Pa~.-., 41 (1990) 133-138
133
Elsevier PAIN 01576
Parturition pain treated by intracutaneous injections of sterile water 1 Lena Ader, Birgit H a n s s o n and G u n n a r Wallin Department of Obstetrics and Gynaecology, Central Hospital, M~lndal (Sweden) (Received 21 July 1989, revision received 30 November 1989, accepted 5 December i989)
Summary Forty-five pregnant women in the first stage of labour presenting with lower back pain were randomized iato 2 groups. One group received intracutaneous injections of sterile water in the iumbosacral region, while the other group was given corresponding subcutaneous injections of isotonic saline, regarded as a placebo treatment. In the group that received intracutaneous sterile wateg injections the mean VAS score was significantly more reduced compared to the placebo group at 10 min ( P < 0.001). 45 min ( P < 0.02), and at 90 min ( P < 0.05) after the treatment. The midwives' blind estimation of the effectiveness of treatment was consistent with the VAS assessment. However, the requirement of pethidine (meperidine) was similar in the 2 groups. The analgesic method presented was found to be an effective treatmem against lower back pain during the first stage of labour and it is speculated that the mode of action resembles acupuncture.
Key words: Anaesthesia, obstetric; lntradermai injections; Sterile water
|na'oduetion
During the first stage of labour, many women suffer from low back pain. The cervix and corpus uteri are supplied by afferent neurones ending in the dorsal horns of spinal segments T10-L1 [5]. Since cutaneous afferents from the lower back converge to the dorsal horns in the same segments there is anatomical support for the lower back pain being a referred pain [6]. Some techniques, using stimulation or anaesthesia of the lumbosacral area to inhibit pain transmission in the dorsal horn, have been tried. Acupuncture and TENS (transcutaneous electrical nerve stimula-
1 The work is supported by grants from Bohuslandstinget.
Correspondence to: Gunnar WaUin, M.D., Ph.D., Department of Obstetrics and Gynaecology, Central Hospital, S-431 80 M~lndal, Sweden.
tion) have been used with success r2~/,22], b,lt contradictory findings have also beor pre~:~ted [19]. Moreover, TENS has the disadvaatage of interfering with foetal electronic monitoring (C I'G) [10]. A method of subcutaneous infiltration of a local anaesthetic into the lumbo-sacral area has also been tried, as first described by Rose [25]. Furthermore, a technique has been described involving topical application of a local anaesthetic agent to the s ~ n over the lower back, but this was not found to be effective [14,23]. Intracutaneous injections of sterile water have previously been shown to relieve pain due to urolithiasis [4]. In the past, this method has also been used during child birth [28], but no placeb~)-treated group was included in that study, and so the observed analgesic effect of treatment might be purely a placebo effect [3,12]. The aim of the present study was to carry out a randomized, double-blind trial, including a pla-
0304-3959/90/$03.50 © 1990 Elsevier Soence Publishers B.V. (Biomedical Division)
134
cebo-treated group, to elucidate the efficiency of sterile water papules against lower back pain during parturition.
