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ORIGINAL RESEARCH |
From the Department of Obstetrics and Gynecology, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
Address reprint requests to: Boonsri Chanrachakul, MD, Department of Obstetrics and Gynecology, Ramathibodi Hospital, Mahidol University, Rama VI Road, Bangkok 10400, Thailand; E-mail: rabcr{at}mahidol.ac.th.
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ABSTRACT |
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METHODS: This double-blind, randomized, controlled trial included 140 women who underwent fractional curettage. Seventy women were allocated to the lidocaine group and 70 to the plain saline group. The main outcome measure was the intensity of pain measured by visual analog scale during and after the procedure.
RESULTS: The intensity of pain was significantly lower in the lidocaine group than in the plain saline group over the course of the procedure (P = .02), especially during fractional curettage. There were no serious adverse effects in this study.
CONCLUSION: Lidocaine is more effective than plain saline for paracervical pain relief during fractional curettage. The anesthetic mechanisms of lidocaine are mechanical distention of tissue and peripheral nerve block.
The paracervical block has been used for minor gynecologic procedures since 1925.1 Although use of general anesthetics provides analgesia, amnesia, and a hypnotic effect, it carries a higher mortality risk than properly administered local anesthetics.2 Lidocaine, the amide-type agent, is used widely for local anesthesia. It has a rapid onset of action and is inexpensive. Although lidocaine is a safe local anesthetic, an overdose carries an appreciable risk of toxic effects, particularly to the cardiovascular system and the central nervous system.3
Earlier observations during pain studies demonstrated that plain saline, used as a placebo, had a significant analgesic effect, and some studies suggested a level of pain relief similar to that achieved with lidocaine.4–6 Miller et al6 compared lidocaine and bacteriostatic saline containing 0.9% benzyl alcohol. However, benzyl alcohol is an active anesthetic agent that has been used as a local anesthetic.7 It is unclear whether an analgesic effect from bacteriostatic saline was due to tissue distention causing disruption of neuronal impulses or to the effect of benzyl alcohol. In their study reports, Johnson et al4 and Ader et al5 did not state whether they used bacteriostatic or plain saline as a control.
The objective of this study was to compare the efficiency of lidocaine with that of plain saline for paracervical pain relief during fractional curettage.
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MATERIALS AND METHODS |
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To indicate intensity of pain, patients used a visual analog scale, marking an "X" on a 10-cm line (0 cm = no pain, 10 cm = intolerable pain).8 Using the visual analog scale, each patient made four assessments of intensity of pain. The first assessment was made immediately after insertion of the speculum and was for intensity of pain during insertion of the speculum. The second assessment was made immediately after curettage and was for intensity of pain during curettage. The third assessment was made for intensity of pain immediately after curettage, and the fourth assessment was made 30 minutes after curettage for intensity of pain at that time. Each patient was advised to ask for a lidocaine paracervical block at any time if she wanted more pain relief and wished to leave the study. The repeated injection was limited to 10 mL of 1% lidocaine so that the total dose of lidocaine did not exceed 300 mg.9
Injections were made with a 23-gauge spinal needle at 3 and 9 o’clock of cervicovaginal reflection.10 Total volumes of solution given to each patient were 20 and 10 mL at the two sites, respectively, at an estimated depth of 1 cm. Intermittent aspiration was performed before and during injection to ensure that paracervical blood vessels were not punctured. Oxygen and vasopressors were always available.
The standard procedure for fractional curettage was performed after waiting 2 minutes for the onset of action of lidocaine.11 The cervical canal was curetted first, followed by the endometrial cavity. The cervical canal was dilated, if necessary, to 8 mm using a Hegar dilator.
Data recorded included marital status, history of vaginal delivery, history of miscarriage, history of curettage, indications for fractional curettage, size of uterus, need for cervical dilation, estimated blood loss, operative time, complications such as infection, lidocaine toxicity, and difficulty of the procedure as rated by the surgeon (1 = not difficult, 4 = extremely difficult).
On the basis of a previous study by Miller et al6 to determine the sample size, we concluded that lidocaine could be considered more beneficial than plain saline (mean [± standard deviation] 6.06 ± 2.77 cm) if it reduced the pain score by at least 25%. Thus, 70 women were required in each group to achieve a power of 90% at a type I error of .05 (two-tailed test). Data were analyzed using the Statistical Package for Social Sciences 7.5 (SPSS Inc., Chicago, IL). The Student t test, the Mann-Whitney U test, and repeated measures analysis of variance were used to compare continuous variables, and the 
2 test was used to analyze proportion. P < .05 (two-tailed test) was considered significant.
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RESULTS |
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The visual analog scale score for plain saline was significantly higher during fractional curettage (Figure 1). A repeated measures analysis of variance showed a significant difference between the visual analog scale scores in the lidocaine group and the visual analog scale scores in the plain saline group (P = .02). There was also a significant difference in visual analog scale scores within each group (P < .001), which supports the validity of the assessment that pain increases from speculum insertion through fractional curettage. There was no time-by-treatment interaction in the repeated measures analysis of variance. No serious adverse effect was found in this study.
