title: The effectiveness of the eutectic mixture of local anaesthetics (EMLA®) as a primary dressing on painful chronic leg ulcers
Creators: name: Purcell, Anne
Publisher: name: Griffith University
Year: 2018
Subjects: subject: Eutectic mixture
subject: Anaesthetics
subject: Primary dressing
subject: Leg ulcers
subject: EMLA

description: Background: People living with chronic leg ulcers frequently experience moderate to severe wound-related pain with the highest level of pain occurring at dressing change. Wound- related pain is not always able to be alleviated by oral analgesics alone. Persistent poorly- controlled leg ulcer pain physiologically impacts wound healing and prevents timely, effective wound management strategies being implemented which can negatively impact wound healing and health-related quality of life (HRQoL). Topical agents such as morphine gel and ibuprofen foam are used as primary dressings as a strategy for managing chronic leg ulcer pain. Studies investigating ibuprofen foam have shown significant improvement in chronic leg ulcer pain compared to standard care. There is insufficient evidence to suggest morphine gel is effective for chronic leg ulcer pain. Topical local anaesthetics, in particular the eutectic mixture of local anaesthetics (EMLA®), have been used for decades to relieve pain associated with debridement of chronic leg ulcers. However, their effectiveness as a primary dressing for managing chronic wound-related pain is yet to be evaluated. Since there was no known evidence regarding the effectiveness of EMLA® as a primary dressing for painful chronic leg ulcers to relieve wound-related pain and its associated impact on wound healing and HRQoL this feasibility study was conducted. Study aims: The primary aim of this study was to assess the processes, resources, management and scientific aspects of the study to ensure implementation of a larger study is feasible and to generate data that could be used for future sample size calculations. Study feasibility was assessed using the following criteria for determining success: recruitment of at least 80% of eligible patients within 12 months; retention of 80% of participants during the study period and achieving at least 80% adherence to the intervention protocol. Secondary aims were to investigate the effectiveness of the daily topical application of EMLA® as a primary dressing to painful chronic leg ulcers as a pain-relieving strategy and the associated impact on wound healing and HRQoL; and whether improvement in pain levels is associated with reduced need for oral analgesia, particularly opiates. Design: A pilot, parallel group, non-blinded, superior, randomised, controlled trial. There was a 4-week intervention period and a 12-week study period. Setting: Six procedure clinics located in a public community nursing service Central Coast, New South Wales, Australia. Participants: Participants (n = 60) were adult patients with painful chronic leg ulcers of varied aetiology. The preliminary screening criteria included a chronic leg ulcer of more than six weeks duration; pain relieving medications required to manage wound-related pain; and, the participant was able to be treated in a community nursing clinic. Intervention: EMLA® was applied to the chronic leg ulcers daily for four weeks as a primary dressing followed by standard care. Data collection: Feasibility data were collected on human resource requirements, number of home visits, use of consumables and study management including ease of administering data collection instruments. Wound-related pain was measured at baseline and each dressing change; chronic leg ulcer surface areas and HRQoL were measured at baseline, weeks 4 and 12. Outcomes: Feasibility: Although all proposed participants were recruited (n=60) the recruitment rate was lower than expected and it is possible some eligible patients were missed during the screening process. Fifty-four participants remained in the study until completion for a 90% retention rate. Intervention fidelity was influenced by resource availability and participant factors such as increased wound-related pain. Data generated from the primary clinical outcome wound- related pain, was used to calculate the sample size for a larger study. Given two-sided significance of 0.05, a power of 0.8%, effect size 0.45 +/- 0.3 and variability/standard deviation of 2.2 +/- 0.2, 274 to 306 participants will be required for a larger randomised controlled trial. The sizes have been adjusted upwards based on an estimated dropout rate of 10%. However, an effect size of 0.45 is not clinically meaningful so a difference of at least two pain scores on the 11-point pain intensity Numerical Rating Scale used in this study is suggested as a clinically important difference. Recalculation using an effect size of two estimated that 52 participants would be needed to detect a clinically meaningful difference between the treatment and control groups based on pain as the primary outcome. Assuming a dropout of 10%, this figure was adjusted upwards to 58. Wound-related pain: Mean pain scores were similar between the two groups at baseline (p = 0.84). During dressing change, mean pain scores across the 4-week intervention period were significantly lower in the intervention compared to the control group (intervention group: Mean (SD) 3.39 (2.16); control group: Mean (SD) 4.82 (2.27), p = 0.02). Mean pain scores after dressing change were also significantly lower for the intervention group over the 4-week intervention period (intervention group: Mean (SD) 2.71(1.94); control group: Mean (SD) 3.92 (2.03), (p = 0.03). Wound healing and HRQoL: During the intervention period there was no significant difference in wound sizes between groups (intervention group - Median (cm2): 2.4, IQR: 1.3 – 12.7 v control group- Median (cm2): 5.0, IQR: 2.5-9.9; p = 0.05). Mean HRQoL scores for all subscales at baseline, weeks 4 and 12 were similar between groups except for Wellbeing, which was significantly higher in the intervention group at the end of the 4-week intervention period (intervention group - Mean 52.41, SD 24.50 vs. control group- Mean: 38.15, SD 21.25; p = 0.03, d = .62). Conclusion: It is feasible to conduct a larger multisite RCT following modifications to the study protocol. The study findings suggest that daily applications of EMLA® as a primary dressing reduces wound-related pain during and after dressing change, do not inhibit wound healing and may improve a person’s well-being.