Methods The study comprises 45 pregnant women admitted to the labour ward of the Central Hospital, MiSlndal, Sweden. To qualify for entry into the trial, they had to be in the first stage of labour and require pain relief of severe lower back pain on admission or during their stay in the ward. In all cases, gestational age was more than 37 weeks. All gave informed consent to be included in the study and the protocol was accepted by the local ethical committee. No one had received analgesics within 3 h prior to participation in the study. The women were randomized into 2 groups. One group received 4 intracutaneous injections of sterile water (no salt content) in the lumbar-sacral region (Michaelis' rhomboid; Fig. 1). The other group, called the placebo group, received subcutaneous injections of isotonic saline in the same region. In both groups, a 1 ml plastic syringe (Luer. B. Braun, Melsungen) with a thin needle (0.4 × 19,
1
/
Luer. Becton, Dickinson) was used. The volume of each injection was 0.1 ml. The injections of sterile water gave a sharp local pain sensation lasting for about 20 sec. The subcut.aneeus injections of isotonic saline were almost painless. In order to blunt the difference in pain sensation between the 2 treatments, the injections were given during a contraction. The patient's regular midwife was not present in the room during the injections. These were given by another midwife who did not take part either in the patient's care or in the pain assessment. This midwife was ordered not to inform the other staff about what kind of injections were given or about the patient's reaction during the treatment. The patient's regular midwife, unaware of the type of treatment, recorded clinical data, including the need for other analgesic therapy and finally, after the delivery, she made her own judgement about the analgesic efficiency of the treatment the patient had received. Furthermore, she asked the patient to fill in an ungraded horizontal visual analogue scale (VAS)just before tbe injections and 10, 45 and 90 rain after the treatment. The scale ranged from ' n o pain' to 'pain as bad as it could be.' When evaluating the VAS it was graded from 0 to 10. Statistics Group comparisons of categorical data were made by Fisher's exat~t test (one-sided). A linear model (ANOVA) was used to reveal correlations between background factors and VAS pain scores and to calculate differences in pain score reduction between the two groups.
, . s....... &..:" s¼ N &"\.
',,,. & ." ,..
Results
/&
.\...
Fig. 1. Localisation of sterile water papules or subcutaneous saline injections in relation to the Michaelis' rhomboid.
The women in the 2 groups were similar with regard to age, parity, gestational age and other clinical data (Table I). The total number of women investigated was 50, but when evaluating the data it was found that i patient in the treatment group and 4 patients in the placebo group did not fulfill the inclusion criteria and were therefore excluded. The mean VAS pain score 10 min after treatment was found to be reduced compared to that
135 TABLE I
TABLE II
D E M O G R A P H I C A N D CLINICAL DATA TREATMENT OF 45 WOMEN IN LABOUR
BEFORE
CLINICAL DATA AFTER TREATMENT IN 45 WOMEN IN LABOUR
Data are presented as me,an and range. Fisher's exact test was used. No significant differences were found between the 2 groups.
Data are presented as mean and range. Fisher's exact test was used. No significant diff~renoes w'¢rc found between the 2 groups.
Treatment group Age (years) Primapara/multipara Weight (kg) Gestational age (weeks) Length of each contraction (see) Duration between contractions (min) Orifice (cm) Rupture of membranes (yes/no)
( n = 24)
Placebo group (n = 21)
27.8 (21-36) 16/8 77.5 (61-107) 39.9 (38-42)
26.4 (19-37) 14/7 74.5 (63-93) 40.3 (38-42)
45 (30-55)
45 (30-60)
3.5 (2--7) 5.3 (2-9)
3.2 ( 2 - 6 ) 5.2 (3-8)
10/13
Treatment group (n = 24)
9/12
before treatment in both groups (Fig. 2), but the difference was more pronounced in the group treated with intracutaneous injections of sterile
!
5.0 oo !
E 3
!
o !
!
4.0
c o
"o
~
5.5 (1-14)
4.7 (1-16)
5/19
3/18
11/ 13
10/11
1/23
2/19
1/23 3 2
0/21 3 1
water than in the placebo group ( P < 0.001). The mean VAS pain scores were significantly more reduced in the treatment group compared to the placebo group also at 45 min ( P < 0.02) and 90 min ( P < 0.05) after the treatment (Fig. 2). The requirement for pethidine (meperidire) ~nd N20 / 02 mixture (Entonox) after treatment v,~s similar in the 2 groups (Table II). In the treatment group 1 woman, and in the placebo group 2 wo, nen, required pethidine before the end of the VAS registration time. In these 3 women, VAS measurements after the administration of pethidine
ooo !
Duration between treatment and delivery (h) Women requiring pethidine after treatment (yes/no) Women using N 2 0 / O : mixture after treatment (yes/no) Women requiring paracervical blockade after treatment (yes/no) Women requiring epidural blockade after treatment (yes/no) Vacuum extractions (numb) Caesarean sections (numb)
Placebo group ( n = 21)
3.0
.c_ 2.0 Q.
