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Original articles |
Emergency Department, Royal Childrens Hospital, Murdoch Childrens Research Institute and University of Melbourne, Melbourne, Australia
Correspondence to:
Franz E Babl, MD, MPH, FRACP, FAAP, Paediatric Emergency Physician, Clinical Associate Professor, University of Melbourne, Emergency Department, Royal Childrens Hospital, Parkville, Victoria, Australia 3052; franz.babl{at}rch.org.au
Accepted for publication 24 August 2007
| ABSTRACT |
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Design: Double-blind, randomised, placebo-controlled trial.
Setting: Tertiary childrens hospital emergency department.
Patients and interventions: Children aged between 3 and 17 years with earache and AOM without evidence of perforation were eligible. Patients were randomised to receive either 2% lignocaine or saline eardrops (placebo).
Main outcome measures: Pain scores were measured before and after ear-drop administration. Patient and physician-interpreted pain scores were measured by using the Bieri faces pain scale and visual analogue scale at 10, 20 and 30 minutes. The primary outcome measure was reduction in patient-measured pain scores by 50% from the baseline. Secondary outcome measures were reduction in patient- measured pain scores by 25% or by at least two points. Telephone follow-up occurred after 1 day and 1 week. Analysis was by intention to treat.
Results: 63 children (31 were treated with lignocaine, 32 with placebo) aged 3 to 12 years were enrolled. The groups were demographically and clinically similar, with similar proportions having received analgesia in the preceding 4 hours. Children receiving lignocaine showed significantly lower patient-measured pain scores with a reduction by 50% from baseline at 10 minutes (RR 2.06, 95% CI 1.03–4.11, p = 0.03) and 30 minutes (RR 1.44, 95% CI 1.07–1.93, p = 0.009) but not at 20 minutes (RR 1.35 95% CI 0.88–2.06). The response to lignocaine treatment showed significantly lower patient-measured pain scores for 25% reduction at all time points and for two-point reduction at 10 minutes and favoured lignocaine at 20 minutes and 30 minutes without reaching statistical significance. There were no serious adverse events during the 30 minute follow-up period.
Conclusion: This study suggests that topical aqueous 2% lignocaine eardrops provide rapid relief for many young children presenting with ear pain attributed to AOM. The concurrent use of simple oral analgesia is a likely contributor to effective management of this painful childhood condition.
The optimal management of ear pain associated with AOM has not been well studied,5 and no systematic reviews were available at the time of this study. A Cochrane review published in 2006 has attempted to address this issue.6 The authors concluded that of the four studies that had been conducted, only Hoberman and colleagues study7 addressed the question of efficacy of topical agents for ear pain of otitis media, and that the data were insufficient to reach a conclusion. They asserted the need for high-quality placebo-controlled trials. Hoberman et al7 had reported a double-blind randomised controlled trial (RCT) where 54 participants with AOM were randomised to Auralgan (benzocaine, antipyrine and glycerine) or olive oil (placebo). All patients also received 15 mg/kg of paracetamol. Significant benefit (25% reduction in pain) of Auralgan over the placebo was demonstrated only at 30 minutes (96% Auralgan patients, 70% olive oil placebo, p = 0.02).7 However, the anaesthetic ear drops were favoured at all time points, irrespective of outcome measures used.
Lignocaine hydrochloride is a widely available local anaesthetic with rapid onset (peak effect in 2–5 minutes) and effect duration of 30–45 minutes.8 However, owing to its low lipid solubility it is poorly absorbed through the epidermis of the intact tympanic membrane (TM).9 Lignocaine is described for myringotomy-related anaesthesia with variable results, using a number of techniques to aid penetration of the drug.9–13 None of these lignocaine applications are applicable or practical for emergency department (ED) use in children; however, they do support the safety of low concentration lignocaine application to the TM. Anecdotally, topical aqueous lignocaine does provide relief for pain of AOM and is recommended by the clinical practice guidelines at the authors institution.14 However, there are no data as to lignocaines efficacy for this indication.
We sought to investigate the efficacy of aqueous 2% lignocaine ear drops for relief of pain associated with AOM, in a double-blind, randomised, placebo-controlled trial. Primary outcome measure was a drop in patient-measured pain scores by 50% from the baseline. Secondary outcome measures were a drop in pain scores by 25% or by at least two points and rates of adverse events. If effective, aqueous lignocaine, an easily available and stable preparation, would be a valuable adjunct to the management of childrens ear pain associated with AOM.
| METHODS |
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The study was approved by the hospital ethics committee and the Australian Therapeutic Goods Administration Clinical Trial Notification drugs scheme.
Study design
This study was a randomised, placebo-controlled trial. Patients and parents, those administering ear drops and those assessing ear pain were blinded to group assignment. All enrolled patients were randomly assigned to receive either 2% aqueous lignocaine or normal saline (placebo) ear drops. Both solutions were colourless and odourless, presented in identical 2 ml dropper bottles. The drops were randomised in blocks of 10. Three drops of study solution were instilled in the painful ear while the child lay with that ear upward for 5 minutes. If the ear pain was bilateral, the most painful ear was treated first.
Ear pain was initially measured at triage before enrollment, then during the study period at baseline (T0), ten (T10), twenty (T20) and thirty (T30) minutes by the patient and at T0 and T30 by the treating physician. Ear pain was measured using a faces pain scale for patients up to 6 years of age (Bieri Faces Pain Scale-Revised)15–17 and a visual analogue scale (VAS; score 0–10) for use by staff and patients 7 years and upwards. Patients and parents were read written instructions and staff had been trained in the use of these pain scales. Physicians were aware of patient scores.
