Can Mitomycin C Really Prevent Airway Stenosis?

An Acquired Anterior Glottic Web Model by Heat Injury with a Laryngoscopic Approach in a Rabbit

Acquired anterior glottic webs (AGW) can lead to abnormally elevated phonatory pitch, dysphonia, and airway obstruction requiring urgent intervention. In this study, we construct a novel AGW rabbit model using heat injury by a laryngoscopic way. A primary study was conducted to identify the injury depth in rabbits' vocal folds (VFs) by graded heat energy, and the heat energy for the incurrence of epithelial layer, lamina propria, and muscular layer (ML) injury was 25, 30 and 35 W, respectively. Then, four different models were designed based on the depth and degree of the injury to determine the optimal procedure for AGW formation. Morphological features, vibratory capacity, and histopathologic features of the AGW were correspondingly evaluated. The procedure for conferring the heat injury to the depth of ML and the extent of anterior commissure and middle part of bilateral VFs showed the highest success rate of AGW formation (95%, 19/20). For its low cost, effectiveness, and stability for AGW formation, the heat injury rabbit model with a laryngoscopic approach may provide a new platform for testing novel anti-adhesion materials and bioengineered therapies. Impact Statement Tissue engineering based on biomaterials has been a very hot research field and may be introduced to prevent the acquired anterior glottic web (AGW) formation. However, lacking a widely recognized animal model for AGW has limited the trial of anti-adhesion materials in the larynx. In this study, we have developed a novel rabbit model for AGW formation by conferring a heat injury under a laryngoscope; this model is cheap, effective, and stable for the anti-adhesion materials and bioengineered therapies. Thus, this research would arouse crucial interest and be widely employed.

The Effects of Rapamycin on the Proliferation, Migration, and Apoptosis of Human Tracheal Fibroblasts (HTrF) and Human Tracheal Epithelial Cells (HTEpiC)

Background: Restenosis after airway stenting needs to be addressed urgently. Rapamycin has been proven to inhibit restenosis elsewhere. This study aimed at observing its effects on the respiratory tract. Methods: CCK-8, wound healing, Transwell and apoptosis assays were performed to detect the effects of rapamycin on the survival, migration, and apoptosis, respectively, of human tracheal fibroblasts (HTrF) and human tracheal epithelial cells (HTEpiC). Results: The effective concentrations of paclitaxel, mitomycin C and rapamycin on HTrF were 10⁻⁷–10⁻⁴ mol/L, 10⁻⁶–10⁻⁴ mol/L, and 10⁻⁵–10⁻⁴ mol/L, respectively. At the effective concentrations, the inhibition rates of paclitaxel on HTEpiC were (43.03 ± 1.12)%, (49.49 ± 0.86)%, (55.22 ± 1.43)%, and (93.19 ± 0.45)%; the inhibition rates of mitomycin C on HTEpiC were (88.11 ± 0.69)%, (93.82 ± 0.96)%, and (94.94 ± 0.54)%; the inhibition rates of rapamycin on HTEpiC were (10.19 ± 0.35)% and (94.55 ± 0.71)%. At the concentration of (1–4) × 10⁻⁵ mol/L, the inhibition rate of rapamycin on HTrF was more than 50%, and that on HTEpiC was less than 20% (p < 0.05). Conclusions: Compared to paclitaxel and mitomycin C, rapamycin had the least effect on HTEpiC while effectively inhibiting HTrF. The optimum concentration range was (1–4) × 10⁻⁵ mol/L.

Risk Factors for Adult Laryngotracheal Stenosis: A Review of 74 Cases

Objectives:

We sought to identify risk factors for and review our experience in the management of adult acquired laryngotracheal stenosis (LTS) at an academic urban medical center.