>
1.0
TABLE IIl
I lO
45
90
Time after treatment (rain)
Fig. 2. Average pain score reduction on a VAS divided into 0-10 cm compared with the initial value. Shaded b a r s = treatment group, open bars = placebo group. ANOVA test was used. * P < 0.05, * * P < 0.02, * * * P < 0.001. S.E.M. is indicated.
ASSESSMENT BY MIDWIVES OF THE ANALGESIC EFFECT OF TREATMENT IN 45 WOMEN IN LABOUR Effect of treatment
Treatment group (n -- 24)
Placebo group (n = 21)
Yes No Unsure
17 4 3
4 * 12 * 5
Fisher's exact test. * P < 0.001.
136
were excluded from the calculations. The requirement for paracervical blockades or epidural blockades after the treatment was low in both groups (Table II) and no woman received any blockade during the VAS assessment period. The midwives blind estimation of the effectiveness of the treatment revealed a significant difference between the 2 groups ( P < 0.001; Table III). The mean period between injections and delivery was 5.5 h in the treatment group and 4.7 h in the placebo group (Table II). The difference is non-significant. In the ANOVA test, no background factors, except being part of the group was correlated to VAS pain scores.
Discussion
The present study indicates an analgesic effect of treatment with intracutaneous papules of sterile water on low back pain during the first stage of labour. However, our placebo treatment also had a significant analgesic effect. This is in accordance with earlier observations during pain studies in which placebo treatments have shown a considerable analgesic potency [11,13,18]. This effect is more pronounced during comparable high initial pain levels [12]. However, in the treatment group the analgesic effect was significantly more pronounced than in the placebo group (Fig. 2). Uterine contractions are felt as back pain because the rami of T10-L1 supplying the uterus also supply the skin over the lumbo-sacral area [5]. The cutaneous branches of the lumbar and the lower thoracic nerves cover a considerably caudal area. They transmit a referred pain from the uterus to a skin area over the vertebrae L3-$2 [5]. The injections were given adjacent to the Michaelis" rhomboid, because this is where referred pain from the uterine contractions were felt. The same choice of injection area was made earlier in preliminary reports [28]. Needling in a referred pain area has also been shown to be effective during urolithiasis [4]. One might speculate that the stimulation of the skin during administration of sterile water papules gives rise to a similar gate control effect and/or a stimulation of the cndogenous opioid system as TENS and acupuncture do.
Acupunture for analgesic purposes can be applied to specified traditional points following meridians. These points are often located far from the painful area. However, needling at sites segmentally related to the painful site may be equally or even more effective [1]. The intracutaneous injections of sterile water may act as a long lasting segmental acupunture. The action of acupunture and TENS is supposed to work through at least 2 different mechanisms. Firstly: stimulation of fast conducting A fibres which affect interneurones in the substantia gelatinosa, producing pain inhibition as described in the 'gate control theory' [21]. Secondly: in some studies, acupuncture and electroacupuncture have been shown to raise the fl-endorphic levels in the cerebro-spinal fluid (CSF) concomitantly with pain relief [8,26]. It is stated that the fl-endorphins act as endogenous pain modulators [24,27]. Furthermore, acupuncture[20] and TENS-produced [7] analgesia can be reversed by r,alo:- no, an agent able to antagonize endogenous opioid action. However, in the present s~udy, no attempts were made to define the mechanisms of action more exactly. In order to investigate if the t~eatment with sterile water papules acts thrc,ugh activation of the endorphic system, sample,,; of /3-endorphin would have to be taken from the CSF. A n t ' h e r possibility would have been to try to antagomze the analgesic effect by using naloxone [15,20]. However, placebo treatment has also been shown to be antagonized by naloxone [13,17], supporting the theory that placebo treatment is partly mediated by endogenous opioids. Therefore, even in the treatment group, there may be some elevation of fl-endorphins due to the placebo effect which naloxone will antagonize with resultant reduction in analgesia, even if the analgesia in the treatment group is due to some other mechanism. Kubista and Kucera [16] found that after repeated treatments with manual acupunture during the final weeks of pregnancy in primaparous women, the labour time was significantly reduced. On the other hand, Lyren~is et al. [19] described a prolonged labour time in acupuncture-treated patients. The explanation given was that acupuncture may cause uterine relaxation. However, the 2
137
studies were not comparable, in that the former study [16] presented the time from start of painful contractions to parturition, while the latter authors [19] preferred to measure the time from admission to the delivery ward to parturition. If one defines them according to the length of each contraction, the frequency of contractions and the degree of cervical opening, the 2 groups in our study were at a similar stage of labour when included in the study (Table I). The time from this point until delivery did not differ significantly between the 2 groups (Table II). Accordingly, the described interference by acupunture [16,19] did not seem to be present during treatment with sterile water papules. In summary, sterile water papules given intracutaneously seem to be an efficient and simple method for antagonizing parturition low back pain. It can easily be administered by the patient's midwife and no side effects have been observed other than a burning pain lasting for a few seconds.
