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Original articles: Penny Bolt, Peter Barnett, Franz E Babl, and Lisa N Sharwood Topical lignocaine for pain relief in acute otitis media: results of a double-blind placebo-controlled randomised trial Arch Dis Child 2008; 93: 40-44 [Abstract] [Full text] [PDF]

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Is Topical Lignocaine for pain relief in Acute Otitis Media really effective?

Bhavneet Bharti, Sahul Bharti   (26 March 2008)

Is Topical Lignocaine for pain relief in Acute Otitis Media really effective? 26 March 2008
Bhavneet Bharti, Doctor Assistant Professor, Department of Pediatrics, Advanced Pediatric Centre, PGIMER, Chandigarh, INDIA, Sahul Bharti Send letter to journal: Re: Is Topical Lignocaine for pain relief in Acute Otitis Media really effective? bhavneetb{at}yahoo.com Bhavneet Bharti, et al.	We read with interest the superiority placebo-controlled trial by Bolt et al 1 where primary outcome was proportion of children with acute otitis media having reduction of pain scores in lignocaine vs. saline ear- drop groups at 10, 20 & 30 minutes from baseline. The significant response in lignocaine group could be attributed to skewed pain scores at baseline in the placebo group. This was reflected by 95% CI for relative risk (0.98-3.8) crossing 1 when outcome of 50% pain reduction at 10 minutes was reanalyzed after excluding two patients with zero score at baseline from placebo treatment arm. Moreover, authors’ approach to analyze ‘time-to-event’ data is fraught with two statistical disadvantages.2 First, it is difficult to define proportions achieving given pain reduction in an efficient and unbiased manner largely due to presence of censoring (i.e. patients not achieving outcome at given time point). Second, it is potentially misleading to compare two groups separately at various arbitrarily chosen time points. Indeed, authors should have compared “median time-to-relief” using Kaplan Meier survival analysis with censoring of patients having a baseline pain score of less than 3. Latter was as an exclusion criterion in the study by Hoberman et.al.3 Also, study findings show pharmacological discordance with lignocaine action. Peak anesthetic effect following topical application of lignocaine occurs within 2 to 5 minutes and it dissipates after 30 to 45 minutes.4 However, upper quartile (3rd) for pain scores in lignocaine group at baseline, 10, 20 and 30 minutes were approximately 8, 6, 6.5 and 2 respectively, lowest at 30 minutes (figure 2). This indicates confounding effect of preceding or concurrent oral administration of analgesics. Based on these observations, evidence provided in the study lacks power to reject the null hypothesis of equivalence of two topical ear drops in treatment of ear pain in children with acute otitis media. References: 1.Bolt P, Barnett P, Babl FE, Sharwood LN. Topical lignocaine for pain relief in acute otitis media: results of a double-blind placebo- controlled randomized trial.Arch Dis Child 2008;93:40-44. 2.Altman DG. Practical statistics for medical research.London:Chapman and Hall,1991:371- 75. 3.Hoberman A, Paradise JL, Reynolds EA et al. Efficacy of Auralgan for treating ear pain in children with acute otitis media. Arch Pediatr Adolesc Med 1997;151:675-78. 4.Catterall W, Mackie K. Local anesthetics. Goodman and Gilman’s The Pharmacological basis of therapeutics. Chapter 15, 381: 11th Edition 2006.