Further oral analgesia was offered between 10 (T10) and 30 minutes (T30) of the study period at the discretion of the treating doctor. Any analgesia given in hospital was recorded. The study ear drops were taken home with instructions prescribing three drops for ear soreness, up to 3 hourly for 24 hours only and to cease use if ear discharge occurred. Prescription of additional oral antibiotics was at the discretion of the treating physician. Follow-up phone calls were made the next day and at 1 week to determine clinical course, adverse events and medication use.
Statistical analysis
An indicative power calculation was based on comparison of groups at 30 minutes. We considered a 50% reduction in pain at each time point (T10, T20, T30) from the baseline pain score (T0) to be clinically significant and used this as the primary outcome measure. On the basis of the power calculations of the similar study by Hoberman et al,7 we estimated that 80% of children in the lignocaine group and 40% in the placebo group would attain this reduction by 30 minutes. Using these proportions (and a two group t test with two-sided 0.05 significance level), a sample size of 28 per group for this study was calculated to give 80% probability (power) of producing a significant finding. We noted that in Hobermans study, 56% (rather than the estimated 40%) of the placebo group patients showed 50% improvement by 30 minutes; however, it is debatable whether their placebo (olive oil) was truly inert, as commented on by the editor, DeAngelis.7 18 A relative-risk analysis was used to calculate the difference in proportions of patients improving in each group. Analysis was by intention to treat.
| RESULTS |
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2-point reduction from baseline in patient-reported pain was significant only at T10, with trends favouring the lignocaine-treated group at later time points (Table 2). At T30, 81% (25/31) of children in the lignocaine group and 59% (19/32) in the placebo group reported minimal (pain score
2) or no pain. Although doctor-measured pain scores at T30 also favoured lignocaine for reduction by 50%, 25% and two-point reduction, these outcomes were not statistically significant. The analysis of the primary outcome measure was repeated excluding the two patients with no pain at T0 to determine their effect, if any, on these results. Significant results favouring lignocaine for a 50% reduction of patient measured pain were still achieved at T10 (RR 1.94; 95% confidence interval 0.98–3.8, p = 0.04) and T30 (RR 1.35; 95% confidence interval 1.02–1.78, p = 0.02).
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| DISCUSSION |
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Although aqueous lignocaine has previously been shown to be ineffective on un-inflamed squamous epithelium, including the external TM,19 the fact that an altered epithelium in other settings, such as napkin rash8 and under occlusive dressings,20 has demonstrated increased uptake of the drug may give good reason to explain the greater effectiveness to the TM when it is inflamed.
Most children presenting with ear pain in both groups of our study demonstrated rapid improvement in their pain. After 30 minutes, the majority of children in our study reported minimal (pain score < = 2) or no ear pain regardless of which ear drops were used (lignocaine 81%, placebo 59%). This rapid improvement regardless of intervention is consistent with findings in other studies of topical analgesic ear drops6 7 21 22 and has been interpreted as possibly owing to the natural course of the illness, the placebo effect of being in a clinical setting or the soothing effect of any liquid on the inflamed TM.6 An interpretation of our results is the adjunctive effect of simple oral analgesia that reduces acute ear pain associated with AOM. However, it remains evident that over and above concurrent analgesic administration, pain reduction is improved using lignocaine otic drops. The Cochrane review considering antibiotic use in AOM4 also found that two-thirds of children were pain-free by 24 hours regardless of antibiotic use and that 80% had recovered spontaneously without antibiotics by 2–7 days. Van Buchem et al (4,860 children) also reported over 90% spontaneous recovery of AOM in children within a few days without treatment.23 Thirty-eight percent of children in our study had received antibiotics by 1 week. This is substantially less than the 98% prescribing rate found by Froom et al in their 1990 International Primary Care Network report24 and recent data from our ED.25
Our findings of a relatively high rate of ear discharge (8%) compared with data by van Buchem et al23 are difficult to interpret. Some discharge may represent perforation of the TM; however, it could also represent discharge of study ear drops or of dissolved wax.
The study population represents a convenience sample. An analysis of the ED database identified a further 179 patients (mean age 6.5 years) who were potentially eligible with diagnosis of AOM but were not approached for enrollment. Limitations to this study also include the variability of preceding analgesia and the additional analgesia given during the study period; however, no children received further medication until 10 minutes after the ear drops were administered. At the time, we felt that it was unethical to withhold simple analgesic therapy as the current standard of care for pain in the ED. In retrospect, it would have been better to exclude patients with prior analgesic use. The accurate measurement of pain in young children is problematic and the direct comparison between two different pain scales is potentially flawed, but the Bieri Faces Pain Scale-Revised16 has been shown to correlate with VAS.17 Physicians were aware of patient scores and might have inadvertently approximated patient scores.
| CONCLUSIONS |
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Further studies might use longer acting or more lipid-soluble local anaesthetics. AOM will continue to be a common and distressing problem in childhood but is mostly a self-limited condition. Emphasis must therefore remain on effective and safe symptom control.
What is already known on this topic
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What this study adds
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| ACKNOWLEDGMENTS |
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| FOOTNOTES |
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| REFERENCES |
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A. Sattout and R. Jenner BET 1. THE ROLE OF TOPICAL ANALGESIA IN ACUTE OTITIS MEDIA Emerg. Med. J., February 1, 2008; 25(2): 103 - 104. [Full Text] [PDF] |
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