References 1 Andersson, S.A. and Holmgren, E., On acupuncture analgesia and the mechanism of pain, Am. J. Chin. Med., 3 (1975) 311-334. 2 Augustinsson, L.E., Bohlin, P., Bundsen, P., Cadsson, C.A., Forssman, L., Sjttberg, P. and Tyreman, N.O., Pain relief during delivery by transcutaneous electrical nerve stimulation, Pain, 4 (1977) 59-65. 3 Beecher, H.K., The Measurement of Subjective Responses: Quantitative Effects of Drugs, Oxford University Press, New York, 1959. 4 Bengtsson, J., Worning, A.M., Gertz, J. et al., Urolithiasissmerter behandlet med intrakutane sterilvandspapler, Ugeskr. Laeger, 143 (1981) 3463-3465. 5 Bonica, J.J., Peripheral mechanisms and pathways of parturition pain, Br. J. Anaesth., 51 (1979) $3-$9. 6 Cervero, F. and TattersaU, J.E.H., Somatic and visceral sensory integration in the thoracic spinal cord. In: F. Cervero and J.F.B. Morrison (Eds.), Visceral Sensation. Progress in Brain Research, Vol. 67, Elsevier, Amsterdam, 1986, pp. 189-205. 7 Chapman, C.R. and Benedetti, C., Analgesia following transcutaneous electrical stimulation and its partial reversal by a narcotic antagonist, Life Sci., 21 (1977) 1645-1648. 8 Clement-Jones, V., McLoughlin, L., Tomlin, S., Besser, G.M., Rees, L.H. and Wen, H.L., Increased fl-endorphin
but not met-enkephalin levels in human cerebrospinal fluid after acupuncture for recurrent pain, Lancet, ii (1980) 946949. 9 Deen, P. and Yuelan, H., Use of acupuncture analgesia during childbirth, J. Tradit. Chin. Med., 5 (1985) 253-255. 10 Erkkola, R., Pikkola, P. and Kanto, J., Transcutaneous nerve stimulation for pain relief during labour: a controlled study, Ann. Chir. Gynaecol., 69 (1980) 273-277. 11 Fedele, L., Marchini, M., Acaia, B., Garagiola, U. and Tiengo, M., Dynamics and significance of placebo response in primary dysmenorrhea, Pain, 36 (1989) 43-47. 12 Fields, H.L., Pain. II. New approaches to management, Ann. Neurol., 9 (1981) 101-106. 13 Grevert, P., Albert, L.H. and Goldstein, A., Partial antagonism of placebo analgesia by naloxone, Pain, 16 (1983) 129-143. 14 Jouppila, R., Nuoranne, L., Tervil~i, L. and Gustafsson, B., Epicutaneous application of A2358 compresses containing ketocaine ~'or pain relief in labor, Acta Obstet. Gynecol. Scand., 62 (1983) 321-324. 15 Kitade, T., Odahara, Y., Shinohara S. et al., Studies on the enhanced effect of acupuncture analgesia and acupuncture anesthesia by D-phenylalanine (first report) - effect on pain threshold and inhibition by naloxone, Acupunt. Electrother. Res., 13 (1988) 87-97. 16 Kubist~, E. und Kucera, H., Uber die Anwendung der Akupu,aktur zur Geburtsvorbereitung, Z. Geburtsh. Perinatol., 178 (1974) 224-229. 17 Levine, J.D. and Gordon, N.C., Influence of the method of 5rug administration ovI analgesic response, Nature, 312 (] 9~;4) 755-756. 18 Lieberman, R., An experimental study of the placebo response under three different situation~ of pain, J. Psychiat. Res., 2 (1964) 233-24t6. 