Methods:

A retrospective review of all patients given a diagnosis of acquired LTS between 1997 and 2005 was performed. Seventy-four patients with LTS were identified. Demographic information, medical and surgical history, surgical procedures performed, and outcomes were collected. A control group of 106 patients admitted over the same time period with respiratory distress but without LTS was identified. The data collected for both groups were analyzed by Fisher's exact test and logistic regression analysis.

Results:

Demographically, the control group was not significantly different from the LTS group. Patients who had a previous tracheostomy were 10.99 times more likely to develop LTS than control patients (95% confidence interval [CI], 4.68 to 25.80). Patients irradiated for carcinomas of the oropharynx and larynx were 5.95 times more likely to develop LTS than control patients (95% CI, 1.87 to 18.91). Those previously intubated for more than 48 hours were 3.91 times more likely to develop LTS than control patients (95% CI, 1.91 to 8.02). Finally, patients who were intubated for any non-airway surgery were found to be 2.07 times more likely to develop LTS (95% CI, 1.09 to 3.93).

Conclusions:

Prolonged intubation, tracheostomy, previous non-airway surgery, and irradiation for oropharyngeal and laryngeal tumors are risk factors for LTS. Multiple surgical procedures are often required for treatment. Mitomycin C did not significantly improve decannulation rates.

Benefits and risks of mitomycin use in the traumatized tracheal mucosa

Objective

To investigate the efficacy and early complications of mitomycin C (MMC) in tracheal wound models.

Study Design and Setting

Rabbits (N = 60) were randomized to undergo mucosal injuries to the upper and lower trachea including anterior 120° full thickness (group A, n = 20), anterior 120° partial thickness (group B, 20), and circumferential partial thickness (group C, 20). In each rabbit, the wounds were separately treated with MMC 1.0 mg/mL or saline, and the animals were sacrificed after three weeks.

Results

Twenty-seven of the 60 animals experienced early death because of tracheal rupture or airway obstruction caused by unresolved scabs on the preinjured tracheal mucosa; the incidence of early death was higher in groups A and C than in group B. In each group, the degree of tracheal stenosis was comparable in wounds treated with MMC and saline.

Conclusion

These findings suggest that topical MMC has no benefit when used to prevent tracheal stenosis. Acute airway obstruction may occur in MMC-treated rabbits with tracheal wounds.

Nonstent Combination Interventional Therapy for Treatment of Benign Cicatricial Airway Stenosis

Background:

Benign cicatricial airway stenosis (BCAS) is a life-threatening disease. While there are numerous therapies, all have their defects, and stenosis can easily become recurrent. This study aimed to investigate the efficacy and complications of nonstent combination interventional therapy (NSCIT) when used for the treatment of BCAS of different causes and types.

Methods:

This study enrolled a cohort of patients with BCAS resulting from tuberculosis, intubation, tracheotomy, and other origins. The patients were assigned to three groups determined by their type of stenosis: Web-like stenosis, granulation stenosis, and complex stenosis, and all patients received NSCIT. The efficacy and complications of treatment in each group of patients were observed. The Chi-square test, one-factor analysis of variance (ANOVA), and the paired t-test were used to analyze different parameters.

Results:

The 10 patients with web-like stenosis and six patients with granulation stenosis exhibited durable remission rates of 100%. Among 41 patients with complex stenosis, 36 cases (88%) experienced remission and 29 cases (71%) experienced durable remission. When five patients with airway collapse were eliminated from the analysis, the overall remission rate was 97%. The average treatment durations for patients with web-like stenosis, granulation stenosis, and complex stenosis were 101, 21, and 110 days, respectively, and the average number of treatments was five, two, and five, respectively.

Conclusions:

NSCIT demonstrated good therapeutic efficacy and was associated with few complications. However, this approach was ineffective for treating patients with airway collapse or malacia.

Novel experimental rabbit model of anterior glottic web formation

CONCLUSION

The rabbit model of anterior glottic web (AGW) formation using the laryngofissure technique resulted in reproducible and stable AGW formation that may facilitate research into this area.

