Pretreatment of Lacerations with Lidocaine, Epinephrine, and Tetracaine at Triage: A Randomized Double-blind Trial

OBJECTIVE: Pretreatment of lacerations with topical anesthetics reduces the pain of subsequent anesthetic injection yet requires time. This study was conducted to determine the ability of triage nurses to identify lacerations necessitating closure and pretreat them with a topical anesthetic and to compare the pain levels of lidocaine injection in lacerations pretreated with LET (lidocaine 2%, epinephrine 1:1,000, tetracaine 2%) vs a placebo. METHODS: This was a double-blind, randomized clinical trial that included consecutive emergency department patients aged > or = 1 year with clean, non-bite lacerations < or = 6 hours old. At triage the lacerations were randomized to LET solution or a placebo containing epinephrine 1:1,000. At examination an emergency practitioner assessed the laceration edges for the presence of blanching and adequacy of anesthesia to a 27-gauge needlestick. At the practitioner's discretion, supplemental lidocaine was infiltrated through the wound and the patient (or guardian) recorded the pain of infiltration on a 100-mm visual analog scale marked "most pain" at the high end. The mean levels of pain of lidocaine infiltration were compared between groups with a t-test and the proportions of adequately anesthetized wounds were compared with a chi2 test. A sample of 40 patients had 80% power to detect a 20-mm between-group difference in the pain of injection (alpha = 0.05). RESULTS: Of 43 patients enrolled (mostly children and males), 22 received LET and 21 placebo. The groups were similar for baseline characteristics. Lacerations in the LET group were more frequently adequately anesthetized (46% vs 14%, p = 0.03), and LET patients experienced less pain from injection than controls (22 mm vs 42 mm, p = 0.02). CONCLUSIONS: Application of LET by triage nurses is more effective than placebo in adequately anesthetizing simple lacerations in normal hosts and decreases the pain of local anesthetic infiltration.     

Digital versus Local Anesthesia for Finger Lacerations: A Randomized Controlled Trial

Objectives To compare the pain of needle insertion, anesthesia, and suturing in finger lacerations after local anesthesia with prior topical anesthesia with that experienced after digital anesthesia. Methods This was a randomized controlled trial in a university‐based emergency department (ED), with an annual census of 75,000 patient visits. ED patients aged ≥8 years with finger lacerations were enrolled. After standard wound preparation and 15‐minute topical application of lidocaine‐epinephrine‐tetracaine (LET) in all wounds, lacerations were randomized to anesthesia with either local or digital infiltration of 1% lidocaine. Pain of needle insertion, anesthetic infiltration, and suturing were recorded on a validated 100‐mm visual analog scale (VAS) from 0 (none) to 100 (worst); also recorded were percentage of wounds requiring rescue anesthesia; time until anesthesia; percentage of wounds with infection or numbness at day 7. Outcomes were compared by using Mann‐Whitney U and chi‐square tests. A sample of 52 patients had 80% power to detect a 15‐mm difference in pain scores. Results Fifty‐five patients were randomized to digital (n= 28) or local (n= 27) anesthesia. Mean age (±SD) was 38.1 (±16.8) years, 29% were female. Mean (±SD) laceration length and width were 1.7 (±0.7) cm and 2.0 (±1.0) mm, respectively. Groups were similar in baseline patient and wound characteristics. There were no between‐group differences in pain of needle insertion (mean difference, 1.3 mm; 95% confidence interval [CI] =?17.0 to 14.3 mm); anesthetic infiltration (mean difference, 2.3 mm; 95% CI =?19.7 to 4.4 mm), or suturing (mean difference, 7.6 mm; 95% CI =?3.3 to 21.1 mm). Only one patient in the digital anesthesia group required rescue anesthesia. There were no wound infections or persistent numbness in either group. Conclusions Digital and local anesthesia of finger lacerations with prior application of LET to all wounds results in similar pain of needle insertion, anesthetic infiltration, and pain of suturing.     

Does the Use of Topical Lidocaine,Epinephrine, and Tetracaine Solution Provide Sufficient Anesthesia for Laceration Repair?

