A blinded in‐vitro study to compare the efficacy of five topical ear drops in clearing grommets blocked with thick middle ear effusion fluid1

Objective: To compare the efficacy of 5% NaHCO₃, 3% H₂O₂, Sofradex (dexamethasone sodium metasulphobenzoate 0.05%, framycetin sulphate 0.5%, gramicidin 0.005%), 0.33% acetic acid and 0.9% NaCl eardrops in clearing grommets blocked with harvested thick middle ear effusion fluid. Study design: A blinded in‐vitro study. Setting: District general hospital. Participants: A total of 473 grommets were blocked with freshly harvested unpooled thick middle ear effusion fluid obtained from 68 patients. Main outcome measures: Patency of the grommets before and 7 days after intervention was ascertained by tympanometry and close visual inspection. Results: Instillation of eardrops leads to a statistically significant increase in the clearance of grommets as compared with not using any drops (χ² = 14.3, d.f. = 5, P = 0.006). The numbers needed to treat were 2.8 for NaHCO₃, 3.2 for 0.9% NaCl, 3.9 for 0.33% acetic Acid, 4.4 for Sofradex and 9.5 for H₂O₂ eardrops. Pair‐wise comparison was only significant for comparison between 5% NaHCO₃ and 3% H₂O₂ eardrops (Bonferroni corrected P = 0.01, odds ratio = 4.3, CI = 1.9–9.9). Conclusions: Use of eardrops leads to a clinically and statistically significant increase in the clearance of blocked grommets. Of the five drops used, 5% NaHCO₃ was the most efficacious and 3% H₂O₂ the least efficacious. Limitations of this in‐vitro study are recognized and a prospective in‐vivo double blind randomized controlled trial is planned.