19 Lyreniis, S., Lutsch, H., Hetta, J. and Lindberg, B., Acupuncture before delivery: effect on labor, Gynecol. Obstet. Invest., 24 (1987) 217-224. 20 Mayer, D.J., Price, D.D. and Rafii, A., Antagonism of acupuncture analgesia in man by the narcotic antagonist naloxone, Brain Res., 121 (1977) 368-372. zl ~lelzack, R. and Wall, P.D., Pain mechanisms: a new theory, Science, 150 (1965) 971-979. 22 Neumark, J., !.aauser, G. und Scherzer, W., Der Wehenschmerz wiihrend der Geburt. Zur Analyse der analgetischen Wirkung der transkutanen Nervenstimulation (TNS) ~m Vergleich mit Pethidin und Plazebos, Prakt. Aniisth., 13 (1978) 13-20. 23 Permin, M., Ipsen, L., Kern Hansen, M. et al., Relief from pain localized zo the lower back in early labour, Z. Geburtsh. Perinatol., 185 (1981) 360-363. 24 Pickar, D., Cohen, M.R. and Dubois, M., The relationship of plasma cortisol and fl-endorphin immunoreactivity to surgical st~'ess and postoperative analgesic requirement. Gen. Hosp. Psychiat., 5 (1983) 93-98. 25 R6se, D . Local anaesthesia in first and second stage labor, New Engl. J. Med., 201 (1929) 117-125.
138 26 SjS!und, B., Terenius, L. and Eriksson, M., Increased cerebrospinal fluid levels of endorphins after electroacupuncture, Acta Physiol. Scand., 100 (1977) 382-384. 27 Tcrenius, L. and Tamsen, A., Endorphins and the modulation of acute pain, Acta Anaesthesiol. Stand., Suppl. 74 (1982) 21-24.
28 Trolle, G.B., Hvidman, L.E. and Guidholt, I.S., Laendesmerter hos fodende behandlet med steriltvandspapler, Ugeskr. Laeger, 148 (1986) 1200-1202.
133
Elsevier PAIN 01576
Parturition pain treated by intracutaneous injections of sterile water 1 Lena Ader, Birgit H a n s s o n and G u n n a r Wallin Department of Obstetrics and Gynaecology, Central Hospital, M~lndal (Sweden) (Received 21 July 1989, revision received 30 November 1989, accepted 5 December i989)
Summary Forty-five pregnant women in the first stage of labour presenting with lower back pain were randomized iato 2 groups. One group received intracutaneous injections of sterile water in the iumbosacral region, while the other group was given corresponding subcutaneous injections of isotonic saline, regarded as a placebo treatment. In the group that received intracutaneous sterile wateg injections the mean VAS score was significantly more reduced compared to the placebo group at 10 min ( P < 0.001). 45 min ( P < 0.02), and at 90 min ( P < 0.05) after the treatment. The midwives' blind estimation of the effectiveness of treatment was consistent with the VAS assessment. However, the requirement of pethidine (meperidine) was similar in the 2 groups. The analgesic method presented was found to be an effective treatmem against lower back pain during the first stage of labour and it is speculated that the mode of action resembles acupuncture.
