Electrocautery versus 23% NaOH infiltration to induce subglottic stenosis in a canine experimental model

Abstract

Subglottic stenosis (SGS) is defined as the narrowing of the lower larynx. Difficulties in the management of subglottic stenosis, especially in the pediatric population, justify the development of experimental models. The objective of this study was to compare the two methods of experimental subglottic stenosis induction. Twenty-three dogs were randomly selected and assigned by lottery to either one of the two groups: Gp I (n = 10) of electrocoagulation; and Gp II (n = 13) of 23% NaOH injection. In Gp I, self-interruption electrocoagulation was applied to one point in each of the four quadrants of the cricoid cartilage. In Gp II, 0.2 ml of 23% NaOH was injected in the submucosal layer in the anterior and posterior portions of the cricoid cartilage. Once a week, endoscopy was performed and the caliber of the subglottic region was measured using endotracheal tubes, and the injection was repeated if there were no signs of subglottic stenosis. The animals were killed on day 21; animals that developed respiratory distress were killed before day 21. One animal in Gp I died on day 14 after the injection and during transportation; two animals in Gp II died, one on day 7 due to a tracheoesophageal fistula, and the other of unknown causes on day 5. Significant subglottic stenosis (over 51% obstruction) was found in 67% of the animals in Gp I and in 64% of those in Gp II (P = 0.99). Median time to development of significant stenosis was 21 days in both groups, and required either two or three injections. Mean time for the performance of the procedures was significantly shorter (P < 0.01) in Gp I (mean: 6.36 min) than in Gp II (mean: 14.88 min). Electrocoagulation and 23% NaOH injection in the subglottic region were effective in the development of significant subglottic stenosis in dogs, both methods leading to stenosis in the same period of time and after the same number of procedures. However, electrocoagulation was the fastest method.

Subglottic injury: A clinically relevant animal model

“…Previously, investigators focused on the stenotic tissue following injury, and large stenoses have been generated in the subglottis of many animal models including canines, porcine, rabbit, and mouse models using direct injury to the mucosa 9–14, 16–25. Stenoses of greater than 85% to 96% have been successfully created in the subglottis of canines using electrocautery 11, 14.…”

“…Animal models for SGS have proved to be invaluable in helping to understand the underlying mechanisms and in developing new prevention strategies. In this regard, successful models have been developed in the dog10–17 pig,18 rabbit,9, 19–24 mouse,25 and ferret 26. All of the above models are successful in the creation of SGS; however, most focus on causing a direct mucosal injury to the subglottic region rather than emulating some of the clinical causes such as long‐term intubation and/or oversized endotracheal tubes.…”

Modelo experimental de estenose traqueal mediante ressecção cirúrgica submucosa de anéis traqueais combinada com instilações de hidróxido de sódio

“…Although tracheoplasty is the treatment of choice for most cases of inflammatory tracheal stenosis, in some situations, as in patients without clinical conditions, nonsurgical procedures are required, such as the placement of silicone tracheal stents. To develop and improve airway orthoses, some experimental models of stenosis and malacia have been described [6][7][8][9][10][11][12][13] . Once the silicone stents are more satisfactorily set in stenoses of more than 50% of the lumen and greater than 1 cm in extension 4 , we seek to adapt and combine two models of stenosis: resection of cartilage rings in a row, originally described by Mair et al 11 , and then modified by Korpela et al 7 and Marquette et al 8 , and the application of caustic solution by bronchoscopy, published by our group 6 .…”

“…The technique of inflammatory stenosis with application of 23% NaOH was previously described and published by two of the authors of this study 6 : through a rigid bronchoscope (Karl Storz Endoskope®, Germany) we applied a cotton swab soaked in 23% NaOH solution (pH = 14) on the lining of the trachea with previously surgically induced malacia. We avoided the contact of the NaOH solution to the posterior wall of the trachea.…”

“…In our setting, the high cost of imported stents prompted the authors to develop new models of silicone tracheal stents, such as the HCPA-1 5 . In this sense, we seek an animal model of tracheal stenosis, based on published experimental studies [6][7][8] , which mimics the pathophysiological conditions found in humans to evaluate our silicone stent. Thus, the purpose of this study is to develop an experimental model of inflammatory tracheal stenosis.…”