Anesth Analg 2000;91:408-409
© 2000 International Anesthesia Research Society
REGIONAL ANESTHESIA AND PAIN MEDICINE
The Superiority of Water-Diluted 0.25% to Neat 1% Lidocaine for Trigger-Point Injections in Myofascial Pain Syndrome: A Prospective, Randomized, Double-Blinded Trial
Hiroshi Iwama, MD*, and
Yoichi Akama, MD
*Department of Anesthesiology, Central Aizu General Hospital, Aizuwakamatsu; and
Department of Anesthesiology, South Tohoku Hospital, Iwanuma, Miyagi, Japan
Address correspondence and reprint requests to Hiroshi Iwama, MD, Department of Anesthesiology, Central Aizu General Hospital, 1-1 Tsuruga-machi, Aizuwakamatsu City 965-0011, Japan.
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Abstract
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Implications: Trigger-point injection with a mixture of commercially available 1% lidocaine in sterile distilled water at a ratio of 1:3 compared with 1% lidocaine alone resulted in better efficacy and less injection pain. This simple procedure may be suitable for treatments of a wide range of myofascial pain syndromes.
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Introduction
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Myofascial pain syndromes are commonly found in the shoulder, neck, or low back and are characterized by the presence of hypersensitive points, called "trigger-points." Treatment includes interruption of the pain cycle by penetrating the trigger-point with a needle, by injection of a local anesthetic or saline, or by a cooled spray of the skin, followed by stretching of the muscle (1). Also, intra- or subcutaneous injection of sterile distilled water has been reported to be effective for low back pain during labor or neck and shoulder pain in whiplash syndrome (2–5), and one report (4) recommended application for other acute or chronic trigger-point pain syndromes. However, water injection causes an intense burning pain lasting a few minutes. During our clinical practice, we discovered that mixing commercially available local anesthetic of 1% lidocaine (ASTRA Japan, Osaka, Japan) with water in a 1:3 ratio causes almost no injection pain and is effective in treating myofascial pain. To clarify the effect of this water-diluted 0.25% lidocaine, we compared its effects with that of neat 1% lidocaine in volunteers with myofascial pain in the shoulder.
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Methods
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After approval of the Institutional Committee of Central Aizu General Hospital, 20 adult volunteers, who were nursing personnel of this hospital, with chronic myofascial pain to the same degree in both shoulders were enrolled in this study. Volunteers with pain caused by organic musculoskeletal disabilities were excluded.
All volunteers had trigger-points in the bilateral suprascapular regions with moderate pain. After disinfecting the skin with an alcohol swab at the most painful trigger-point, 2 mL of a mixture of 0.5 mL 1% lidocaine and 1.5 mL water was injected IM into one side of the trapezius muscle by using a 25-gauge needle in a randomized, double-blinded manner. The other side of the trapezius muscle at the trigger-point received 2 mL 1% lidocaine. For both injections, the subject was asked to grade the pain score on injection as: no pain = 1; mild pain = 2; moderate pain = 3; and severe pain = 4. Regarding the effect of either injection, baseline was considered an improvement score of 4. The effect after the injection was graded as almost complete pain relief = 1; good relief = 2; slight relief = 3; no change = 4; and aggravation = 5. By using this improvement scoring system, the condition of each shoulder was self-assessed 10 min after the injection and each day for 1 to 14 days.
A comparison of the injection pain score between water-diluted 0.25% lidocaine (lidocaine/water) and 1% lidocaine was analyzed by using the Mann-Whitney U-test. A comparison of the time course in the improvement score between the treatments was analyzed by using repeated measure analysis of variance. The time course of improvement after either treatment was analyzed by using the Friedman test, followed by the Wilcoxon signed rank test with Bonferroni correction, in which the preinjection score was compared with other scores. P < 0.05 was considered significant. Data were presented as mean ± SD (range).
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Results
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The age, weight, and height of the volunteers was 35 ± 9 (20–51) yr, 59 ± 10 (43–80) kg, and 160 ± 8 (151–175) cm, respectively. Six volunteers were men and 14 were women. Injection of lidocaine/water was applied to the left shoulder in 10 volunteers and to the right shoulder in 10 volunteers, and injection of 1% lidocaine was applied similarly to the opposite shoulder.