Objective: To determine: 1) the effectiveness of lidocaine, epinephrine, and tetracaine (LET) solution in eliminating or reducing the pain experienced in suturing superficial lacerations in adult patients; and 2) the effectiveness of LET in reducing the pain of local anesthetic injection.
Methods: A prospective, randomized, double-blind study in which 60 adult patients with superficial lacerations were entered was conducted in the ED of a community-based teaching hospital affiliated with the University of Toronto. Following application of the LET or placebo (sterile water) solution to the laceration, a visual analog pain scale was recorded by the patient upon needle probing of the wound margin. If probing was painless, the laceration was repaired using LET alone. If injection of local anesthetic was required, an additional pain scale was elicited to quantify the attenuation of the pain of injection by the prior application of LET.
Results: Pain scale values on needle probing were significantly reduced in the LET group vs the placebo group (medians of 4.0 vs 5.0 cm, respectively; p < 0.05). Only 13 of the 30 patients in the LET group required additional anesthetic, while all 30 patients in the placebo group requested local anesthetic. Pain scale values on injection of local anesthetic were not significantly different between the LET and placebo groups (medians of 3.5 vs 5.0 cm, respectively; p = 0.09), although there was a trend for lower pain scale values for those patients who received LET. No adverse effects were noted after the application of either LET or placebo solution. Follow-up was achieved for 54 of 60 patients with only 1 complication (a wound infection) reported in the LET group.
Conclusions: Significantly fewer patients require an injectable anesthetic when LET is applied. Those who do require an injection may experience less discomfort. These advantages should be balanced against the 20 to 30 minutes necessary for the LET to take effect.     

Principles of office anesthesia: part II. Topical anesthesia

The development of topical anesthetics has provided the family physician with multiple options in anesthetizing open and intact skin. The combination of tetracaine, adrenaline (epinephrine), and cocaine, better known as TAC, was the first topical agent available for analgesia of lacerations to the face and scalp. Cocaine has been replaced with lidocaine in a newer formulation called LET (lidocaine, epinephrine, and tetracaine). For analgesia to nonintact skin, LET gel is generally preferred over TAC because of its superior safety record and cost-effectiveness. EMLA (eutectic mixture of local anesthetics) is perhaps the most well-known topical anesthetic for use on intact skin. EMLA can be used to anesthetize the skin before intramuscular injections, venipuncture, and simple skin procedures such as curettage or biopsy. To be fully effective, EMLA should be applied at least 90 minutes before the procedure. ELA-Max is a new, rapidly acting topical agent for intact skin that works by way of a liposomal delivery system and is available over the counter. Other delivery vehicles for topical anesthesia currently in development, including iontophoresis and anesthetic patches, may one day give patients and physicians even more flexibility.     

Does Topical Lidocaine Attenuate the Pain of Infiltration of Buffered Lidocaine?

Objective: To determine whether topical lidocaine attenuates the pain of buffered lidocaine infiltration.
Methods: This was a prospective, randomized, double-blind, placebo-controlled trial conducted at a university-based ED. The subjects were adults who had lacerations being repaired using local anesthesia. Two 0.5-mL injections of buffered lidocaine were given in a standardized manner. The first was given prior to application of topical study solution. The second was given on the opposite side of the laceration after topical application of study solution, which was 5 mL of either 2% lidocaine or saline placebo. The pain of each infiltration was measured using a visual analog pain scale. Pain scores were calculated and compared using a Wilcoxon test with significance defined as p 0.05.
Results: A total of 54 subjects participated; 29 received lidocaine topically and 25 received placebo. The groups were similar with respect to age, gender, wound length, wound location, and initial pain score. Pain scores decreased by 11.6 ± 18.6 mm for lidocaine and 10.9 ± 20.9 mm for placebo (p > 0.5). The study had the power to detect a 15-mm pain score difference (α = 0.05 and β = 0.20) on a 100-mm scale.
Conclusion: Topical 2% lidocaine does not attenuate the pain of infiltration of buffered lidocaine more than does topical normal saline. Investigation of other topical anesthetics with and without epinephrine in conjunction with buffered lidocaine is warranted.     

