Assessing the Efficacy of Tragal Pumping in a Novel Tympanostomy Tube-Rat Model

Objective

Tragal pumping (TP) is a practice of pushing on the tragus to raise pressure within the external auditory canal and is a commonly recommended adjunctive maneuver believed to facilitate the introduction of ototopical medications into the middle ear cavity via a tympanostomy tube. To investigate the efficacy of TP in the penetration of eardrops into the middle ear cavity via tympanostomy tube, we established the novel tympanostomy tube-rat model. We investigated the histology of the middle ear to determine the efficacy in moving fluid into the middle ear.

Study Design

Prospective controlled animal study.

Setting

Animal laboratory in a university hospital.

Methods

Ten rats were recruited, and a tympanostomy tube insertion and green dye eardrops into outer ears were performed on bilateral ears. TP was performed only on 1 ear and was not applied on the other ear in each rat. Green dye in a middle ear cavity in hematoxylin and eosin-stained temporal bone sections was evaluated by blinded experts in microscopic anatomy (staining grade) and by using Image J software (staining level). The results of these 2 methods were statistically validated.

Results

The staining grade (P < .001) and the staining level (P < .001) were significantly higher in the ears which we applied TP than in the control ears. The results of 2 methods were significantly and positively correlated (r = .898, P < .001).

Conclusion

Our results showed that the TP accelerate the penetration of eardrops into the middle ear cavity in the tympanostomy tube-rat model.

Vestibular Function Change in a Vasopressin-Induced Hydrops Model

HYPOTHESIS

A vasopressin-induced endoymphatic hydrops model can represent an acute vertiginous attack in Menière's disease (MD).

BACKGROUND

Previous animal models are not appropriate to evaluate the efficacy of new treatments for hydrops because they cannot represent an acute attack of MD. Recently, a new dynamic model was introduced for acute hydrops exacerbation using the vasopressin type 2 receptor agonist, desmopressin (1-deamino-8-D-Arginine vasopressin, VP); however, resulting changes in vestibular function have not been investigated.

METHODS

A total of 37 guinea pigs were used. Two to 4 weeks after surgical ablation of endolymphatic sacs in 33 guinea pigs, acute exacerbation of hydrops was induced by a single VP injection in 18 animals (group A). Next, two VP injections at 1 hour interval were administered to investigate the effect of multiple VP doses on vestibular function in the other 15 animals (group B). In the remaining four animals, VP was injected without surgery for the control group (control). Bidirectional sinusoidal harmonic acceleration (SHA) tests of vestibular function were performed. "Type I response" was defined as when the maximum slow-phase velocity (SPV) during left rotation (toward the operated ear) was lower than that during right rotation (toward the normal ear). In contrast, "Type II response" was defined as when maximum SPV at the left rotation was higher than that at the right rotation. Vestibular symmetry scores were analyzed at baseline and after each of two VP injections given 1 hour apart.

RESULTS

Vestibular symmetry scores increased at 1 hour after VP injection in all 18 animals in group A (p < 0.001). Two hours after VP injection, symmetry score decreased to the initial score. Two different types of vestibular response were observed after VP. However, the symmetry scores between type I and II responses were not significantly different (p = 0.173). In all 15 animals of Group B, vestibular asymmetry was sustained over 3 hours when two VP injections were given 1 hour apart. In three of Group B, the type of vestibular response changed from type II response to type I response after the 2nd VP injection; however, no animal demonstrated a shift from type I to type II response.

CONCLUSION

VP can transiently induce an acute exacerbation of hydrops and asymmetric vestibular dysfunction in guinea pigs. This model could help in studying new treatments for acute hydrops and in explaining the mechanism of bidirectional nystagmus in MD.

How do You Select an Anesthesia Method Prior to Tympanostomy Tube Insertion for a Child?

The use of general (face-mask inhalation and intravenous) anesthesia has been the method of choice for tympanostomy tube insertion in children. However, there is no exact guideline for the choice of anesthesia method and there is no evidence to support the use of one anesthesia method over another. Clinically, the anesthesia method used to be decided by old customs and the surgeon's blind faith that children cannot bear tympanostomy tube insertion under local anesthesia. Clinicians should keep in mind that pediatric anesthesia has a potential risk. Despite infrequent serious complications, their seriousness necessitates that sedation or general anesthesia should be done by an anesthesiologist and thus children requiring tympanostomy tube insertion should be referred to secondary or tertiary hospitals, even if they have been followed by a primary care physician for a long time. Previous evidence showed that local anesthesia is appropriate for tympanostomy tube insertion in selected children, especially in children older than 5 years are older. Proper choice of anesthesia method is helpful for both patient and medical service provider. Local anesthesia can give psychological relief to children and their parent. It is easier for the medical service providers to schedule the operation and allocate the medical resources in their hospital. Local anesthesia can reduce individual, social, and national burdens for the health care services.