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DISCUSSION |
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Paracervical block is a convenient, safe, simple, and effective anesthetic technique for curettage. Lidocaine is used widely because of its effectiveness and rapid onset of action. It blocks the movement of sodium across the nerve membrane by binding to a specific receptor located at the internal opening of sodium channels.9 Lidocaine can be associated with adverse effects that range from mild toxicity such as numbness around the mouth and dizziness to convulsion and respiratory arrest.6,12 Grimes and Cates13 reported five deaths from use of lidocaine to induce paracervical anesthesia.
Previous studies have suggested that normal saline also has an analgesic effect.4–6 In our study, the pain level when the speculum was inserted was similar between groups (Figure 1
). This finding suggests that the threshold for pain was comparable between groups. Repeated measures analysis of variance revealed a significantly different level of pain within each group according to time, increasing after speculum insertion through curettage and then decreasing. However, intensity of pain was significantly lower in the lidocaine group than in the plain saline group over the course of the procedure, especially during fractional curettage (Figure 1). Since no patient dropped out or requested analgesic, this difference might not be clinically significant.
Miller et al6 concluded that bacteriostatic saline had the same effect as lidocaine in terms of pain relief during suction curettage. They proposed that the local anesthetic mechanism might be due to distention rather than blockage of a specific nerve, because there was no waiting time after paracervical block to perform the procedure. However, a few minutes pass before lidocaine begins to take effect,11 and benzyl alcohol in bacteriostatic saline also has an analgesic effect.7
We used plain saline in our study to prevent the anesthetic effect of benzyl alcohol that might have influenced the findings of Miller et al.6 The analgesic effect of plain saline was wholly from mechanical pressure on the nerve to stimulate the fast-conducting A fibers producing pain inhibition, the same principle found in acupuncture and transcutaneous electrical nerve stimulation.5,14,15 We also waited for 2 minutes for the onset of action of lidocaine before performing fractional curettage.11
We conclude that lidocaine is more effective than plain saline for paracervical block during fractional curettage. The anesthetic mechanisms of lidocaine are from both mechanical tissue distention and peripheral nerve block.
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Footnotes |
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Received March 5, 2001. Received in revised form June 21, 2001. Accepted July 5, 2001.
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REFERENCES |
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2. Peterson HB, Grimes DA, Cates W, Rubin GL. Comparative risk of death from induced abortion at less than or equal to 12 weeks’ gestation performed with local versus general anesthesia. Am J Obstet Gynecol 1981;141:763–8.[Medline]
3. Covino BG. Local anesthesia. N Engl J Med 1972;286: 975–83.
4. Johnson N, Crompton AC, Ramsden SVB. The efficacy of paracervical injections of lignocaine before laser ablation of the cervical transformation zone. A randomized placebo-controlled double-blind clinical trial. Br J Obstet Gynaecol 1989;96:1410–2.[Medline]
5. Ader L, Hansson B, Wallin G. Parturition pain treated by intracutaneous injections of sterile water. Pain 1990;41: 133–8.[Medline]
6. Miller L, Jensen MP, Stenchever MA. A double-blind randomized comparison of lidocaine and saline for cervical anesthesia. Obstet Gynecol 1996;87:600–4.[Abstract]
7. Macht DI. A pharmacological and therapeutic study of benzyl alcohol as a local anesthetic for skin surgery. J Pharmacol Exp Ther 1918;11:263–79.
8. Revill SI, Robinson JO, Rosen M, Hogg MIJ. The reliability of a linear analogue for evaluating pain. Anaesthesia 1976;31:1191–8.[Medline]
9. Grekin RC, Auletta MJ. Local anesthesia in dermatologic surgery. J Am Acad Dermatol 1988;19:599–614.[Medline]
10. Cooper K, Moir JC. Paracervical nerve block: A simple method of pain relief in labor. Br Med J 1963;1:1372–4.
11. Astra Pharmaceutical Products, Inc. Xylocaine: Chemistry, pharmacology and clinical application. Worcester, Massachusetts: Astra Pharmaceutical Products, 1960: 9–18.
12. Stubblefield PG. Control of pain for women undergoing abortion. Int J Gynaecol Obstet 1989;3:131–4.
13. Grimes DA, Cates W Jr. Deaths from paracervical anesthesia used for first-trimester abortion, 1972–1975. N Engl J Med 1976;295:1397–9.[Abstract]
14. Augustinsson LE, Bohlin P, Bundsen P, Carlsson CA, Forssman L, Sjoberg P, et al. Pain relief during delivery by transcutaneous electrical nerve stimulation. Pain 1977;4: 59–65.[Medline]
15. Deen P, Yuelan H. Use of acupuncture analgesia during childbirth. J Tradit Chin Med 1985;5:253–5.[Medline]
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