Patterns of Use of Topical Skin Adhesives in the Emergency Department

Objectives: The objective was to determine patterns of use of topical skin adhesives (TSA) for laceration repair. The authors hypothesized that TSA use would be more common in children and facial lacerations. Methods: This was a structured retrospective chart review. The setting was a suburban, university‐based emergency department (ED) with an emergency medicine (EM) residency; the annual census is 85,000 visits. Charts from consecutive patients presenting with lacerations in the summer of 2008 (June 2008 through August 2008) were reviewed. Demographic, clinical, and wound characteristics were extracted from electronic medical records by trained investigators using structured data collection forms. Characteristics of lacerations repaired with TSA or other closure devices were compared with bivariate and multivariate analyses using odds ratios (ORs) and 95% confidence intervals (CIs). Results: A total of 755 patients presented to the ED with lacerations over the study period, of whom primary closure was used in 667; nine were excluded because the method of closure was unknown. The most common methods of laceration closure were sutures (485), adhesives (88), and staples (86). Adhesives were used to close 27% of facial lacerations, compared to 4% of all other body locations (difference = 23%, 95% CI = 18% to 29%), and in 20% of pediatric versus 8% of adult lacerations (difference = 13%, 95% CI = 7% to 18%). Adjustment for other potential patient and wound characteristics showed that adhesives were more likely to be used to close facial lacerations (OR = 10.0 CI, 95% CI = 5.5 to 18.0) and lacerations in children (OR = 1.8, 95% CI = 1.1 to 3.0) and less likely to be used as laceration length increased (OR = 0.6, 95% CI = 0.4 to 0.8). Adhesive use was not statistically associated with patient sex or race, laceration edges or shape, or the need for deep sutures. Forty‐three percent of adhesive wounds were closed with no anesthetic, and a topical agent was used in another 48%. In contrast, a local anesthetic agent was injected in 87% of sutured wounds (p < 0.001) and 73% of stapled wounds (p < 0.001). Conclusions: Topical skin adhesives are used more often for children, facial lacerations, and short lacerations. Use of adhesives may improve patient comfort as need for injecting a local anesthetic is reduced. ACADEMIC EMERGENCY MEDICINE 2010; 17:670–672 © 2010 by the Society for Academic Emergency Medicine     

Comparison of tetracaine-adrenaline-cocaine (TAC) with topical lidocaine-epinephrine (TLE): Efficacy and cost

Topical anesthesia in the form of TAC (tetracaine, adrenaline, cocaine) solution has been used for wound repair. This pilot study was designed to determine if the topical anesthesia achieved using a mixture of lidocaine (5%) and epinephrine (1:2000) (TLE) is equivalent to the topical anesthesia obtained using a solution of tetracaine (0.5%), epinephrine (1:2000), and cocaine (10.4%) (TAC). A prospective, randomized, doubleblind trial was carried out from May 1992 to August 1992 at a community-based teaching hospital Emergency Department (ED) that receives 50,000 annual visits. Patients with facial or scalp lacerations suitable for topical anesthesia presenting to the ED were included when study physicians were in attendance. Exclusion criteria included the presence of a sensory altering substance (eg, ethanol), age younger than two years, hypertension, pregnancy, allergy to any of the study's pharmacological agents, wounds greater than six hours old, grossly contaminated wounds, and wounds longer than six centimeters. Either a TAC or TLE solution was applied to lacerations before suturing. The laceration was repaired and the patient or physician evaluated the degree of pain from the procedure by using a standardized visual pain scale. A total of 35 patients were studied. Seventeen patients were in the TLE group; 18 in the TAC group. The mean ages were compared and found to be similar (P = .40) between the two test groups. The pain scale values, the diameter of tissue blanch around laceration (halo size), and the time to laceration repair from the onset of application of anesthetic were compared and no difference was shown between the TAC and TLE groups. The correlation between the pain scores and the halo size was determined. In the TLE group, a small halo size was associated with a higher pain scale score; in the TAC group this correlation was not apparent. TLE is equivalent to TAC in many respects, especially in producing topical anesthesia. In an average month, 4.6% of the patients seen in the ED of the study site have facial and scalp lacerations amenable to topical anesthesia. The annual cost savings from using TLE instead of TAC is estimated to be $60,000 at the institution studied. The TLE solution also eliminates the potential toxicity from cocaine and tetracaine.     