The injection pain score was 1.3 ± 0.2 (1–2) after the injection of lidocaine/water and 3.0 ± 0.4 (2–4) after the injection of 1% lidocaine, showing significantly less pain in the former. The time course of the improvement score after either injection is shown in Figure 1. There was a significant difference between the injection of lidocaine/water and 1% lidocaine, with a greater improvement in lidocaine/water. Also, the improvement score returned to pretreatment levels within 7 days in 1% lidocaine, whereas the injection of lidocaine/water resulted in significant improvement for at least 14 days.
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Figure 1. Time course of the improvement score after injection of 1% lidocaine or water-diluted 0.25% lidocaine. Scores are 1 = almost complete pain relief, 2 = good relief, 3 = slight relief, 4 = no change from precondition, and 5 = aggravation. *P < 0.05 versus preinjection score. Values are mean ± SD.
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Discussion
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Our study demonstrated that a mixture of 1% lidocaine with water at a ratio of 1:3 causes less injection pain than 1% lidocaine alone and has a greater improved effect on myofascial pain in the shoulder. We had routinely treated patients with a variety of myofascial pain using a local anesthetic injection at the trigger-point, but the effect in many patients was transient. Although the subcutaneous injection of water seemed to be more effective, many patients rejected subsequent injection because of its severe pain. These problems were almost resolved after clinical application of our mixture. Because the solution used is a mixture of safe drugs and the dose of 1% lidocaine is reduced markedly, it would not be possible to incur complications from the injectate itself. Although we used 1% lidocaine in this study, 1% mepivacaine seems to have the same effect, based on our experience. However, other considerations, such as the optimal concentration or type of local anesthetic, and the ratio of anesthetic to water, have not yet been evaluated. Regarding other treatments such as dry needling or saline injection (1), although some reports (6,7) described good results, their superiority to local anesthetic injection has not been recognized (1,8,9). Thus, our mixture may be more effective than not only local anesthetic injection but also other procedures.
The mechanism by which injection of water-diluted 0.25% lidocaine causes less injection pain and better efficacy for myofascial pain is unknown. The pain caused by local anesthetic injection may be a result of slight acidity and of the water injection’s low osmotic pressure. Because 1% lidocaine is mixed with water at a ratio of 1:3, the pH reaches neutrality and the osmotic pressure is decreased markedly. Byrn et al. (5) suggested that the effect of water injection is caused by its stimulation of C fibers, which results in severe injection pain but evokes long-lasting pain relief. Although the injection pain of water-diluted 0.25% lidocaine is reduced, the improvement may be attributed to the similar mechanism of water.
In conclusion, trigger-point injection with a mixture of 1% lidocaine with water at a ratio of 1:3 is more effective than injection with neat 1% lidocaine. We hope that our new procedure is reexamined in the treatment of various myofascial pain syndromes.
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References
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Sola AE, Bonica JJ. Myofascial pain syndromes. In: Bonica JJ, ed. The management of pain. 2nd ed. Philadelphia:Lea and Febiger, 1990:352–67.
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Martensson L, Wallin G. Labor pain treated with cutaneous injections of sterile water. a randomized controlled trial. Br J Obstet Gynaecol 1999;106:633–7.[Medline]
-
Labrecque M, Nouwen A, Bergeron M, Rancourt JF. A randomized controlled trial of nonpharmacologic approaches for relief of low back pain during labor. J Fam Pract 1999;48:259–63.[ISI][Medline]
-
Byrn C, Borenstein P, Linder LE. Treatment of neck and shoulder pain in whip-lash syndrome patients with intracutaneous sterile water injections. Acta Anaesthesiol Scand 1991;35:52–3.[Medline]
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Byrn C, Olsson I, Falkheden L, et al. Subcutaneous sterile water injections for chronic neck and shoulder pain following whiplash injuries. Lancet 1993;341:449–52.[Medline]
-
Han SC, Harrison P. Myofascial pain syndrome and trigger-point management. Reg Anesth 1997;22:89–101.[ISI][Medline]
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Frost FA, Jessen B, Siggaard-Andersen J. A control, double-blind comparison of mepivacaine injection versus saline injection for myofascial pain. Lancet 1980;1:499–500.[Medline]
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Hong CZ. Lidocaine injection versus dry needling to myofascial trigger point: the importance of the local twitch response. Am J Phys Med Rehabil 1994;73:256–63.[ISI][Medline]
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Hameroff SR, Crago BR, Blitt CD, et al. Comparison of bupivacaine, etidocaine, and saline for trigger-point therapy. Anesth Analg 1981;60:752–5.[Abstract/Free Full Text]
Accepted for publication April 13, 2000.
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Abstract
Introduction
