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

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 (chi2 = 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.