Topical Tetracaine Attenuates the Pain of Infiltration of Buffered Lidocaine

Objective: To determine whether topical tetracaine attenuates the pain of buffered lidocaine infiltration.
Methods: A prospective, randomized, double-blind trial was conducted involving adults with lacerations being repaired following local anesthesia. Two 0.5-mL injections of buffered lidocaine were given in a standardized manner. Injection 1 was given prior to application of topical study solution. Injection 2 was given on the opposite side of the laceration after topical application of a study solution that was 4 mL of either tetracaine or normal saline. Pain of each infiltration was measured using a visual analog pain scale. Pain score differences (injection 1 - injection 2) were compared for the 2 study solutions using a Wilcoxon 2-sample signed-rank test.
Results: Of 57 subjects studied, 29 received tetracaine and 28 received saline. The groups were similar in age, gender, wound length, wound location, and initial pain score. Pain scores decreased significantly in the tetracaine group as compared with the saline group. The median pain score difference for tetracaine was 12.0 mm, with an interquartile range (IQR) of 2 to 43 mm, as compared with 2 mm, with an IQR of —17 to 21 mm for saline (p = 0.048).
Conclusion: Topical tetracaine attenuates the pain of infiltration of buffered lidocaine.     

Lidocaine via lontophoresis in laceration repair: A preliminary safety study

Iontophoresis is a painless technique for topical anesthesia that uses an electric field to drive charged ions across an epithelial surface. The safety of this technique for laceration repair has never been demonstrated. The purpose of this study was to investigate the effect of iontophoretic fields on rapidly proliferating cells involved in laceration wound healing. The study was a prospective single-blinded animal study using a guinea pig model. Twelve guinea pigs each received four induced, uncontaminated lacerations. Each guinea pig was randomly assigned to 1 of 3 groups (4 guinea pigs in each group). One group received lidocaine via iontophoresis, one group received injected lidocaine, and one group received half iontophoresis and half injected lidocaine. After anesthetic treatment, wounds were then repaired in a standard fashion. The wounds were examined grossly on a daily basis and on day 10 the incised skin containing the laceration was examined by a pathologist blinded to the treatment group. A total of 48 wounds were assessed for wound healing, 24 of which received lidocaine via iontophoresis and 24 lidocaine via injection. The power of the study to determine a 40% difference between the two groups was 0.8. There was significantly more granuloma and granulation tissue formation in the iontophoresis group than in the injected lidocaine control group (P = .0004, Fisher's exact test). There were no statistically significant differences in degree of inflammation between the two groups (lidocaine via injection v lidocaine via iontophoresis) measured by amount of dermal fibrosis (P = .14, Fisher's exact test), giant cell formation (P = .21, Fisher's exact test), and presence of acute and/or chronic inflammation (P = .17, Wilcoxon's rank sum test). Wound healing proceeded normally with 100% in both groups having normal scar formation and healing at day 10. In conclusion, iontophoresis appears to be a safe method of anesthesia delivery in this guinea pig model with lacerations. Increased granuloma and granulation tissue formation may indicate an enhancement of wound healing via iontophoresis.     

Comparison Trial of Four Injectable Anesthetics for Laceration Repair

Objectives: To compare four injectable anesthetics (buffered 1% lidocaine, buffered 1% lidocaine with epinephrine, plain 1% lidocaine with epinephrine, and 0. 5% diphenhydramine with epinephrine) for pain of infiltration and effectiveness of anesthesia during suturing of minor lacerations. Methods: A prospective, randomized, double-blind, comparison trial of the above agents was performed in an urban ED; adults with simple linear lacerations without vascular compromise were enrolled. Physicians and patients ranked the pain of injection and suturing according to a 10-cm visual analog scale (VAS). Fisher's exact and Kruskal-Wallis tests were used to compare demographic data, and Kruskal-Wallis and Newman-Keuls tests were used in analysis of VAS rankings. The power of the study was 0. 8 to detect a 1. 4-cm difference in VAS readings, and 0. 9 to detect a 1. 7-cm difference. Results: Seven of 200 enrolled patients were excluded due to improper data collection and 13 were removed from final statistical analysis due to need for additional anesthetic (treatment failures), leaving 180 subjects for final analysis. Demographic data were similar for the four groups (p > 0.05). Diphenhydramine with epinephrine was significantly more painful to inject than was buffered lidocaine or buffered lidocaine with epinephrine, according to both the patients (p = 0.0003) and the physicians (p = 0.0037). The two buffered compounds were slightly less painful to inject than was lidocaine with epinephrine, but statistical comparisons did not reach significance. For anesthesia effectiveness, lidocaine with epinephrine and buffered lidocaine with epinephrine were statistically better than buffered lidocaine or diphenhydramine with epinephrine (p = 0.0001 for the patients and the physicians). Conclusions: Buffered lidocaine with epinephrine and lidocaine with epinephrine were more effective anesthetics during suturing, according to both the physicians and the patients. There was a tendency toward less pain with infiltration in buffered solutions, compared with plain lidocaine with epinephrine, but the comparisons did not reach statistical significance. Diphenhydramine with epinephrine was more painful to inject than were buffered lidocaine with epinephrine and lidocaine with epinephrine, and was less effective anesthetically than the other three solutions.     

