3 DISCUSSION
Cysts on the tongue are one of the major diseases that cause upper airway obstruction in pediatric patients.2 The origin of the cysts varies including those derived from the thyroglossal or lingual ducts, those derived from the cystic degeneration of the lingual thyroid, retention cysts arising from the mucous glands at the base of the tongue, and cysts generated from remnant cells during the embryonic stage.3 In the present report, the cyst was a thyroglossal duct cyst as revealed by the histopathological diagnosis after the surgery, and the common sites are shown in Figure 3.4
The first concern of this case is a difficult airway management. Kumanomido et al.2 described that the necessity of tracheostomy, subglottic space, presence/absence of a tracheal shift, mandibular size, and necessity of fiberscope-guided intubation should be assessed when evaluating the difficulty of tracheal intubation according to the cyst size. The possibility of tracheostomy was excluded in our patient because the cyst was near the dorsum of the tongue, anterior to the typical site of origin, and snoring was the only daily symptom reported. Furthermore, the patient aged only 5 years; therefore, fiberscope-guided intubation while conscious was not considered to be feasible. Moreover, preoperative computed tomography images revealed no subglottic space or tracheal deviation, and the patient did not present with micrognathia. Therefore, slow induction with sevoflurane was performed as usual, with the preparation for emergency airway maintenance. A route was secured prior to the induction to prepare for the difficult airway that was expected after the induction of anesthesia. After the onset of anesthesia, mask ventilation temporarily was difficult due to the effects of the tongue mass and glossoptosis; however, mask ventilation was sufficiently performed with the use of muscle relaxants and an oral airway. Mask ventilation would have still been difficult if the cyst would have been localized near the base of the tongue.
For tracheal intubation, McGRATH was used in our patient and its utility has been reported in pediatric patients.4, 5, 6 Airway scope with pediatric Intlock blades are useful in pediatric patients with difficult airways.7 However, in our patient, McGRATH was used for intubation because the blade of the McGRATH was thin and had good operability. Although the tongue could not be completely excluded using McGRATH, the Cormack–Lehane view was Grade 2, and intubation could be performed in the first attempt without any issues.
The second concern of this case is airway obstruction associated with tongue swelling after surgery. In our case, intraoperative findings included no fistulous tract connected to the cyst, no resection of the hyoid bone, and no tongue swelling at the end of the surgery. Therefore, the patient was extubated in the operating room; however, as a precaution, the patient’s respiratory condition was observed under sedation with Dexmedetomidine in the ICU. In Japan, Dexmedetomidine for the sedation of non-intubated pediatric patients is being used since 2018. Without intubation, respiratory depression is a major issue, particularly in pediatric sedation; Dexmedetomidine does not have a less respiratory depressant effect and is also used for postoperative sedation in pediatric patients.8 In our patient, we were concerned about respiratory depression by sedation, but it was necessary to keep the patient on bed rest to avoid tongue swelling after surgery. Therefore, Dexmedetomidine was used. In addition, Dexmedetomidine has analgesic effects; the analgesic effects, to some degree, seem to have contributed to the patient being on bed rest.