Background: Difficult intubation is defined as the need for multiple attempts to intubate with or without tracheal disease. One of the causes is subglottic stenosis. Congenital subglottic stenosis usually presents with varying degrees of dyspnea. Acquired causes include prolonged intubation, tumors or trauma. In symptomatic patients, the diagnosis can be made by x-ray or CT-scan. Rarely there are asymptomatic patients, and these are a challenge to the anesthesiologist, as they present as unexpected difficult intubation because of difficulty in the progression of the tube after it has passed between the vocal cords.
Case report: 46-year-old patient ASA II (obesity) admitted for elective vaginal hysterectomy to correct a complete uterovaginal prolapse. No previous surgeries or trauma or predictive signs for difficult ventilation or intubation. No relevant changes in the pre-op exams. General anesthesia with ev induction. Grade I laringoscopy. It was only possible to intubate with a number 4 mycrolaryngeal tube because of resistance to progression encountered after the vocal cords. The surgery was postponed and the patient was extubated without incidents. The patient referred no dyspnea or dysphagia, only occasional dysphonia. Otolaryngologic evaluation, fibroscopy and CT-scan showed narrowing in a level immediately sub-glottic with an extension of 13mm with airway permeability preserved. It was considered that the cause was congenital. The surgery was rescheduled and a sequential anesthesia was performed without incidents.
Discussion: This case presented as an unexpected difficult intubation. There are few reports of asymptomatic subglottic stenosis and the decision on how to proceed varies with the ability to approach the airway and with the type of surgery.
References: Rani N. U. Ramez S. M. Michael, F. Richard. L. F. MD (1995) Acute Management of Unsuspected Subglottic Stenosis by Tracheal Dilation. Anesthesia & Analgesia Volume 80 Issue 4 - pp 841-843
Low, J. H. Smith, R. The management of laryngeal and subglottic stenosis (2006) Br. J. Anaesth. 96 (6): 803-804.
Learning points: Asymptomatic subglottic stenosis is a rare condition that may present as an unexpected difficult intubation and has high anesthetic risk. The necessity and urgency of the surgery must be considered when deciding how to procede - awake the patient and find the diagnosis or approach the airway differently (subglottic device or invasive surgical airway).

Difficult intubation in a patient with unknown subglottic stenosis