Key words: Anaesthesia, obstetric; lntradermai injections; Sterile water
|na'oduetion
During the first stage of labour, many women suffer from low back pain. The cervix and corpus uteri are supplied by afferent neurones ending in the dorsal horns of spinal segments T10-L1 [5]. Since cutaneous afferents from the lower back converge to the dorsal horns in the same segments there is anatomical support for the lower back pain being a referred pain [6]. Some techniques, using stimulation or anaesthesia of the lumbosacral area to inhibit pain transmission in the dorsal horn, have been tried. Acupuncture and TENS (transcutaneous electrical nerve stimula-
1 The work is supported by grants from Bohuslandstinget.
Correspondence to: Gunnar WaUin, M.D., Ph.D., Department of Obstetrics and Gynaecology, Central Hospital, S-431 80 M~lndal, Sweden.
tion) have been used with success r2~/,22], b,lt contradictory findings have also beor pre~:~ted [19]. Moreover, TENS has the disadvaatage of interfering with foetal electronic monitoring (C I'G) [10]. A method of subcutaneous infiltration of a local anaesthetic into the lumbo-sacral area has also been tried, as first described by Rose [25]. Furthermore, a technique has been described involving topical application of a local anaesthetic agent to the s ~ n over the lower back, but this was not found to be effective [14,23]. Intracutaneous injections of sterile water have previously been shown to relieve pain due to urolithiasis [4]. In the past, this method has also been used during child birth [28], but no placeb~)-treated group was included in that study, and so the observed analgesic effect of treatment might be purely a placebo effect [3,12]. The aim of the present study was to carry out a randomized, double-blind trial, including a pla-
0304-3959/90/$03.50 © 1990 Elsevier Soence Publishers B.V. (Biomedical Division)
134
cebo-treated group, to elucidate the efficiency of sterile water papules against lower back pain during parturition.
Methods The study comprises 45 pregnant women admitted to the labour ward of the Central Hospital, MiSlndal, Sweden. To qualify for entry into the trial, they had to be in the first stage of labour and require pain relief of severe lower back pain on admission or during their stay in the ward. In all cases, gestational age was more than 37 weeks. All gave informed consent to be included in the study and the protocol was accepted by the local ethical committee. No one had received analgesics within 3 h prior to participation in the study. The women were randomized into 2 groups. One group received 4 intracutaneous injections of sterile water (no salt content) in the lumbar-sacral region (Michaelis' rhomboid; Fig. 1). The other group, called the placebo group, received subcutaneous injections of isotonic saline in the same region. In both groups, a 1 ml plastic syringe (Luer. B. Braun, Melsungen) with a thin needle (0.4 × 19,
1
/
Luer. Becton, Dickinson) was used. The volume of each injection was 0.1 ml. The injections of sterile water gave a sharp local pain sensation lasting for about 20 sec. The subcut.aneeus injections of isotonic saline were almost painless. In order to blunt the difference in pain sensation between the 2 treatments, the injections were given during a contraction. The patient's regular midwife was not present in the room during the injections. These were given by another midwife who did not take part either in the patient's care or in the pain assessment. This midwife was ordered not to inform the other staff about what kind of injections were given or about the patient's reaction during the treatment. The patient's regular midwife, unaware of the type of treatment, recorded clinical data, including the need for other analgesic therapy and finally, after the delivery, she made her own judgement about the analgesic efficiency of the treatment the patient had received. Furthermore, she asked the patient to fill in an ungraded horizontal visual analogue scale (VAS)just before tbe injections and 10, 45 and 90 rain after the treatment. The scale ranged from ' n o pain' to 'pain as bad as it could be.' When evaluating the VAS it was graded from 0 to 10. Statistics Group comparisons of categorical data were made by Fisher's exat~t test (one-sided). A linear model (ANOVA) was used to reveal correlations between background factors and VAS pain scores and to calculate differences in pain score reduction between the two groups.
, . s....... &..:" s¼ N &"\.