OBJECTIVE

To introduce and validate a novel experimental animal model of AGW formation using the rabbit.

METHODS

The inner larynges of eight New Zealand white rabbits were exposed through the laryngofissure technique. The mucosa of the bilateral true vocal fold was stripped off using the bevel of a needle tip. On the basis of the laryngoscopic findings at 8 weeks postoperatively, the extent of AGW was measured, and the success of this procedure was validated. Laryngeal specimens were sampled at 8 weeks for high-speed recording and histological analysis.

RESULTS

In seven (87.5%) rabbits, laryngoscopic examination revealed the formation of a scar band involving the anterior commissure. The mean extent of AGW ratio on the left and right sides was 0.58 ± 0.073 and 0.55 ± 0.075, respectively. The symmetric formation of AGW (p = 0.655, p = 0.128) and stability of the AGW procedure (p = 0.491, left; p = 0.501, right) were statistically validated. On high-speed recording, the vocal mucosal wave was hindered by AGW formation. Histologically, fibro-connective tissue, especially collagen fiber, was observed in the anterior commissure.

The use of mitomycin C in pediatric airway surgery: does it work?

PURPOSE OF REVIEW

To describe the efficacy of mitomycin C in combating airway stenosis.

RECENT FINDINGS

Recent publications discussing mitomycin C utility have not altered the mixed results previously established by prospective trials.

SUMMARY

Mitomycin C has been used for the past 16 years to inhibit pediatric airway fibroblast proliferation. Its benefit remains more hypothetical than proven and its future role remains uncertain.

Topical application of mitomycin-C as an adjuvant treatment to bronchoscopic procedures in post-intubation tracheal stenosis

INTRODUCTION

Post-intubation tracheal stenosis (PITS) continues to be challenging in terms of diagnosis, management and prevention. Recurrence is common because of excessive granulation tissue formation and an insidious process of scar contracture. Topical application of mitomycin-C (MMC) as an adjuvant treatment for endoscopic management of stenosis has shown good results. The authors aimed to evaluate the results of MMC topical application following bronchoscopic dilatation as an adjuvant in PITS treatment.

METHODS

Retrospectively selected patients with PITS who had had rigid bronchoscopy (RB) dilatation followed by MMC application as adjuvant to endoscopic treatment. MMC in a concentration of 0.4 mg/ml was applied with a cotton stiletto around the stenotic lesion and granulation tissue for 3 minutes.

RESULTS

Eleven patients with PITS, with a median initial tracheal stenosis of 75% of the lumen, underwent RB/MMC treatment. Mean MMC sessions performed/patient was 3.5, with good response and prolonged decrease in granulation tissue formation in 55% of cases, moderate in 18% and relapse in 27%. Mean stenosis improvement was 34%.

CONCLUSIONS

Topical MMC application at 0.4 mg/ml concentration seems to be associated with good results as adjuvant in PITS management with decrease in granulation tissue and sustained improvement in lumen diameter.

Topical use of MMC in the upper aerodigestive tract: a review on the side effects

Not much is known about the side effects of mitomycin C (MMC), an anti-fibrogenetic agent, in the upper aerodigestive tract. However, its use in ophthalmology is widely known and without quantitatively important side effects. A literature review was performed for side effects of MMC in the upper aerodigestive tract. Forty-six articles, describing the use of MMC to prevent scarring, were retracted from PubMed. Thirty-two are human studies. MMC is used in different concentrations (0.1–10 mg/ml) with different application times (2–5 min) and frequencies (up to 4 times). Five hundred and thirty-eight patients were included in those publications, of whom 19 developed side effects (3.53%). No side effects developed in studies, where post-application irrigation with saline was reported. The longest mean follow-up period is 75.5 months. Direct relations between the reported side effects and MMC seem absent in most studies. Serious complications seem to occur when MMC is used in high concentrations. Unfortunately, sometimes crucial information is lacking. One patient was described who supposedly developed laryngeal carcinoma after repeated treatment of hyperkeratosis and anterior commissure webbing. Animal studies show that excessive fibrin production can lead to acute airway obstruction. In conclusion, topical application of MMC on a wound with consecutive irrigation with saline can be performed safely to prevent scar formation in circular structures of the upper aerodigestive tract. Long-term yearly control of the application site seems advisable.