Warmed versus room temperature saline for laceration irrigation: a randomized clinical trial

BACKGROUND: Patient comfort is an important part of laceration repair. METHODS: The study was a randomized single-blind cross-over trial in which each participant received 250 ml warmed and 250 ml room temperature saline irrigation in simple linear wounds after a local anesthetic was instilled. The solutions and the order of irrigation (warmed first versus second) were separately randomized with a washout period between. Investigators obtaining scores were blinded. Participants determined preferred solution, whether the solution was soothing, and which caused the most discomfort. Participants rated the pain of irrigation using separate Visual Analog Scale scores. RESULTS: Thirty-eight patients were enrolled in the study. Significantly more preferred warmed to room temperature solutions (difference, 34%; 95% confidence interval, 5.7-63). A Wilcoxon signed-rank test for paired data showed no order effect (P = 0.49) or difference in pain measured according to the Visual Analog Scale (P = 0.082). CONCLUSION: Warmed saline was more comfortable and soothing than room temperature saline as a wound irrigant among patients with linear lacerations.     

Comparing lignocaine-adrenaline-tetracaine gel with lignocaine infiltration for anesthesia during repair of lacerations: A randomized trial

BACKGROUND:

This study aimed to compare the topical anesthetic lignocaine, adrenaline, and tetracaine (LAT) (4% lignocaine, 1:2 000 adrenaline, 1% tetracaine) with the conventional lignocaine infiltration(LI) for repair of minor lacerations, for the comfort of anesthetic administration, efficacy, adverse effects and cost.

METHODS:

This was a prospective randomized clinical trial. Forty Asian patients who required toilet and suture for minor lacerations in the emergency department of the Singapore General Hospital over a 4-month period. The patients were assigned randomly to 2 arms of treatment. The first was the LAT gel group who had LAT gel applied to the laceration prior to suturing. The second was the control group in whom the anesthetic administered was lignocaine infiltration (LI) via a syringe. The pain of the process of administering anesthetic and efficacy of anesthesia were scored using the visual pain scale included within. The efficacy of LAT vs. lignocaine infiltration as an anesthetic prior to the toilet and suture of minor lacerations and complications of therapy.

RESULTS:

Twenty patients were randomized to LAT gel and 16 to LI on an intention to treat analysis. The mean pain score by patients in the LAT gel group was 2.5 (0.52 SE), and 2.5 (0.58 SE) in the LI group. The pain score for pain during application of the anesthetic was 1.5 (0.40) in the LAT gel group, and 3.5 (0.46) in the LI group. There was no difference in complications between the LAT and LI groups

CONCLUSION:

LAT gel prior to the toilet and suture of minor lacerations is proven to be as efficacious as LI in terms of patient comfort and effectiveness of anesthesia. The complications are also comparable to those treated with LI.KEY WORDS: Lignocaine infiltration, Lacerations, Emergency department, Pain score     

Minimizing the pain of local infiltration anesthesia for wounds by injection into the wound edges

This study on low contamination wounds was conducted to compare the pain of local infiltration anaesthesia administered into the skin surrounding the wound with administration directly into the incised edges of the wound. Eighty-one adult patients were randomized by date of presentation to receive infiltration anesthesia by one of the two methods. Pain of anesthetic administration was rated on a visual analogue scale and recorded as a pain score in millimeters. The results demonstrated that the average pain score for infiltration into the wound was significantly lower than the average pain score for infiltration into skin surrounding the wound.     