',,,. & ." ,..
Results
/&
.\...
Fig. 1. Localisation of sterile water papules or subcutaneous saline injections in relation to the Michaelis' rhomboid.
The women in the 2 groups were similar with regard to age, parity, gestational age and other clinical data (Table I). The total number of women investigated was 50, but when evaluating the data it was found that i patient in the treatment group and 4 patients in the placebo group did not fulfill the inclusion criteria and were therefore excluded. The mean VAS pain score 10 min after treatment was found to be reduced compared to that
135 TABLE I
TABLE II
D E M O G R A P H I C A N D CLINICAL DATA TREATMENT OF 45 WOMEN IN LABOUR
BEFORE
CLINICAL DATA AFTER TREATMENT IN 45 WOMEN IN LABOUR
Data are presented as me,an and range. Fisher's exact test was used. No significant differences were found between the 2 groups.
Data are presented as mean and range. Fisher's exact test was used. No significant diff~renoes w'¢rc found between the 2 groups.
Treatment group Age (years) Primapara/multipara Weight (kg) Gestational age (weeks) Length of each contraction (see) Duration between contractions (min) Orifice (cm) Rupture of membranes (yes/no)
( n = 24)
Placebo group (n = 21)
27.8 (21-36) 16/8 77.5 (61-107) 39.9 (38-42)
26.4 (19-37) 14/7 74.5 (63-93) 40.3 (38-42)
45 (30-55)
45 (30-60)
3.5 (2--7) 5.3 (2-9)
3.2 ( 2 - 6 ) 5.2 (3-8)
10/13
Treatment group (n = 24)
9/12
before treatment in both groups (Fig. 2), but the difference was more pronounced in the group treated with intracutaneous injections of sterile
!
5.0 oo !
E 3
!
o !
!
4.0
c o
"o
~
5.5 (1-14)
4.7 (1-16)
5/19
3/18
11/ 13
10/11
1/23
2/19
1/23 3 2
0/21 3 1
water than in the placebo group ( P < 0.001). The mean VAS pain scores were significantly more reduced in the treatment group compared to the placebo group also at 45 min ( P < 0.02) and 90 min ( P < 0.05) after the treatment (Fig. 2). The requirement for pethidine (meperidire) ~nd N20 / 02 mixture (Entonox) after treatment v,~s similar in the 2 groups (Table II). In the treatment group 1 woman, and in the placebo group 2 wo, nen, required pethidine before the end of the VAS registration time. In these 3 women, VAS measurements after the administration of pethidine
ooo !
Duration between treatment and delivery (h) Women requiring pethidine after treatment (yes/no) Women using N 2 0 / O : mixture after treatment (yes/no) Women requiring paracervical blockade after treatment (yes/no) Women requiring epidural blockade after treatment (yes/no) Vacuum extractions (numb) Caesarean sections (numb)
Placebo group ( n = 21)
3.0
.c_ 2.0 Q.
>
1.0
TABLE IIl
I lO
45
90
Time after treatment (rain)
Fig. 2. Average pain score reduction on a VAS divided into 0-10 cm compared with the initial value. Shaded b a r s = treatment group, open bars = placebo group. ANOVA test was used. * P < 0.05, * * P < 0.02, * * * P < 0.001. S.E.M. is indicated.
ASSESSMENT BY MIDWIVES OF THE ANALGESIC EFFECT OF TREATMENT IN 45 WOMEN IN LABOUR Effect of treatment
Treatment group (n -- 24)
Placebo group (n = 21)
Yes No Unsure
17 4 3
4 * 12 * 5
Fisher's exact test. * P < 0.001.
136
were excluded from the calculations. The requirement for paracervical blockades or epidural blockades after the treatment was low in both groups (Table II) and no woman received any blockade during the VAS assessment period. The midwives blind estimation of the effectiveness of the treatment revealed a significant difference between the 2 groups ( P < 0.001; Table III). The mean period between injections and delivery was 5.5 h in the treatment group and 4.7 h in the placebo group (Table II). The difference is non-significant. In the ANOVA test, no background factors, except being part of the group was correlated to VAS pain scores.
