Magnetic resonance imaging (MRI) for veterinary neurological assessment often requires general anesthesia to ensure immobility (9,10). Given the strong magnetic field in MRI rooms, objects containing iron or stainless steel, regardless of their size, can become dangerous projectiles. Therefore, procedures involving equipment such as laryngoscopes or oxygen cylinders must be performed outside the MRI room. Consequently, the anesthesia preparation area and the MRI room are typically located separately. This necessitates the transportation of anesthetized patients into the MRI room for imaging and then moving them back out for recovery.

In addition, owing to the noninvasive nature of the procedure, light anesthesia is commonly used during MRI (2). However, this procedure is associated with an increased risk of premature awakening, particularly when the animal is disconnected from the breathing circuit (adaptor disconnections) during transport between the MRI room and the preparation or recovery area. This disconnection can accelerate the decline in anesthetic depth (9).

In the present case, the dog prematurely regained consciousness during transport and bit through its endotracheal tube (ETT), resulting in tracheal foreign body lodging, which required bronchoscopic intervention.

A 2-year-old, 5.0 kg Maltese Poodle mix-breed dog was anesthetized for brain MRI due to episodic ataxia. Comprehensive pre-anesthetic evaluations, including hematology, serum biochemistry, thoracic radiography, urinalysis, and electrolyte analysis, revealed no abnormalities. Premedication included midazolam (0.2 mg/kg) and butorphanol (0.2 mg/kg). Anesthesia was induced with propofol (4 mg/kg), and a 5.5 mm Murphy-type cuffed ETT was inserted. Anesthesia was maintained using isoflurane (0.8-1.1%) in oxygen, and end-tidal carbon dioxide levels, respiration, and heart rate were continuously monitored. Oscillometric blood pressure was monitored every 2 min. Immediately after intubation, the heart rate was recorded at 80 bpm, and the mean arterial pressure (MAP) was 45 mmHg. Glycopyrrolate was administered at a dose of 10 µg/kg, resulting in an increase in heart rate to 100 bpm and a rise in MAP to 70 mmHg. As spontaneous breathing was not observed, mechanical ventilation was initiated using pressure-controlled ventilation mode. The respiratory rate was set at 12 breaths per minute, with an inspiration:expiration ratio of 1:3. The end-tidal carbon dioxide level remained stable at approximately 33-35 mmHg. Based on the patient’s vital signs and the absence of motion artifacts in the images, the anesthetic depth was adjusted accordingly. The isoflurane concentration was initially set at 1.1%. However, owing to a tendency for the heart rate to decrease, the vaporizer setting was gradually reduced, maintaining an overall concentration of 0.8% for anesthesia. To monitor for any unexpected patient movement, real-time observations were made through the closed-circuit television system installed in the MRI room. No motion artifacts were observed in the images obtained during the MRI scan. The total anesthesia time was 40 min, during which the vital signs remained stable with minimal variation (heart rate: 90-100 bpm, MAP: 70-80 mmHg) throughout the procedure.

During the transfer from the MRI room to the recovery area (approximately 5 m apart), the breathing circuit was disconnected, leading to a rapid decrease in anesthetic depth and premature awakening. As a result, the dog bit through the ETT, causing a distal fragment to become lodged in its trachea. Despite coughing caused by airway irritation from the ETT, the fragments were not expelled from the airway. Consequently, an emergency bronchoscopy was performed immediately. To perform reintubation, an additional dose of propofol (4 mg/kg) was administered. An ETT one size larger (6.0 mm) than the original was selected to allow a 3.5 mm flexible bronchoscope with alligator forceps to pass through the tube smoothly. After reintubation, a bronchoscopy was performed, and the tube fragment was successfully retrieved (Fig. 1). No tracheal injury or other complications were observed, and the dog recovered uneventfully. The patient developed a mild cough after recovery that resolved within 2 h. MRI revealed no significant findings, raising suspicion of idiopathic epilepsy or paroxysmal dyskinesia.

Figure 1. Removal of an endotracheal tube (ETT) fragment lodged in the airway. The arrow indicates the ETT fragment. (a) Portable radiograph showing the ETT fragment lodged in the trachea. The image also displays the reintubated ETT, bronchoscope, and forceps positioned to retrieve the ETT. (b) Tracheoscopic view capturing the moment just before removing the tracheal foreign body using forceps.

