Tracheal tears commonly occur in cats following dental procedures,1 often due to over inflation of the endotracheal tube cuff; this is typically done to prevent fluid or debris from leaking around the endotracheal tube.1 Low-volume, high-pressure cuffs may be more likely to cause tears than are high-volume, low-pressure cuffs. Other causes of tracheal tears include trauma, improper endotracheal tube placement and/or size, injury from an endotracheal tube stylet, and failure to deflate the cuff when repositioning and/or extubating.2,3 In 2 feline case series (n = 16 and n = 20), 2 cats had tracheal ruptures induced by a stylet; all other cases of tracheal rupture were caused by cuff overinflation.2,4 In intubated cats, approximately 1.6 ± 0.7 mL of air is needed to form an airtight seal; more than 6 mL of air in the cuff can increase the risk for tracheal rupture.2 Ruptures are often linear tears of the trachealis muscle. Tears extending into the carina typically have a poorer prognosis.2 Most commonly, tears are longitudinal, 2 to 5 cm in length, extra thoracic, and located in the dorsal longitudinal trachealis muscle or dorsolateral aspect of the trachea at the junction of the tracheal rings.2,4 In a feline cadaver study, ruptures were linear and located at the attachment of the trachealis muscle to the tracheal cartilage, which was also located directly over the enlarged cuff.2 In the cadavers, the trachealis muscle split from the left side of the trachea and rolled to the right, which suggests there is less support on the left side of the trachea in cats.2
The endotracheal tube should be inspected after every extubation. If blood on the endotracheal tube and/or aberrant swelling or crepitus in the neck region—potentially extending to the sternal area—are present, a tear could be involved.3 Clinical signs generally develop 4 hours to 6 days after the anesthetic episode2 because the mediastinum, which tightly covers the trachea, may prevent air from escaping until coughing and tracheal irritation develop, which then allows air to escape.2 Subcutaneous emphysema is evident in all tracheal tear cases due to the migration of air into the mediastinum and subsequently into the subcutaneous tissues.1,2,4 It has been reported in 100% of tracheal tear cases.5,6 Other clinical signs of tracheal tears include anorexia, coughing, noise from the upper airway, tachypnea, expiratory dyspnea, gagging, exertional cyanosis, exercise intolerance, and muffled heart sounds.1,4
Explore how to prevent, detect, and manage this common life-threatening sequela to dental and other procedures requiring intubation in cats.
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