Discussion
The present study indicates an analgesic effect of treatment with intracutaneous papules of sterile water on low back pain during the first stage of labour. However, our placebo treatment also had a significant analgesic effect. This is in accordance with earlier observations during pain studies in which placebo treatments have shown a considerable analgesic potency [11,13,18]. This effect is more pronounced during comparable high initial pain levels [12]. However, in the treatment group the analgesic effect was significantly more pronounced than in the placebo group (Fig. 2). Uterine contractions are felt as back pain because the rami of T10-L1 supplying the uterus also supply the skin over the lumbo-sacral area [5]. The cutaneous branches of the lumbar and the lower thoracic nerves cover a considerably caudal area. They transmit a referred pain from the uterus to a skin area over the vertebrae L3-$2 [5]. The injections were given adjacent to the Michaelis" rhomboid, because this is where referred pain from the uterine contractions were felt. The same choice of injection area was made earlier in preliminary reports [28]. Needling in a referred pain area has also been shown to be effective during urolithiasis [4]. One might speculate that the stimulation of the skin during administration of sterile water papules gives rise to a similar gate control effect and/or a stimulation of the cndogenous opioid system as TENS and acupuncture do.
Acupunture for analgesic purposes can be applied to specified traditional points following meridians. These points are often located far from the painful area. However, needling at sites segmentally related to the painful site may be equally or even more effective [1]. The intracutaneous injections of sterile water may act as a long lasting segmental acupunture. The action of acupunture and TENS is supposed to work through at least 2 different mechanisms. Firstly: stimulation of fast conducting A fibres which affect interneurones in the substantia gelatinosa, producing pain inhibition as described in the 'gate control theory' [21]. Secondly: in some studies, acupuncture and electroacupuncture have been shown to raise the fl-endorphic levels in the cerebro-spinal fluid (CSF) concomitantly with pain relief [8,26]. It is stated that the fl-endorphins act as endogenous pain modulators [24,27]. Furthermore, acupuncture[20] and TENS-produced [7] analgesia can be reversed by r,alo:- no, an agent able to antagonize endogenous opioid action. However, in the present s~udy, no attempts were made to define the mechanisms of action more exactly. In order to investigate if the t~eatment with sterile water papules acts thrc,ugh activation of the endorphic system, sample,,; of /3-endorphin would have to be taken from the CSF. A n t ' h e r possibility would have been to try to antagomze the analgesic effect by using naloxone [15,20]. However, placebo treatment has also been shown to be antagonized by naloxone [13,17], supporting the theory that placebo treatment is partly mediated by endogenous opioids. Therefore, even in the treatment group, there may be some elevation of fl-endorphins due to the placebo effect which naloxone will antagonize with resultant reduction in analgesia, even if the analgesia in the treatment group is due to some other mechanism. Kubista and Kucera [16] found that after repeated treatments with manual acupunture during the final weeks of pregnancy in primaparous women, the labour time was significantly reduced. On the other hand, Lyren~is et al. [19] described a prolonged labour time in acupuncture-treated patients. The explanation given was that acupuncture may cause uterine relaxation. However, the 2
137
studies were not comparable, in that the former study [16] presented the time from start of painful contractions to parturition, while the latter authors [19] preferred to measure the time from admission to the delivery ward to parturition. If one defines them according to the length of each contraction, the frequency of contractions and the degree of cervical opening, the 2 groups in our study were at a similar stage of labour when included in the study (Table I). The time from this point until delivery did not differ significantly between the 2 groups (Table II). Accordingly, the described interference by acupunture [16,19] did not seem to be present during treatment with sterile water papules. In summary, sterile water papules given intracutaneously seem to be an efficient and simple method for antagonizing parturition low back pain. It can easily be administered by the patient's midwife and no side effects have been observed other than a burning pain lasting for a few seconds.
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