Combination of topical EMLA with local injection of lidocaine: superior pain relief after Ferguson hemorrhoidectomy

OBJECTIVE: To determine whether a combination of topical anesthetic (EMLA) and local injection with lidocaine is better than lidocaine alone for pain relief after Ferguson hemorrhoidectomy. METHODS: Sixty patients scheduled for hemorrhoidectomy were randomized into 2 groups: (1) control group (CG, n=30) received neomycin ointment (5 g), and (2) EMLA group (EG, n=30) received EMLA (5 g), both agents applied topically after surgery. Before the surgical incision was made, lidocaine (10 mL of a 1% solution) was locally injected into all 60 patients. After surgery, analgesics were provided when necessary. The visual analog scale score was recorded at 4 time points: (1) upon arrival in the postanesthesia room, (2) 2 hours after arriving in the postanesthesia room, (3) between 9 and 10 PM on the first postoperative evening, and (4) on the first postoperative morning. The frequency of meperidine requests, 1-time catheterizations for urinary retention, and patient satisfaction with postoperative pain management, were also recorded. RESULTS: The median visual analog scale scores and cumulative dosages of meperidine were significantly lower in the EG than the CG (P<0.05). Patient satisfaction with postoperative pain control was also significantly higher in the EG than the CG (P<0.01). No systemic complications occurred. DISCUSSION: EMLA is considered a breakthrough in cutaneous analgesia, capable of reducing pain in many cutaneous procedures. Because Ferguson hemorrhoidectomy has been performed for years with ongoing concerns over postoperative pain, we felt that using EMLA could lower postoperative pain intensity and the number of requests for additional medication.     

Comparison of topical anaesthesia methods for venous cannulation in adults.

A prospective, randomized clinical trial was performed in order to assess the efficacy and side-effects of commonly used topical anaesthesia methods in adults receiving peripheral venous cannulation. The study was double-blinded to the degree that the methodologies allowed. One hundred and fifty healthy adults undergoing elective surgery were allocated at random to five groups: EMLA cream, ethyl chloride spray, intracutaneous infiltration with 2% lidocaine, placebo cream and no treatment. Venipuncture was performed with a 18G cannula on the dorsal side of the hand. Puncture pain and pain caused by the topical treatment itself were measured using a visual analogue scale (VAS, range: 0-100 mm). Haemodynamic response, difficulties in performing the puncture and side-effects were recorded. All analgesic techniques were well tolerated. Haemodynamic response and degree of puncture difficulty showed no differences among the groups. Puncture pain (median mrnVAS) following infiltration (1.0) and EMLA (10.0) was significantly lower than no treatment (30.0) or placebo (30.0). The benefit of local infiltration was altered by injection pain (11.5). Spray did not significantly lower puncture pain (26.5) and, in addition, was associated with discomfort (10.5). In adults, EMLA cream significantly reduces puncture pain and represents an acceptable alternate method for topical anaesthesia in venous cannulation. Local lidocaine infiltration is impaired by applicational pain, whereas spraying the puncture site with ethyl chloride has no analgesic benefit.     

Anesthetic properties and toxicity of bupivacaine and lidocaine for infiltration anesthesia

The purpose of this study was to measure the toxicity and anesthetic properties of two anesthetic agents, bupivacaine and lidocaine. These anesthetic agents did not damage tissue defenses or invite infection in experimental animals. In addition, the pain of subdermal injection, the onset of anesthesia, and the frequency of satisfactory anesthesia in human volunteers were remarkably similar. Because the duration of anesthesia induced by bupivacaine was nearly four times longer than that by lidocaine, bupivacaine is recommended for infiltration anesthesia of lacerations treated in the emergency department.     

Local Anesthesia for Lacerations: Pain of Infiltration inside vs outside the Wound

Objective: To compare the pains of infiltration of a local anesthetic for simple lacerations when used from within the wound vs through intact skin.
Methods: A randomized, prospective, single-blind, experimental protocol was conducted on a convenience sample of adults with simple lacerations. Subjects received two 0.5-mL injections of buffered lidocaine in each of the sites being compared. Immediately following each injection, pain was measured using a visual analog pain scale. Pain scores were converted to a numerical score and analyzed by a Wilcoxon signed-rank test. Subjects also were asked which injection hurt more, the first or the second (analyzed by a x ² test).
Results: A total of 63 subjects were enrolled. The first injection was within the wound and the second injection through intact skin (group 1) for 32 patients, and the order was reversed for 31 patients (group 2). Median pain scores for all inside-the-wound injections (14 mm) were lower than those with intact skin injections (37 mm; p < 0.0001). In group 1, 4 subjects reported the first injection (within wound) hurt most, 23 thought the second (intact skin) hurt most, and 5 found no difference. In group 2, 18 subjects reported the first injection (intact skin) hurt most, 5 believed the second injection (within wound) hurt most, and 8 found no difference, p < 0.0001.
Conclusion: Local anesthesia is less painful when injected from within a laceration as compared with intact skin.     

