Anesth Analg 2003;97:713-714
© 2003 International Anesthesia Research Society
AMBULATORY ANESTHESIA
The Efficacy of 5% Lidocaine-Prilocaine (EMLA) Cream on Pain During Intravenous Injection of Propofol
A. McCluskey,
B. A. Currer, and
I. Sayeed
Department of Anesthesia, Stepping Hill Hospital, Stockport, United Kingdom
Address correspondence and reprint requests to A. McCluskey, Department of Anesthesia, Stepping Hill Hospital, Stockport, SK2 7JE, United Kingdom. Address e-mail to amccluskey{at}mcmail.com
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Abstract
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Topical anesthesia using 60% lidocaine tape reduces the incidence of propofol injection pain. We conducted a randomized prospective double-blinded placebo-controlled study to assess the analgesic efficacy of pretreatment with topical 5% lidocaine-prilocaine (EMLA) cream in 90 ASA physical status I and II adult patients scheduled to undergo day-case gynecological surgery. Propofol injection pain was not reduced by pretreatment with EMLA cream, whereas the addition of lidocaine to propofol did significantly reduce propofol injection pain compared with the control group (P = 0.002). We conclude that topical anesthesia with EMLA cream applied for 60 min does not significantly reduce propofol injection pain.
IMPLICATIONS: Topical local anesthesia with 60% lidocaine tape reduces the incidence of propofol injection pain. However, we found no reduction after pretreatment with topical 5% lidocaine-prilocaine (EMLA) cream.
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Introduction
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Propofol is a popular IV anesthetic for day-surgery providing smooth induction and rapid recovery from anesthesia. One of its main drawbacks is pain on injection. Although numerous strategies have been described to alleviate propofol injection pain, the most common method in routine clinical practice is mixing lidocaine 10–40 mg to the syringe of propofol immediately before injection (1,2).
The use of topical 60% lidocaine tape has been as effective as the addition of lidocaine 40 mg to propofol in reducing the incidence and severity of injection pain (3,4). The aim of our study was to determine whether topical local anesthesia with EMLA cream (eutectic mixture of lidocaine 2.5%/prilocaine 2.5%; AstraZeneca, London, United Kingdom) had a similar effect on propofol injection pain.
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Methods
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After approval by the local ethics committee and written informed consent, 90 ASA physical status I and II patients aged 18–70 yr presenting for gynecological day-surgery were allocated randomly by sealed envelope into three groups, which are as follows: Control group = placebo cream applied over a wide area to the dorsum of the nondominant hand and distal forearm 60 min before surgery and anesthesia induced with 18 mL of 1% propofol (Diprivan®) mixed with 2 mL of 0.9% saline; EMLA group = EMLA cream applied as described above and anesthesia induced with 18 mL of 1% propofol mixed with 2 mL of 0.9% saline; and Lidocaine group = placebo cream applied as described above and anesthesia induced with 18 mL of 1% propofol mixed with 2 mL of 2% lidocaine. The study cream was applied widely to ensure that when the cannula was inserted, both the initial entry point and final position of the tip of the cannula were well within the area covered by the cream.
None of the patients received premedication. On arrival at the anesthetic room, the cream was completely removed by an anesthetic nurse, and a blinded investigator inserted a 20-gauge cannula into a suitable vein on the dorsum of the nondominant hand. The investigator then asked patients to grade any pain experienced during insertion of the cannula using a 4-point verbal rating scale. Five milliliters of the propofol solution was then injected over 15 s, and patients were asked to grade any associated pain using the same scale as before.
Data from a preliminary pilot study we conducted suggested an incidence of propofol injection pain of approximately 70% using the methodology described above. A power calculation was performed indicating that 28 subjects in each group would be required to detect a reduction in the incidence of propofol injection pain from 70% to 35% (P 
0.05; power 80%). Analyses were performed using SPSS version 7.5 statistical package (SPSS, Chicago, IL). A P value of <0.05 was considered significant.
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Results
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The three study groups were comparable with respect to age, weight, and cream application time (Table 1). EMLA cream significantly reduced the incidence of pain experienced during insertion of the cannula (
2; P = 0.015; Table 2). However, the frequency of propofol injection pain was no different after pretreatment with EMLA cream compared with the control group and was significantly more frequent than in the lidocaine group (2; P = 0.002).
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Discussion
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Addition of lidocaine 10–40 mg to propofol is common in routine clinical practice to reduce associated injection pain. However, addition of lidocaine may destabilize the propofol emulsion with an attendant potential risk of pulmonary fat embolism if droplet size exceeds 5 µm (5). Two studies have suggested that topical local anesthesia using 60% lidocaine tape may obviate the need to premix propofol with lidocaine (3,4). The use of topical local anesthesia also has the dual benefit of decreasing pain caused by the insertion of the IV cannula.
Lidocaine tape is not currently available in the United Kingdom, although EMLA cream is widely used to reduce the discomfort of IV cannulation, particularly in children. Our study is the first to have evaluated the effect of EMLA cream on propofol injection pain in adults. Previous studies of propofol injection pain in children have failed to demonstrate any beneficial effect of EMLA cream (6,7). However, as attenuation of propofol injection pain was not the primary end-point of these studies, it is unlikely that their authors applied EMLA cream as widely as our study protocol dictated to ensure that the final position of the tip of the IV cannula was within the area covered by the cream.
We did not find any reduction in propofol injection pain after pretreatment with EMLA cream 60 min before surgery. Two possible reasons for this may be different application times and concentrations of the topical local anesthetic. In the two studies from Japan (3,4), 60% lidocaine tape was applied for 120 and 150 min, respectively, whereas in our study, 5% EMLA cream was applied for 60 min in accordance with our routine practice. The manufacturer of EMLA cream recommends that the application time should be within the range 1–5 h. It has been suggested that 60 min may not be a sufficient application time for EMLA cream (8,9), and we accept that a longer time might have resulted in a demonstrable analgesic effect of EMLA cream on propofol injection pain. It is also possible that the much larger concentration of local anesthetic in lidocaine tape (60%) compared with that in EMLA cream (5%) may have influenced the rate and extent of absorption of local anesthetic.
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References
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Accepted for publication April 16, 2003.
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Abstract
Introduction