Tracheal foreign bodies, while extremely rare in veterinary practice, can occur in both dogs and cats (6). The present case highlighted the potential risks associated with patient transport necessitated by the spatial separation of the anesthesia preparation area and the MRI suite. During such transfers, adaptor disconnection can lead to a rapid decrease in anesthetic depth, significantly increasing the risk of premature patient awakening (2,9). This risk is particularly pronounced in MRI procedures, where immobilization can often be achieved even under light anesthesia. Consequently, adaptor disconnection may result in an even more rapid decline in anesthetic depth, as observed in this case, where the dog unexpectedly regained consciousness during transport and bit through the ETT, resulting in a foreign body lodging in its trachea.

During MRI procedures, sedation or general anesthesia is commonly employed to prevent patient movement, with light anesthesia often preferred over the deeper levels used in surgeries (9). Despite close monitoring, animals may recover from general anesthesia more rapidly than anticipated. Moreover, adaptor disconnection during patient transport can further contribute to sudden awakening, particularly when the anesthetic depth is light. To mitigate these risks, a thorough assessment of anesthetic depth using human senses is essential. Human senses are among the most reliable tools for assessing anesthetic depth, including the evaluation of eye position, palpebral reflexes, jaw tone, and heart and respiratory rates (8). In light planes of anesthesia, jaw tone typically increases, and the palpebral reflex becomes positive, serving as a reliable indicator of light anesthesia (3). If signs of light anesthesia, such as a pronounced palpebral reflex, are observed, administering a small dose of propofol before transport can help maintain adequate anesthetic depth. Additionally, manually securing the muzzle during transport may help minimize the risk of complications.

Tracheal foreign bodies require prompt and effective management owing to their critical location and the potential for complications. These complications can range from mild respiratory distress and discomfort to more severe issues, such as upper airway lacerations, injuries, or airflow obstructions (4,11). In the present case, the dog regained consciousness more rapidly than expected, inadvertently biting through the ETT, which resulted in the formation of a tracheal foreign body. Although coughing is a natural reflex triggered by airway irritation and serves as a mechanism for expelling foreign materials, it was ineffective in this instance, leaving the fragment lodged within the trachea (1). Prolonged airway irritation from a retained foreign body may lead to complications, including inflammation or infection. This emphasizes the necessity for timely intervention, such as bronchoscopy, to effectively resolve the issue (4,6).

Bronchoscopy remains the preferred method for removing tracheal foreign bodies owing to its accuracy and ability to minimize trauma (6). In the present case, flexible bronchoscopy with grasping forceps was successfully employed to extract the foreign body. Following the procedure, the patient exhibited a mild cough, which rapidly resolved without any clinical significance. However, for clinics without access to endoscopy, alternative methods may be considered, such as using a smaller cuffed ETT or a Foley catheter to dislodge and remove the obstruction (5,7). This approach involves passing a smaller cuffed ETT or a Foley urinary catheter into or through the obstructing ETT. Once positioned, the cuff can be inflated, allowing the foreign body and tube to be removed together. While this method can be effective, care must be taken to avoid over-inflating the cuff, particularly if it is positioned beyond the obstruction, as this may cause tracheal damage. Additionally, throughout the removal process, visual inspection of the larynx is recommended to minimize the risk of trauma. Nevertheless, such techniques can serve as viable options in facilities without endoscopy, provided they are performed with appropriate caution and attention to patient safety.

Tracheal foreign bodies caused by ETTs are rare in dogs and cats but may occur during recovery from general anesthesia, necessitating prompt intervention. Securing the ETT effectively and monitoring anesthetic depth closely are critical in preventing complications. Trained personnel should be equipped to address sudden patient awakening, including administering a small dose of propofol or manually stabilizing the muzzle if required. In cases where tracheal foreign bodies do arise, bronchoscopy combined with grasping forceps remains a reliable and effective removal technique.

The authors gratefully acknowledge the financial and facility support provided by the director of the Ilsan Animal Medical Center, Woongjoo Chae.

The authors have no conflicting interests.