Effects of thrombolytic agents on tympanostomy tubes occluded by blood clots

Objective: To investigate the efficacy of various topical applications in opening a clotted tympanostomy tube (TT) using an in vitro model. Design: In vitro clinical trial. Interventions: Fresh human blood was allowed to clot in the lumen of TTs. Seven agents were tested: 0.9% saline (control), 1-mg/mL alteplase, 100-U/mL unfractionated heparin,3%hydrogen peroxide (H ₂O ₂),3%acetic acid, 5% acetic acid, and a mixture of 3% H ₂O ₂ and 3% acetic acid. Each agent was added twice a day for 14 days to TTs that were incubated and humidified to simulate ear canal conditions. The tubes were analyzed with binocular microscopy to determine the status of the obstruction. Results: A total of 16 trials per agent, including a saline control, were performed. The saline control, alteplase, and heparin failed to open any TTs in any of the trials. Compared with the control, H ₂O ₂ also was not effective (P=.23). Acetic acid was increasingly effective, with a 3% concentration completely clearing 5 of 16 tubes and a 5% concentration completely clearing 11 of 16 tubes (P=.006). The addition of 3% H ₂O ₂ to 3% acetic acid did not significantly increase clearance (P=.21). Conclusions: Thrombolytic agents and H2O2 were not effective in resolving TTs that were clotted with blood in an in vitro environment simulating the ear canal. Increasing concentrations of acetic acid are increasingly effective in this capacity.