Pain comparison of unbuffered versus buffered lidocaine in local wound infiltration.

The purpose of this study was to compare the pain of infiltration between unbuffered lidocaine and buffered lidocaine in a traumatic laceration. Solutions of unbuffered 1% lidocaine and buffered 1% lidocaine were randomly assigned to Site I or Site II of a single laceration for each subject, with the patient serving as self-control. Pain scores were recorded for each site, and an anesthetic preference was determined for each patient. It was found that buffered lidocaine had a preference ratio of 3.0 over unbuffered lidocaine (95% confidence interval, 1.86 to 4.84; P less than 0.0001). It was also found that Site I was preferred more often than Site II regardless of which medication was used. The conclusion is that buffered lidocaine is preferred over unbuffered lidocaine and that the order of injection is an important factor in trials that involve multiple sequential injections in the same patient.     

The Effects of Warming and Buffering on Pain of Infiltration of Lidocaine

OBJECTIVES: To investigate the effects of warming vs buffering, and warming with buffering, on the pain of lidocaine infiltration. METHODS: A randomized, double-blind clinical trial was conducted using volunteers aged 18 years or more and without an allergy to lidocaine. The study consisted of two parts, each comparing two solutions. The solutions for Part I were warm (38.9 degrees C; 102 degrees F) plain lidocaine and room-temperature buffered lidocaine. Warm buffered lidocaine and room-temperature buffered lidocaine were used for Part II. The subjects received two standardized 0.5-mL intradermal injections, one study solution in each forearm. Immediately after each injection, pain was assessed using a 100-mm visual analog pain scale. Pain scores were analyzed by the sign test, with significance defined as p < 0.05. RESULTS: Part I (n = 10): Nine subjects reported room-temperature buffered lidocaine to be less painful than warm plain lidocaine. Mean pain scores were 28 mm lower for room-temperature buffered lidocaine than they were for warm plain lidocaine (p < 0.01). Part II (n = 24): Eleven subjects found warm buffered lidocaine to be the least painful, 11 reported room-temperature buffered lidocaine to be the least painful, and two reported no difference. A mean pain score difference of 2.1 mm favoring warm buffered lidocaine was not statistically significant. Part II had a power of 80% to detect a 10-mm difference between the two solutions at alpha = 0.05. CONCLUSION: To reduce the pain of lidocane infiltration, buffering is more effective than warming. Warming does not enhance buffering.     

Cutaneous Tape Stripping to Accelerate the Anesthetic Effects of EMLA Cream: A Randomized, Controlled Trial

Abstract. Most medications are not absorbed topically due to the stratum corneum barrier. While effective as a topical anesthetic, EMLA cream is absorbed slowly, delaying its effects for up to one hour, thereby limiting its usefulness.
Objective: To determine whether removal of the cornified layer of the skin by tape stripping (TS) would allow more rapid onset of anesthesia after topical application of EMLA cream prior to IV catheterization (IVC).
Methods: This was a prospective, randomized, controlled trial comparing the levels of pain of IVC 15 minutes after topical application of EMLA cream in patients who had TS vs patients who did not. The setting was a suburban university-affiliated ED. A convenience sample of 68 alert adult patients requiring IVC were enrolled. The primary outcomes measured were pain of IVC and pain of TS using a previously validated 100-mm visual analog scale as well as the IVC success rate.
Results: The pain of IVC was less for TS vs control patients [29.7 mm (95% CI = 20.4 to 39.0 mm) vs 15.9 mm (95% CI = 9.1 to 22.6 mm), p = 0.017]. The mean pain of TS was 4.8 ± 7.4 mm. The IVC success rate for TS vs control patients was 91% vs 74% (p = 0.056). There were no adverse events after TS.
Conclusions: Removal of the cornified layer of the skin resulted in a more rapid anesthetic effect of EMLA cream as evidenced by lower IVC pain scores after TS. The effectiveness of TS for enhanced absorption of other medications should be investigated.