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From the *Department of Anesthesiology and Intensive Care, University Hospital of Toulouse, University Paul Sabatier, Toulouse, France; and Department of Anesthesiology and Critical Care, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania.
Address correspondence and reprint requests to Vincent Minville, MD, Department of Anesthesiology and Intensive Care, University Hospital of Toulouse, Rangueil Hospital-Orthopedic Section, 1, Avenue Jean Poulhès, Toulouse, France. Address e-mail to vincentminville{at}yahoo.fr.
Abstract
BACKGROUND: We evaluated the potential role of an euctectic mixture of local anesthetic (EMLA®) cream application before performing midhumeral block.
METHODS: Sixty patients undergoing surgery distal to the elbow amenable to a humeral block were prospectively recruited for the study. The patients were randomly allocated to 1 of 3 groups: Group E: topical EMLA cream 60 min before block plus 2 mL IV normal saline 5 min before procedure; Group P: topical sham cream plus 2 mL IV normal saline, and Group S: topical sham cream plus 0.1 µg/kg of sufentanil in 2 mL solution IV. Pain experienced during skin puncture, and overall pain for the whole procedure were rated using a 100-mm visual analog scale (0: no pain to 100: worst pain).
RESULTS: Patients in Group E experienced less pain compared with those in Groups P and S (5 ± 3 mm vs 33 ± 20 mm and 30 ± 18 mm, respectively, P < 0.0001). The pain experienced throughout the complete humeral block was more substantial in Group P than in Group E (P = 0.01).
CONCLUSION: The patients who received EMLA cream had less pain with needle puncture as well as throughout the performance of humeral block.
Humeral block allows for surgical intervention from elbow to hand with a high rate of success and a few side effects (1,2). However, the procedure itself causes patient discomfort, which is typically attenuated by routine sedation (3). Previous studies have evaluated the potentially painful steps involved in regional anesthesia (RA) techniques (i.e., neurostimulation, repeated needle punctures, etc.) none has focused specifically on skin puncture (4–6), a known source of pain in humeral block (7).
EMLA®, a eutectic mixture of two local anesthetics (lidocaine 2.5% and prilocaine 2.5%), provides several millimeters of skin analgesia by diffusion of local anesthetic through the epidermis and the dermis to the nociceptive receptors and nerve endings of the skin. The depth of analgesia depends on how long the cream is applied; 60 min are usually required (8,9).
The goal of the study was to evaluate the potential role of EMLA in decreasing the pain associated with a humeral block in nonsedated patients, both at skin puncture and during the procedure.
METHODS
After approval from the local ethics committee, a prospective, randomized, double-blind study was performed from November 2005 through August 2006 at the University Hospital of Rangueil, Toulouse, France. After providing written informed consent, patients undergoing elective surgery of the hand and/or forearm were randomized, by drawing assignments from an opaque envelope, into 1 of the 3 following groups: Group E: topical EMLA cream 60 min before block plus 2 mL IV normal saline 5 min before procedure; Group P: topical sham cream 60 min before block plus 2 mL IV normal saline, and Group S: topical sham cream 60 min before block plus 0.1 µg/kg of sufentanil in 2 mL solution IV. No patient received local anesthetic skin infiltration. Exclusion criteria included: patient refusal, a contraindication to RA (allergy to local anesthetics, hemostasis disorders, infection localized to the site of puncture, neurologic sensorimotor disorders), contraindication to EMLA (allergy to any of its components, congenital methemoglobinemia, porphyria), emergency surgery, or psychiatric disorder and dementia.
One hour before the block was performed, a nurse from the orthopedic service applied EMLA cream (2.5 g) (Group E), or a sham cream (Groups S and P), to the appropriate site and covered it with a transparent occlusive dressing. To ensure strict adherence to protocol and proper positioning of the dressing, the nurses involved attended three training sessions. The appropriate or inappropriate application of EMLA cream was judged by the anesthesiologist who performed the block in the operating room (OR). EMLA cream application was judged inappropriate if it did not cover the puncture site.
When the patient arrived in the OR, standard monitors were applied and an IV line was started. Five minutes before the humeral block, sufentanil (0.1 µg/kg) (Group S) or normal saline (Groups E and P) was administered IV by an anesthesiologist who did not participate further in the block. Unlike the usual procedure in our OR, none of these patients received midazolam. After an hour of application, the occlusive dressing was removed. The skin puncture was performed after local disinfection. The blocks were performed by anesthesiologists blinded to the patient’s allocation group using a 50-mm, 22-gauge, insulated needle (Stimuplex®, B Braun, Mesungen, Germany) and a nerve stimulator (HNS 11, B Braun, Mesungen, Germany). The nerve stimulator was set to deliver an initial current of 1.5 mA at 2 Hz and 0.1 ms. The humeral block was performed as previously described (7), with the patient in the supine position, the relevant limb abducted and externally rotated, with the elbow flexed at a right angle. After an adequate response to a current of 0.3–0.5 mA, a slow injection of 10 mL of 1.5% lidocaine plus 1:200,000 epinephrine per individual nerve was performed with frequent aspirations.
If the patient became uncomfortable during the humeral block, an IV injection of sufentanil (0.1 µg/kg) was administered. The time it took to perform the block was determined as the time between skin puncture and withdrawal of the needle. Onset of the block was defined as the withdrawal of the needle until development of anesthesia tested by cold sensation in the sensory area of each single terminal nerve. The sedation score was rated from 0 to 2 (0: absence of sedation, 1: eye-opening to verbal command, 2: eye-opening to painful stimulus). After completion of the humeral block, the patients identified the stages of the block (skin puncture, repetitive needle passages, electrostimulation, local anesthetic injection) that were the most unpleasant and quantified their perceived pain by visual analog scale (VAS) by moving a cursor between "no pain" and "greatest pain imaginable" corresponding to a value between 0 and 100 for each of the stages and for the block as a whole. Upon discharge from the postanesthesia care unit, the patients rated their postinterventional satisfaction on a scale of 0–100 (0: no satisfaction, 100: complete satisfaction). They were then asked if they would wish to undergo the same technique in the event of a future intervention. The occurrence of complications was noted postoperatively by the anesthesiologist and secondarily by the surgeon.
