be determined in advance but has to be correlated to the need of the patient during the course of delivery. With these facts in mind and in view of the relatively good results we think that the method is recommendable as a primary pain-relieving method. In those cases where TNS does not give a satisfactory result, other methods for pain relief have to be added. In most cases it is then possible to reduce the amount of drug therapy. If TNS is quite without effect and the patient has severe pain, epidural anesthesia or comparable forms of anesthesia have


to be used. It has to be emphasized, however, that methods which give a complete analgesia, also eliminate pain as a diagnostic tool. A complete analgesia therefore requires a more intense observation. The TNS treatment has the obvious advantage that it can be interrupted whenever needed and thus a more reliable clinical evaluation is possible. Nor does TNS influence the consciousness of the woman which implies that she can actively take part in and experience the whole course of delivery. REFERENCES 1 Anderson,



4 5 6 7 8 9 10 11 12 13 14 15 16 17

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Pain relief during delivery by transcutaneous electrical nerve stimulation.

59 Pain, 4 (1977) 59-65 0 Elsevier/North-Holland PAIN RELIEF ELECTRICAL LARS-ERIK CARLSSON, Biomedical Press DURING DELIVERY BY TRANSCUTANEOUS N...
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