[Adjuvants in operative laryngology: corticosteroids, fibrin adhesives, Mitomycin C]

Medicinal adjuvants are often used in operative laryngology but their value is judged very differently. The scientific evidence is unsatisfactory for most of these substances. For corticosteroids it is proven that in pediatric intensive care they reduce stridor following extubation. Routine prophylactic use for intubation does not seem to be justified and methylprednisolone and dexamethasone are the preferred preparations. Fibrin adhesives are well tolerated and low in side-effects. The indications for their use should be primarily limited due to the cost factor. Their use in laryngology remains a decision on an individual case-to-case basis. Mitomycin C is used because of its antiproliferative effect on fibroblasts in order to reduce scar tissue formation. Many positive effects have been attributed to the topical application but there are large differences in dosage and exposure time.

Study of Wound Healing in Rats Treated with Topical and Injected Mitomycin C

Objectives:

Mitomycin C, a widely used chemotherapeutic drug, has been proposed as a potential adjuvant for the control of scar tissue in surgical wounds because of its capacity to inhibit fibroblast proliferation. The current study used a combination of topical and injected mitomycin C to slow the healing process of surgical wounds in rats.

Methods:

An experimental model of surgical wounding at the dorsum of rats was used. A total of 43 animals were subdivided into 3 groups: Control, topical mitomycin C, and a combination of topical treatment and intradermal injections of the drug at 30 and 60 days after the initial topical treatment. After 3 months, the animals were painlessly sacrificed and the surgical scars were removed for microscopic analysis.

Results:

The group that received only topical mitomycin C presented milder inflammatory signs and consequently had a less intense healing process than the control group. The group treated with a combination of both topical and injected mitomycin C presented results comparable to those of the control group.

Conclusions:

The toxic characteristics of mitomycin C were most likely responsible for the greater tissue damage that occurred when it was used in the injected form, causing increased scar tissue formation. Mitomycin C slows the healing process of surgical wounds when used topically, but causes enhanced scar tissue formation when injected.

Cricotracheal Resection in Nontracheotomized Adults: A Prospective Case Series

Objectives:

Cricotracheal resection is a modern technique of airway reconstruction used in cases of subglottic stenosis. We report a case series of adult, nontracheotomized patients.

Methods:

Fifteen patients with significant subglottic stenosis were identified as presenting with dyspnea and stridor. The stenosis was grade III in 14 cases and grade II in 1 case, according to the Cotton classification. The causes were manifold, with intubation and tracheostomy being the predominant risk factors. Cricotracheal resection was performed in all cases with preoperative and postoperative videotracheoscopy.

Results:

The mean postoperative intubation time was 41.7 hours (11 to 103 hours), and the mean length of stay in the intensive care unit was 2.6 days (3 to 9 days). Videotracheoscopy for reassessment was performed after 96 days (average). In 13 of the 15 patients the subglottic lumen was returned to a normal diameter. In 1 case a recurrent stenosis was managed with repeated endoscopic interventions. One patient died on postoperative day 4 because of a pulmonary embolism. Additional complications consisted of 1 axillary venous embolism, 4 cases of ventilator-associated pneumonia, and 1 case of transient unilateral recurrent nerve palsy that recovered completely.

Conclusions:

Cricotracheal resection is a reliable and versatile technique for the reconstruction of the subglottic airway, almost regardless of the underlying cause. Most complications observed have not been associated directly with the procedure, but reflect the significant comorbidity of the patient population. There seems to be an increased risk for thromboembolic events that may be a consequence of the preoperative immobilization of dyspneic patients.