[Effect of the hyaluronic acid on tracheal healing. A canine experimental mode]

Several drugs have been used to modulate of the tracheal healing process in order to prevent tracheal stenosis. Hyaluronic acid (HA) is a modulator of the fibrogenesis. In this work we evaluate the effect in order the application of hyaluronic acid has on tracheal healing, after cervical tracheoplasty in dogs. A cervical tracheal resection and tracheoplasty was performed in 12 dogs and they were treated following surgery as follows: Group I (n = 6) Topical application of normal saline solution (0.9%) on the anastomosis site. Group II Topical application of hyaluronic acid on the trachea anastomosed. The animals were evaluated clinical, radiological and tracheoscopically during 4 weeks and were submitted to euthanasia. Macroscopic and microscopic examinations of the tracheal anastomotic healing were evaluated. Biochemical collagen quantification by the Woessner method was performed to evaluate the collagen development at the anastomotic site. All the animals survived the surgical procedure and the study time. No animal presented differences in clinical evaluation. Radiological and endoscopical findings both two showed more development of the tracheal stenosis in-group than in group II. The tracheoscopy and macroscopic studies showed major inflammation and development of fibrotic tissue with a firm consistency in the healing of the group I than in group II. Microscopic examination in group I showed severe fibrosis and inflammatory reaction. The group II presented deposits of a thin and organized collagen fibers and minimal inflammatory reaction. Biochemical collagen concentration was larger in-group I, however significantly. We conclude that the hyaluronic acid applied after cervical tracheoplasty in dogs reduces postsurgical tracheal stenosis and inflammation, as well as improve the quality of the tracheal healing.