Before the study, the necessary sample size was estimated according to the results of previous studies (10,11) and our own recent study comparing humeral and infraclavicular blocks (7). We hypothesized that the pain of skin puncture estimated by VAS would be decreased by 50% after EMLA application compared with that after placebo and sufentanil administration. The calculation of power for a difference of 50% of VAS with a probability level of 0.05 and a power of 0.80 (1 – ß) yielded a sample size of 18 patients per group. Sixty patients were enrolled in anticipation of exclusions in the course of the study. The statistical analysis was performed with Statview® software (version 5.0, CA). Results were expressed as mean ± sd, ratio or percentage. We used 
2 and Student’s t-test, as well as ANOVA. We considered P < 0.05 to be statistically significant.
RESULTS
Sixty patients undergoing elective surgery of the hand and/or forearm under humeral block were included in the study. The occlusive dressing was incorrectly positioned in nine patients (three in each group). Demographic, procedure, and surgical data were comparable among the three groups (Table 1).
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The intensity of pain, evaluated by VAS, for the skin puncture was less intense in Group E than in Group P (5 ± 3 mm vs 33 ± 20 mm, P < 0.0001) and in Group S (30 ± 18 mm, P < 0.0001) (Fig. 1). The pain experienced throughout the entire humeral block was greater in Group P than in Group E (P = 0.01), as well as during repeated needle passages (Fig. 1).
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The satisfaction score was 92% in Group E, 81% in Group P, and 76% in Group S (NS). The majority of patients (90% in all three groups) reported that they would have the same anesthesia for an identical intervention. No complications were noted.
DISCUSSION
This is the first study demonstrating improved patient comfort during RA by electrostimulation with prior application of EMLA cream. We have shown in this study that the pain of skin penetration was significantly less in the group receiving skin anesthesia by EMLA cream compared with that in the groups receiving a placebo and to IV sufentanil injection. This benefit extended to the perceived pain from repetitive needle sticks and to the humeral block procedure as a whole, when compared with placebo.
Some aspects of RA may be inconvenient or unpleasant for the patient. Indeed, multistimulation blocks may cause the patient pain (3,12), which can be significant (13). Furthermore, while fear of needles is a significant cause of patient refusal of RA (14,15), the pain experienced during performance of the block could make the patient reluctant to undergo a similar procedure in the future. Fanelli et al. (16) showed that despite a high success rate with RA, 26% of their patients would not choose the same anesthesia technique again. De Andres et al. (17), on the other hand, showed that 18.1% of patients undergoing RA complain of pain at the puncture site. We did not find any statistically significant difference in satisfaction in our study.
To our knowledge, EMLA cream has not been used to decrease pain at the puncture site in peripheral RA techniques. Only recently has pain related to skin puncture been specifically studied (7). In fact, previous studies sought to identify the most painful step in the block without considering the pain associated with needle punctures (4–6). In these studies, skin anesthesia was performed beforehand by local injection without considering its inherent pain. As this study seems to show, the discomfort associated with skin puncture in nonsedated patients receiving a humeral block is at least as significant as the pain associated with other steps of the technique.
In addition to diminishing the pain associated with skin puncture, EMLA decreased perceived pain for the entire block, including repeated needle passages. The sedation obtained with widely used benzodiazepines and/or opioids improves patient comfort and facilitates performance of RA (3). However, there is individual variation in sensitivity among patients that may lead to excessive sedation, the risk of respiratory depression (18), and early detection of possible complications in these patients (19). We have shown in our study that the use of EMLA leads to decreased pain upon puncture of the skin during RA such that sedation is not required (global VAS <20), even if we did not see adverse effects in patients who received sedation.
The use of EMLA for humeral block analgesia in the ambulatory patient requires prior training for nurses, additional effort, and minor modification to the organization of our clinical service, such as considering the effects of the application time upon patient arrival times and scheduling. In our study, after three demonstration sessions, the occlusive dressing was correctly positioned in 85% of patients.
Our study has some limitations. First, the results may not be generalized to other RA techniques. Second, use of EMLA cream requires an application at least 1 h before the block. That could have been a major drawback compared to eutectic lidocaine–tetracaine, liposome lidocaine, or tetracaine alone. However, the EMLA cream application was performed by a nurse from the orthopedic service, so there was no modification of OR turnover. Conversely, only 85% of patches were well applied. As our objective was to show that EMLA could constitute an alternative to sedation, most clinicians would give IV sedation because it is faster and at least as effective.
In conclusion, skin puncture is a painful first step and a frequent source of stress, but it is essential to the performance of a humeral block. By acting locally, EMLA decreases the pain experienced upon skin puncture, as well as pain throughout the procedure of humeral block, and its use could decrease the necessity for sedation without sacrificing patient discomfort. Its ease of use could lead to its prescription for all RA procedures so as to improve patient acceptance.
Footnotes
Accepted for publication April 19, 2007.
REFERENCES
This article has been cited by other articles:
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  M. J. O'Sullivan Patient Comfort in Regional Anesthesia Anesth. Analg., January 1, 2008; 106(1): 349 - 349. [Full Text] [PDF]
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V. Minville and D. Samson Patient Comfort in Regional Anesthesia Anesth. Analg., January 1, 2008; 106(1): 349 - 350. [Full Text] [PDF]
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